Dry Suit training...

[sharkmasterbc]

When training in a drysuit should you use only the dry suit for buoyency or a combination of your BC and the suit ? Some say to use the suit to just eliminate the squeeze and the BC as normal but others I've dived with say they use only the suit...is it more of a personal choice ?

 

[Bob3]

Wellll ... if you're diving with a single tank & are properly weighted, you'll be starting the dive being only about 6 lbs heavy. By the time you squirt a little air in the suit to relieve the squeeze, you're going to be pretty back "close" to neutral again.
Most of the guys I dive with can accommodate a few lbs weight swing by varying their tidal volume, the end result is no air (or very little) being needed in the BC at all during the dive. In that sense they're using "only the suit".
Things start changing as you add more tanks, tools, etc. When that happens you're way better off using the BC because you can control your trim a whole lot better than you can with a big air bubble rampaging around in your suit.
Make sense?

 

[Warren_L]

It is a combination of both, and there are different schools of thought on this, but I prefer to minimize the use of the drysuit as a buoyancy device. There will be some, of course, as long as there is air in the suit, but I add enough to relieve the squeeze and that's about it.

 

[OWSI176288]

Put only enough air in the drysuit to overcome squeeze. Too much gas in the suit will lead to dynamic instability which causes poor trim and buoyancy control. Remember: use your dry suit for what it's designed for (i.e. to keep you warm) and your buoyancy control device for what it's designed for (i.e. buoyancy control) and you’ll be much better off.

 

[Genesis]

DO NOT use the suit for buoyancy control. You have a device designed for that - its called a BC!

Drysuits should be dove with the dump FULLY OPEN. This way all excess gas, provided you're horizontal or vertical with your dump at the highest point will automatically exit without drama or effort.

You then squirt gas into the suit to relieve the squeeze. If you put in too much, it comes back out. "Too much" is more than you NEED to relieve squeeze.

If you dive it this way, then you do not have stability problems, the suit is comfortable, your drag is minimized, and your trim will be far better. Its also safer.

One of the dangers of using the suit as a BC is that if you get inverted all the air will go to your feet! This can be quite dangerous, as in extreme cases it can cause your fins to be ejected! Now what? You're headed up to the surface, unable to fin, and you're hosed - that's what.

Now going inverted is sometimes desirable. What if you want to stick your head in a hole somewhere to see what's inside (a wreck, etc)? If you dive the suit with no extra air, then while you feel a shift its fairly subtle and not dangerous. If you have a big bubble of air, that does not apply.

My recommendation to test the amount of air in the suit is that you stop for a moment, assume a left-arm-up position, and raise your hand. The "bubble" of air should not come below your elbow; the rest of your arm and body should be "shrink-wrapped." Even better is if you have only a slight looseness in your forearm but not a noticable "bubble."

BTW the agencies all teach you to dive the suit as a BC. IMHO they're all wrong. I note as well that DUI recently revised their information - they used to recommend using the suit as a BC, but the owners manual I recently received with my new TLS350 now recommends that you have no more air in the suit that you get from a small "bubble" in one arm when it is at the highest point! Bravo DUI!

 

[Warren_L]

It is nice, of course, to be able to use the drysuit as a buoyancy device in the event of an emergency if needed..... but I wouldn't do so in the normal course of diving.

 

[Rick Inman]

I agree that when I'm properly weighted, a little air in the suit to offset squeeze does the trick - until I get some real depth, then it's all about the BC.

BTW the agencies all teach you to dive the suit as a BC. IMHO they're all wrong. b][/i]

I recently sat pool-side during a PADI dry suit class and watched them teach the dry-suit-as-a-BC method. When I questioned the instructor later, he said that to teach otherwise is to create a situation with new divers that is too task-intensive. Adding the dry suit inflater to someone using the BC for buoyancy is too much multitasking.
I say, if you have issues with multitasking, you should take something like... watching TV.
Also, wanna' know how to make sure you're using for BC for buoyancy and not your dry suit? Get a pony and use argon. At a buck a CF, you'll think twice about using it instead of the free BC air! :satisfied

 

[norcaldiver]

It is nice, of course, to be able to use the drysuit as a buoyancy device in the event of an emergency if needed

I agree and think that that's the only time it should be used. It's been said before, but that's what a BC is for, the drysuit is not called an AltBC, it's called a drysuit.

One of the dangers of using the suit as a BC is that if you get inverted all the air will go to your feet! (snip) Now what? You're headed up to the surface, unable to fin, and you're hosed - that's what.

That's a good chicken little impression. Ummm, howsabouts this? Dump gas/disconnect the inflator/TUCK AND ROLL! This is the 1st and only task tought in the class. Why is it such a scary thing for people to understand?

In extreme cases it can cause your fins to be ejected!

Name 5

 

[Genesis]

That's a good chicken little impression. Ummm, howsabouts this? Dump gas/disconnect the inflator/TUCK AND ROLL! This is the 1st and only task tought in the class. Why is it such a scary thing for people to understand?

Tuck and roll doesn't work real well if your fins have departed, and you aren't going to be dumping the suit if you're upside down - the dump is in the wrong place! Dumping your BC in that situation will actually make the problem WORSE, as you are subtracting buoyancy from the upper part of your body (which is pointing down) and that's the part that you want to be ON THE TOP.

You can tuck until you're blue in the face, but your buoyancy in that case is still on top of your body. Without your fins to provide thrust rolling in that situation is NOT trivial. All your weight is from your weight belt up and all your buoyancy is above that - in your feet! NOT good.

Try it in a pool if you don't believe me. Take off your fins, get in the water, go upside down, take all the air out of your BC and then add air to the suit until you just start up, having filled your feet. Now try to tuck and roll.

You'll wind up on the surface before you can generate enough rolling moment to get righted. The "way out" is, paradoxially, to add air to your BC so you have lift in your chest/midsection and can roll around! Of course in a runaway ascent situation you just made it worse, but on the surface, that's how you "get out" of that situation.

You MUST get upright or close to it to arrest such an ascent, either by dumping or in an emergency by venting through a seal, and it just ain't gonna happen if your fins get blown off your feet once things get going.

 

[Warren_L]

Might be time to get out that knife .... and well, you know.