Silly question about dry suit air usage

[Bubbletrubble]

I fully assume the poster is turning into a paper (the usual path with such things in academia, at least in my field). I don't doubt the findings, though. In any case, few single studies are ever really "conclusive", but this is admittedly strong scientific evidence finding a difference between argon (not a weak argon+air mix you'd get without *some* purge cycles) and air.

@Rainer: You were correct. The abstract did evolve into a paper published in IEEE. There are some nice pics of the thermal mannequin and the experimental setup. I particularly enjoyed the definition of the unit of thermal protection being used (CLO).

So I guess that the hardcore (and affluent) drysuit divers should be using xenon or krypton, eh?

 

[boulderjohn]

@Rainer:

So I guess that the hardcore (and affluent) drysuit divers should be using xenon or krypton, eh?

I have to be really careful if anyone is using krypton because of a severe allergy I have.

Or was that kryptonite?

 

[TSandM]

I'm a huge believer in Argon, and I've never really understood suit flushing, unless you are doing hot drops off a boat. By the time I have stood in the water and done gear checks, there isn't much gas in my drysuit at all!

To the OP -- like Rainer, I can get at least 2 or 3 dives off an Al6 full of Argon, so you're using no more than 1 to 2 cubic feet of gas in the suit total (and I run my suit really loose in Puget Sound, for warmth). It doesn't have to be factored into rock bottom because you don't add gas to the suit on ascent, as previously stated. And even if you had to add a little because of some yo-yoing, there's enough slop built into the rock bottom calculations that it shouldn't be an issue.

 

[sabbath999]

Thanks... I don't tend to do square profiles, I tend to dive where the cool little critters are (photographer), so my rock bottom calculations are a bit trickier (i.e. I build in a lot of error). I generally do a lot of "gradually up the slope" ascending instead of going up the mooring line from 90 feet kind of dives (in fact, I have only done ONE of those kind of dives, ascending from 110 feet with a couple safety stops).

Argon is a bit beyond me at the moment (not even sure where to get fills in my area).

 

[Rainer]

Rock bottom doesn't care about what your profile looks like. It just addresses how much gas you need to get you and a teammate up from some depth. Change depth all you want, RB will follow.

Thanks... I don't tend to do square profiles, I tend to dive where the cool little critters are (photographer), so my rock bottom calculations are a bit trickier (i.e. I build in a lot of error). I generally do a lot of "gradually up the slope" ascending instead of going up the mooring line from 90 feet kind of dives (in fact, I have only done ONE of those kind of dives, ascending from 110 feet with a couple safety stops).

Argon is a bit beyond me at the moment (not even sure where to get fills in my area).

 

[sabbath999]

Rock bottom doesn't care about what your profile looks like. It just addresses how much gas you need to get you and a teammate up from some depth. Change depth all you want, RB will follow.

Yes, I am phrasing what I am trying to say badly. Let me rephrase. I like a lot of "headroom" in my calculations because I may drop 20 or 30 feet near the end of the dive to check out a spot... hmmm.... well, I think you know what I am trying to say (badly).

 

[b1gcountry]

To give you an idea of how much gas an experienced DS diver uses, I have a small 6cf inflation bottle. I can get 2 deep dives off of one fill with plenty reserve left. I can get about 4-5 recreational level dives off the same bottle. That works out to about 1-2cf of inflation gas per dive. You can do the math to figure out how much psi that is in your tanks.

Tom

PS, I know this doesn't account the the additional air used because of the increased drag of a drysuit.

 

[sschlesi]

Yes, I am phrasing what I am trying to say badly. Let me rephrase. I like a lot of "headroom" in my calculations because I may drop 20 or 30 feet near the end of the dive to check out a spot... hmmm.... well, I think you know what I am trying to say (badly).

You don't need extra "headroom" in case you go deeper, here are some rock bottom pressures I use with an HP100.

60ft. 750psi
80ft. 1000psi

My rock bottom for 80 feet is 1000psi, so if I'm at 60' and see something cool at 80' (it's a good vis day), as long as I have >1000psi + NDL, no problem and no need for extra "headroom" in the calculations. If I have 900psi, I'm fine at 60', but I shouldn't return to 80'.

Don't add extra headroom to your rock bottom pressures in case you willfully break the rules, how will you know when you have gone too far? You may as well not bother with rock bottom and just "come back with 500psi".

 

[Sas]

If you are new to a dry suit, your SAC is bound to go up initially.

No it isn't 'bound to go up'. My SAC dropped by a few litres because I was way warmer as soon as I switched to a drysuit.

I think the air used in drysuit inflation is negligible, if you are properly weighted. I have never worried about it.

 

[Belmont]

@Rainer: You were correct. The abstract did evolve into a paper published in IEEE. There are some nice pics of the thermal mannequin and the experimental setup. I particularly enjoyed the definition of the unit of thermal protection being used (CLO).

So I guess that the hardcore (and affluent) drysuit divers should be using xenon or krypton, eh?

Radon??

Would keep you even warmer.