Drysuit for buoyancy control??

[RTodd]

Yeah, you only have to look at the standard DIR trim to see that putting extra air into the suit would be ridiculous. The lower legs and feet are the highest point and that is precisely where that air wants to be. Putting more air into the suit than needed to prevent squeeze is just going to make your dive miserable as you fight to prevent going feet up the whole time. Remember, ideal trim means that you can remain motionless in a horizontal position. That is only possible whilst you are balanced around your centre.

Not true at all. XL Jets have a fair amount of weight and a bit of extra air helps some balance out plus it can make the feet more comfotable. It takes more comfort with your bouyancy to do this but many people move on from the need for gaitors and prefer to be able to put a bit of gas on their feet/ legs. On scooter dives, particularly when towing extra scooters and stages, extra gas in the feet/ legs is helpful.

 

[TSandM]

In Fundies, I was told to relieve squeeze and use the wing for buoyancy. In my Helitrox class with AG, he disabled my wing . . . In my recent cave class, not a word was said about it either way, so long as we had our buoyancy and trim under control.

 

[jagfish]

If you are in trim and got your sheet together its all irrelevant. If you are freezing, ignore the pundits and put more gas in the suit (get better undies too). If you are constantly head down, maybe a bit more gas in the wing. Feet dragging, an extra puff in the DS and a tad less in the wing. Assuming the tanks are appropriate for you in the first place, there are a few tank/body combos that just don't work but generally speaking a skilled diver can manage most doubles by using the various suit/wing/plate combos available. Sometimes you can dive the ideal "constant volume" Tobin mentions, but in reality its rarely that smooth. Either the suit or the wing has "taken over" depending on where you are in the dive, how much gas you have remaining, how cold you are, how well the tanks 'align' with you body shape, etc.

This post makes good sense to me. If I recall, the counsel I received in Tech 1 was the BC buoyancy/drysuit warmth approach.

Since then, I've modified my practice a bit...
At the begining of a dive, my rig is naturally heaviest and my profile likely deepest, compressing any buoyancy my hood, gloves and boots may have had. At this point, I definitely need to use the wing to have a manageable size bubble in my suit.

However, at the end of the dive, the opposite is true. My primary tanks are much lighter, any neoprene equipment is exerting its upward force...my usual case at the end of the dive is to dump all wing air somewhere between 15 and 9 meters and go the rest on drysuit only.

Near the surface where buoyancy swings can be more tricky, especially in surge, I find this doubly advantageous since for me it's easier to make quick air adjustments with my drysuit than BC in the 2 to 6 meter range if I get pulled up with some surge.

 

[Jeff Toorish]

Just so I am clear --the instructor wasn't simply teaching how to use the drysuit for buoyancy in the event of a wing failure, right?

With doubles redundant buoyancy is a good idea, either a redundant bladder wing or a wing and a dry suit; hence my question.

I experimented with using both my dry suit and wing for buoyancy control and found the drysuit impractical. I want my dry suit as trim as possible and I use the wing for buoyancy. When diving a rebreather with a dry suit the difficulty of trying to use a dry suit for buoyancy control becomes extremely apparent.

Jeff

 

[nadwidny]

With doubles redundant buoyancy is a good idea, either a redundant bladder wing...

BUUZZZZZ!!!! Wrong. Thanks for playing...

Next time check what forum that you're posting to before hitting the 'send' button.

 

[rainman_02]

In all my classes with AG, he has never mentioned "shrink wrap" other than to say it was a stupid idea.

Step 1) DS neutral (i.e. to the point that it will vent if you add any more air).

Step 2) Wing filled to offset the weight of gas in your tanks.


This is the only way you can end the dive with ~500 psi, an effectively empty wing, and neutral...yet still have the ability to stay down if you have less than 500 psi.

 

[BarryNL]

Not true at all. XL Jets have a fair amount of weight and a bit of extra air helps some balance out plus it can make the feet more comfotable. It takes more comfort with your bouyancy to do this but many people move on from the need for gaitors and prefer to be able to put a bit of gas on their feet/ legs. On scooter dives, particularly when towing extra scooters and stages, extra gas in the feet/ legs is helpful.

There's a big difference between a bit and doing your buoyancy with your suit. I like to put a bit of air into my legs to help with movement, but double-12s contain 4.5kg of gas - you cannot balance that with a drysuit and remain either comfortable or in trim.

I'd also point out that this is the DIR forum and every GUE-F course teaches gas in the drysuit to avoid squeeze and gas in the wing for buoyancy. Case closed.

 

[DIR-Atlanta]

I'd also point out that this is the DIR forum and every GUE-F course teaches gas in the drysuit to avoid squeeze and gas in the wing for buoyancy. Case closed.

I'm curious as to the basis for your claim that "every GUE-F course" teaches this. Just out of curiousity, how many GUE-F courses have you personally taught and/or observed?

In point of fact, RTodd's explanation is spot on, and does not contravene any DIR principle of which I am aware. The mantra of putting "only enough gas in the drysuit to avoid squeeze" is a sound byte at best (kind of like "no steel tanks with a wetsuit"), and does not reflect the fact that there can be a great deal of variability in managing this particular aspect of the dive.

In general, the amount of gas that is used for suit inflation should be sufficient to (a) relieve squeeze, (b) maintain loft in the undergarment for warmth, and (c) allow for adequate freedom of movement. It should obviously not be such an excessive amount that it becomes difficult to control, particularly during decompression stops. That still allows for quite a bit of latitude in just how much a diver adds.

Given that "how much is enough" is a purely subjective measure (even by the relatively weak standard of "just enough to avoid squeeze"), then I would say that the only logical choice here is to allow individual divers to determine this for themselves (or in the words of AG, "every diver is responsible for his own buoyancy"). As long as it does not negatively affect the safety of the diver or the team, then I see no reason to try and micro-manage.

 

[BarryNL]

In general, the amount of gas that is used for suit inflation should be sufficient to (a) relieve squeeze, (b) maintain loft in the undergarment for warmth, and (c) allow for adequate freedom of movement.

That's just three ways of saying the same thing.

It should obviously not be such an excessive amount that it becomes difficult to control, particularly during decompression stops. That still allows for quite a bit of latitude in just how much a diver adds.

Yes, but the issue here was whether the drysuit could be used for buoyancy control. We're not talking about 'quite a bit', but enough to balance 4.5kg of gas in doubles and perhaps twice that on a dive with stages.