View Full Version : drysuit bouyancy questions

07-05-2008, 12:42
I am thinking of buying a drysuit. Right now I get away with a 26lb wing, even with my 7 mil farmer suit. With that 7mil suit, I use 10-11lbs of weight (HP120 and SS backplate). I was reading up on drysuits, and I was under the impression you can use the drysuit for some bouyancy along with your wing. Is this accurate? Are there drawbacks to inflating the suit some. Or is inflating the suit even a option at all? Do you have two inflator hoses on your settup?(one for your wing and one for the drysuit)
I just want to be aware, that if I go dry, I might have to buy a 35-40lb lift wing due to the extra weight I will need to be carrying. It seems to me that if you can inflate the drysuit you could get away with a small wing such as my 26lber. But I may not be aware of issues doing this. I am thinking of getting a Whites Fusion and the Mk2 garments. So I'm wondering how my weight and bouyancy requirments are going to change compared to the 7 mil wetsuit.

07-05-2008, 14:56
I'll try to address all of your questions.

1. There are 2 ways to use the drysuit at depth. Some people use the drysuit as their sole buoyancy device. The reasoning behind this is twofold: (a) it's less complicated to deal with one buoyancy device rather than two and (b) with more air in the suit, the diver will probably stay a little warmer. The other way that people dive a drysuit is that they add just enough air to keep the "squeeze" off but then use the BCD to adjust buoyancy over and beyond that. The reasoning behind this method is that the BCD was designed to be the sole buoyancy device and it has several exhaust valves located in different places making it easier to dump air in various body positions. Good arguments can be made to use the drysuit in either way.

2. The drawback I see to inflating the drysuit over and above keeping the "squeeze" off is that the diver has to manage the bubble. This is where trim/body position can make it easy/difficult to dump air. Keep in mind that you usually only have one exhaust valve which probably doesn't vent so well when the diver is in an inverted position (with feet above head).

3. Yes, in addition to the BCD inflator hose, you will need to install a drysuit inflator hose that attaches to a LP port on your first stage. The other end connects to the drysuit inflation assembly usually located in the middle of your chest. Normal hose routing is under the left arm. The drysuit inflator hose is usually included with the purchase of a drysuit.

4. The wing size should be determined by the larger of the two following requirements: (a) required lift to float your rig without you in it or (b) enough lift to compensate for a total loss of buoyancy of your drysuit. You really need to calculate these two numbers (including size/model of tank, drysuit undergarments, etc.) in order to determine how big a wing you need. For reference, I have a drysuit that has about 24 lbs. of inherent positive buoyancy. My rig is 26 lbs. negatively buoyant. Therefore, a 30 lb. wing is enough for my needs.

5. Weighting requirements are specific to the individual. When I test-dove the Fusion with MK2 undergarments a few months ago, I found that my weighting requirements were similar to what I need with my own drysuit + undergarments (Bare Nex-Gen Pro + T100). I find that with my 7mm wetsuit I require 6 lbs. less lead. With so many unknown variables with your own configuration, it is impossible to know your weighting requirements without doing a proper weight check with the new gear.

Hope this info is helpful.

Charles R
07-05-2008, 16:17
Wow that about sum's it up.:smiley20:

07-05-2008, 21:24
Once you find your trim and your weight for the drysuit, you're a submarine. :D

07-05-2008, 21:55
Do you have two inflator hoses on your settup?(one for your wing and one for the drysuit)

Only if you ever want to have children :smiley36:

07-06-2008, 03:21
Do you have two inflator hoses on your settup?(one for your wing and one for the drysuit)

Only if you ever want to have children :smiley36:

Ya gotta love a reference to "crotch squeeze."

07-06-2008, 08:47
I had that the other day, it's not pleasant and can happen sometimes no matter how careful you are. You can often over inflate and grab the crotch and maneuver the jewels and be good, sometimes you can't.

07-06-2008, 10:45
Avoid using weight pockets on the BP/W harness as it it will increase the amount of buoyancy needed to to float your rig at the surface. Instead wear a weight belt or weight harness. It will be that much less weight your wing will have to float at the surface (without you in it).

I dive a HP steel 100 tank with an H-valve, 2 regs, a 6 lbs SS back plate, pony tank, and 2 lights clipped to the rig. My 30 lbs Venture wing floats it without a problem.

When wearing your rig properly weighted you should be negative equal to the weight of the air in your full tank(s), any additional gear that you may hand off or shed underwater (pony/stage bottle, hand held lights...) and an extra pound or two to help during the safety stop. Factor in an extra 10 pounds of lift for "head weight" (to keep your head above water at the surface) and that should be you minimum wing capacity.

For me that equals 20 lbs of lift needed in fresh water with a 19 cf pony and 2 lights (YMMV). That gives me an extra 10 pounds of lift in case I flood the dry suit and have to use the wing.

BTW- most of the time if I am diving singles I only use the dry suit for buoyancy. I find that when I put enough air in my dry suit to control the squeeze I am neutral. When diving doubles I have 8 more pounds of weight (air in the second tank) to compensate for, so I divide the buoyancy between the dry suit and my wing to reduce the size of the air bubble in the suit. As I use the air in my tanks I reduce the buoyancy in the wing first then if needed the air in the suit.

07-07-2008, 09:02
Thank you all for that. That clears up alot of what I had no clue about.

Here's a question that might help me a little more. Does anyone know the difference between how much lead they carry with same settups, except using their drysuit vs a 7 mil suit? Or something comparable to that. Meaning, about how much weight should I expect to be carrying, going from my 7 mil to a drysuit. I'm just curious as to if I will be adding 5 or 15 lbs of lead, or what?, when I go dry. I know there are many variables, but a few WAGs would give me a idea of what to expect.

07-07-2008, 09:43
For me the answer varies depending on the undergarment. For some there is no extra weight, and with my heaviest undergarment I carry another 10 lbs of lead.