Proper weighting with a drysuit.

[MikeS]

My drysuit is on order and in anticipation; I’m attempting to figure out the theoretical differences in proper weighting and trim. I’ll start with weighting. When weighting is properly adjusted with a wet suit, you are neutrally buoyant at the surface with a near empty tank. But the dynamics of dry buoyancy are controlled not only be depth but by the amount of air that you put in. So I’m guessing that with a drysuit you want to be neutrally buoyant at the surface with a near empty tank and enough air in the suit to eliminate squeeze. Is this correct?

Any help is appreciated,
Mike

 

[MikeFerrara]

MikeS once bubbled...
My drysuit is on order and in anticipation; I’m attempting to figure out the theoretical differences in proper weighting and trim. I’ll start with weighting. When weighting is properly adjusted with a wet suit, you are neutrally buoyant at the surface with a near empty tank. But the dynamics of dry buoyancy are controlled not only be depth but by the amount of air that you put in. So I’m guessing that with a drysuit you want to be neutrally buoyant at the surface with a near empty tank and enough air in the suit to eliminate squeeze. Is this correct?

Any help is appreciated,
Mike

That's about it. And if you keep the volume in the suit close to the same your buoyancy and trim don't change with depth like it does with a wet suit. The less air in the suit the better as long as your not too squeezes. The better the underwear the less air needed in the suit for warmth.

 

[MechDiver]

What you said, but I prefer to do the check at 10 ft after a normal dive. I want to still be negative enough to remain at 10 ft, tanks down, and normal configuration. I also prefer to do this after a dive because I always have a little more air/argon in the suit after diving, even with purging while ascending. Air trapping, whatever, its somewhat more than if I'm on the surface and descend to 10 ft.

MD

 

[MikeS]

Thanks for the replies and now on to:

Part Two, calculating the required bladder lift. When diving wet, I have been operating under the premise that the bladder lift should exceed the swing weight of the tank, the swing in buoyancy of the wet suit, plus the negative buoyancy of the pony. The case requiring the most lift is at depth (most compression) at the start of the dive (full tank).

With a drysuit, I’m guessing it should exceed the swing weight of the tank, the swing in buoyancy of the dry suit, plus the negative buoyancy of the pony. The swing in buoyancy of the wetsuit would be the difference between the drysuit with enough air to eliminated squeeze versus a fully flooded drysuit. The case requiring the most lift is a flooded suit at the start of the dive (full tank) and is independent of depth. Is this correct, and if so is there a good method for estimating the buoyancy swing of the drysuit?

 

[WJL]

MikeS once bubbled...
is there a good method for estimating the buoyancy swing of the drysuit?

If the drysuit fills up with water, it will be neutrally bouyant. It's the same water, whether it's inside the suit or outside the suit. When the suit fills up with water, you lose whatever positive bouyancy was residing in the air/gas that used to be inside, decreasing your positive bouyancy down to zero. Just how positive a non-flooded suit is depends on what's inside it - how much gas in the underwear/clothing and "air space" you introduce to avoid the squeeze.

 

[MikeS]

WJL once bubbled...


If the drysuit fills up with water, it will be neutrally bouyant. It's the same water, whether it's inside the suit or outside the suit. When the suit fills up with water, you lose whatever positive bouyancy was residing in the air/gas that used to be inside, decreasing your positive bouyancy down to zero. Just how positive a non-flooded suit is depends on what's inside it - how much gas in the underwear/clothing and "air space" you introduce to avoid the squeeze.

Bill,

Makes sense, Is there any means other than flooding the drysuit to measure that buoyancy, or if not is there a practical means to estimate it?

Mike

 

[detroit diver]

It's really trial and error based on what you wear underneath it. My suggestion is to get into a pool and bring a bunch of weights with you. Add or subtract as needed. Try to do this near the bottom-9 or 10 feet is good-with a nearly empty tank.

Remember to add weight for seawater.

 

[MikeS]

detroit diver once bubbled...
It's really trial and error based on what you wear underneath it. My suggestion is to get into a pool and bring a bunch of weights with you. Add or subtract as needed. Try to do this near the bottom-9 or 10 feet is good-with a nearly empty tank.

Remember to add weight for seawater.

Maybe I’m missing something here, are you proposing that I try to determine the swing in buoyancy from dry to fully flooded by trial and error? I guess that would mean getting neutral, flooding the suit and seeing how much weight you could drop to get back to neutral. Seems a bit extreme and a lot uncofortable.

Mike

 

[detroit diver]

MikeS once bubbled...


Maybe I’m missing something here, are you proposing that I try to determine the swing in buoyancy from dry to fully flooded by trial and error? I guess that would mean getting neutral, flooding the suit and seeing how much weight you could drop to get back to neutral. Seems a bit extreme and a lot uncofortable.

Mike

No. That's not at all what I was suggesting. If you flood a suit, it will be uncomfortable, but neutral. I was just suggesting that you do your weighting in the pool with the drysuit on and the undergarments that you plan on wearing. Purge the suit as best as you can, and then do your weighting. If you are neutral at 10 feet or so, and your drysuit floods, you will be slightly negative. But you should be able to swim up that amount of negative weight.

 

[bwerb]

getting dialed into my drysuit has been complicated by the fact that it is really easy to go out and get perfect weighting for a near empty tank at 10 to 15 feet, no air in suit, no air in BC in a "practice" situation but...sometimes you get bubbles of air "trapped" in your suit during a dive which can really screw you up as you find yourself suddenly a little more bouyant than you thought as you go through some really neat contortions to move the bubble to the left arm dump.

I don't know if anyone else will agree, but I like to be a pound or so heavier than my "tryout" perfect bouyancy weight to ensure I don't find myself too bouyant with not enough overhead water to compensate quickly enough. I had this happen once when I got a bubble caught in my boots, I hit the surface feet first, rolled over and saw one of my dive buddy's wives filming our ascent...great, just what I need to see my totally screwed-up ascent saved for prosperity.

And, if you want to have some real fun independent of just diving, inflate your suit as big as it gets and go out into the water. It's hilarious to float a foot off the surface looking like the Michilan man...ok, maybe I don't get out enough...anyhow it makes for really funny looks from OW students diving for the first time.ut: