Safety margin of backplate/ wing if drysuit floods or other problems ?

[Roger Hobden]

I am currently reading a lot of stuff in relation for GUE Fundamentals. One aspect that seems important is to make sure that the wing avoids having excessive lift in relation to total weight.

A question that came into my mind is the following: what happens if you have a flood in your dry suit ? If you want to make sure to make a controlled ascent, without ditching your weights, wouldn't it be a good thing to have more lift then necessary in the case of such an problem ?

Same question, if you have to rescue a diver who has a malfunctioning wing ?

Any advice and explanations would be very appreciated.

 

[MaxBottomtime]

A liftbag would be your third option, but GUE stresses weighting yourself so that you can swim up at any point in the dive without using your wing.

 

[PfcAJ]

If your wing can float your gear without you in it, it’ll be fine. Here’s why.

Since a bag full of water (a flooded drysuit with no risidual air in it) will be roughly neutral, a wing which can support your kit on the surface without any additional buoyancy will be fine if your suit floods.

 

[Stoo]

If you're properly weighted, a flooded suit won't be an issue. I had the SiTech neck ring let go oh my suit and it literally filled to my neck with water. It really didn't change things much. I dive from a RHIB though, so after removing my tanks and weightbelt, hauling myself over the side was a little challenging.

The thing is that water isn't negatively bouyant. It's completely neutral. If your suit floods, all you are doing is losing the bit of air in there that you use to trim your buoyancy. And realistically, even fully flooded a suit will likely hold a lot of air. Assuming you have a proper horizontal trim, there really isn't any way to lose all the air in your suit unless the back of your suit splits open!

In my case, when I hit my suit inflator, I could hear bubbling. Some of the air escaped out my neck, but most of it was trapped in the back of my suit just like it always it. When I surfaced, and went vertical, it burped out. (The hole was big enough that I could put my hand through it!

But as others have said, after your wing, a lift bag or DSMB can work fine.

 

[NAM001]

If you dry suit needs 30# of lead to keep you down then a flood will being in 30#
figure that into the wing size just like you would wet suit compression at 100 ft

 

[Roger Hobden]

The thing is that water isn't negatively bouyant. It's completely neutral.

Come to think of it, in retrospect, it's pretty obvious ... Thanks for the reality check !

Now, about that buddy who's wing would lose it's lift capacity ? Same answer ? Lift bag, SMB, etc. ?

 

[doctormike]

The thing is that water isn't negatively bouyant. It's completely neutral.

Come to think of it, in retrospect, it's pretty obvious ... Thanks for the reality check !

Well, while water may be neutrally buoyant, you are comparing the situation before the flood to after.

If you were to completely flood your suit (which as Stoo pointed out isn't that likely), you would experience a negative buoyancy swing (buoyancy loss) equal to the total positive buoyancy of your inflated undergarments, which is not trivial. So don't oversimplify the situation. More important is the second point that he made, which is that most flooded suits have some residual buoyancy.

Also, this is one of the advantages of running your dry suit tight - you aren't adding so much positive buoyancy that needs to be offset by ballast.

From what I understand, GUE stresses the importance of a balanced rig, which means that you should be able to swim up with a non-functioning wing. So very large wings imply that the diver is overweighted and not diving a balanced rig.

 

[Roger Hobden]

Well, while water may be neutrally buoyant, you are comparing the situation before the flood to after.

If you were to completely flood your suit (which as Stoo pointed out isn't that likely), you would experience a negative buoyancy swing (buoyancy loss) equal to the total positive buoyancy of your inflated undergarments, which is not trivial. So don't oversimplify the situation. More important is the second point that he made, which is that most flooded suits have some residual buoyancy.

Also, this is one of the advantages of running your dry suit tight - you aren't adding so much positive buoyancy that needs to be offset by ballast.

From what I understand, GUE stresses the importance of a balanced rig, which means that you should be able to swim up with a non-functioning wing. So very large wings imply that the diver is overweighted and not diving a balanced rig.

Great observations. Thanks !

 

[Stoo]

I probably should have emphasized that the key in all of that is the so-called balanced rig. If you're way over-weighted such that you're having to add a lot of air to your suit, then that's a different thing altogether.

I'm off to BC again in a couple of weeks. I wear a 40 pound weight harness there with a steel 100 (as opposed to 12 pounds at home with twin steel 80s) but that doesn't mean I have "gallons" of air in my suit. The loss of the buoyancy in my suit wouldn't cause me to sink like a rock. The lead is to counteract MY buoyancy, not the buoyancy of the air in my suit (OK, it is a bit). I keep only enough air in my suit to prevent squeeze and to fine tune my buoyancy.

 

[doctormike]

I probably should have emphasized that the key in all of that is the so-called balanced rig. If you're way over-weighted such that you're having to add a lot of air to your suit, then that's a different thing altogether.

I'm off to BC again in a couple of weeks. I wear a 40 pound weight harness there with a steel 100 (as opposed to 12 pounds at home with twin steel 80s) but that doesn't mean I have "gallons" of air in my suit. The loss of the buoyancy in my suit wouldn't cause me to sink like a rock. The lead is to counteract MY buoyancy, not the buoyancy of the air in my suit (OK, it is a bit). I keep only enough air in my suit to prevent squeeze and to fine tune my buoyancy.

Exactly, you shouldn't use a suit to control buoyancy. Just enough gas to keep from getting squeezed, and to keep air in the undergarments for insulation. An overfilled dry suit is a recipe for a feet first uncontrolled ascent!

Ideally, you should have just enough weight to be neutral with an empty wing and near empty tank(s) in shallow water. During the dive, the wing should just have enough gas in it to compensate for suit compression at depth and the extra weight of gas that you have at the beginning of the dive, and it should be empty at your safety stop.