Date: 30/05/2021 07:32:58
From: Spiny Norman
ID: 1744706
Subject: DWFTTW

A wind-powered car, running down wind faster than the wind.

Link

Reply Quote
Date: 30/05/2021 07:42:54
From: mollwollfumble
ID: 1744708
Subject: re: DWFTTW

Spiny Norman said:


A wind-powered car, running down wind faster than the wind.

Link

Thanks for that.

A chap I knew at CSIRO developed a water powered car that drove upstream.

I also did some work for a company that developed a wind/water turbine that would always turn the same way irrespective of the direction of the wind/water flow. He used to demonstrate it by throwing objects from random directions at the propeller, with it turning in the same direction no matter where the object was thrown from.

Reply Quote
Date: 30/05/2021 07:49:49
From: JudgeMental
ID: 1744710
Subject: re: DWFTTW

mollwollfumble said:


.

A chap I knew at CSIRO developed a water powered car that drove upstream.

yeah, jet boats are good at that.

Reply Quote
Date: 30/05/2021 08:17:59
From: mollwollfumble
ID: 1744717
Subject: re: DWFTTW

Spiny Norman said:


A wind-powered car, running down wind faster than the wind.

Link

I still don’t understand this.

Let’s suppose that a yacht can travel downwind faster than the wind …
… then why do yachts have spinnakers?

Reply Quote
Date: 30/05/2021 08:19:42
From: roughbarked
ID: 1744719
Subject: re: DWFTTW

mollwollfumble said:


Spiny Norman said:

A wind-powered car, running down wind faster than the wind.

Link

I still don’t understand this.

Let’s suppose that a yacht can travel downwind faster than the wind …
… then why do yachts have spinnakers?

A yacht cannot travel directly downwing faster than the wind. Spinnakers are like half a propellor in that they cut across the wind.

Reply Quote
Date: 30/05/2021 08:22:05
From: Tamb
ID: 1744720
Subject: re: DWFTTW

JudgeMental said:


mollwollfumble said:

.

A chap I knew at CSIRO developed a water powered car that drove upstream.

yeah, jet boats are good at that.

The AC75s angle downwind but in a 15kt wind achieve 40+ kts downwind

Reply Quote
Date: 30/05/2021 09:01:36
From: Spiny Norman
ID: 1744734
Subject: re: DWFTTW

mollwollfumble said:


Spiny Norman said:

A wind-powered car, running down wind faster than the wind.

Link

I still don’t understand this.

Let’s suppose that a yacht can travel downwind faster than the wind …
… then why do yachts have spinnakers?

To catch as much wind as possible. But where possible fast sailing boats (cats, single-hulls that can get up on the plane, etc) prefer to sail on the reaching leg as that will let them gain a heck of a lot more apparent wind speed and so go faster. And the faster they go, the closer to directly downwind they can get.

Reply Quote
Date: 30/05/2021 09:05:51
From: roughbarked
ID: 1744736
Subject: re: DWFTTW

Spiny Norman said:


mollwollfumble said:

Spiny Norman said:

A wind-powered car, running down wind faster than the wind.

Link

I still don’t understand this.

Let’s suppose that a yacht can travel downwind faster than the wind …
… then why do yachts have spinnakers?

To catch as much wind as possible. But where possible fast sailing boats (cats, single-hulls that can get up on the plane, etc) prefer to sail on the reaching leg as that will let them gain a heck of a lot more apparent wind speed and so go faster. And the faster they go, the closer to directly downwind they can get.

The propellor blades make two spinnakers and tacks both ways but as it drives the wheels, the wheels drive the propellor backwards which also creates thrust.

Reply Quote
Date: 30/05/2021 09:07:16
From: Dark Orange
ID: 1744737
Subject: re: DWFTTW

mollwollfumble said:


Spiny Norman said:

A wind-powered car, running down wind faster than the wind.

Link

I still don’t understand this.

Let’s suppose that a yacht can travel downwind faster than the wind …
… then why do yachts have spinnakers?

Traditionally, they were for allowing the ship to go directly downwind. You will see that modern boats have the spinnaker off centre, effectively another “wing”.

Great video Bill!

For all those still struggling with the concept, it helps to understand that when foils and wings are included, airflow is an accelleration rather than an absolute velocity.

Reply Quote
Date: 30/05/2021 09:37:45
From: The Rev Dodgson
ID: 1744747
Subject: re: DWFTTW

Spiny Norman said:


A wind-powered car, running down wind faster than the wind.

Link

A bit long, but I did scan some of the comments, and these replies seemed pretty sensible:

“yes, that was it for me as well, its a fan powered by the car being pushed by the wind.”

“its actually a propeller.”

Reply Quote
Date: 30/05/2021 09:40:18
From: The Rev Dodgson
ID: 1744748
Subject: re: DWFTTW

roughbarked said:


mollwollfumble said:

Spiny Norman said:

A wind-powered car, running down wind faster than the wind.

Link

I still don’t understand this.

Let’s suppose that a yacht can travel downwind faster than the wind …
… then why do yachts have spinnakers?

A yacht cannot travel directly downwing faster than the wind. Spinnakers are like half a propellor in that they cut across the wind.

A yacht with rigid sails could travel downwind faster than the wind, but it doesn’t work with old-fashioned fabric sails.

Reply Quote
Date: 30/05/2021 09:43:12
From: Spiny Norman
ID: 1744750
Subject: re: DWFTTW

The Rev Dodgson said:


roughbarked said:

mollwollfumble said:

I still don’t understand this.

Let’s suppose that a yacht can travel downwind faster than the wind …
… then why do yachts have spinnakers?

A yacht cannot travel directly downwing faster than the wind. Spinnakers are like half a propellor in that they cut across the wind.

A yacht with rigid sails could travel downwind faster than the wind, but it doesn’t work with old-fashioned fabric sails.

Yep, creating an efficient lift force vs just being a big parachute.

Reply Quote
Date: 30/05/2021 09:46:33
From: mollwollfumble
ID: 1744751
Subject: re: DWFTTW

Dark Orange said:


mollwollfumble said:

Spiny Norman said:

A wind-powered car, running down wind faster than the wind.

Link

I still don’t understand this.

Let’s suppose that a yacht can travel downwind faster than the wind …
… then why do yachts have spinnakers?

Traditionally, they were for allowing the ship to go directly downwind. You will see that modern boats have the spinnaker off centre, effectively another “wing”.

Great video Bill!

For all those still struggling with the concept, it helps to understand that when foils and wings are included, airflow is an accelleration rather than an absolute velocity.

> You will see that modern boats have the spinnaker off centre, effectively another “wing”.

Ta, yeah, I’d wondered about that.

What I’d like to see is a drawing of the speed envelope for a yacht relative to wind angle.

Reply Quote
Date: 30/05/2021 09:51:00
From: Tamb
ID: 1744752
Subject: re: DWFTTW

Spiny Norman said:


The Rev Dodgson said:

roughbarked said:

A yacht cannot travel directly downwing faster than the wind. Spinnakers are like half a propellor in that they cut across the wind.

A yacht with rigid sails could travel downwind faster than the wind, but it doesn’t work with old-fashioned fabric sails.

Yep, creating an efficient lift force vs just being a big parachute.


AC75 typical speeds: With the wind at about 15 knots the boat can achieve 43 knots angling downwind and 25 knots angling upwind.

Reply Quote
Date: 30/05/2021 09:55:39
From: captain_spalding
ID: 1744754
Subject: re: DWFTTW

Spiny Norman said:


The Rev Dodgson said:

roughbarked said:

A yacht cannot travel directly downwing faster than the wind. Spinnakers are like half a propellor in that they cut across the wind.

A yacht with rigid sails could travel downwind faster than the wind, but it doesn’t work with old-fashioned fabric sails.

Yep, creating an efficient lift force vs just being a big parachute.

But sails are not just big parachutes. They’re airfoils, and that’s why they sail faster at an angle to the wind (typically about 55deg to the wind, but it varies from boat to boat) than they do when running directly before the wind.

Even then, there’s still a pressure differential on the ‘back’ and the ‘front’ of the sail, with the lower-pressure area created on the ‘front’ lending some assistance to ‘suck’ the boat along.

Reply Quote
Date: 30/05/2021 10:26:18
From: Spiny Norman
ID: 1744766
Subject: re: DWFTTW

captain_spalding said:


Spiny Norman said:

The Rev Dodgson said:

A yacht with rigid sails could travel downwind faster than the wind, but it doesn’t work with old-fashioned fabric sails.

Yep, creating an efficient lift force vs just being a big parachute.

But sails are not just big parachutes. They’re airfoils, and that’s why they sail faster at an angle to the wind (typically about 55deg to the wind, but it varies from boat to boat) than they do when running directly before the wind.

Even then, there’s still a pressure differential on the ‘back’ and the ‘front’ of the sail, with the lower-pressure area created on the ‘front’ lending some assistance to ‘suck’ the boat along.

Yes, that’s essentially what I wrote.
But when they are going directly downwind they aren’t an aerofoil, they are just an inefficient parachute.

Reply Quote
Date: 30/05/2021 10:34:59
From: The Rev Dodgson
ID: 1744772
Subject: re: DWFTTW

The Rev Dodgson said:


roughbarked said:

mollwollfumble said:

I still don’t understand this.

Let’s suppose that a yacht can travel downwind faster than the wind …
… then why do yachts have spinnakers?

A yacht cannot travel directly downwing faster than the wind. Spinnakers are like half a propellor in that they cut across the wind.

A yacht with rigid sails could travel downwind faster than the wind, but it doesn’t work with old-fashioned fabric sails.

Actually that’s probably wrong.

You need some means of extracting energy from the movement of the hull through the water.

Reply Quote
Date: 30/05/2021 10:35:27
From: Tamb
ID: 1744773
Subject: re: DWFTTW

Spiny Norman said:


captain_spalding said:

Spiny Norman said:

Yep, creating an efficient lift force vs just being a big parachute.

But sails are not just big parachutes. They’re airfoils, and that’s why they sail faster at an angle to the wind (typically about 55deg to the wind, but it varies from boat to boat) than they do when running directly before the wind.

Even then, there’s still a pressure differential on the ‘back’ and the ‘front’ of the sail, with the lower-pressure area created on the ‘front’ lending some assistance to ‘suck’ the boat along.

Yes, that’s essentially what I wrote.
But when they are going directly downwind they aren’t an aerofoil, they are just an inefficient parachute.


Some high tech racing yachts have twin mainsails attached to the sides of the mast. They are individually trimmable to give an airfoil section on either tack.

Reply Quote
Date: 30/05/2021 10:38:27
From: Tamb
ID: 1744774
Subject: re: DWFTTW

The Rev Dodgson said:


The Rev Dodgson said:

roughbarked said:

A yacht cannot travel directly downwing faster than the wind. Spinnakers are like half a propellor in that they cut across the wind.

A yacht with rigid sails could travel downwind faster than the wind, but it doesn’t work with old-fashioned fabric sails.

Actually that’s probably wrong.

You need some means of extracting energy from the movement of the hull through the water.


Why?

Reply Quote
Date: 30/05/2021 10:45:56
From: The Rev Dodgson
ID: 1744775
Subject: re: DWFTTW

Tamb said:


The Rev Dodgson said:

The Rev Dodgson said:

A yacht with rigid sails could travel downwind faster than the wind, but it doesn’t work with old-fashioned fabric sails.

Actually that’s probably wrong.

You need some means of extracting energy from the movement of the hull through the water.


Why?

Because when the boat gets up to exactly wind speed there will be zero air flow over the sails, regardless of their shape, orientation, or stiffness, so the force of the air on them will be exactly zero.

Reply Quote
Date: 30/05/2021 10:49:59
From: roughbarked
ID: 1744776
Subject: re: DWFTTW

The Rev Dodgson said:


Tamb said:

The Rev Dodgson said:

Actually that’s probably wrong.

You need some means of extracting energy from the movement of the hull through the water.


Why?

Because when the boat gets up to exactly wind speed there will be zero air flow over the sails, regardless of their shape, orientation, or stiffness, so the force of the air on them will be exactly zero.

Correct.

Reply Quote
Date: 30/05/2021 10:51:46
From: roughbarked
ID: 1744777
Subject: re: DWFTTW

roughbarked said:


The Rev Dodgson said:

Tamb said:

Why?

Because when the boat gets up to exactly wind speed there will be zero air flow over the sails, regardless of their shape, orientation, or stiffness, so the force of the air on them will be exactly zero.

Correct.

This is why this video works so well. Because it is a light frame on light wheels, no water. Very little drag.

Reply Quote
Date: 30/05/2021 10:59:58
From: Dark Orange
ID: 1744778
Subject: re: DWFTTW

Tamb said:


The Rev Dodgson said:

The Rev Dodgson said:

A yacht with rigid sails could travel downwind faster than the wind, but it doesn’t work with old-fashioned fabric sails.

Actually that’s probably wrong.

You need some means of extracting energy from the movement of the hull through the water.


Why?

Note the word “Downwind” needs to be clarified in this discussion – There is a subtle difference between “Directly downwind” (The definition used in the video) and “Downwind” (the definition used in sailing which means “a generally downwinf direction”)

A sailboat can go in a generally downwind direction faster than the actual wind speed. A sailboat would have difficulty going directly downwind faster than the actual wind speed.

Reply Quote
Date: 30/05/2021 11:01:17
From: Dark Orange
ID: 1744780
Subject: re: DWFTTW

roughbarked said:


roughbarked said:

The Rev Dodgson said:

Because when the boat gets up to exactly wind speed there will be zero air flow over the sails, regardless of their shape, orientation, or stiffness, so the force of the air on them will be exactly zero.

Correct.

This is why this video works so well. Because it is a light frame on light wheels, no water. Very little drag.

…and a high friction contact with a solid surface.

Reply Quote
Date: 30/05/2021 11:01:47
From: The Rev Dodgson
ID: 1744781
Subject: re: DWFTTW

Dark Orange said:


Tamb said:

The Rev Dodgson said:

Actually that’s probably wrong.

You need some means of extracting energy from the movement of the hull through the water.


Why?

Note the word “Downwind” needs to be clarified in this discussion – There is a subtle difference between “Directly downwind” (The definition used in the video) and “Downwind” (the definition used in sailing which means “a generally downwinf direction”)

A sailboat can go in a generally downwind direction faster than the actual wind speed. A sailboat would have difficulty going directly downwind faster than the actual wind speed.

Yeah, we are talking directly downwind here.

Reply Quote
Date: 30/05/2021 11:04:10
From: party_pants
ID: 1744783
Subject: re: DWFTTW

OK, you’ve stumped me.

What does DWFTTW mean?

Reply Quote
Date: 30/05/2021 11:04:44
From: Tamb
ID: 1744784
Subject: re: DWFTTW

The Rev Dodgson said:


Tamb said:

The Rev Dodgson said:

Actually that’s probably wrong.

You need some means of extracting energy from the movement of the hull through the water.


Why?

Because when the boat gets up to exactly wind speed there will be zero air flow over the sails, regardless of their shape, orientation, or stiffness, so the force of the air on them will be exactly zero.


There are two “downwinds” The wind direction for the general area and the wind direction across the sails (the apparent wind) This means that the boat can end up running directly downwind.

Reply Quote
Date: 30/05/2021 11:05:18
From: party_pants
ID: 1744785
Subject: re: DWFTTW

party_pants said:


OK, you’ve stumped me.

What does DWFTTW mean?

Stand down, I figured it out

Reply Quote
Date: 30/05/2021 11:05:27
From: JudgeMental
ID: 1744786
Subject: re: DWFTTW

party_pants said:


OK, you’ve stumped me.

What does DWFTTW mean?

down wind faster that the wind.

Reply Quote
Date: 30/05/2021 11:05:30
From: roughbarked
ID: 1744787
Subject: re: DWFTTW

party_pants said:


OK, you’ve stumped me.

What does DWFTTW mean?

Down wind faster than the wind?

Reply Quote
Date: 30/05/2021 11:05:48
From: JudgeMental
ID: 1744788
Subject: re: DWFTTW

party_pants said:


party_pants said:

OK, you’ve stumped me.

What does DWFTTW mean?

Stand down, I figured it out

now you tell me.

Reply Quote
Date: 30/05/2021 11:06:38
From: dv
ID: 1744790
Subject: re: DWFTTW

Hmmm, it’s interesting. I understand the theory but it’s still a bit weird when you think about it.

Once the craft reaches wind speed, then it is stationary with respect to the mass of air.

Reply Quote
Date: 30/05/2021 11:09:12
From: The Rev Dodgson
ID: 1744792
Subject: re: DWFTTW

Tamb said:


The Rev Dodgson said:

Tamb said:

Why?

Because when the boat gets up to exactly wind speed there will be zero air flow over the sails, regardless of their shape, orientation, or stiffness, so the force of the air on them will be exactly zero.


There are two “downwinds” The wind direction for the general area and the wind direction across the sails (the apparent wind) This means that the boat can end up running directly downwind.

If the boat is going exactly downwind at wind speed, there is no motion of the air relative to the sails, so it doesn’t have a direction.

Reply Quote
Date: 30/05/2021 11:11:59
From: The Rev Dodgson
ID: 1744797
Subject: re: DWFTTW

The Rev Dodgson said:


Tamb said:

The Rev Dodgson said:

Because when the boat gets up to exactly wind speed there will be zero air flow over the sails, regardless of their shape, orientation, or stiffness, so the force of the air on them will be exactly zero.


There are two “downwinds” The wind direction for the general area and the wind direction across the sails (the apparent wind) This means that the boat can end up running directly downwind.

If the boat is going exactly downwind at wind speed, there is no motion of the air relative to the sails, so it doesn’t have a direction.

But if you have rotors, they do have a motion relative to the air, so they can act as propellers, if they have some external source of power (i.e. the motion of the wheels over the ground).

Reply Quote
Date: 30/05/2021 11:12:11
From: SCIENCE
ID: 1744798
Subject: re: DWFTTW

under this name it was covered extensively in one of the old forums but it’s still a while before we can find the archive

Reply Quote
Date: 30/05/2021 11:15:01
From: The Rev Dodgson
ID: 1744801
Subject: re: DWFTTW

SCIENCE said:


under this name it was covered extensively in one of the old forums but it’s still a while before we can find the archive

I do recall (vaguely) discussing this all before.

But presumably not with reference to that video, since it was just posted today.

Reply Quote
Date: 31/05/2021 11:49:03
From: SCIENCE
ID: 1745155
Subject: re: DWFTTW

Reply Quote
Date: 31/05/2021 11:52:11
From: dv
ID: 1745157
Subject: re: DWFTTW

SCIENCE said:



You’ve hit the forum image limit

Reply Quote
Date: 31/05/2021 11:56:58
From: SCIENCE
ID: 1745161
Subject: re: DWFTTW

dv said:


SCIENCE said:


You’ve hit the forum image limit

sorry we’ll do it HTML style

From: black hamster ®16/01/2004 4:11:56 PM
Subject: yacht speedpost id: 888236

Can a yacht sail faster than wind speed? If so, how? Wouldn’t this violate the law of conservation of energy?
From: elfin vampire ®16/01/2004 4:15:13 PM
Subject: re: yacht speedpost id: 888239
wild guess: ocean currents? Hull design vs inertial motion?
From: Donde ®16/01/2004 4:16:41 PM
Subject: re: yacht speedpost id: 888244
What if sailing with the current as opposed to against it?
From: Elephant ®16/01/2004 4:30:43 PM
Subject: re: yacht speedpost id: 888264
Can a yacht sail faster than wind speed? If so, how? Wouldn’t this violate the law of conservation of energy?

I would not think so. I could travel faster than the wind speed it it were going downstream, but that’s not sailing, is it…
From: Donde ®16/01/2004 4:33:59 PM
Subject: re: yacht speedpost id: 888270
Sailing is sailing whatever the direction.
From: PeterT ®16/01/2004 4:35:51 PM
Subject: re: yacht speedpost id: 888273
When tacking, a sailing boat can travel faster than the wind speed. There is a paper on it some where. I’ll have a look later on when I have time, if somebody dosent beat me to it.
From: Elephant ®16/01/2004 4:36:37 PM
Subject: re: yacht speedpost id: 888275
Sailing is sailing whatever the direction.

I wasn’t talking about direction. Sailing is being pushed (or pulled) by the wind. It’s not sailing if there is no wind at all, but you are moving in the current of the water you are in.
From: Spudd ®16/01/2004 4:37:25 PM
Subject: re: yacht speedpost id: 888277
>>Can a yacht sail faster than wind speed?

Yes.

>>If so, how?

It can only do this when its cutting along the wind at 90 deg. If it were traveling with the wind, its max speed is slightly less than the speed of the wind. The reason it can go faster than the wind is because the sails harness the energy of the wind, but dont change their speed relative to the wind eg the wind is always passing over the sails at the same speed. This allows the boat to keep gaining energy from the wind to a max speed that often is faster than the wind speed.

>>Wouldn’t this violate the law of conservation of energy?

Nope. There is heaps of energy in wind. The sail only converts it from one direction to another. Its only when a boat is going with the wind that this makes sense, becuase as the boat speeds up, the relative wind speed and hence the amount of energy the sails can extract decrease.







From: Elephant ®16/01/2004 4:39:15 PM
Subject: re: yacht speedpost id: 888282
When tacking, a sailing boat can travel faster than the wind speed. There is a paper on it some where. I’ll have a look later on when I have time, if somebody dosent beat me to it.

PeterT, the winds on the open ocean are in the range of 100’s of kph. I’ve never seen a sail boat go anywhere near that fast, even while tacking.

Did you mean when the boat is heading into the wind, or only for the actual time the boat is tacking, which is only a few seconds?
From: Quenda ®16/01/2004 4:43:25 PM
Subject: re: yacht speedpost id: 888287
Yes, sailing vessels can go faster than the wind.
Google on ‘Physics of Sailing’ and/or see the analysis at http://www.phys.unsw.edu.au/~jw/sailing.html
From: PeterT ®16/01/2004 4:43:49 PM
Subject: re: yacht speedpost id: 888289
I was not talking about the actual act of tacking but rather the general term of sailing into the wind at an angle on a tacking leg.

During a tacking leg a boatcan sail faster than the wind and racing boats do it regularly.

As I said Elephant, I will look up the principle involved when I finish work.
From: Peter© ®16/01/2004 4:45:33 PM
Subject: re: yacht speedpost id: 888291

Does a the splash of a wave breaking against a breakwater at an angle travel many times faster than the wave itself? Sure does.

The easiest way for a sailing boat to travel faster than the wind is ‘downwind tacking’ where heaps of ‘reaching’ sail – a ‘shy’ or angle-tacking flat spinaker – is used for high-speed sailing.

You’ll notice that since the huge fixed ‘spinaker poles’ – tubes poking right out the front about the same length of the boat – on Sydney Harbour 18 Footers with, say, Iain Murray’s series of ‘Channel Seven’ superboats they never use the formerly familiar bulbous parachute kites (spinakers) and never sail dead-straight downwind. They all go downwind in a series of angled tacks. Ultimately higher Vmg (Velocity made good).

In some conditions – light wind – some monohull small boats can exceed the windspeed when going to windward. Since John Bertrand’s work on mailsails (a PhD before winning the America’s Cup) mains are circular in section – rather than the section of the traditional wing – and are VERY efficient. Famous for high speed to windward, too, are the very efficent class catamarans – lots of sail, big beam, narrow, small drag, hulls.

But your question refers to yachts; since the development of lightweight yachts from Bruce Farr, Doug Petersen, Ron Holland, Laurie Davidson, et al (and the measures taken to stop the early ones breaking up) yachts have gone much faster. I’d venture to say that only in the very lightest breezes could a displacement yacht (as opposed to a planing skiff) exceed the speed of the wind, under wind-power alone.

In big rolling seas (large waves) these boats can get up and plane (dynamic support of hull rather than flotation) and go very quickly – 25kts, say – but still that’s unlikely to be faster than windspeed.

Go n Sail!
From: Mr Staypuft ®16/01/2004 4:46:42 PM
Subject: re: yacht speedpost id: 888293

The link is good
How can boats sail faster than the wind?





From: pooch ®16/01/2004 4:52:01 PM
Subject: re: yacht speedpost id: 888299
You cannot sail directly into a wind.
On a tacking leg you are sailing obliquely.
If the wind was a steady 20 knots, you may reach 30 knots in surface speed, but you could never reach a point that is directly into the wind at a faster speed than the wind.



From: Peter© ®16/01/2004 4:55:42 PM
Subject: re: yacht speedpost id: 888305

Very true, pooch. And….?
From: pooch ®16/01/2004 4:58:56 PM
Subject: re: yacht speedpost id: 888309
So the simple answer is yes, it can sail faster than wind speed.
From: black hamster ®16/01/2004 5:01:39 PM
Subject: re: yacht speedpost id: 888313

So if it’s not being blown along, what generates the propulsion?

It is lift acting over an aerofoil sail?
From: Peter© ®16/01/2004 5:24:20 PM
Subject: re: yacht speedpost id: 888326

It’s both, ham.

(If it’s not surfing nor drifting with the current, and the motor’s off…:) )

It’s being blown along, but the redirection mechanisms (sail, hull, fin) make the pushing of the hull a little phenomenal – to those looking at it without delving into the physics.

And, yes, it’s lift from the aerofoil. Enough of the ‘lift’ acts forward to give motion. In some conditions the motion is faster than the factor-causing-it’s own speed. No big deal.

Consider ice-boats: they hardly EVER travel at less than the windspeed – frictionless. Boats have to get through the water – friction/drag.

Voila!
From: Richard C ®16/01/2004 8:49:32 PM
Subject: re: yacht speedpost id: 888589
Spud’s right, most yachts can,on a beam reach (the point of sailing s/he’s descibing) under some wind conditions, sail faster than the wind speed.

the winds on the open ocean are in the range of 100’s of kph.

Not very often, elephant, 100km/h is storm force. The trade winds tend to be in the range 10-25kts.
From: thersites ®16/01/2004 10:19:41 PM
Subject: re: yacht speedpost id: 888723
Now someone should ask how heavier than air machines can fly. The answer is somewhat similar.
I think sailboards reaching are probably the fastest wind-powered craft. At least the ones I see when there’s a decent north-easter blowing.
But some people here are now using a kind of surfboard and a harness tethering the sailor/surfer to a large arced kite. They sometimes sail/slither in about ten centimetres of water on the edge of the waves on the beach.
Modelling the forces involved with them must be fun.
From: Spaghettification ®16/01/2004 10:23:39 PM
Subject: re: yacht speedpost id: 888730
The catamaran I used to sail often went faster than the speed of the wind.
On a close reach (sailing term thingy, not a drink term!) I could often get the cat up to nearly 20kts with a little over 10kts of wind.
The stronger the wind and the faster the bost, the less close you can sail into the wind, as the ‘apparent’ wind travelling over the boat makes it ‘see’ the wind as coming more from the sides rather than the front.
From: Richard C ®16/01/2004 10:27:04 PM
Subject: re: yacht speedpost id: 888737
as the ‘apparent’ wind travelling over the boat makes it ‘see’ the wind as coming more from the sides rather than the front

That looks back to front to me, S. As the boat accelerates it draws the apparent wind direction (the direction it’s blowing from) further towards the bow.
From: Richard C ®16/01/2004 10:28:56 PM
Subject: re: yacht speedpost id: 888742
I think sailboards reaching are probably the fastest wind-powered craft

Yes. IIRC, the world kilometre record is held by a two-man sailboard.
From: Spaghettification ®16/01/2004 10:30:00 PM
Subject: re: yacht speedpost id: 888744
Strange but true, Richard.
The faster you go, the further away from directly into the wind you can point the yacht.
From: Dark Orange ®16/01/2004 10:31:55 PM
Subject: re: yacht speedpost id: 888748

”I think sailboards reaching are probably the fastest wind-powered craft”

Ice yachts do well over a 100mph.


From: Dark Orange ®16/01/2004 10:34:10 PM
Subject: re: yacht speedpost id: 888752

”Strange but true, Richard.
The faster you go, the further away from directly into the wind you can point the yacht.”

A boat can only point so far into the wind. The faster you go, the more the wind comes from the bow, reducing the angle to the true wind you can sail.

I’m with Richard on this one.

What direction does the apparent wind come from in a 747?



From: Spaghettification ®16/01/2004 10:34:23 PM
Subject: re: yacht speedpost id: 888753
Ice yachts do well over a 100mph.

I suspected as much when I posted that here – > Fastest before cars thread.
From: Richard C ®16/01/2004 10:36:09 PM
Subject: re: yacht speedpost id: 888756
Strange but true, Richard.
The faster you go, the further away from directly into the wind you can point the yacht.


Oh, I see what you mean. You can point further down and still sail faster than the wind.

Obviously, if you aren’t concerned about travelling faster than the wind you can point up to 180o away from the wind (i.e. running square).
From: Spaghettification ®16/01/2004 10:36:31 PM
Subject: re: yacht speedpost id: 888757
A boat can only point so far into the wind. The faster you go, the more the wind comes from the bow, reducing the angle to the true wind you can sail.

I’m with Richard on this one.

Um, you’re agreeing with me actually.
I probably didn’t write that quoted sentence very well.
From: Spaghettification ®16/01/2004 10:38:56 PM
Subject: re: yacht speedpost id: 888760
You can point further down

You don’t have a choice – the faster the yacht, the further front straight-into-the-wind you can go.
Cats go a heck of a lot faster than monomarans, but they have to cover more distance to go on an effective track directly upwind.
From: Richard C ®16/01/2004 10:42:27 PM
Subject: re: yacht speedpost id: 888766
There isn’t actually a disagreement, it was just my initial interpretation of Spaggys post.

As an illustration of his point, racing catamarans going downwind will start on a broad reach and bear away from the wind as speed increases – the idea is not to stall the sail but maintain a flow over it. You are fastest going downwind in a series of broad reaches than running square. (With exciting gybes between the reaches.)
From: turnip ®16/01/2004 11:34:08 PM
Subject: re: yacht speedpost id: 888832
NO!!!!!!

I’ve been Yacht Racing for 8yrs now and never have we been faster than the wind never never ever

fastest speed downwind 18 knts downwind in a 30-34knt wind if the wind gets stronger then the sails area is minimised so we do not loose control of the boat, Broach/Capsize.

The Current & Wave motion does factor into the equation (Set and Drift) also the Length/Shape of Water Line (Hull/Water Contact Point) ,
Water Displacement & Depth of Draft (Depth of Keel)
and then you have the annabatic Winds and/or Kattabatic Winds influence, and the Lifts & Knocks of the wind itself.
From: Spaghettification ®16/01/2004 11:36:17 PM
Subject: re: yacht speedpost id: 888834
I’ve been Yacht Racing for 8yrs now and never have we been faster than the wind never never ever

shrug
Well I have.
Cats can, displacement monohulls and perhaps even some planing ones can’t.
From: Richard C ®16/01/2004 11:36:41 PM
Subject: re: yacht speedpost id: 888835
You won’t go faster than the windspeed downwind, turnip, your sail is stalled, but you might reaching or close-hauled.
From: Rod ®16/01/2004 11:39:36 PM
Subject: re: yacht speedpost id: 888839
Sorry – I have not read the thread.

Sail boats have a therotical speed of square root of 2 times the speed of the wind. Of course friction from the hull, and inefficiencies in the sail design will drop that.

The most efficient sailing direction is a broad reach – about 120 degress to the direction to the wind.

It is easy to sail faster than the wind. The wind is not pushing you.


From: turnip ®16/01/2004 11:40:12 PM
Subject: re: yacht speedpost id: 888840
No way

Unless our speedometer is stuck…..
prehaps it’s making miso soup from the jelly fish
:0)

anyone who believs that they can sail faster than the wind obviously never sails

Richard you could be right we could all do with an extra tweek here and there but never would/could we sail faster than the wind
From: Spaghettification ®16/01/2004 11:42:01 PM
Subject: re: yacht speedpost id: 888843
anyone who believs that they can sail faster than the wind obviously never sails

Well I’m sorry, but you’re wrong.
I’ve done it many times.
From: Rod ®16/01/2004 11:42:24 PM
Subject: re: yacht speedpost id: 888844
“anyone who believs that they can sail faster than the wind obviously never sails “

I sail, and I can sail faster than the wind. I sail windsurfers.


From: turnip ®16/01/2004 11:42:52 PM
Subject: re: yacht speedpost id: 888845
RE:The most efficient sailing direction is a broad reach – about 120 degress to the direction to the wind.

10 degres Off the wind is the best a Broad Reach slows the boat down due to overt Heel angle as opposed to optimal Heel Angle

From: turnip ®16/01/2004 11:44:14 PM
Subject: re: yacht speedpost id: 888848
re: Well I’m sorry, but you’re wrong.
I’ve done it many times.


Prehaps on a Wind Surfer or Parasailing
From: turnip ®16/01/2004 11:45:30 PM
Subject: re: yacht speedpost id: 888849
Well done Rod I was being Biased and thinking Yacht
From: Spaghettification ®16/01/2004 11:46:36 PM
Subject: re: yacht speedpost id: 888850
FWIW the last boat I sailed & raced was the only 16ft Kula Cat ever made. I had a 135sq ft main sail on it, a ~15sqft wing-shaped mast on a rotating foot, (Like an A-Class Cat has) and a trapese.
I could often race again a lot of other A-Class’s & Tornado’s and beat them.
My Dad had a 18 Square Metre class cat – no, not Nacra – and it was perhaps the fastest one-man sailing boat in Aus. Apart from sail boards of course.
From: turnip ®16/01/2004 11:48:31 PM
Subject: re: yacht speedpost id: 888852
Spaggy
What was the Fastest Speed attained on your 16ft Kula Cat ??
From: Richard C ®16/01/2004 11:49:00 PM
Subject: re: yacht speedpost id: 888853
10 degres Off the wind is the best a Broad Reach slows the boat down due to overt Heel angle as opposed to optimal Heel Angle


10 degrees off the wind means 10 degrees from dead into wind to me, is that what you meant? I don’t know of any sailing boats that can point anywhere near that high.
From: Rod ®16/01/2004 11:50:42 PM
Subject: re: yacht speedpost id: 888857
The sailing record is about 46 knots, and is held by a high tech beast (Telstra?). Windsufing is second at about 45knots was achieved in wind speeds of around 40 knots.

There are 2 problems with higher wind speeds. Firstly they are rarely constant, and tend to deform the sails (Telstra had solid sails I think). Secondly they chop the ware creating extra drag.

However I expect the sailing record to break (on water) 100 k soon. Maybe by a kite surfer (maybe robbie Naish).
From: turnip ®16/01/2004 11:50:53 PM
Subject: re: yacht speedpost id: 888858
Well you know I didn’t have my protractor at the time but it is never more than 15 Deg.
Point to wind all the sailing books would Vouch for me
From: Spaghettification ®16/01/2004 11:50:57 PM
Subject: re: yacht speedpost id: 888859
Spaggy
What was the Fastest Speed attained on your 16ft Kula Cat ????

Not sure, but I could usally give the club’s 10hp dingy a good run for it’s money.
The boat would be spraying water everywhere, the rudder screaming, and the rigging humming loudly.
It made it very clear that it was working hard!
From: turnip ®16/01/2004 11:52:18 PM
Subject: re: yacht speedpost id: 888861
The Syd/Hobart race average speeds was 12knots in approx. 30knt wind
From: Richard C ®16/01/2004 11:53:09 PM
Subject: re: yacht speedpost id: 888863
but it is never more than 15 Deg.
Point to wind all the sailing books would Vouch for me

What sort of yacht is this that can point within 15o of the wind?
From: turnip ®16/01/2004 11:53:58 PM
Subject: re: yacht speedpost id: 888865
Spaggy it sounds like great FUN!!!!!! :0)
From: Rod ®16/01/2004 11:53:58 PM
Subject: re: yacht speedpost id: 888866
It is impossible for a sail boat to sail closer than 45 degrees into the wind, and often it is more like 75 degrees.
From: turnip ®16/01/2004 11:54:47 PM
Subject: re: yacht speedpost id: 888867
not if your racing rod
From: Rod ®16/01/2004 11:55:47 PM
Subject: re: yacht speedpost id: 888868
45 is the theroretic limit. Where is alan when you need him.
From: Spaghettification ®16/01/2004 11:57:00 PM
Subject: re: yacht speedpost id: 888870
Spaggy it sounds like great FUN!!!!!! :0)

Yep – Until there was so much spray I could see where I was going, or the downwind hull nosed under and the whole thing pitched ove, catapulting me halfway up the mast … :)

It is impossible for a sail boat to sail closer than 45 degrees into the wind, and often it is more like 75 degrees.

Yeah, you can but the sail & centreboard, etc have to be very efficient. Look at the 12 Metre yachts and they go as close as about 30° odd.
From: Richard C ®16/01/2004 11:58:02 PM
Subject: re: yacht speedpost id: 888871
It is impossible for a sail boat to sail closer than 45 degrees into the wind

Impossible might be a bit strong. People who sail Solings claim to be able to point at 40o or even better but they’d still be beaten upwind by a 16ft centrboard cat that won’t point inside 45-50o.
From: turnip ®16/01/2004 11:58:30 PM
Subject: re: yacht speedpost id: 888872
OUCH!!!!!1
From: Spaghettification ®16/01/2004 11:59:25 PM
Subject: re: yacht speedpost id: 888873
It is impossible for a sail boat to sail closer than 45 degrees into the wind, and often it is more like 75 degrees.

The Cunningham C-Class cats of the 70’s that had the solid wing systems could also sail quite close to the wind if it wasn’t too strong.
A google might turn up something on them, looking now …
From: turnip ®16/01/2004 11:59:46 PM
Subject: re: yacht speedpost id: 888874
PREHAPS IT’S ONLY FIXED KEELS THAT CAN GO THAT CLOSE HAULED?

I’ve never wind surfed
From: turnip ®17/01/2004 12:00:58 AM
Subject: re: yacht speedpost id: 888875
I sail a FARR 9.2 ……….Foredecky
Crew of 5-6
From: Richard C ®17/01/2004 12:01:25 AM
Subject: re: yacht speedpost id: 888876
I pitch-poled an Alpha Omega 14 ft cat while on trap once. At some stage in the proceedings the masthaed hit me in the chest. Pretty untidy sailing which broke 5 battens and tore the sail. I was only bruised.
From: Rod ®17/01/2004 12:02:38 AM
Subject: re: yacht speedpost id: 888877
Forgetting cenreboards (and currents). Using sail/wind theory on my 45degrees.
From: turnip ®17/01/2004 12:03:08 AM
Subject: re: yacht speedpost id: 888878
Lucky Man Richard
Very Lucky
From: Spaghettification ®17/01/2004 12:04:07 AM
Subject: re: yacht speedpost id: 888879
Here’s a pic of a similar yacht to the Cunnigham’s.



Note the very efficient rig.
From: turnip ®17/01/2004 12:05:50 AM
Subject: re: yacht speedpost id: 888882
meant to be Ocean Racing this weekend but last race I chipped my elbow (so I’ve since found out)
and the small piece of bone is jambing in the Elbow Joint causing me Strife and unable to race till I can pay $1500 to remove it :0(
From: Richard C ®17/01/2004 12:07:19 AM
Subject: re: yacht speedpost id: 888885
Sounds V. nasty, Turnip. Good luck with it.
From: turnip ®17/01/2004 12:07:33 AM
Subject: re: yacht speedpost id: 888886
Wow that Cunningham Mast seems so out of Ratio
Does it Capsize alot ??
From: Spaghettification ®17/01/2004 12:08:42 AM
Subject: re: yacht speedpost id: 888887
There’s a good page on them to be found here.

Some quotes from that site -
“The C Class catamaran is the most technically sophisticated and efficient sailing machine in existence. To design and construct a new vessel capable of beating the previous winner Cogito from the United States is an enormous challenge only possible with truly excellent engineering.”

“In the early 1970’s the first truly practical wing sail was designed for “Miss Nylex” by Roy Martin . Then a senior project engineer for General Motors Holden, Martin used a sound engineering process to create an original solution to the problem; his wing sail represented a true break through. The elegant simplicity of his design remains a landmark.”

“This wing produced more lift for less drag than a conventional sail; the wing leading to increased performance. The wing was constructed from plywood and fabric and as a result Miss Nylex was significantly heavier than an equivalent soft sailed boat, this lead to her losing the Cup to the lightly built American boat “Aquarius V” in 1975. In wind strengths of over 12 knots Miss Nylex was clearly dominant, however, in the light winds of that series the US challenger had the advantage because of her extremely light construction.”

“These wings were fiendishly complicated and it has been said that Lindsay was the only person who ever really understood how they worked.”
From: turnip ®17/01/2004 12:10:11 AM
Subject: re: yacht speedpost id: 888889
Thanks Richard

For a lil piece of bone (2mm Dia.) it sure is causing Problems even lifting a kettle full of water is a problem let alone a wet kite or pulling out a wine glass (knot in Spiniker)
kite = Spiniker
From: Spaghettification ®17/01/2004 12:10:29 AM
Subject: re: yacht speedpost id: 888890
Does it Capsize alot ??

I’m not sure, but since they make a lot more power for the same size as a regular sail you’d have to work very hard at keeping them from going over.
And once it did go over, it’d be a right bugger to get back up as the sail/mast would fill with water I reckon. :(
From: Richard C ®17/01/2004 12:12:15 AM
Subject: re: yacht speedpost id: 888892
I think a C-class capsize is in the nature of a shipwreck.
From: Spaghettification ®17/01/2004 12:13:33 AM
Subject: re: yacht speedpost id: 888893
I think a C-class capsize is in the nature of a shipwreck.

… and you just know that CASA will want to be involved. :)
From: Rod ®17/01/2004 12:14:09 AM
Subject: re: yacht speedpost id: 888895
Yellow pages – not Telstra. Anyone could make that mistake.

Anyway this boat has the world speed record – which annoys me a lot.

here
From: Richard C ®17/01/2004 12:15:03 AM
Subject: re: yacht speedpost id: 888896
It’s got a wing, hasn’t it?
From: turnip ®17/01/2004 12:18:22 AM
Subject: re: yacht speedpost id: 888899
Was it not Enza the NZ Cat. that got that got the round the world Non stop Speed Record??
From: Peter© ®17/01/2004 2:19:02 AM
Subject: re: yacht speedpost id: 888998

Don’t forget the subject of this thread, fellas.

’Yachts’. Boats with a bit of lead in them, ISTM.
From: Greg Mc ®18/01/2004 12:52:11 AM
Subject: re: yacht speedpost id: 890572
Bit of a dead thread by now, but Yellow pages achieved its record of 46+ knots in less than 20 knots of wind.
An ice yacht can travel up to seven times wind speed and a land yacht around the same.
From: Peter© ®18/01/2004 4:23:42 AM
Subject: re: yacht speedpost id: 890675

Don’t forget the subject of this thread, Greg Mc.

’Yachts’. Boats with a bit of lead in them, ISTM.

From: Alan™ ®18/01/2004 3:11:24 PM
Subject: re: yacht speedpost id: 891025
Without reading the thread, yes a sailing boat can sail faster than the wind, because as the boat goes faster the apparent wind direction changes, eventually the boat gets to a speed where it’s virtually creating it’s own wind.
From: Alan™ ®18/01/2004 3:18:26 PM
Subject: re: yacht speedpost id: 891048
Greg Mc® was involved in the yellow pages campaign and design. A mate of mine is the principle designer of the next Australian challenger of the Little Americas Cup in C Class cats, he’s already won West Australian design awards for some of his work in the solid wing sail.
From: Spaghettification ®18/01/2004 3:22:15 PM
Subject: re: yacht speedpost id: 891062
Greg Mc® was involved in the yellow pages campaign and design. A mate of mine is the principle designer of the next Australian challenger of the Little Americas Cup in C Class cats, he’s already won West Australian design awards for some of his work in the solid wing sail.


Gosh darn good stuff!
We nearly built a wing sail for my 16 footer, but never got around to it.
From: Peter© ®19/01/2004 1:08:45 AM
Subject: re: yacht speedpost id: 892116

Sounds as though the ‘Cognition’ team has a lot of smarts. Let’s hope the Westaussies are catching up.

Good Luck, fellas. We’ll be rooting for you….

(We’ll need a stream of update threads, Alan, when things start happening.)
From: Alan™ ®19/01/2004 12:24:27 PM
Subject: re: yacht speedpost id: 892538
The Americans are running pretty scared it seems, they have already delayed the series by 12 months.
The views and opinions expressed on this forum are those of the individual poster and not the ABC. The ABC reserves the right to remove offensive or inappropriate messages. ABC conditions of use statement.
Reply Quote
Date: 31/05/2021 11:58:12
From: The Rev Dodgson
ID: 1745162
Subject: re: DWFTTW

SCIENCE said:



That’s QI in the context of the current thread.

Perhaps that Rev Dodgson person was a little too sure of himself.

Reply Quote
Date: 31/05/2021 12:00:25
From: SCIENCE
ID: 1745164
Subject: re: DWFTTW

The Rev Dodgson said:

SCIENCE said:

That’s QI in the context of the current thread.

Perhaps that Rev Dodgson person was a little too sure of himself.

shrug we haven’t checked closely to see if you made any mistakes but everyone makes mistakes and sometimes we admit it shrug

we think we stayed out of (posting to) most of those threads because we didn’t know the correct answer

one of them linked to a video with some funky gearing but we’re not sure which one it is

Reply Quote
Date: 31/05/2021 12:07:17
From: SCIENCE
ID: 1745171
Subject: re: DWFTTW
From: LifeIsPeachy ®24/09/2004 7:01:49 PM
Subject: centripetal force?post id: 1277633
just say someone on a skate board is holding onto a rope behind a car doing 100 km/h, and they are doing s’ behind the vehicle, it stands to reason that they cover more distance than the car. if the skate board travels further that the car, then it also stands to reason that it must be travelling faster.
if the car is travelling at 100 and towing the skate board at the same speed, then where does the skate board get the extra energy to travel faster from?
From: Bubblecar ®24/09/2004 7:05:20 PM
Subject: re: centripetal force?post id: 1277636
It isn’t travelling faster. In fact its deviations from a straight line will be slowing both it & the car down.
From: Rahn ®24/09/2004 7:09:45 PM
Subject: re: centripetal force?post id: 1277640
From the car. It will slow the car down a bit as the skateboarder pulls himself to the side.
From: Dog ®24/09/2004 7:15:24 PM
Subject: re: centripetal force?post id: 1277645

>>It isn’t travelling faster.

I waterski and wakeboard. This doesn’t make sense to me.
From: Langy ®24/09/2004 7:17:38 PM
Subject: re: centripetal force?post id: 1277647
Some of the energy is transferred from the car to the skater, the effect of which is to slow down the car and speed up the skateboard.


From: Plankton Warrior ®24/09/2004 7:18:26 PM
Subject: re: centripetal force?post id: 1277651
>>>>It isn’t travelling faster.

>>I waterski and wakeboard. This doesn’t make sense to me.

I do none of the above and I can’t grasp the concept either…. if the car is slowing down to compensate for the extra distance covered by the skateboard then if the skateboarder continued in this fashion for long enough surely the car would be brought to a complete halt? (if the theory holds true)
From: Bubblecar ®24/09/2004 7:19:27 PM
Subject: re: centripetal force?post id: 1277652
>>This doesn’t make sense to me.

Don’t take my word for it, I’m no rocket scientist :)

From: Dog ®24/09/2004 7:19:30 PM
Subject: re: centripetal force?post id: 1277653

What if the car/boat didn’t slow down?
From: LifeIsPeachy ®24/09/2004 7:20:45 PM
Subject: re: centripetal force?post id: 1277656
the car/boat has to slow down due to friction

From: Dog ®24/09/2004 7:21:14 PM
Subject: re: centripetal force?post id: 1277657


>>I’m no rocket scientist.

Lab notified. ;)
From: Langy ®24/09/2004 7:21:38 PM
Subject: re: centripetal force?post id: 1277658
If no energy is transfered from the car, the only way you could keep your S-shaped path would be if there is continuous energy given to the skater from another external source.


From: FishFace ®24/09/2004 7:34:35 PM
Subject: re: centripetal force?post id: 1277681
This is the same way boats can travel faster than the wind.

Obviously the load on the car is greater when the skateboard is not travelling the same direction as the car.
From: jmacans ®24/09/2004 7:35:16 PM
Subject: re: centripetal force?post id: 1277684
If you pile a few bricks on a skate board, do this. Pull the skate via a string attached to the front, with sting and skate in line.
Result, the skate moves as fast as "your" end of the string.
Now, pull the skate, with the string at an angle to the line throught the skate. Result?………..
This is identical to a skier, being towed by a boat, and the skier angles off to the left (or right) of the line the boat is making.
Now just a bit of physics. Say the boat is heading north (up), and the skier is angled to the left (west).
The boat is moving up, only.
The skier is moving up (with respect to the water) and to the left (with respect to the water).
Over any distance, the skier moves further than the boat. (up the hypotenuse).
This is the first part.
ask q if confused.
From: Dog ®24/09/2004 7:36:27 PM
Subject: re: centripetal force?post id: 1277688

>>This is the same way boats can travel faster than the wind.

Now that really doesn’t make sense. ‘Less of course they have a motor…
From: FishFace ®24/09/2004 7:39:06 PM
Subject: re: centripetal force?post id: 1277697
Boats are guided through the water by there keels, like a skateboard uses it’s wheels.

When travelling at an angle to the wind they can have a higher speed, just like the skateboard being pulled at an angle.
From: Schmuck ®24/09/2004 7:39:31 PM
Subject: re: centripetal force?post id: 1277700
>>This is the same way boats can travel faster than the wind.

more like the way sail boats can sail across or into the wind.
From: leong ®24/09/2004 7:41:53 PM
Subject: re: centripetal force?post id: 1277709
acceleration is caused by FORCE not SPEED.

That is, you dont follow the car because the car is moving, you follow it because its imparting a force that moves you.

Think about the components of the force.



Combined with the force from the road/water , the thing being towed is being accelerated to one side of the vehicle towing it. AS was said, either the thing being towered is pulled with stronger and stronger force to keep up with the vehicle, or the vehicle is slowed down, or the rope breaks.

So that thing behind can exceed the velocity of the towed vehicle. pretty quickly after that, the force on the towed object reduces drastically, as the scaler distance between towed person and vehicle becomes shorter than the length of the rope !








From: Skeptic ®24/09/2004 7:42:43 PM
Subject: re: centripetal force?post id: 1277711
>> then where does the skate board get the extra energy to travel faster from?

when it changes direction it accelerates and removes energy from the car
From: jmacans ®24/09/2004 7:48:44 PM
Subject: re: centripetal force?post id: 1277721
Part 2.

The skier is now going faster than the boat but on a differant line.
There is only one way the skier (or skater) can do this without falling off. He has to angle his body outwards, causing the ski or skate to to dig into the surface. So he uses friction, both to stay on the angle to the vertical and to supply the sideways force.

The boat (or car) towing the skier (or skater), easily compensates and tows harder, providing the force need to over come the friction wihch is required for the skater to proceed up the hypotenuse. (The path of which may look like a curve).
From: jmacans ®24/09/2004 7:55:38 PM
Subject: re: centripetal force?post id: 1277731
Just a bit of physics.
There are two components of velocity of the skier.
One is vertical and is parallel tothe line of the vehicle.
The other is to the left at right angles to the first.

The result of the two is instantaneous velocity of the skier.
(And that is an exaple of vector addition of two velocities, if you want to sound fancy.)
From: Manfred ®24/09/2004 8:56:15 PM
Subject: re: centripetal force?post id: 1277821
In this proposition I don’t think you can change the parameter of the car’s speed. It is going 100 km/h irrespective of what happens behind, so there must be a speed controller in the car that provides additional energy every time the tugger behind draws on more energy by weaving from side to side which is analagous to amplitude in a wave.
The skateboarder therefore does in effect go faster than the car because it has to cover more distance but taken as a whote both the car and the skate boarder travel at the same speed. It is like you were sitting inside the car while it is travelling at 100 kph and you were jumping from one side of the car to the other. If you traced the movement of yourself relative to the ground against the movement of the car you would be travelling faster even though you are in the car.
From: jmacans ®24/09/2004 9:07:52 PM
Subject: re: centripetal force?post id: 1277830
Except that inside the car, the friction of the skater is internal and does not slow the car.
The skater, or skier, has friction with the road or water, imposeing an extra load on the dragging viehicle.
From: Manfred ®24/09/2004 9:26:20 PM
Subject: re: centripetal force?post id: 1277864
We are talking here, I think, about a theoretical car where friction can be ignored.
From: Langy ®24/09/2004 9:27:40 PM
Subject: re: centripetal force?post id: 1277867
"We are talking here, I think, about a theoretical car where friction can be ignored."

You mean the spherical one in a vacuum? How’s the sketer supposed to breathe?


From: Max Rockatansky ®24/09/2004 9:28:57 PM
Subject: re: centripetal force?post id: 1277872
We are talking here, I think, about a theoretical car where friction can be ignored.
**

Cars don’t work without friction – Tyres wouldn’t grip.
From: Rule 303 ®24/09/2004 9:32:59 PM
Subject: re: centripetal force?post id: 1277876

"Tyres wouldn’t grip"

Das Banana waltzen?


:)
From: jmacans ®24/09/2004 9:35:56 PM
Subject: re: centripetal force?post id: 1277881
With a hovercraft as the tractor vehicle, and frictionless skater behind, the skater would no be able to move left or right, as long as the hovercraft drove straight.

If the hovercraft then executed a right angle turn, the (frictionless) skater, would continue along the original course, but then jerked in the direction of tractor.
Depending on the speeds and massess, the skater would eventually oscillat from one side to the other and following the vehicle.
From: Rahn ®24/09/2004 11:14:41 PM
Subject: re: centripetal force?post id: 1278051
Or maybe go in a little circle (eliptical) pattern :), depending on speeds/masses etc.
One thing you’ve got to remember, is that the energy transferred to the skier by the boat is negligible in comparrison to the friction from water – the engine easily compensates for both without noticing.
From: jmacans ®24/09/2004 11:28:14 PM
Subject: re: centripetal force?post id: 1278061
Yep Rann, rushed it and neglected a circle. A possible major complication in water is waves.
Things would be differant on ground. Yes, I thought, or left out that change in load, would easily be handled by vehicle.
From: The Rev Dodgson ®24/09/2004 11:30:07 PM
Subject: re: centripetal force?post id: 1278066
>>>>It isn’t travelling faster.

I waterski and wakeboard. This doesn’t make sense to me.<<

That’s ‘cos Bubblecar was wrong :)
From: redbaron ®25/09/2004 2:49:49 AM
Subject: re: centripetal force?post id: 1278244
If the skate-boarder produces less friction than the breaking car, then his momentum will continue, until the same braking force is applied.
From: bellfree campanile ®26/09/2004 3:50:45 PM
Subject: re: centripetal force?post id: 1279644
acceleration is caused by FORCE not SPEED.

That is, you dont follow the car because the car is moving, you follow it because its imparting a force that moves you.

Think about the components of the force.


I’d rather not. Acceleration is caused by steering in and out of the wake. Aerodynamic drag(in extra meters = S curve) helps bleed off excess energy due to the better efficiency of load. Momentum is transfered and the steering is complete.

++++++++++__++++++
|\/| . |_ _ *|)
| | |)*|__(|**|__)ELFRY
++++++++++++++++++
Oh and btw, if you have any doubts that a paticular model of reality may not be wrong; one has a theory! Dated: 5July2004
From: jmacans ®26/09/2004 4:02:25 PM
Subject: re: centripetal force?post id: 1279645
Mr Bellfree.
You have the qualities required to become an outstanding dictator.
But alas, your teaching abilities are poor, regrettable for you perhaps, but a good result for anyone unfortunate enough to suffer tuition from you.

Belicose, obscurantist ravings.
You really think highly of yourself, don’t you.
Yes, it shows.
From: bellfree campanile ®26/09/2004 4:06:50 PM
Subject: re: centripetal force?post id: 1279647
Funny! I don’t view the Kingdom of Heaven as a dictorship.
++++++++++__++++++
|\/| . |_ _ *|)
| *| |)*|__(-|**|__)ELFRY
++++++++++++++++++
Oh and btw, if you have any doubts that a model of reality may not be wrong; one has a theory!
From: jmacans ®26/09/2004 4:08:34 PM
Subject: re: centripetal force?post id: 1279648
He seem to have delegated all truth, all authority to you.
Be a good chap and use it selectively and wisely.
Have an nice day, Mr Bellfree.
From: PeterT ®26/09/2004 4:10:28 PM
Subject: re: centripetal force?post id: 1279650
>>Funny! I don’t view the Kingdom of Heaven as a dictorship.

Did you mean dickship or maby dipstick or possibly sheepdip, I love a good riddle.
From: Inductor ®26/09/2004 4:13:59 PM
Subject: re: centripetal force?post id: 1279652

>>Funny! I don’t view the Kingdom of Heaven as a dictorship.<<

Hmmm, Kingdom vs Dictatorship. I know, how about The Peoples Republic of Heaven

From: bellfree campanile ®26/09/2004 4:14:19 PM
Subject: re: centripetal force?post id: 1279653
I love a good riddle.

Try Daniel 11.
++++++++++__++++++
|\/| . |_ _ *|)
| *| |)*|__(-|**|__)ELFRY
++++++++++++++++++
Oh and btw, if you have any doubts that a model of reality may not be wrong; one has a theory!
From: PeterT ®26/09/2004 4:16:34 PM
Subject: re: centripetal force?post id: 1279654
>>Try Daniel 11.

No, the discombobulations of your crazy posts are enough.

From: Richard C ®26/09/2004 4:19:33 PM
Subject: re: centripetal force?post id: 1279656
I just read this thread and it seems to have become a bit derailed a couple of times. As was pointed out, the skateboarder does travel at higher speeds than the car and the energy from that comes, of course, from the car.

The reason the car doesn’t slow down and come to a halt is because it has an engine and the energy for the movement of both the car and the skateboarder is coming from the conversion of chemical energy of fuel and air being converted first to heat and then to mechanical motion by the car’s engine.
From: bellfree campanile ®26/09/2004 4:26:15 PM
Subject: re: centripetal force?post id: 1279658
higher speeds

I don’t think so. I(we) view acceleration as absolute.
++++++++++__++++++
|\/| . |_ _ *|)
| *| |)*|__(-|**|__)ELFRY
++++++++++++++++++
Oh and btw, if you have any doubts that a model of reality may not be wrong; one has a theory!
From: The Beervatar ®26/09/2004 4:36:36 PM
Subject: re: centripetal force?post id: 1279660
>>>I don’t think so. I(we) view acceleration as absolute.

Well, all three of you need to do some catching up then…
From: bellfree campanile ®26/09/2004 5:23:40 PM
Subject: re: centripetal force?post id: 1279668
An example of steering absolutely:


Ezekiel 1:14-25 & 1-13

CHAPTER 1


14 And the living creatures ran back and forth, in appearance like a flash of lightning.
15 Now as I looked at the living creatures, behold, a wheel was on the earth beside each living creature with its four faces.
16 The appearance of the wheels and their workings was like the color of beryl, and all four had the same likeness. The appearance of their workings was, as it were, a wheel in the middle of a wheel.
17 When they went, they went toward any one of four directions; they did not turn aside when they went.
18 As for their rims, they were so high they were awesome; and their rims were full of eyes, all around the four of them.
19 When the living creatures went, the wheels went beside them; and when the living creatures were lifted up from the earth, the wheels were lifted up.

20 Wherever the spirit wanted to go, they went, because there the spirit went; and the wheels were lifted together with them, for the spirit of the living creatures was in the wheels.
21 When those went, these went; when those stood, these stood; and when those were lifted up from the earth, the wheels were lifted up together with them, for the spirit of the living creatures was in the wheels.
22 The likeness of the firmament above the heads of the living creatures was like the color of an awesome crystal, stretched out over their heads.
23 And under the firmament their wings spread out straight, one toward another. Each one had two which covered one side, and each one had two which covered the other side of the body.
24 When they went, I heard the noise of their wings, like the noise of many waters, like the voice of the Almighty, a tumult like the noise of an army; and when they stood still, they let down their wings.
25 A voice came from above the firmament that was over their heads; whenever they stood, they let down their wings.
(NKJ)

Is it not the completed action that makes everything absolute?


1 Now it came to pass in the thirtieth year, in the fourth month, on the fifth day of the month, as I was among the captives by the River Chebar, that the heavens were opened and I saw visions of God.
2 On the fifth day of the month, which was in the fifth year of King Jehoiachin’s captivity,
3 the word of the LORD came expressly to Ezekiel the priest, the son of Buzi, in the land of the Chaldeans by the River Chebar; and the hand of the LORD was upon him there.
4 Then I looked, and behold, a whirlwind was coming out of the north, a great cloud with raging fire engulfing itself; and brightness was all around it and radiating out of its midst like the color of amber, out of the midst of the fire.
5 Also from within it came the likeness of four living creatures. And this was their appearance: they had the likeness of a man.
6 Each one had four faces, and each one had four wings.
7 Their legs were straight, and the soles of their feet were like the soles of calves’ feet. They sparkled like the color of burnished bronze.
8 The hands of a man were under their wings on their four sides; and each of the four had faces and wings.
9 Their wings touched one another. The creatures did not turn when they went, but each one went straight forward.
10 As for the likeness of their faces, each had the face of a man, each of the four had the face of a lion on the right side, each of the four had the face of an ox on the left side, and each of the four had the face of an eagle.
11 Thus were their faces. Their wings were stretched upward; two wings of each one touched one another, and two covered their bodies.
12 And each one went straight forward; they went wherever the spirit wanted to go, and they did not turn when they went.
13 As for the likeness of the living creatures, their appearance was like burning coals of fire, and like the appearance of torches. Fire was going back and forth among the living creatures; the fire was bright, and out of the fire went lightning.
++++++++++__++++++
|\/| . |_ _ *|)
| *| |)*|__(-|**|__)ELFRY
++++++++++++++++++
Oh and btw, if you have any doubts that a model may not be wrong; one has a theory!
From: LifeIsPeachy ®26/09/2004 5:29:00 PM
Subject: re: centripetal force?post id: 1279671
ok so if i understand correctly, the energy for the skate boarder comes from the car, which means that the car is burning more fuel to compensate keeping its speed constant. what i do do understand properly is centripetal force. has anyone got any good analogies or explanations on how this force works?
From: bellfree campanile ®26/09/2004 5:32:47 PM
Subject: re: centripetal force?post id: 1279672
It should therefore be noted that travel faster is not equivalent to higher speeds even if this is the case.
++++++++++__++++++
|\/| . |_ _ *|)
| *| |)*|__(-|**|__)ELFRY
++++++++++++++++++
Oh and btw, if you have any doubts that a model may not be wrong; one has a theory!
From: jmacans ®26/09/2004 5:34:00 PM
Subject: re: centripetal force?post id: 1279673
Lifeis.. I have left this thread, I give up, it is cursed. Maybe somene else.
From: LifeIsPeachy ®26/09/2004 5:37:51 PM
Subject: re: centripetal force?post id: 1279676
how could travelling faster not be attributed to higher speeds? i think we can agree that if the car travels 100 km in one hour, then the skate board being towed behind it that is doing s’ may travel 120 km in that same hour. therefore it is travelling 120km/h which means it is travelling at a higher speed

From: bellfree campanile ®26/09/2004 5:46:55 PM
Subject: re: centripetal force?post id: 1279690
has anyone got any good analogies or explanations on how this force works?


The biblical notion of forces is more akin to fortresses which is why I mentioned Daniel 11.
In physics where general relativity comes in:
forces are stupid ghosts. The heading of this thread makes no sense to me except as a stupid superstition of a bygone era when biblical literacy had not yet reached its zenith with the Millerites . Centripetal is centre seeking force that was part of Newton’s plan that the Earth was indeed rotating on an axis. Newton is a fraud as an axiom of choice for the evidence is that the Earth does not rotate!
++++++++++__++++++
|\/| . |_ _ *|)
| *| |)*|__(-|**|__)ELFRY
++++++++++++++++++
Oh and btw, if you have any doubts that a model may not be wrong; one has a theory!
From: LifeIsPeachy ®26/09/2004 5:51:37 PM
Subject: re: centripetal force?post id: 1279709
i see what they mean by belfree being a troll. well damn you to hell, i will not feed you, mr belfree
From: Skeptic ®26/09/2004 5:52:28 PM
Subject: re: centripetal force?post id: 1279714
>> the evidence is that the Earth does not rotate!

Hiya Mr belfry…

Tell me why you think this and why the Earth is so special…

is it all because of a text book, that was written long ago before people knew what space and its contents were like??????

I am faintly curious
From: bellfree campanile ®26/09/2004 5:53:08 PM
Subject: re: centripetal force?post id: 1279717
No, I think experiments will prove that it may travel further but that it will take longer.
I was thinking of a fixed motor which does not travel… say like a treadmill.
++++++++++__++++++
|\/| . |_ _ *|)
| *| |)*|__(-|**|__)ELFRY
++++++++++++++++++
Oh and btw, if you have any doubts that a model may not be wrong; one has a theory!
From: macx ®26/09/2004 5:54:11 PM
Subject: re: centripetal force?post id: 1279723
From: Skeptic ® 26/09/2004 5:52:28 PM
Subject: re: centripetal force? post id: 1279714


"I am faintly curious".

___________________________________________________

Gold Mr Zarkov…gold!!!

:)

macx


From: Skeptic ®26/09/2004 6:01:51 PM
Subject: re: centripetal force?post id: 1279743
>> Gold Mr Zarkov…gold!!!

hiya Macx

yep since everything in the Universe is *moving (energy circulation)

I am shocked that one thing isn’t.

More like skeptical!!!!

gone
From: bellfree campanile ®26/09/2004 6:05:28 PM
Subject: re: centripetal force?post id: 1279753
"Our sun is far from typical: 95% of all the stars in the universe are less massive than our sun. Our sun, and our solar system, are also unusual in their high metal content."
http://mysite.verizon.net/vze495hz/id34.html as retrieved on Aug 27, 2004 by some well known search engine. But this is just icing. Plus I haven’t seen it confirmed thereby acceptable as common knowledge.
++++++++++__++++++
|\/| . |_ _ *|)
| | |)*|__(|**|__)ELFRY
++++++++++++++++++
Oh and btw, if you have any doubts that a particular model of reality may not be wrong; one has a theory!
From: LifeIsPeachy ®26/09/2004 6:15:46 PM
Subject: re: centripetal force?post id: 1279770
has anyone heard of the foucault (fookoh) pendulum? i think this is evidence enough that the earth rotates. damn i said no feeding the trolls didn’t i? oh well lets see bellfree come up with an explanation to the absolute obvious fact that this pendulum proves that the earth rotates
From: LifeIsPeachy ®26/09/2004 6:17:11 PM
Subject: re: centripetal force?post id: 1279771
how the hell did my thread about bloody cars and skate boards get side tracked onto whether the earth rotates or not?
From: PeterT ®26/09/2004 6:21:30 PM
Subject: re: centripetal force?post id: 1279775
evolution.
From: jmacans ®26/09/2004 6:21:35 PM
Subject: re: centripetal force?post id: 1279777
Lifeis…
Stay away from the Evil ones, they are detrimental to the mind, wearying to the soul and just plain mad.
From: tauto ®26/09/2004 6:25:29 PM
Subject: re: centripetal force?post id: 1279782
how the hell did my thread about bloody cars and skate boards get side tracked onto whether the earth rotates or not?

—-

Well Belfry’s Lord does work in mysterious ways.

:)
From: Artemis ®26/09/2004 6:26:59 PM
Subject: re: centripetal force?post id: 1279786
Isnt it related to spin gravity?
From: Inductor ®26/09/2004 6:38:12 PM
Subject: re: centripetal force?post id: 1279797

>>Isnt it related to spin gravity?<<

Then just when the submit button was clicked the throaty roar of a water powered Landrover with no exhaust pipe anounced the arrival of the aluminium hatted owner of the above theory…..



;)
From: bellfree campanile ®26/09/2004 6:58:50 PM
Subject: re: centripetal force?post id: 1279805
From: bellfree campanile ® 23/09/2004 6:37:07 PM

Subject: re: Allais Effect post id: 1276180

From: bellfree campanile ® 11/08/2003 6:48:48 PM

Subject: re: Newton’s physics. post id: 638403

Foucault and the Allias effect; y’all might want to check into.
Mister Belfry

http://allais.maurice.free.fr/English/media18-5.jpg An example of something, i forget what, just knew it was in my history file.
From: bellfree campanile ® 31/07/2003 4:00:27 PM

Subject: re: Newton’s physics. post id: 621906

No Zarky,
I am upholding to a scientific format.
Tricksters are like the late great Feynman who I seem to remember said something about the geo center. Something like, a bias is held against it with out any real proof. Not that Richard wanted it proved mind you. But that he thought he noticed it in his fellow scientists.

It is this lack of eagerness to build pendulums under future eclipses to collect data that prophecy of doom is necessary imo. Like Moulder and company "the truth is out there." The unbelievers are no doubt poisoned, oh well, goodnight Zarky.

Mister Belfry

REPEATED in TOPIC#1266144

From: Skeptic ®26/09/2004 7:05:32 PM
Subject: re: centripetal force?post id: 1279811
>> anounced the arrival

you rang

Oh wrong number !!!!

*gone

From: Shambolic ®27/09/2004 10:04:12 AM
Subject: re: centripetal force?post id: 1280407
LifeIsPeachy, sorry about how trashed this thread has been by a certain troll of biblical proportions…

A centripetal force is any force that acts towards a point (or ‘centre’). Motion in a circle is the simplest example. Let’s say you are travelling anti-clockwise around a circle, so you are always ‘turning left’. A little bit of thought will tell you that there must be a constant force on you directed towards the centre of the circle. As such, it is always at right angles to the direction you’re travelling, so it doesn’t change your speed – only your direction.

For elliptical motion, which also results from a centripetal force, there will be a component of the force parallel to your velocity. That’s why things speed up and slow down as they travel in an elliptical orbit.

I hope that makes some sense.
:)
From: Shambolic ®27/09/2004 10:24:51 AM
Subject: re: centripetal force?post id: 1280480
>>For elliptical motion, which also results from a centripetal force<<

I should be a bit careful there – elliptical motion can be caused by a centripetal force obeying an inverse-square law – like gravity. I don’t think an arbitrary centripetal force will give rise to elliptical orbits.

Ignore all that if you don’t want to get technical, though.
:-)
From: Brendon ®27/09/2004 10:26:04 AM
Subject: re: centripetal force?post id: 1280483
>>I should be a bit careful there – elliptical motion can be caused by a centripetal force obeying an inverse-square law – like gravity.<<

You can get elliptical orbits from a F=kr force law. But the origin is at the centre of the ellipse, not the focus.
The views and opinions expressed on this forum are those of the individual poster and not the ABC. The ABC reserves the right to remove offensive or inappropriate messages. ABC conditions of use statement.
Reply Quote
Date: 31/05/2021 12:18:18
From: SCIENCE
ID: 1745174
Subject: re: DWFTTW

SCIENCE said:


The Rev Dodgson said:
SCIENCE said:

That’s QI in the context of the current thread.

Perhaps that Rev Dodgson person was a little too sure of himself.

shrug we haven’t checked closely to see if you made any mistakes but everyone makes mistakes and sometimes we admit it shrug

we think we stayed out of (posting to) most of those threads because we didn’t know the correct answer

one of them linked to a video with some funky gearing but we’re not sure which one it is

ok got it

here are the links

https://www.youtube.com/watch?v=xHsXcHoJu-A
https://www.youtube.com/watch?v=k-trDF8Yldc

also it has some annoying fella “mzl” and identities complicating matters and also using a precursor to dv’s proposed we(1,2,3) pattern videre licet

So, ah, Copernicus, are we (‘u and I) still trying to confuse the issue here?

From: Dr Matt ®24/08/2009 9:44:03 PM
Subject: Downwind faster than the wind?post id: 4291936
I stumbled upon a blog post about this today, usually I would ignore this sort of stuff but the comments by the Cambridge professor got me interested. I the past I vaguely recall explaining this effect to be false to people but now I’m not so sure:

”…The second exciting thing was to discover, thanks to James from Isentropic, what I now consider to be the two best videos on there internet. Namely: Downwind Faster than the Wind (DWFTTW) and Under the ruler faster than the ruler .
What intrigues me philosophically about the wind-powered-travel expositions is that it reveals how fragile and weak “understanding” can be: I thought I understood wind-powered travel, and I already knew about wind-powered vessels that can sail directly upwind (eg, Revelation II, pictured). But I got the answer to the question “is DWFTTW possible?” wrong! – even though the principle by which upwind travel works is just the same as the principle of DWFTTW travel. So it seems that when I “understood” upwind travel, what I really did was append to my stack of physics heuristics another heuristic, permitting upwind travel; I didn’t add a piece of knowledge that was capable of working in new situations.”

The blog post and comments:
http://withouthotair.blogspot.com/2009/07/two-exciting-things-dii-and-dwfttw.html

The DWFTTW vid in question:
http://www.youtube.com/watch?v=xHsXcHoJu-A
The ruler vid in question:
http://www.youtube.com/watch?v=k-trDF8Yldc

I’ve had a look on the net, I’m not convinced by either camp at the moment, and haven’t had a chance to do the maths, but MacKay (who I have a mixed opinion of, but has a big fan on this forum) seems very sure of himself.

Apparently this topic can cause quite a stir on internet forums, but we’ll see how the sssf goes.

I’ll leave my comments till after a few people have had a go :)
From: starling_bird ®24/08/2009 10:15:23 PM
Subject: re: Downwind faster than the wind?post id: 4291996
interesting. It’s hard to deny what you see in the vid.

At a guess, wheels are very efficient at converting energy into motion. More efficient than the aero component. Still trying to nut out the details in my head, but do I get half points?
From: The Beervatar (Beer)24/08/2009 10:20:25 PM
Subject: re: Downwind faster than the wind?post id: 4292004
Any argument that quotes the bumblebee argument loses marks from the start…
From: Copernicus ®24/08/2009 10:45:14 PM
Subject: re: Downwind faster than the wind?post id: 4292053
Isn’t this just showcasing the standard efficiency of a propellor in focussing kinetic energy. Not perpetual motion considering the wider input energy source from the moving treadmill through the wheels versus the reduced output energy which is nevertheless focussed to a condensed point of pressure behind the blades?

With respect to the wind assisted demo you would have to respect that the energy of input (the wind) is constituted of moving molecules that also have transverse motion and hence can assist movement of the propellor through lateral movement of the blades increasing power efficiency. The average direction of the wind molecules may appear to be slower than the cart but the sum total energy of input would also have to include any molecular motion that is not moving in the direction of the average system:))
From: Stealth ®24/08/2009 10:53:18 PM
Subject: re: Downwind faster than the wind?post id: 4292065
Don’t think it is possible. Upwind yes, downwind no. Even more not possible from a standing start.
From: Copernicus ®24/08/2009 11:00:24 PM
Subject: re: Downwind faster than the wind?post id: 4292080
>>Don’t think it is possible. Upwind yes, downwind no. Even more not possible from a standing start.

I have seen large wave fronts hit small fishing vessels and throw them forward faster than the wave front itself. The wave front transmits energy across a broad front which is compressed on the small vessel enabling it to outrun the wave provided friction plus the kinetic energy of the boat does not exceed the kinetic energy of the contributing wave front. I think the same principle is happenning here. :))
From: starling_bird ®24/08/2009 11:00:36 PM
Subject: re: Downwind faster than the wind?post id: 4292081
=
Upwind yes, downwind no
=

slaps forehead which is of course what they were doing on the treadmill. But they looked so scientific!
From: Copernicus ®24/08/2009 11:06:40 PM
Subject: re: Downwind faster than the wind?post id: 4292091
>>Upwind yes, downwind no

I’ll bet ya. I go for upwind yes and downwind yes provided we are using a propellor. :))
From: Copernicus ®24/08/2009 11:09:23 PM
Subject: re: Downwind faster than the wind?post id: 4292092
Same principle as a jet turbine IMO :))
From: Stealth ®24/08/2009 11:09:40 PM
Subject: re: Downwind faster than the wind?post id: 4292093
I’ll bet ya. I go for upwind yes and downwind yes provided we are using a propellor. :))
———————
So how does the craft accelerate when the apparent wind is 0km/h?
From: Copernicus ®24/08/2009 11:11:15 PM
Subject: re: Downwind faster than the wind?post id: 4292095
>>So how does the craft accelerate when the apparent wind is 0km/h?
The average wind speed may be close to zero but wind molecules also have tangential movemenet which can transfer power to the lateral components of the propellor blades IMO :))
From: Stealth ®24/08/2009 11:14:08 PM
Subject: re: Downwind faster than the wind?post id: 4292098
The average wind speed may be close to zero but wind molecules also have tangential movemenet which can transfer power to the lateral components of the propellor blades IMO :))
—————
So why is the average ‘tangential movement’ in a useful direction?
From: Copernicus ®24/08/2009 11:14:39 PM
Subject: re: Downwind faster than the wind?post id: 4292099
>>The average wind speed may be close to zero but wind molecules also have tangential movemenet which can transfer power to the lateral components of the propellor blades IMO

A better way of saying this is sum up the total energy of the wind molecules irrespective of the average wind speed and then subtract the kinetic motion of the vehicle. There will be energy lost through friction but the propellor more efficiently transfers the energy to a compression point to provide power. :))
From: Copernicus ®24/08/2009 11:16:25 PM
Subject: re: Downwind faster than the wind?post id: 4292100
>>So why is the average ‘tangential movement’ in a useful direction?

A bit like angling a sail to the wind to give forward motion :))
From: Copernicus ®24/08/2009 11:21:02 PM
Subject: re: Downwind faster than the wind?post id: 4292102
Where’s the flying boys like Bill when you need him? Actually Rev’s an engineer and he would know this I reckon. :))
From: Kingy ®25/08/2009 12:09:40 AM
Subject: re: Downwind faster than the wind?post id: 4292150
>>Upwind yes, downwind no<<

Upwind no, downwind no.


You can go directly upwind using only the wind, but not as fast as the wind.

The machine in the vid going down the road is obviously being towed.

The little machine on the treadmill is interesting. I will have a think about what is going on there.

One of the vids by the same person show a “self start” by blowing it with a fan. WTF? If that is the quality of his science, then I don’t hold much hope for the rest of his stuff.
From: stumpy_seahorse ®25/08/2009 12:17:44 AM
Subject: re: Downwind faster than the wind?post id: 4292155
>>You can go directly upwind using only the wind, but not as fast as the wind.

you can go faster than the wind on an angle, but i don’t believe it’s possible to go directly downwind or upwind.
From: Post_apocalyptic state of mind ®25/08/2009 12:18:58 AM
Subject: re: Downwind faster than the wind?post id: 4292156
you can make anything happen with youtube
From: Copernicus ®25/08/2009 12:32:55 AM
Subject: re: Downwind faster than the wind?post id: 4292162
Interesting. It appears to further help the situation that the wheels may be ‘geared’ to the propellor prop…..sneaky b*&ers!!!! :))
From: Kingy ®25/08/2009 12:33:53 AM
Subject: re: Downwind faster than the wind?post id: 4292164
>>Interesting. It appears to further help the situation that the wheels may be ‘geared’ to the propellor prop…..sneaky b*&ers!!!! :))<<

Yes, they all are.

From: Kingy ®25/08/2009 12:40:51 AM
Subject: re: Downwind faster than the wind?post id: 4292167
Upon some thought, it may be possible to go faster than the wind this way. Once the machine reaches wind speed, the propeller(geared to ground speed) is spinning fast enough to push against the relatively stationary air mass, and make a small speed gain.

If this is right, you would be able to get maybe a 10% gain or thereabouts.

Seems counterintuitive, so I am happy to be corrected.


If you get the diff ratio wrong, the machine would go against the wind.
From: Twoy ®25/08/2009 12:43:44 AM
Subject: re: Downwind faster than the wind?post id: 4292169
<< The ruler vid in question:
http://www.youtube.com/watch?v=k-trDF8Yldc >>

Slight diversion…This just about broke my brain… but has anyone tried it? I just tried to build one with an old Toro set (like Mechano) and couldn’t get it to move at all. However, my materials were not at all like his and I want to know if mine just had too much friction, or if it’s a fake.
From: Kingy ®25/08/2009 12:49:11 AM
Subject: re: Downwind faster than the wind?post id: 4292175
>>http://www.youtube.com/watch?v=k-trDF8Yldc >>

Slight diversion…This just about broke my brain… but has anyone tried it? I just tried to build one with an old Toro set (like Mechano) and couldn’t get it to move at all. However, my materials were not at all like his and I want to know if mine just had too much friction, or if it’s a fake.<<

It looks legit to me. Notice that where the cotton reels touch the ground, they have a diameter of about twice that of where they touch the big wheel. This is the gearing that it requires.


From: Twoy ®25/08/2009 12:53:52 AM
Subject: re: Downwind faster than the wind?post id: 4292178
<< It looks legit to me. Notice that where the cotton reels touch the ground, they have a diameter of about twice that of where they touch the big wheel. This is the gearing that it requires. >>

Hmmm, I may be able to replicate that… I’ll report back tomorrow.

Cheers.
From: mzl ®25/08/2009 1:11:11 AM
Subject: re: Downwind faster than the wind?post id: 4292187
// Hmmm, I may be able to replicate that… I’ll report back tomorrow.
You probably will.
From: mzl ®25/08/2009 1:15:10 AM
Subject: re: Downwind faster than the wind?post id: 4292190
// Same principle as a jet turbine IMO :))
Pftf, ever seen skilled balloon-powered toy vehicles…
From: mzl ®25/08/2009 1:53:15 AM
Subject: re: Downwind faster than the wind?post id: 4292201
/*
Apparently this topic can cause quite a stir on internet forums, but we’ll see how the sssf goes.

I’ll leave my comments till after a few people have had a go :)
/
To be fair, I would suggest it’s more the way the matter is presented, than the actual matter itself, that raises the dust.
From: mzl ®25/08/2009 1:55:26 AM
Subject: re: Downwind faster than the wind?post id: 4292203
/
Slight diversion…This just about broke my brain… but has anyone tried it?
/
Has anyone ever driven a car, what happen there?










































* ground push forward, car move forward…
From: mzl ®25/08/2009 2:07:16 AM
Subject: re: Downwind faster than the wind?post id: 4292209
// Same principle as a jet turbine IMO :))
Same principle as a rocket.
From: Alan™ (Metallurgy)25/08/2009 7:52:42 AM
Subject: re: Downwind faster than the wind?post id: 4292277
FFS, sailing boats do go downwind faster than the windspeed. The boats are being driven by the apparent wind, which means the angle of attack will clock forward of the boat. The current world speed record for a boat is about twice the windspeed at the time and is the result of this apparent wind.
From: Carmen Sandiago ®25/08/2009 7:56:50 AM
Subject: re: Downwind faster than the wind?post id: 4292278

I think they are referring to “Directly” downwind, Alan.

From: Alan™ (Metallurgy)25/08/2009 8:04:41 AM
Subject: re: Downwind faster than the wind?post id: 4292280
>>I think they are referring to “Directly” downwind, Alan.

Yes, it still works, you start off on a reach as as the speed increases, the apparent wind goes further forward, which allows you bear off further until you are sailing directly downwind. As long as you maintain speed, the apparent wind will allow you to keep going directly downwind.
From: Copernicus ®25/08/2009 8:05:04 AM
Subject: re: Downwind faster than the wind?post id: 4292281
>>I think they are referring to “Directly” downwind, Alan.

How can we treat wind in this manner? While the average motion of the sum of air molecules may be moving in a set direction, the same can’t necessarily be said of all the molecules comprising it. Provided the blades of a propellor or angle of a sail etc. are designed to impart forward motion to the vehicle, don’t they harness this effect? :))
From: Copernicus ®25/08/2009 8:11:46 AM
Subject: re: Downwind faster than the wind?post id: 4292282
>>How can we treat wind in this manner? While the average motion of the sum of air molecules may be moving in a set direction, the same can’t necessarily be said of all the molecules comprising it.

I am looking at this from a conservation of momentum perspective :))
From: Dr Matt ®25/08/2009 8:57:08 AM
Subject: re: Downwind faster than the wind?post id: 4292300
Ah good, I was hoping to get some input from a sailor :)

I think Alan’s take is the best so far.

As I said before I have not done the math and haven’t been able to picture what the steam tube would look like. I wouldn’t be 100% till I’ve seen some energy equations. The momentum equations may be more interesting but energy is critical.

For it to work you need to extract energy from the wind. The immediate response to many people is how can you accelerate with an apparent wind speed of zero? That is the tricky bit IMO, but I will come back to that.

Traveling faster or slower than the wind speed you still need to extract energy. This would mean an expansion of the streamtube ‘downstream’ of the rotor (to conserve mass flow, any loss in velocity requires a greater area for the stream tube).

If slower, then there are no energy problems as device could act like a wind turbine. Note that the wind would create a torque turning the wheels and a trust pushing the cart and turning the wheels which is kinda cool. There would be an expansion of the streamtube ahead of the cart (which the cart would travel into, but there would always be some energy left).

If faster, then this would require an expansion behind the cart. Picturing the flow is difficult but I can not think of a reason why this is not possible. Basically the cart would be chasing the wind, extracting energy from the wind then moving forward. Hence there would be a wake of expanded / slowed down wind behind the cart which is where the energy comes from. Note that the apparent velocity != 0.

As for the case when the apparent velocity = 0, this would only work in a perfectly linear flow with no turbulence, no friction etc. Even in this case you have an apparent wind speed on the blades of radius * angular velocity, not 0.

Hope that helps :)
From: Alan™ (Metallurgy)25/08/2009 10:46:24 AM
Subject: re: Downwind faster than the wind?post id: 4292354
Greg Mc is the expert in this area, he’s been involved in the design of at least one sail powered record attempt.

Sailing boats work in a fair more complex manner than the boat moving because of wind in the sails. They are actually squeezed forward by the pressure on the centreboard/keel/hull in combination with the sail. It’s this squeezing action that permits them to sail towards the wind and also what permits them to sail down wind faster than the actual windspeed. Take away the interaction with the centreboard with the water and the boat will just drift sideways with the wind.
From: goomerah ®25/08/2009 10:54:15 AM
Subject: re: Downwind faster than the wind?post id: 4292357
If the blades of the prop are, say, 45 degrees to the wind they have a vector of 2:1. This means that gross power (forget friction) should be enough to power the vehicle upwind. Yachts on a reach or surfers 45 degrees to a wave. Props at 45 deg?
From: Skeptic Pete ®25/08/2009 10:58:42 AM
Subject: re: Downwind faster than the wind?post id: 4292358
That was very well explained ALan.
From: mollwollfumble (Physics)25/08/2009 12:55:29 PM
Subject: re: Downwind faster than the wind?post id: 4292406
mollwollfumble, who is something of an expert in aerodynamics and who works with someone who is an expert in propellers, has decided to stay conspicuously silent.

Though perhaps I can say that the expert in propellers has used the power of water on a propeller to make a submerged wheeled craft go against the flow of water.
From: Stealth ®25/08/2009 1:46:33 PM
Subject: re: Downwind faster than the wind?post id: 4292446
Though perhaps I can say that the expert in propellers has used the power of water on a propeller to make a submerged wheeled craft go against the flow of water.
——————-
But this is logical and if the OP was asking this craft to go directly upwind then I would say it is possible. But the reverse does not seem possible.

Alan has mention boats and apparent wind and centreboards which do allow for faster than wind speeds but not directly down wind.
From: ellemm ®25/08/2009 1:50:34 PM
Subject: re: Downwind faster than the wind?post id: 4292450
If we are talking about ice boats which have extremely low resistance to forward movement then faster thsan the wind is quite possible.
Provided that the wind direction if relative to a stationary observer.
From: The Rev Dodgson (Eng Sci)25/08/2009 2:02:11 PM
Subject: re: Downwind faster than the wind?post id: 4292453
>>
But this is logical and if the OP was asking this craft to go directly upwind then I would say it is possible. But the reverse does not seem possible.
<<

The point is that moving directly upwind can be viewed as moving directly downwind at faster than wind speed simply by changing the frame of reference.
From: The Rev Dodgson (Eng Sci)25/08/2009 2:03:40 PM
Subject: re: Downwind faster than the wind?post id: 4292454
OTOH, I remain to be convinced that a traditional sailing boat can sail either directly upwind, or directly downwind faster than the wind.
From: ellemm ®25/08/2009 2:06:38 PM
Subject: re: Downwind faster than the wind?post id: 4292455
> OTOH, I remain to be convinced that a traditional sailing boat can sail either directly upwind, or directly downwind faster than the wind.

And I agree with the Rev. Close but no banana.
From: Copernicus ®25/08/2009 2:09:25 PM
Subject: re: Downwind faster than the wind?post id: 4292462
>>OTOH, I remain to be convinced that a traditional sailing boat can sail either directly upwind, or directly downwind faster than the wind.

If each molecule of air behaved identically in concert to the whole system, then I would agree with you Rev, but I think in reality when we talk about wind direction and speed, we are talking about an average. Use the vector approach to each distinct molecule then we are getting close IMO. :))
From: ellemm ®25/08/2009 2:13:42 PM
Subject: re: Downwind faster than the wind?post id: 4292468
>> Use the vector approach to each distinct molecule then we are getting close IMO. :))

That’s what I said > Close but no banana.
From: mzl ®25/08/2009 2:14:24 PM
Subject: re: Downwind faster than the wind?post id: 4292470
Why, you want to bring the daemon?
From: Copernicus ®25/08/2009 2:19:53 PM
Subject: re: Downwind faster than the wind?post id: 4292480
All we need is sufficient wind variation away from the average on a sustained basis to harness the power of the propellor and exceed friction lost and we are away. They need to kick start the process with a push in calm conditions to start the process rolling and provide sufficient power to overcome initial inertia. The vehicle moves through the wind front but the wind variation around the mean as it travels sustains it IMO :))
From: The Rev Dodgson (Eng Sci)25/08/2009 2:22:29 PM
Subject: re: Downwind faster than the wind?post id: 4292487
>>
If each molecule of air behaved identically in concert to the whole system, then I would agree with you Rev, but I think in reality when we talk about wind direction and speed, we are talking about an average. Use the vector approach to each distinct molecule then we are getting close IMO. :))
<<

Call me a boring old traditionalist, but I would have thought that air pressure was an adequate measure of the average of the sum of the molecular forces.
From: ellemm ®25/08/2009 2:22:58 PM
Subject: re: Downwind faster than the wind?post id: 4292490
>. All we need is sufficient wind variation away from the average

Wouldn’t that much off-average wind raise the average?
From: mzl ®25/08/2009 2:23:57 PM
Subject: re: Downwind faster than the wind?post id: 4292495
/*
Call me a boring old traditionalist, but I would have thought that air pressure was an adequate measure of the average of the sum of the molecular forces.
/
Nah, we’ll just call ‘u a quasistatistic.
From: The Rev Dodgson (Eng Sci)25/08/2009 2:24:08 PM
Subject: re: Downwind faster than the wind?post id: 4292496
>>
That’s what I said > Close but no banana.
<<


And what did you mean by that, exactly?
From: Stroke Off Genius ®25/08/2009 2:25:25 PM
Subject: re: Downwind faster than the wind?post id: 4292499
/
>>
That’s what I said > Close but no banana.
<<
And what did you mean by that, exactly?
/
’e‘s not touching it with a 10 mm poll?
From: Post_apocalyptic state of mind ®25/08/2009 2:28:34 PM
Subject: re: Downwind faster than the wind?post id: 4292504
Would it work in 120 mph winds?
From: ellemm ®25/08/2009 2:28:46 PM
Subject: re: Downwind faster than the wind?post id: 4292506
That’s what I said > Close but no banana.
<<
And what did you mean by that, exactly?

It’s possible to getclose to wind speed in a sailing boat but not equal or exceed it.
There is too much water resistance.
Ice boats are a different matter.


From: ellemm ®25/08/2009 2:32:24 PM
Subject: re: Downwind faster than the wind?post id: 4292509
120mph winds

The water would be very lumpy, lots of noise generated, spray thrown about, all removing energy from the system
From: The Rev Dodgson (Eng Sci)25/08/2009 2:32:47 PM
Subject: re: Downwind faster than the wind?post id: 4292511
>>
It’s possible to getclose to wind speed in a sailing boat but not equal or exceed it.
There is too much water resistance.
Ice boats are a different matter.
<<

I don’t believe that any sort of wind powered vehicle that uses a fabric sail with an aerofoil profile to provide propulsion will work either directly upwind, or faster than windspeed directly downwind.
From: Stroke Off Genius ®25/08/2009 2:33:01 PM
Subject: re: Downwind faster than the wind?post id: 4292513
It’s like wave drag!
From: Copernicus ®25/08/2009 2:36:38 PM
Subject: re: Downwind faster than the wind?post id: 4292518
>>Call me a boring old traditionalist,

I’d never call you that Rev :))

>>but I would have thought that air pressure was an adequate measure of the average of the sum of the molecular forces.

I’d agree when we are talking about normal fluid dynamics but you have to fight with fire here when these ‘upstarts’ are talking about breaking physical laws to see what in reality is happenning. There is some Shenaigans going on and this is where you have to drill down to the molecular level of the system IMO.

Shenanigan 1 – Air speed 0. Is it really, I mean really?

Shenigan 2 – Let’s give it a push to start it off. Why?

Shenigan 3 – Lets apply gears on the wheels to link it to the prop and not tell us about it. Why?

Conclusion: The intent is to make a case for *yawn perpetual motion. So unnecessary. Yes we have a demonstration of an efficient wind turbine at work….but that is all IMO :))
From: Alan™ (Metallurgy)25/08/2009 2:37:04 PM
Subject: re: Downwind faster than the wind?post id: 4292519
snicker
From: Alan™ (Metallurgy)25/08/2009 2:38:15 PM
Subject: re: Downwind faster than the wind?post id: 4292520
Actually giggle is more appropriate.
From: Stroke Off Genius ®25/08/2009 2:39:05 PM
Subject: re: Downwind faster than the wind?post id: 4292521
/*
Conclusion: The intent is to make a case for yawn perpetual motion. So unnecessary. Yes we have a demonstration of an efficient wind turbine at work….but that is all IMO :))
/
Well, they did say that
/
To be fair, I would suggest it’s more the way the matter is presented, than the actual matter itself, that raises the dust.
/
From: The Rev Dodgson (Eng Sci)25/08/2009 2:42:16 PM
Subject: re: Downwind faster than the wind?post id: 4292527
>>
Shenanigan 1 – Air speed 0. Is it really, I mean really?

Shenigan 2 – Let’s give it a push to start it off. Why?

Shenigan 3 – Lets apply gears on the wheels to link it to the prop and not tell us about it. Why?

Conclusion: The intent is to make a case for *yawn perpetual motion. So unnecessary. Yes we have a demonstration of an efficient wind turbine at work….but that is all IMO :))
<<

I don’t see any of those as being shenigans, and I don’t think they were making any claim of perpetual motion (at least not in the links in the OP, no doubt some people would).
From: The Rev Dodgson (Eng Sci)25/08/2009 2:43:28 PM
Subject: re: Downwind faster than the wind?post id: 4292529
What are you snickering and giggling about?
From: Post_apocalyptic state of mind ®25/08/2009 2:43:33 PM
Subject: re: Downwind faster than the wind?post id: 4292530
As said earlier, you can make anything happen on youtube
From: Post_apocalyptic state of mind ®25/08/2009 2:44:35 PM
Subject: re: Downwind faster than the wind?post id: 4292532
Just because youtube is peer reviewed, doesn’t make it right!

p
From: Stroke Off Genius ®25/08/2009 2:45:50 PM
Subject: re: Downwind faster than the wind?post id: 4292534
/*
I don’t see any of those as being shenigans, and I don’t think they were making any claim of perpetual motion (at least not in the links in the OP, no doubt some people would).
/
While I agree formally, I would still suggest that their presentation was deliberately constructed for surprise impact and to give an impression of “this will break ‘ur rules”, even if it would not break ‘ur rules: such that if ‘ur rules forbid perpetual motion, one might think that it was that rule they were pretending to break.
From: The Rev Dodgson (Eng Sci)25/08/2009 2:46:21 PM
Subject: re: Downwind faster than the wind?post id: 4292535
What does youtube have to do with it?
From: Post_apocalyptic state of mind ®25/08/2009 2:47:30 PM
Subject: re: Downwind faster than the wind?post id: 4292537
What does youtube have to do with it?


The OP

the ‘evidence’ being presented..
From: Stroke Off Genius ®25/08/2009 2:48:18 PM
Subject: re: Downwind faster than the wind?post id: 4292538
// What does youtube have to do with it?
I don’t know, I don’t think anyone mentioned it earlier.
From: Post_apocalyptic state of mind ®25/08/2009 2:48:36 PM
Subject: re: Downwind faster than the wind?post id: 4292539

“Apparently this topic can cause quite a stir on internet forums, but we’ll see how the sssf goes.”


Anyone looked for other forum postings of this particular youtube video and claim?
From: The Rev Dodgson (Eng Sci)25/08/2009 2:48:41 PM
Subject: re: Downwind faster than the wind?post id: 4292540
>>

The OP

the ‘evidence’ being presented..
<<

OK, but aren’t we now discussing whether what was presented is physically possible, rather than just accepting the “evidence”?
From: The Rev Dodgson (Eng Sci)25/08/2009 2:49:32 PM
Subject: re: Downwind faster than the wind?post id: 4292541
>>
Anyone looked for other forum postings of this particular youtube video and claim?
<<

Yes, but I’d rather not talk about it.
From: Post_apocalyptic state of mind ®25/08/2009 2:50:36 PM
Subject: re: Downwind faster than the wind?post id: 4292542
OK, but aren’t we now discussing whether what was presented is physically possible, rather than just accepting the “evidence”?


you’re telling the story…

;)

Nah, I was just reminding myself where it all began, not specifically current comments or discussion.

:)
From: Copernicus ®25/08/2009 2:53:22 PM
Subject: re: Downwind faster than the wind?post id: 4292543
>>Anyone looked for other forum postings of this particular youtube video and claim?


I did. The machine on the U-tube video at the commencement of this post I think was constructed by two blokes who did their best on one of these forums to rebut critics of perpetual motion saying “well it worked, so you try explaining it” That’s what started getting my back up and that’s why I suggested that there is more to the demonstration that is being let on :))
From: Stroke Off Genius ®25/08/2009 3:00:52 PM
Subject: re: Downwind faster than the wind?post id: 4292544
/
OK, but aren’t we now discussing whether what was presented is physically possible, rather than just accepting the “evidence”?
you’re telling the story…
;)
Nah, I was just reminding myself where it all began, not specifically current comments or discussion.
:)
/
Besides, I agree: Dr Matt presented some internet videos, and it does seem that internet videos are physically possible.
From: Stroke Off Genius ®25/08/2009 3:08:11 PM
Subject: re: Downwind faster than the wind?post id: 4292545
/ I did. The machine on the U-tube video at the commencement of this post I think was constructed by two blokes who did their best on one of these forums to rebut critics of perpetual motion saying “well it worked, so you try explaining it” That’s what started getting my back up and that’s why I suggested that there is more to the demonstration that is being let on :)) /
So we’re thinking:
1. there are dudes believe in backyard thermodynamic violation
2. there are dudes who don’t
3. dudes from (1) build nonviolating machine as indicated, and challenge dudes from (2)
4. subset of dudes from (2) get tricked, and start to believe
5. subset of dudes from (2) don’t get tricked, but can’t explain
6. subset of dudes from (2) don’t get tricked, but acknowledge it is pretty neat
7. subset of dudes (5) believe inexplicability arises from invalid machine
8. subset of dudes from (6) think it would be cool to p\\/n some n00bs
9. dudes from (8) build nonviolating machine as indicated, and challenge dudes from (7)
10. entertainment on internet forums follows
?

Sounds plausible.
I won’t disagree.
From: Copernicus ®25/08/2009 3:13:04 PM
Subject: re: Downwind faster than the wind?post id: 4292546
Is it possible to transfer energy through a collision to make something move away faster than the velocity of the original system. Yes. For example I could use 3 billiard balls on a table and hit one billard ball with the other two at such an angle that the two incoming billiard would collectively slow down and transfer momentum to the 3rd billiard ball accelerating it away from the other 2 balls. Can this principle be applied here. Yes if I treat air molecules as billard balls and tally up the incoming momentum as wind and the resulting momentum of the moving cart recognising that energy is also lost in the process. This principle is continuously applied with the addition of additional wind to the system.

The example is further exemplified by using a propellor which provides a solution to how the system can be sustained through the principles of turbine operation asnd further enhanced through application of gear mechanisms to utilise the energy of motion of the wheels to also drive the propellor.

:))


From: Deity Of Your Choice ®25/08/2009 3:15:06 PM
Subject: re: Downwind faster than the wind?post id: 4292547
reminds me of how when I was a teenager, I had to ride my bike to work for night shift past an abbatoir.
From: Alan™ (Metallurgy)25/08/2009 3:16:32 PM
Subject: re: Downwind faster than the wind?post id: 4292548
>>What are you snickering and giggling about?

People thinking that modern high performance boats behave like “traditional” sailing boats. It sort of like using Newtonian physics in quantum situations.

Anyway, I’ve got to head off down the coast. Hopefully Greg Mc pops along and can explain it in ways you’ll accept.
From: The Rev Dodgson (Eng Sci)25/08/2009 3:20:50 PM
Subject: re: Downwind faster than the wind?post id: 4292550
>>
People thinking that modern high performance boats behave like “traditional” sailing boats. It sort of like using Newtonian physics in quantum situations.
<<

Do some people think that?
From: Copernicus ®25/08/2009 3:27:04 PM
Subject: re: Downwind faster than the wind?post id: 4292554
I am struggling to understand why there aren’t a large number of forum members here who aren’t prepared to take this challenge.

What’s wrong with you all……chicken

*cluck cluck cluck

Let’s put it conclusively to bed people. I dare yaz all. :))
From: burko ®25/08/2009 3:41:12 PM
Subject: re: Downwind faster than the wind?post id: 4292558

Meh…I canna see what the wind has to do with it as the toy traveled on the road.

The DWFTTW vid in question:
http://www.youtube.com/watch?v=xHsXcHoJu-A

From: mrgoiter ®25/08/2009 3:53:49 PM
Subject: re: Downwind faster than the wind?post id: 4292561
http://en.wikipedia.org/wiki/Flettner_ship

Rotor ship anyone?
From: Stealth ®25/08/2009 3:54:18 PM
Subject: re: Downwind faster than the wind?post id: 4292562
The point is that moving directly upwind can be viewed as moving directly downwind at faster than wind speed simply by changing the frame of reference.
—————
Are you sure?
From: Stealth ®25/08/2009 3:58:51 PM
Subject: re: Downwind faster than the wind?post id: 4292564
All we need is sufficient wind variation away from the average on a sustained basis to harness the power of the propellor and exceed friction lost and we are away. They need to kick start the process with a push in calm conditions to start the process rolling and provide sufficient power to overcome initial inertia. The vehicle moves through the wind front but the wind variation around the mean as it travels sustains it IMO :))
——————-
If you had a boat that was only a few molecules big then you variations argument might work.
From: Copernicus ®25/08/2009 4:14:06 PM
Subject: re: Downwind faster than the wind?post id: 4292571
>>If you had a boat that was only a few molecules big then you variations argument might work.

So long as the theory works then I can retire appeased. Who knows, as another forum suggested, there could well be a motor driving the wheels in the axle, but then that would be cheating :))
From: The Rev Dodgson (Eng Sci)25/08/2009 4:48:35 PM
Subject: re: Downwind faster than the wind?post id: 4292606
>>
Are you sure?
<<


No :)
From: Dr Matt ®25/08/2009 6:29:42 PM
Subject: re: Downwind faster than the wind?post id: 4292783
Conclusion: The intent is to make a case for yawn perpetual motion. So unnecessary. Yes we have a demonstration of an efficient wind turbine at work….but that is all IMO :))
====

No :)

The case is for a wind powered vehicle traveling downwind faster than the wind. The turbine looks (and likely is) incredibly inefficient. The turbine simply has to extract enough energy out of the wind to overcome frictional forces and accelerate the craft.

Perpetual motion doesn’t come into it.

If the wind is blowing at 10km/h it has the same amount of energy whether you are traveling at 0 km/h or 10km/h or 15 km/h.

If the wind behind the path of he vehicle is slowed down then both energy and momentum can be conserved.
From: Dr Matt ®25/08/2009 6:34:01 PM
Subject: re: Downwind faster than the wind?post id: 4292789
OTOH, I remain to be convinced that a traditional sailing boat can sail either directly upwind, or directly downwind faster than the wind.
=====

Oh what grounds?
From: Dr Matt ®25/08/2009 6:41:12 PM
Subject: re: Downwind faster than the wind?post id: 4292796
Anyone looked for other forum postings of this particular youtube video and claim?
====

Yes.

http://www.physicsforums.com/showthread.php?t=274996
http://www.physicsforums.com/showthread.php?t=274416
http://echochamber.me/viewtopic.php?f=18&t=31905
http://richarddawkins.net/forum/viewtopic.php?f=5&t=80402&start=125
http://forum.mythbustersfanclub.com/index.php?topic=13182.0
http://www.energeticforum.com/renewable-energy/3324-dwfttw-down-wind-faster-than-wind.html
http://www.advancedphysics.org/forum/showthread.php?t=10550


From: TriangleSerf ®25/08/2009 7:13:07 PM
Subject: re: Downwind faster than the wind?post id: 4292843
“If the wind behind the path of he vehicle is slowed down then both energy and momentum can be conserved.”

But wouldn’t the amount conserved be less than or equal to the potential energy the wind could transfer to the vehicle?

Note I’m not a physicist so don’t know what the hell I’m talking about.

From: Dr Matt ®25/08/2009 7:46:46 PM
Subject: re: Downwind faster than the wind?post id: 4292931
If the wind is blowing at 10km/h it has the same amount of energy whether you are traveling at 0 km/h or 10km/h or 15 km/h.
====

Ooops, I meant wrt the ground :)

wrt you it is a different story.
From: The Rev Dodgson (Eng Sci)25/08/2009 7:57:07 PM
Subject: re: Downwind faster than the wind?post id: 4292951
>>
OTOH, I remain to be convinced that a traditional sailing boat can sail either directly upwind, or directly downwind faster than the wind.
=====

Oh what grounds?
<<

On the grounds that fabric sails require some transverse component of the wind to fill the sails and to provide a forward thrust.
From: Dr Matt ®25/08/2009 8:34:34 PM
Subject: re: Downwind faster than the wind?post id: 4293013
TRD, just re-read you post and I see what you are saying now :)
From: Kingy ®25/08/2009 10:07:28 PM
Subject: re: Downwind faster than the wind?post id: 4293199
>>If the wind behind the path of he vehicle is slowed down then both energy and momentum can be conserved.<<

That is the crux of the matter in question.

The prop is geared to the wheels. When the machine is on the treadmill, it powers itself forwards in a stationary(to it) mass of air. When it is being blown downwind and reaches almost windspeed, it powers itself forwards the same as on the treadmill. There is a gain of a few percent, no more. It will not power itself, it needs wind.

It is not a perpetual motion machine and does not claim to be.
From: Stealth ®25/08/2009 10:11:39 PM
Subject: re: Downwind faster than the wind?post id: 4293207
The prop is geared to the wheels. When the machine is on the treadmill, it powers itself forwards in a stationary(to it) mass of air. When it is being blown downwind and reaches almost windspeed, it powers itself forwards the same as on the treadmill. There is a gain of a few percent, no more. It will not power itself, it needs wind.
—————
With the treadmill, the guy holds it still as it the prop winds up. This is the equivilant of giving a massive push to the road going one. Either system may run DWFTTW for a short while but will lose the additional extra energy provided. The treadmill is too short for the system to lose its energy before it runs out of space.
From: Kingy ®25/08/2009 10:18:20 PM
Subject: re: Downwind faster than the wind?post id: 4293219
>>With the treadmill, the guy holds it still as it the prop winds up. This is the equivilant of giving a massive push to the road going one<<

I disagree, the guy holds it still as the prop winds up, yes. But this is the equivalent of the machine speeding up on the road until it reaches wind speed.

In both cases, the air mass is not moving in relation to the machine, but the prop is spinning, moving it slightly forwards.
From: Stealth ®25/08/2009 10:21:28 PM
Subject: re: Downwind faster than the wind?post id: 4293224
Another show that it is fake is that the prop, on the road version, should slow down as it approaches wind speed (the apparent wind is decreasing). And it should go backwards when it exceeds windspeed. This does not happen.
From: Kingy ®25/08/2009 10:23:57 PM
Subject: re: Downwind faster than the wind?post id: 4293230
>>Another show that it is fake is that the prop, on the road version, should slow down as it approaches wind speed (the apparent wind is decreasing). And it should go backwards when it exceeds windspeed. This does not happen.<<

The prop is geared to to axle, it spins faster as the ground speed increases regardless of whether it is – slower than/at/faster – than wind speed.
From: Post_apocalyptic state of mind ®25/08/2009 10:26:46 PM
Subject: re: Downwind faster than the wind?post id: 4293236
This is a dismal video.

Why the pathetic sound quality and video?

Why is the treadmill not level, as clearly shown by the level device?

What the hell has a treadmill got to do with anything anyway? It’s a source of energy, a totally irrelevant addition to this supposed test. What speed is the treadmill supposed to go? As fast as the wind? Get real!
From: Stealth ®25/08/2009 10:27:08 PM
Subject: re: Downwind faster than the wind?post id: 4293238
The prop is geared to to axle, it spins faster as the ground speed increases regardless of whether it is – slower than/at/faster – than wind speed.
—————
That is fine for a prop that is driven by an engine (ie a plane) but not when the prop IS the power source. If the prop powers the wheels then you can’t have the wheels powering the prop.
From: Post_apocalyptic state of mind ®25/08/2009 10:27:53 PM
Subject: re: Downwind faster than the wind?post id: 4293240
Geez, if it spins more that seven Mississippians….!
From: Martin Smith (Avatar)25/08/2009 10:29:58 PM
Subject: re: Downwind faster than the wind?post id: 4293245

>>
On the grounds that fabric sails require some transverse component of the wind to fill the sails and to provide a forward thrust.
>>

I don;t think that is actually true. You just get a lot less thrust.


From: Kingy ®25/08/2009 10:30:03 PM
Subject: re: Downwind faster than the wind?post id: 4293246
>>What the hell has a treadmill got to do with anything anyway? It’s a source of energy<<


Just as the wind is the source of energy.
From: Kingy ®25/08/2009 10:33:05 PM
Subject: re: Downwind faster than the wind?post id: 4293248
>>That is fine for a prop that is driven by an engine (ie a plane) but not when the prop IS the power source. If the prop powers the wheels then you can’t have the wheels powering the prop.<<

The wind pushes against the prop blades forcing the entire machine forwards. If you look closely you will see the blades actually turn against the wind, because the gearing to the wheels is higher than the twisting force of the prop.

The prop is driven by the wheels.


From: Kingy ®25/08/2009 10:35:27 PM
Subject: re: Downwind faster than the wind?post id: 4293249
>>Why is the treadmill not level, as clearly shown by the level device?<<

The treadmill is not level to prove that the machine is going uphill, not just rolling down a hill.
From: Stealth ®25/08/2009 10:35:51 PM
Subject: re: Downwind faster than the wind?post id: 4293250
The prop is driven by the wheels.
—————
But that would mean your source of energy must come from the wheels. And if the road is sloped then there is not energy source.
From: Stealth ®25/08/2009 10:36:46 PM
Subject: re: Downwind faster than the wind?post id: 4293253
sloped=not sloped
From: Post_apocalyptic state of mind ®25/08/2009 10:36:59 PM
Subject: re: Downwind faster than the wind?post id: 4293254
The treadmill is not level to prove that the machine is going uphill, not just rolling down a hill.


Not to stop it being spat off the end due to the friction?
From: Post_apocalyptic state of mind ®25/08/2009 10:38:27 PM
Subject: re: Downwind faster than the wind?post id: 4293256
you can keep a ball hovering in the air too with a blast from a fan.

Gravity


sloped treadmill


gravity holds it in place
From: Kingy ®25/08/2009 10:38:29 PM
Subject: re: Downwind faster than the wind?post id: 4293257
>>But that would mean your source of energy must come from the wheels. And if the road is sloped then there is not energy source.<<

The source of energy is the wind. The drag of the machine against the wind is what makes it move. That drag is what makes the wheels turn, and powers the prop.


From: mzl ®25/08/2009 10:40:33 PM
Subject: re: Downwind faster than the wind?post id: 4293260
/*
>>
Are you sure???
<<
No :)
/
Correct, it also depends on how fast the road moves.
From: Copernicus ®25/08/2009 10:40:58 PM
Subject: re: Downwind faster than the wind?post id: 4293261
Has the video been validated. It may be a hoax. I am like Post Apocalyptic sceptical why they should show us the treadmill version if not designed to throw us off the scent. It may well be possible that two different processes are occurring here. For example a prop that is driven by the wheels in the treadmill versus a prop driven by the wind in the road demo. The difference being the design of the prop blades. :))
From: Kingy ®25/08/2009 10:41:19 PM
Subject: re: Downwind faster than the wind?post id: 4293262
>>you can keep a ball hovering in the air too with a blast from a fan.

Gravity

sloped treadmill

gravity holds it in place<<


Not sure what you are getting at.

The machine is pushing itself uphill, against gravity.
From: Copernicus ®25/08/2009 10:41:55 PM
Subject: re: Downwind faster than the wind?post id: 4293263
>>The difference being the design of the prop blades

….and whether the wheels are geared to the propellor or not :))
From: Kingy ®25/08/2009 10:42:05 PM
Subject: re: Downwind faster than the wind?post id: 4293264
The prop rotates *against the wind in both cases.
From: mzl ®25/08/2009 10:43:09 PM
Subject: re: Downwind faster than the wind?post id: 4293266
/* Has the video been validated. It may be a hoax. I am like Post Apocalyptic sceptical why they should show us the treadmill version if not designed to throw us off the scent. It may well be possible that two different processes are occurring here. For example a prop that is driven by the wheels in the treadmill versus a prop driven by the wind in the road demo. The difference being the design of the prop blades. :)) /
Didn’t you tell everyone else to do the experiment,
From: Copernicus ®25/08/2009 10:43:09 PM
Subject: re: Downwind faster than the wind?post id: 4293267
>>The prop rotates *against the wind in both cases.


….and the wind direction is validated in both cases? :))
From: mzl ®25/08/2009 10:43:40 PM
Subject: re: Downwind faster than the wind?post id: 4293268
// The machine is pushing itself uphill, against gravity.
So, no need wind?
From: Post_apocalyptic state of mind ®25/08/2009 10:44:30 PM
Subject: re: Downwind faster than the wind?post id: 4293270
How does this tie in to the jet trying to take off on a giant treadmill runway?

p


From: mzl ®25/08/2009 10:44:32 PM
Subject: re: Downwind faster than the wind?post id: 4293271
So, ah, Copernicus, are we (‘u and I) still trying to confuse the issue here?
From: Copernicus ®25/08/2009 10:44:38 PM
Subject: re: Downwind faster than the wind?post id: 4293273
>>Didn’t you tell everyone else to do the experiment,

Yeah. I’ve had by best shot. I’m outa here. :))
From: Kingy ®25/08/2009 10:45:31 PM
Subject: re: Downwind faster than the wind?post id: 4293276
>>….and the wind direction is validated in both cases? :))<<

On the treadmill, there is no wind. It is to show that when wind speed = machine speed (0 = 0), it will move forwards, as long as ground speed is greater than 0.
From: mzl ®25/08/2009 10:45:46 PM
Subject: re: Downwind faster than the wind?post id: 4293277
/*
>>Didn’t you tell everyone else to do the experiment,
Yeah. I’ve had by best shot. I’m outa here. :))
/
Dr Karl’s Self Service Ivory Tower Science Forum
From: mzl ®25/08/2009 10:46:30 PM
Subject: re: Downwind faster than the wind?post id: 4293279
/ On the treadmill, there is no wind. It is to show that when wind speed = machine speed (0 = 0), it will move forwards, as long as ground speed is greater than 0. /
+1
From: Copernicus ®25/08/2009 10:47:38 PM
Subject: re: Downwind faster than the wind?post id: 4293281
>>Dr Karl’s Self Service Ivory Tower Science Forum

People who live in ivory towers should never throw bones :))
From: Stealth ®25/08/2009 10:49:49 PM
Subject: re: Downwind faster than the wind?post id: 4293286
The source of energy is the wind. The drag of the machine against the wind is what makes it move. That drag is what makes the wheels turn, and powers the prop.
——————-
I can follow your line of thinking for this but for the wheels to extract some energy they will increase the total resistance of the craft to the push of the wind. This increase in resistance would be greater than the additional thrust that could be provided by the prop.
From: Post_apocalyptic state of mind ®25/08/2009 10:50:57 PM
Subject: re: Downwind faster than the wind?post id: 4293291
youtube has a lot to answer for!



From: Kingy ®25/08/2009 10:52:58 PM
Subject: re: Downwind faster than the wind?post id: 4293294
>>I can follow your line of thinking for this but for the wheels to extract some energy they will increase the total resistance of the craft to the push of the wind. This increase in resistance would be greater than the additional thrust that could be provided by the prop.<<


That’s where I got to last night.

How could you measure one against the other?

A treadmill?




From: mzl ®25/08/2009 10:54:11 PM
Subject: re: Downwind faster than the wind?post id: 4293295
/
The source of energy is the wind. The drag of the machine against the wind is what makes it move. That drag is what makes the wheels turn, and powers the prop.
——————-
I can follow your line of thinking for this but for the wheels to extract some energy they will increase the total resistance of the craft to the push of the wind. This increase in resistance would be greater than the additional thrust that could be provided by the prop.
/
OK Stealth, try this: two tracks, one contraption, two sets of wheels (one on each track), no dissipative loss, and a bit of differential.
Now, if the tracks are fixed, the contraption will travel forward at some speed.

What if one track is moving forward as well, and steering is applied to keep forward direction?
From: Post_apocalyptic state of mind ®25/08/2009 10:54:56 PM
Subject: re: Downwind faster than the wind?post id: 4293296
That’s where I got to last night.

How could you measure one against the other?

A treadmill?



Don’t forget the Seven Mississippians!
From: mzl ®25/08/2009 10:55:59 PM
Subject: re: Downwind faster than the wind?post id: 4293297
If ‘u’r’ not happy with the steering bit, try 3 tracks and 3 sets of wheels, and the middle track moving differently to the outside ones.
From: Kingy ®25/08/2009 10:57:09 PM
Subject: re: Downwind faster than the wind?post id: 4293299
>>If ‘u’r’ not happy with the steering bit, try 3 tracks and 3 sets of wheels, and the middle track moving differently to the outside ones.<<

Thats just confusing the issue.

One wheel would do if you could balance it.

From: Post_apocalyptic state of mind ®25/08/2009 10:57:34 PM
Subject: re: Downwind faster than the wind?post id: 4293300
If ‘u’r’ not happy with the steering bit, try 3 tracks and 3 sets of wheels, and the middle track moving differently to the outside ones.


You need a plastic take-away fork to give it a poke now and then too.



Did you like the ‘look no hidden strings’ bit.

Where do you normally hear that sort of thing?

ppppppppppppppp
From: mzl ®25/08/2009 10:57:45 PM
Subject: re: Downwind faster than the wind?post id: 4293302
I was trying to avoid the concerns about wind.
From: Post_apocalyptic state of mind ®25/08/2009 10:58:39 PM
Subject: re: Downwind faster than the wind?post id: 4293303
I was trying to avoid the concerns about wind.


It’s nothing to do with wind!

Are you crazy?

;)
From: Kingy ®25/08/2009 10:58:51 PM
Subject: re: Downwind faster than the wind?post id: 4293305
pasom, I take it that you don’t understand how it works?

From: Stealth ®25/08/2009 10:58:55 PM
Subject: re: Downwind faster than the wind?post id: 4293306
That’s where I got to last night.

How could you measure one against the other?

A treadmill?
————-
How to exactly measure all the factors would be quite complex. But isn’t nessacery if you are just looking for viability of concept. If you have a geared system that can increase the thust of the craft by more than the thrust reduction for the generator you have an overunity system.
From: mzl ®25/08/2009 10:59:16 PM
Subject: re: Downwind faster than the wind?post id: 4293307
/
Did you like the ‘look no hidden strings’ bit.

Where do you normally hear that sort of thing?
/
Free love?
From: Copernicus ®25/08/2009 10:59:48 PM
Subject: re: Downwind faster than the wind?post id: 4293308
>>Don’t forget the Seven Mississippians!

*Guffaws heard from Copernicus’s corner :))
From: Post_apocalyptic state of mind ®25/08/2009 11:00:10 PM
Subject: re: Downwind faster than the wind?post id: 4293309
pasom, I take it that you don’t understand how it works?



It’s magic!
From: mzl ®25/08/2009 11:01:00 PM
Subject: re: Downwind faster than the wind?post id: 4293312
/* How to exactly measure all the factors would be quite complex. But isn’t nessacery if you are just looking for viability of concept. If you have a geared system that can increase the thust of the craft by more than the thrust reduction for the generator you have an overunity system. /
OK, do you agree that even unity is a practical impossibility?
From: Kingy ®25/08/2009 11:02:06 PM
Subject: re: Downwind faster than the wind?post id: 4293313
>>If you have a geared system that can increase the thust of the craft by more than the thrust reduction for the generator you have an overunity system.<<

You are getting close. It is not an overunity system because the energy is taken from the wind. As the wind blows it along, it reaches wind speed minus a bit for friction. As it is now moving, and driving the prop *against the wind, it gains a little more.
From: Stealth ®25/08/2009 11:03:12 PM
Subject: re: Downwind faster than the wind?post id: 4293315
OK, do you agree that even unity is a practical impossibility?
—————-
In your imperfect world, yes. But in my perfect no-friction, no-losses, no-worries world unity is achievable.
From: Kingy ®25/08/2009 11:03:33 PM
Subject: re: Downwind faster than the wind?post id: 4293316
>>OK, do you agree that even unity is a practical impossibility?<<

I do, yes.

All the energy is coming from the wind, it loses some to friction etc as you would expect.

From: Kingy ®25/08/2009 11:05:08 PM
Subject: re: Downwind faster than the wind?post id: 4293319
>>It’s magic!<<

Can you explain what part you don’t understand?

From: Stealth ®25/08/2009 11:06:21 PM
Subject: re: Downwind faster than the wind?post id: 4293321
You are getting close. It is not an overunity system because the energy is taken from the wind. As the wind blows it along, it reaches wind speed minus a bit for friction. As it is now moving, and driving the prop against the wind, it gains a little more.
——————
Your ‘little bit for friction’ becomes ‘a bit more friction’ when you engage the prop. And this bit more is more than you will get back from the prop. You will lose energy to friction of the gear train and to the inefficencies of the prop itself.
From: Post_apocalyptic state of mind ®25/08/2009 11:08:41 PM
Subject: re: Downwind faster than the wind?post id: 4293323
>>It’s magic!<<

Can you explain what part you don’t understand?


Why do people take youtube so seriously, especially when it it riddled with misdirection and irrelevant detail?


Tony Delroy is talking about a $130 device that protects you from your mobile phone.

There are magic carpet underlays

You can look 10 years younger in 10 days.
From: Kingy ®25/08/2009 11:11:39 PM
Subject: re: Downwind faster than the wind?post id: 4293328
>>Why do people take youtube so seriously, especially when it it riddled with misdirection and irrelevant detail?<<

So your logic is that because some of it is crap, therefore all of it is crap?

From: Post_apocalyptic state of mind ®25/08/2009 11:14:35 PM
Subject: re: Downwind faster than the wind?post id: 4293331
So your logic is that because some of it is crap, therefore all of it is crap?



I don’t think it forms any useful basis for scientific discussion, any more than UFO videos.
From: Stealth ®25/08/2009 11:15:49 PM
Subject: re: Downwind faster than the wind?post id: 4293332
Kingy, I can explain this better with an experiment, and in person.

The experiment requires:

Bobcat (Kingy to supply)
Dumptruck (Kingy to supply)
Digger Operator (Kingy)
35m^3 soil (Stealth to supply)
Beer (Stealth to supply)

Tell me when you want to do it.
From: Kingy ®25/08/2009 11:16:36 PM
Subject: re: Downwind faster than the wind?post id: 4293334
>>Your ‘little bit for friction’ becomes ‘a bit more friction’ when you engage the prop. And this bit more is more than you will get back from the prop. You will lose energy to friction of the gear train and to the inefficencies of the prop itself.<<

At the prop turns against the wind, it creates more drag, which provides the extra power needed to turn the prop.

It sounds like overunity, but it isn’t. Nothing moves without energy from the wind.

It is a gain of a few percent over wind speed.
From: mzl ®25/08/2009 11:17:02 PM
Subject: re: Downwind faster than the wind?post id: 4293335
Now, I haven’t done this experiment, so I won’t show any results until I have, but I do seem to remember that there have been more than zero occasions when people here haven’t Done The Experiment, and were pretty wrong.
From: mzl ®25/08/2009 11:17:31 PM
Subject: re: Downwind faster than the wind?post id: 4293336
Well, I won’t say it gets faster and faster against the wind, that’s f’s‘re.
From: Post_apocalyptic state of mind ®25/08/2009 11:22:19 PM
Subject: re: Downwind faster than the wind?post id: 4293347
Well, I won’t say it gets faster and faster against the wind, that’s f’s‘re.



That would be wrong,

and dangerous!

Amazing how the first version on the road never crashed. Almost defies the odds.


Clearly, the explanation for how this all works would equally account for why it will not reach the sound barrier
From: Kingy ®25/08/2009 11:25:07 PM
Subject: re: Downwind faster than the wind?post id: 4293354
>>Clearly, the explanation for how this all works would equally account for why it will not reach the sound barrier<<

Yes, it gains a few percent over wind speed. It uses the energy from the wind. If the wind speed was 99% of the sound barrier, I would expect the machine to fail catastrophically.
From: Copernicus ®26/08/2009 6:53:32 AM
Subject: re: Downwind faster than the wind?post id: 4293381
Kingy is right, I concede. After a bit of googling the answer appears to have been clearly explained here http://wordmunger.com/?p=1002


Result.

1. Wind at 10kph blows cart say at 9kmph with say a loss of 1kph from friction. Note the wind blows against the propeller which in this example is acting merely as say a square sail.



2. Moving wheels from cart motion of 1) above supply power to prop to rotate and create power equivalent to say 2kph of additional speed.



Result is that cart moves marginally faster than wind speed.



The treadmill demo is used to simply show the efficiency of the prop in generating the additional incremental speed through the action of the moving treadmill on the wheels which turn the propeller.



That is all….grumble, grumble, grumble


From: Dr Matt ®26/08/2009 8:29:04 AM
Subject: re: Downwind faster than the wind?post id: 4293405
Why do people take youtube so seriously, especially when it it riddled with misdirection and irrelevant detail?
======

No idea, but this is nothing to do with utube or perpetual motion.

It is clever counter intuitive aerodynamics which is cool IMO.
From: Dr Matt ®26/08/2009 8:35:52 AM
Subject: re: Downwind faster than the wind?post id: 4293406
Clearly, the explanation for how this all works would equally account for why it will not reach the sound barrier
=====

Well yes, like any vehicle drag forces mean there will likely be a terminal velocity, which may only be a little bit above the wind speed.
From: Copernicus ®26/08/2009 8:47:38 AM
Subject: re: Downwind faster than the wind?post id: 4293408
It’s a nice device. Now my thoughts are if you attach a tail rudder to the fan so you can apply it to a changing wind direction, and have some steering arrangemenet for the wheels can this beat energy lost through friction and be harnessed for useful applications? :-))
From: Copernicus ®26/08/2009 8:51:01 AM
Subject: re: Downwind faster than the wind?post id: 4293409
>>It’s a nice device. Now my thoughts are if you attach a tail rudder to the fan so you can apply it to a changing wind direction, and have some steering arrangemenet for the wheels can this beat energy lost through friction and be harnessed for useful applications?

Excuse me……scrub last post. I think I may be referring to a land yacht….ooops
From: burko ®26/08/2009 9:11:54 AM
Subject: re: Downwind faster than the wind?post id: 4293416

“Amazing how the first version on the road never crashed. Almost defies the odds.”

Perzactly.

Experiment 1.

Find a road that has wind travelling directly up it…

Build a three wheeled one propeller device with no means of steering.

Make sure the wheels are as small as possible to limit it in tracking straight.

Attach a fishing line from it to your kids bike.

Instruct said kid to hug the curb and watch out for oncoming traffic.

Edit video.

Done.


From: Martin Smith (Avatar)26/08/2009 9:18:21 AM
Subject: re: Downwind faster than the wind?post id: 4293426


The only good use for a treadmill

http://www.youtube.com/watch?v=pv5zWaTEVkI


From: Stroke Off Genius ®27/08/2009 5:38:28 PM
Subject: re: Downwind faster than the wind?post id: 4295301
// No idea, but this is nothing to do with utube or perpetual motion.
Except where right at the start, links were provided to the former, which then mentioned (in many places) the latter.

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Date: 31/05/2021 12:19:36
From: SCIENCE
ID: 1745176
Subject: re: DWFTTW

sorry about the iframe residuals we blame Old Forum Hax and didn’t manage to wipe every one of them

note that there were like 5 threads about it in half the archive so there are probably about 5 more but we’re going to go do something else now

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Date: 31/05/2021 12:20:12
From: SCIENCE
ID: 1745177
Subject: re: DWFTTW

a university take

https://newt.phys.unsw.edu.au/~jw/sailing.html

enjoy

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Date: 1/06/2021 14:03:44
From: mollwollfumble
ID: 1745630
Subject: re: DWFTTW

Dark Orange said:


Tamb said:

The Rev Dodgson said:

Actually that’s probably wrong.

You need some means of extracting energy from the movement of the hull through the water.


Why?

Note the word “Downwind” needs to be clarified in this discussion – There is a subtle difference between “Directly downwind” (The definition used in the video) and “Downwind” (the definition used in sailing which means “a generally downwinf direction”)

A sailboat can go in a generally downwind direction faster than the actual wind speed. A sailboat would have difficulty going directly downwind faster than the actual wind speed.

Again. What does the speed envelope vs direction look like?
Cardioid? Ovate?

Also you need to distinguish between “speed” and “downwind component of velocity”. Just because “speed” is greater than windspeed for a yacht, it doesn’t automatically imply that “downwind component of velocity” is greater than windspeed.

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Date: 1/06/2021 14:57:10
From: esselte
ID: 1745644
Subject: re: DWFTTW

Here is an old paper with some maths and stuff for those interested.
Link is to a PDF, so not sure how that will work for you.

Faster Than the Wind
Andrew B Bauer
26 April 1969

projects.m-qp-m.us/donkeypuss/wp-content/uploads/2009/06/Bauer-Faster-Than-The-Wind-The-Ancient-Interface.pdf

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