Reg Braithwaite
Contributor
With havy doubles you end up not controlling nouyancy with the drysuit. YOu'd hve to add too much air. You end up managing bouyancy with both wing and suit, essentially putting enough ait in the suit to just avoid the squeeze.
Which raises the issues of the utility of this concept when diving dry. There are plenty of rigs out there you can't make bouyant with a drysuit. Twin steel 120s with two slung steel 40s (with all the stuff that goes with that) is not going to be swum up no matter you what do with the drysuit.
Ok, let me try to explain my understanding and please tell me if I am completely confused. It could be that my 30/30 Bolivian/Haitian mix hasn't kicked in yet this morning (That's coffee, folks, hold the jokes).
At the end of my dive, doing a 10' stop, I should be neutral with nearly empty tanks and no air in my wing or suit. Therefore, when I first enter the water and do a bubble check at 10', , I need enough air in my wing/suit to compensate for the weight of the air in all my (full) tanks. If my rig is balanced, that's all the lift I need.
So given a balanced rig, the question is whether a dry suit has enough lift to compensate for the weight of all that air. I would expect that much air to weigh 25 pounds, which is a lot of lift to expect from a dry suit.
If that was all that mattered, we would dive 30 pound wings. Which leads me to infer that a set of twin 120s and two slung 40s is not balanced, meaning that with all tanks empty you cannot hover at 10' with an empty wing and suit, but you must have some air in the wing at all times during the dive.
I started this thing wondering about fixed floatation. The question of stages/deco bottles complicates things, because it seems dangerous to me to assume you will not drop a bottle. So I think that the best you could do with fixed floatation doo-hickies would be to balance the back gas cylinders. I conjecture, you could arrange things such that the twin 120s are balanced, and if you hover at 10' with empty cylinders the only air needed would be to compensate for the weight of the slung 40s less their buoyancy.