Negative Weights

[Skippums]

Does anyone know of something I could use to make myself more buoyant when I have my scuba equipment on? When wearing a 7mm wetsuit, a 5mm hood, 5 mm gloves, and a steel LP80 scuba tank in fresh water, I am very much over weighted (with no weights). I am looking for something that won't compress (ie, doesn't change buoyancy with depth), and can give me two pounds of extra lift on either side of the tank to prevent me from putting so much air into my BCD. Does anyone know of such a product or material? Thanks,

-Jeff

 

[RonFrank]

Your lungs!

If you need no weight with that much exposure protection on, than you are in some kind of serious shape! I've never heard of such a thing. Dead people float... always, so we are buoyant.

However, you answered your own question. Why do you care if you need to put air in your BC to stay neutral? Just don't jump in the water without checking all your hoses because if what you say is true, you are going to sink quickly.

I assume you are a newer diver. You will discover that your lungs are powerful buoyancy devices, just NEVER hold your breath.

A redundant buoyancy device is not a bad idea so IOW's a drysuit. Unfortunately, those are not all that comfortable if you are not diving in cold conditions.

 

[ptyx]

I've heard - but it might be an urban legend - about old style divers (heavy steel doubles, minimal exposure protection, and no BC) using cork blocks to stay neutral at depth.

In your case, switching to a more buoyant tank is probably the easiest way to get positive.

 

[Skippums]

Actually, my problem is two-fold... my first problem is that I have to change depth pretty often in the quarries here in Ohio (which are shallow to begin with), so continuously changing the amount of air in my BCD is really annoying, and uses a lot of air. I don't have such a problem with an AL80 tank, because I can leave my BCD nearly empty and, as you noted, control my depth with my lungs.

The second problem is actually due to torque that occurs when I use the steel tank. With aluminum, I can add some weights to ensure that my weight is symmetrical along my longitudinal axis, which allows me to dive comfortably in any position. However, once I don the steel tank, I am very back-heavy (since I have to remove the weights in the front, and no longer have something positively buoyant on my back). Because of this uneven weight distribution, the slightest twist underwater, and I start to capsize (and yes, it is a little funny to watch). This forces me to compensate with a lot of arm and leg motion to keep my body torso in any position except head-down looking upward (unless I am moving forward... then I am fine. The problem only exists when I stop). Again, at this point I don't have any problem maintaining my depth using my lungs, but I can't figure out how to stop the torque from turning me over.

So in summary, anything I could do to "remove" weight from my back and (potentially) add it to the front would benefit my diving tremendously. The reason I am concerned about this is that I am looking to purchase a higher capacity tank, but don't want the bulk of Aluminum. If I can't figure out how to weight myself properly with steel (which requires, well, weights I think), then I will be forever relegated to diving aluminum . You are correct in assuming I am relatively new to diving, as I have only 48 dives behind me (although I will surely hit 50 this weekend!) Thanks for any advice you can give to help me further with these two problems specific to steel tanks,

-Jeff

 

[Web Monkey]

Does anyone know of something I could use to make myself more buoyant when I have my scuba equipment on? When wearing a 7mm wetsuit, a 5mm hood, 5 mm gloves, and a steel LP80 scuba tank in fresh water, I am very much over weighted (with no weights). I am looking for something that won't compress (ie, doesn't change buoyancy with depth), and can give me two pounds of extra lift on either side of the tank to prevent me from putting so much air into my BCD. Does anyone know of such a product or material?

Sure. Swap the steel tank for an aluminum, for starters. That will gain you about +6 Lbs.

Terry

 

[ffhamm]

Take the rocks out of your pockets.


Jeff

 

[Bubbletrubble]

@Skippums: Even if you are properly weighted, at the surface at the beginning of your dive, you should be negatively buoyant by the weight of your gas. With a LP80, you should be about -6 lbs. buoyant at the beginning of your dive. It should be very easy for you to initiate a descent with a full exhale.
My question to you is: Can you hold a safety stop with no air in your BCD with a near empty (500 psi) tank? (If so, then you are properly weighted.)
You didn't mention what kind of a BCD you're using. Any chance that you have a heavyweight backplate? Just curious.
If you're using a conventional BCD (inherently +2 to +4 lbs. buoyant) and are properly weighted, then you might consider attaching some incompressible foam that photographers use to make their camera rigs more positively buoyant. (Just kidding on this point.)
You could always switch over to an AL80 tank.

[Edited later: I see that others agree with the switch-to-an-aluminum-tank recommendation. I type too slow!]

 

[Web Monkey]

So in summary, anything I could do to "remove" weight from my back and (potentially) add it to the front would benefit my diving tremendously. The reason I am concerned about this is that I am looking to purchase a higher capacity tank, but don't want the bulk of Aluminum.

No matter what you do, bigger tanks are going to be more negative, since they contain more air, which has mass. Steel tanks are typically more negative, although not always. You can check out various tank specs here:

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

You could always switch to a drysuit. You'll be nice and warm and dry and won't be negative anymore.

Terry

 

[Damselfish]

I'd consider a more buoyant tank. Steel tanks are popular partly because they're more negative, but that's a drawback when you don't need it. You could probably sell the steel tanks, buy aluminum, and turn a profit.

I type too slow too...

 

[Skippums]

I am using the Seaquest Pro QD, size L, with the stock backplate. At the end of my dives, I am still significantly overweighted with the steel tank. I have surfaced with slightly less than 500 psi after the safety stop, and will still readily sink when I exhale if my BCD is empty.

-Jeff