Watching TV on deep diving. It takes 5 days to decompress from 180 metre depth from long term (17 days straight) high pressure heliox.
My question is this. How does the decompression time vary with depth? eg. how deep could you go long term on 10 days decompression?
I keep feeling that there ought to be a simple formula based on the rate at which gases are released from the bloodstream.
mollwollfumble said:
Watching TV on deep diving. It takes 5 days to decompress from 180 metre depth from long term (17 days straight) high pressure heliox.My question is this. How does the decompression time vary with depth? eg. how deep could you go long term on 10 days decompression?
I keep feeling that there ought to be a simple formula based on the rate at which gases are released from the bloodstream.
mollwollfumble said:
Watching TV on deep diving. It takes 5 days to decompress from 180 metre depth from long term (17 days straight) high pressure heliox.My question is this. How does the decompression time vary with depth? eg. how deep could you go long term on 10 days decompression?
I keep feeling that there ought to be a simple formula based on the rate at which gases are released from the bloodstream.
Pretty sure there are charts with this information and currently used by serious divers.
PermeateFree said:
mollwollfumble said:
Watching TV on deep diving. It takes 5 days to decompress from 180 metre depth from long term (17 days straight) high pressure heliox.My question is this. How does the decompression time vary with depth? eg. how deep could you go long term on 10 days decompression?
I keep feeling that there ought to be a simple formula based on the rate at which gases are released from the bloodstream.
Pretty sure there are charts with this information and currently used by serious divers.
Yes.. The deeper the dive the slower the ascent and the longer the decompression.
wookiemeister said:
mollwollfumble said:
Watching TV on deep diving. It takes 5 days to decompress from 180 metre depth from long term (17 days straight) high pressure heliox.My question is this. How does the decompression time vary with depth? eg. how deep could you go long term on 10 days decompression?
I keep feeling that there ought to be a simple formula based on the rate at which gases are released from the bloodstream.
http://www.diverssupport.com/software.htm
That looks like great software, 305 metres depth max is impressive. Suspect I’d have to buy it and reverse engineer the results to get the formulas, though.
mollwollfumble said:
wookiemeister said:
mollwollfumble said:
Watching TV on deep diving. It takes 5 days to decompress from 180 metre depth from long term (17 days straight) high pressure heliox.My question is this. How does the decompression time vary with depth? eg. how deep could you go long term on 10 days decompression?
I keep feeling that there ought to be a simple formula based on the rate at which gases are released from the bloodstream.
http://www.diverssupport.com/software.htm
That looks like great software, 305 metres depth max is impressive. Suspect I’d have to buy it and reverse engineer the results to get the formulas, though.
as you might suspect the deeper you go the less time you can spend there as decompression times are kind of exponential I think
mollwollfumble said:
wookiemeister said:
mollwollfumble said:
Watching TV on deep diving. It takes 5 days to decompress from 180 metre depth from long term (17 days straight) high pressure heliox.My question is this. How does the decompression time vary with depth? eg. how deep could you go long term on 10 days decompression?
I keep feeling that there ought to be a simple formula based on the rate at which gases are released from the bloodstream.
http://www.diverssupport.com/software.htm
That looks like great software, 305 metres depth max is impressive. Suspect I’d have to buy it and reverse engineer the results to get the formulas, though.
structural strength/ thickness of submarine hulls
is there any rule of thumb or simple formula based on the thickness of particular alloys for submarine hulls
you can work out pressure by depth * density * gravity but how does this translate to hull thickness??
“Pretty sure there are charts with this information and currently used by serious divers.”
‘Serious divers’ would probably equate to ‘living divers’.
Divers who ‘weren’t serious’, and didn’t use information like that wouldn’t be around for long.
“is there any rule of thumb or simple formula based on the thickness of particular alloys for submarine hulls”
No. That’s why people have to go to university, and qualify as naval architects.
If it was ‘a simple rule of thumb’, the shift foreman in the shipyard would be designing the submarine.
captain_spalding said:
“is there any rule of thumb or simple formula based on the thickness of particular alloys for submarine hulls”No. That’s why people have to go to university, and qualify as naval architects.
If it was ‘a simple rule of thumb’, the shift foreman in the shipyard would be designing the submarine.
so did any of those people ever write a formula anywhere relating to structural strength, there might be one based on ribs and hull thickness?
when they designed the Collins class they were just attaching explosives to metal plates to work out empirically what kind of damage could be done – they weren’t modelling it using naval architects
“when they designed the Collins class…”
Who might ‘they’ be?
captain_spalding said:
“when they designed the Collins class…”Who might ‘they’ be?
wookiemeister said:
captain_spalding said:
“when they designed the Collins class…”Who might ‘they’ be?
they weren’t architects
Probably not. But, we’re none the wiser as to who ‘they’ were.
wookiemeister said:
captain_spalding said:
“when they designed the Collins class…”Who might ‘they’ be?
they weren’t architects
they weren’t naval architects, the architects were then given this information so the font of all knowledge doesn’t flow from naval architects alone
you are way too touchy captain
there are people that have built them from scratch , I keep meaning to get in touch with them to see how they worked out the thickness and shape
quite an interesting subject
flow over the shape is very important so I’ve learnt. the best shape isn’t often used because of the nature of whats inside the sub
long shapes aren’t necessary the best shapes, nor a straight teardrop design
wookiemeister said:
you could most likely find formulas for free
as you might suspect the deeper you go the less time you can spend there as decompression times are kind of exponential I think
That’s what I wanted to check. Given that pressure is linear with depth I can’t immediately see any reason why decompression times shouldn’t also be roughly linear with depth, when allowances are made for variable gas mixtures to keep the partial pressure of oxygen in the right ballpark.
Following on through hints on your software link I’ve come across some equations in http://www.divetable.de/skripte/Theory.pdf 30 pages packed with equations is slightly more complicated than I’d hoped, but the maths is easy enough.
wookiemeister said:
long shapes aren’t necessary the best shapes, nor a straight teardrop design
The P-51 efficiency came from a subtle waist in the rear where most would have designed a straight taper.
“it was some fellahs putting explosives on steel plates to see what damage could be done by depth charges
they weren’t naval architects, the architects were then given this information so the font of all knowledge doesn’t flow from naval architects alone
you are way too touchy captain”
I’m not touchy. I just don’t like unreferenced urban myths.
The Collins class were built from HY80 steel, supplied by Bisalloy of Wollongong.
The full properties of HY80 steel are well known, and have been for quite some time. Naval architects would have had no need to explode anything.
If anyone was causing explosions, i suggest it was more for their amusement than for science.
mollwollfumble said:
wookiemeister said:
you could most likely find formulas for free
as you might suspect the deeper you go the less time you can spend there as decompression times are kind of exponential I think
That’s what I wanted to check. Given that pressure is linear with depth I can’t immediately see any reason why decompression times shouldn’t also be roughly linear with depth, when allowances are made for variable gas mixtures to keep the partial pressure of oxygen in the right ballpark.
Following on through hints on your software link I’ve come across some equations in http://www.divetable.de/skripte/Theory.pdf 30 pages packed with equations is slightly more complicated than I’d hoped, but the maths is easy enough.
from what he was saying I picked up that the relationship wasn’t linear
Skunkworks said:
wookiemeister said:
long shapes aren’t necessary the best shapes, nor a straight teardrop design
The P-51 efficiency came from a subtle waist in the rear where most would have designed a straight taper.
that’s the same for concorde
fast aircraft do better with a narrowed waist
captain_spalding said:
“Pretty sure there are charts with this information and currently used by serious divers.”‘Serious divers’ would probably equate to ‘living divers’.
Divers who ‘weren’t serious’, and didn’t use information like that wouldn’t be around for long.
Was thinking of casual diving in shallow water, when you are only down with a single tank of gas. Many people dive like this and have no need for decompression.
captain_spalding said:
“it was some fellahs putting explosives on steel plates to see what damage could be done by depth chargesthey weren’t naval architects, the architects were then given this information so the font of all knowledge doesn’t flow from naval architects alone
you are way too touchy captain”
I’m not touchy. I just don’t like unreferenced urban myths.
The Collins class were built from HY80 steel, supplied by Bisalloy of Wollongong.
The full properties of HY80 steel are well known, and have been for quite some time. Naval architects would have had no need to explode anything.
If anyone was causing explosions, i suggest it was more for their amusement than for science.
10m and above you don’t need decompression times
wookiemeister said:
10m and above you don’t need decompression times
I remember Lloyd Bridges in Sea Hunt, he never decompressed.
Also, he’d get of the water and his hair was perfect.
PermeateFree said:
Was thinking of casual diving in shallow water, when you are only down with a single tank of gas. Many people dive like this and have no need for decompression.
When i did a brief elementary dive course many years ago, it was single tank, and we didn’t got much over 30 -40 feet, often much less.
But, decompression was a must, on EVERY dive.
Three feet under water, and you’ve got twice normal atmospheric pressure. The deeper you go, the bigger the issue.
wookiemeister said:
wookiemeister said:
10m and above you don’t need decompression times
well you could come up from 10m quickly if you had to
Yes. if you had to. But, you wouldn’t feel all that chipper afterwards.
captain_spalding said:
wookiemeister said:
wookiemeister said:
10m and above you don’t need decompression times
well you could come up from 10m quickly if you had toYes. if you had to. But, you wouldn’t feel all that chipper afterwards.
no buggerising around messing around with air bubbles in your bloodstream and brain
wookiemeister said:
I expect it was ‘The Collins Class Submarine: Steel, Spies and Spin’, by Peter Yule and Derek Woolner.
Haven’t read it yet.
I’m not saying the experiment wasn’t done. I just don’t see that it would have been at all necessary for the design and construction of the submarines
captain_spalding said:
PermeateFree said:Was thinking of casual diving in shallow water, when you are only down with a single tank of gas. Many people dive like this and have no need for decompression.
When i did a brief elementary dive course many years ago, it was single tank, and we didn’t got much over 30 -40 feet, often much less.
But, decompression was a must, on EVERY dive.
Three feet under water, and you’ve got twice normal atmospheric pressure. The deeper you go, the bigger the issue.
Sorry but you are incorrect. I have dived around 30’ many, many, times, even doing marine surveys with reputable people. I can assure you that you do not need to decompress after using a single tank of gas in that situation. Also 30’ is double the normal atmospheric pressure, not 3’.
PermeateFree said:
captain_spalding said:
PermeateFree said:Was thinking of casual diving in shallow water, when you are only down with a single tank of gas. Many people dive like this and have no need for decompression.
When i did a brief elementary dive course many years ago, it was single tank, and we didn’t got much over 30 -40 feet, often much less.
But, decompression was a must, on EVERY dive.
Three feet under water, and you’ve got twice normal atmospheric pressure. The deeper you go, the bigger the issue.
Sorry but you are incorrect. I have dived around 30’ many, many, times, even doing marine surveys with reputable people. I can assure you that you do not need to decompress after using a single tank of gas in that situation. Also 30’ is double the normal atmospheric pressure, not 3’.
I am willing to be corrected. It was many years ago (not sure that i didn’t see Lloyd Bridges down there one time) and the little grey cells are not all where they used to be. But, we did do brief decompression stops. Maybe a bit of ‘better safe than sorry’ with us novices.
wookiemeister said:
Well, you do, sort of.
Dunno about these days, but submariners had to all learn to escape from a submarine at 100 feet. Free ascent, and decompressing on the way up.
Used to be one of the attractions of submarines. We didn’t have deep dive tank in Australia, so all submariners got a free trip to the UK.
captain_spalding said:
PermeateFree said:
captain_spalding said:When i did a brief elementary dive course many years ago, it was single tank, and we didn’t got much over 30 -40 feet, often much less.
But, decompression was a must, on EVERY dive.
Three feet under water, and you’ve got twice normal atmospheric pressure. The deeper you go, the bigger the issue.
Sorry but you are incorrect. I have dived around 30’ many, many, times, even doing marine surveys with reputable people. I can assure you that you do not need to decompress after using a single tank of gas in that situation. Also 30’ is double the normal atmospheric pressure, not 3’.
I am willing to be corrected. It was many years ago (not sure that i didn’t see Lloyd Bridges down there one time) and the little grey cells are not all where they used to be. But, we did do brief decompression stops. Maybe a bit of ‘better safe than sorry’ with us novices.
Apprentices often learn things they don’t comprehend until they have to use them.
wookiemeister said:
mollwollfumble said:
wookiemeister said:
you could most likely find formulas for free
as you might suspect the deeper you go the less time you can spend there as decompression times are kind of exponential I think
That’s what I wanted to check. Given that pressure is linear with depth I can’t immediately see any reason why decompression times shouldn’t also be roughly linear with depth, when allowances are made for variable gas mixtures to keep the partial pressure of oxygen in the right ballpark.
Following on through hints on your software link I’ve come across some equations in http://www.divetable.de/skripte/Theory.pdf 30 pages packed with equations is slightly more complicated than I’d hoped, but the maths is easy enough.
funny enough I was talking to someone who does diving just recently
from what he was saying I picked up that the relationship wasn’t linear
That tallies with the 5 day decompression for 180 metres deep. If linear that would mean 1 day decompression for 36 metres deep, 6 hrs decompression for 9 metres deep, that’s definitely false, totally ridiculious. I still don’t see why, though.
In the reference, the Haldane equation is so trivial the I don’t see why it needs a name. The Schreiner Equation, although not exactly trivial is to my eyes obvious. The Workman equation and M-values of “maximum partial pressure of an inert gas in a compartment” is obvious as well. But equation 16, an empirical equation setting the M-value proportional to the inverse of the fourth root of the half life doesn’t make sense to me yet. Where the heck does that come from? Is that just a solution to the diffusion equation (like Fick’s equation), is it biologically inspired, or did they just get it by drawing an approximate curve through measured datapoints? By equation 19 they’ve also picked the inverse square root and inverse cube root of the half life out of nowhere. The following table of body tissues ignores the blood, don’t they think that bubble formation in the blood limits decompression times?
I want to make the assumption that decompression times are minimised, and thus I allow myself to have complete control over both the mixture fractions and partial pressures in the alveolae.
There used to be a differentiation between “Sport” and “Professional”, but the tools available to the professional divers (such as various gas mixes and multiple tanks) means the line is now blurred. “Serious” and “Casual”, seems to be valid nomenclature.
As for the actual depths, 30’ of water weighs the same amount as all the atmosphere above you, so at 30’ you experience twice atmospheric pressure, 60’ you have three times, 90’ you have 4 times. etc. I am not sure it is an arbitrary cut-off of based on a convenient point or there is an actual reason for it (I suspect the former) but 30’ is treated as a “safe” depth, and decompression is not required if you do not dive beyond this point. A lot of sport diving charters enforce a “every diver will make a decompression stop” rule just to be sure, as the tables were developed (as far as I know) by trial and error using human subjects by the US navy and not extrapolated from some basic scientific basis.
Note also the tables use a sea level base for their calculations. If you were diving in high altitude lakes or more commonly, flying after your dive, then you need to factor that in. A base rule of thumb is 12 hours between when it is safe to be at sea level and when it is safe to be flying.
Good luck with finding a base formula behind it all, but I am not sure one exists.
captain_spalding said:
wookiemeister said:
it was shown in a book on the building of the Collins class
I expect it was ‘The Collins Class Submarine: Steel, Spies and Spin’, by Peter Yule and Derek Woolner.
Haven’t read it yet.
I’m not saying the experiment wasn’t done. I just don’t see that it would have been at all necessary for the design and construction of the submarines
they were simulating depth charges
wookiemeister said:
captain_spalding said:
wookiemeister said:
it was shown in a book on the building of the Collins classI expect it was ‘The Collins Class Submarine: Steel, Spies and Spin’, by Peter Yule and Derek Woolner.
Haven’t read it yet.
I’m not saying the experiment wasn’t done. I just don’t see that it would have been at all necessary for the design and construction of the submarines
I need decompression after leaving this forum .. every time.
roughbarked said:
wookiemeister said:
captain_spalding said:I expect it was ‘The Collins Class Submarine: Steel, Spies and Spin’, by Peter Yule and Derek Woolner.
Haven’t read it yet.
I’m not saying the experiment wasn’t done. I just don’t see that it would have been at all necessary for the design and construction of the submarines
they were simulating depth chargesI need decompression after leaving this forum .. every time.
why? we mostly play in the shallow end…
mollwollfumble said:
Watching TV on deep diving. It takes 5 days to decompress from 180 metre depth from long term (17 days straight) high pressure heliox.My question is this. How does the decompression time vary with depth? eg. how deep could you go long term on 10 days decompression?
I keep feeling that there ought to be a simple formula based on the rate at which gases are released from the bloodstream.
Does this help? I haven’t read it, looks useful, if old.
http://jap.physiology.org/content/20/6/1267.short
http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0620879
moll,
When deep diving the body will eventually reach what is referred to as super saturation. Super saturation is when the nitrogen that has desolved in body has reached a point where no more can be added.
There are several different algorithms / models used for dive tables and dive computers all with differing pros and cons. None of these models have 100% rates of success as a lot is still unknown about decompression and the associated sickness.
If you are interested in a more in depth analysis I’d recommend researching the work of the following men.
Dr Simon Mitchell. An NZ diver and specialist in ryperbaric medicine.
john Lippmann. Heavily involved in the technical dive industry in Australia
Also search on microbubbles and supersaturation diving.