Frustrated with Dry Suit Buoyancy - HELP!

[scubascobey]

I'm looking for input and advice from you veteran divers. I'm in the process of getting my Advanced OW cert and for the Dry Suit Class I am required to hover for 5 minutes using only my Dry Suit for flotation and using my lungs to hover (so I can't adjust air or move my arms/feet).

Stats: I weigh 116 lbs, lean body mass, 4'5", steel tank (I think a 110), BARE dry suit with a heavy undergarment. My most recent dive I wore 27.5 lbs of weight (8 on belt positioned on front, 18 in BC and 1.5 on my tank). I'm diving in 54 degree salt water.

My problem: My feet/legs are heavy so they pull me down, and my tank is rolling me onto my back. Then the tank seems to pull me to the bottom as I'm unable to stay up with just inhaling a huge breath. So then I have to start the timed hover over again.

I try holding my arms and legs way out to provide balance from my gloves and fins, but my upper body floats straight up...well, the air bubble in my dry suit gets into my back and arms and then my fins hit the bottom. Again, causing me to start over.

I think I might be overweighted or the weights just not distributed correctly. I'm going to try this: 25 lbs (2.5 less weight), distributed as 8 on belt, 14 in BC and 3.0 on my tank. A veteran diver friend thinks 25 is still too much weight for me.

Any ideas?

 

[TSandM]

I'd say start with doing a formal weight check. You can either do that at the beginning of a dive or at the end. If at the beginning, what you want to do is find a weight where, with BC and drysuit as empty as you can get them, you float at eye level with a normal breath, and can sink when you exhale. Then add the weight of the gas you intend to use from your tank, which in your case will be in the neighborhood of 7 or 8 pounds. Or you can do the same thing at the end of a dive, with the tank blown down to whatever your emergency reserve is. (A lot of people do this at 500 psi; I prefer to do it at 3, because getting a little light at the end of a dive where something's gone wrong and I've used my tank to minimum is not something that appeals to me.)

If you are going to use the drysuit alone for buoyancy, getting your weight very right is extremely important, because the air bubble in the dry suit has a lot of freedom of motion, and a big bubble renders you pretty unstable. (Google "dynamic instability" for a discussion of this.)

I have also noticed that, once the tank is below me, I am more negative than I was right-side-up. The best explanation I've gotten for this is that moving the air bubble in my wing below my body compresses it just enough to make me no longer neutral -- But that doesn't work if there's no air in the BC, which makes me wonder if you've still got a little air trapped there.

Anyway, for fixing your trim, once you've got your weighting down to the minimum necessary, try this: Get neutral, get into a good trim position (head up, back slightly arched, knees slightly bent) and get horizontal. You'll need your buddy to verify your position, unless you have a mirror. Then stop moving, and see what happens. If you tilt, first try really correcting your posture (eg. if you're head down, really arch your upper back and push your head into your regulator; if you're going feet down, make sure your hips aren't flexed and they're the lowest part of your body), and if that doesn't correct things, you most likely need to move some weight. This process is rendered far more difficult by having all the gas in the drysuit, but if you have your weight trimmed down, you should still be able to do it.

Who's teaching a class where you have to hover for five minutes without moving? I think that's a very cool thing to have students do, although doing it with the drysuit is making your life more difficult.

 

[philmayer]

What agency are you getting your cert through? PADI only requires 1 minute.

I couldn't hover for 5 minutes without moving my hands or feet if I was only wearing a pair of swim trunks, much less a dry suit!

 

[TSandM]

I have a feeling my fins would have to twitch a few times during five minutes, too. That's a LONG time!

 

[Jim Baldwin]

I'm looking for input and advice from you veteran divers. I'm in the process of getting my Advanced OW cert and for the Dry Suit Class I am required to hover for 5 minutes using only my Dry Suit for flotation and using my lungs to hover (so I can't adjust air or move my arms/feet).

Stats: I weigh 116 lbs, lean body mass, 4'5", steel tank (I think a 110), BARE dry suit with a heavy undergarment. My most recent dive I wore 27.5 lbs of weight (8 on belt positioned on front, 18 in BC and 1.5 on my tank). I'm diving in 54 degree salt water.

My problem: My feet/legs are heavy so they pull me down, and my tank is rolling me onto my back. Then the tank seems to pull me to the bottom as I'm unable to stay up with just inhaling a huge breath. So then I have to start the timed hover over again.

I try holding my arms and legs way out to provide balance from my gloves and fins, but my upper body floats straight up...well, the air bubble in my dry suit gets into my back and arms and then my fins hit the bottom. Again, causing me to start over.

I think I might be overweighted or the weights just not distributed correctly. I'm going to try this: 25 lbs (2.5 less weight), distributed as 8 on belt, 14 in BC and 3.0 on my tank. A veteran diver friend thinks 25 is still too much weight for me.

Any ideas?

I agree with Lynn, do a good weight check. Looks like you might be a bit on the heavy side. As you get more comfortable with your suit you will find you need less weight. I dive a SS b/p which weigh about six pounds and eight pounds on my weight belt. I use a steel HP 100 or 120 and sink very slowly.

My drysuit is a 7.5mm O'Neil. At 6' 175 I don't displace a lot of water and am very relaxed. The only undergarments I wear are normally a t-shirt and a pair of warmup paints as long as I've diving in temps above 50 degrees.

Do get in a good horizontial position, arch your back slightly and be sure and bend your knees and get your feet up. Try putting your hands together and pretent you're flying or skydiving. Remember if you look up too hard it will have a tendency to force your legs down. Move your arms in or out slightly as they will help change your center of gravity.

Are you fins positive or negative? I use the black Scuba Pro Twin Jets because they are negative and they help to counteract the positive buoyancy of my neoprene suit. When I dive wet with a full 3mm suit I much prefer the blue or yellow versions as they float and keep my feet from sinking.

 

[Cave Diver]

Proper weighting is likely to be one issue. If you have too much weight, the size of the air bubble in your drysuit will be larger. The larger the bubble, the more likely it is to shift and throw your "balance" off.

You should be able to have just enough air in the drysuit to prevent it from squeezing you. With proper weighting, this should have you close to neutral and you can fine tune your bouyancy with your wing or breathing.

Re: Heavy feet. Try moving your feet closer to your tank. Horizontal position, legs bent at 90 angle at the knees. Bending your knees to bring your fins closer to tank should put you in slightly heads down position, extending legs further out should go slightly head up.

If you can't change your position through moving your legs, you may need to redistribute where your weight is placed or the balance of your rig.

 

[Blackwood]

I have a feeling my fins would have to twitch a few times during five minutes, too. That's a LONG time!

Better be in a pool. Any current will screw that pooch.

 

[Colliam7]

.I think I might be overweighted or the weights just not distributed correctly. I'm going to try this: 25 lbs (2.5 less weight), distributed as 8 on belt, 14 in BC and 3.0 on my tank. A veteran diver friend thinks 25 is still too much weight for me.

Several knowledgeable folks have recommended a good, procedurally proper, weight check, and that is definitely where you should start. Given your size, the 27.5 lbs sounds like a lot, especially with a steel cylinder. But, that is so hard to judge from afar, and you are talking about salt water. You mention weight in your BC, suggesting a weight-integrated unit like a Zeagle Ranger, most of which are positively buoyant, and may be adding to the weight requirement. The other factor to address is weight distribution. If your height really is 4'5" then any normal sized cylinder (presuming it really is a 100+ cf) will put quite a bit of weight toward your feet, especially a steel cylinder. Is it possible that a smaller, shorter steel cylinder will work for you?

 

[philmayer]

Stats: I weigh 116 lbs, lean body mass, 4'5", steel tank (I think a 110), BARE dry suit with a heavy undergarment. My most recent dive I wore 27.5 lbs of weight (8 on belt positioned on front, 18 in BC and 1.5 on my tank). I'm diving in 54 degree salt water.

I think I might be overweighted or the weights just not distributed correctly. I'm going to try this: 25 lbs (2.5 less weight), distributed as 8 on belt, 14 in BC and 3.0 on my tank. A veteran diver friend thinks 25 is still too much weight for me.

How much weight do you wear with a wetsuit? I wear 8lbs in my shorty in fresh water. In my drysuit 16lbs is overweighted in the same conditions. And I have A LOT more natural bouyancy than you do! I know the thick undergarments are going to add quite a bit of air/bouyancy.

The ideas posted here for a weight check are spot on. Get your weight correct and then you can worry about distribution.

 

[Debraw]

I would definitely look at the tank and try for a shorter steel tank. With your height and low body weight, it sounds like you have to much tank. Is the Bare dry suit a neoprene or a tri-laminate? I also think you may be carrying to much weight, but that is adjusted as you get more experience. I do notice if i am even two pounds over weighted I have a more difficult time with bouyancy. Heck 5 minutes does sound like a long time. I think I may try that the next time I go out to my local watering hole this winter with my dry suit. I dive a neoprene Bare CD4.