"floaty" feet and lead-head....is it my tank?

[porkpiehat]

I don't remember having this problem when I first started diving, but now I almost invariably find myself struggling at the end of my dives to keep level in the water. I've been diving for five years and usually dive in the standard horizontal position, lower back slightly arched, frog-kicking with knees bent, but my legs end up floating with my head down without a lot of effort as my tank empties.

I dive with a steel 80 or 100, backplate and wing. We lowered the tank plate and raised the wing hoping it would help, and I think it did a little. The only factors I can think are:

-I use a semi-dry suit so I don't have a double-layer of neoprene on my torso
-I'm not the biggest/broadest guy, so my legs aren't very heavy
-I never use aluminum tanks anymore.

After looking at my equipment the guys at my LDS say "I dunno man, it's just you" which isn't super helpful. I think they are sick of hearing about it and they're friends so they are OK being snarky.

Any thoughts would be helpful! I bought a set of ankle weights but I don't wear them because it feels like a band aid approach and I'll get a rash of sh*t. LOL.

Cheers,
Craig

 

[divad]

Switching to an AL BP (with doubles) so I could get the weight lower helped me a lot with the same problem.

 

[tbone1004]

what fins, what plate, what wing?
Need to know all of those first. How is your plate oriented in relation to your body? I.e. where is the waist strap when it comes straight forward.

need that information first.

 

[redacted]

The fact that this only bothers you at the end of a dive suggests that is is a fairly small weight shift that is required. Ankle weights are a kludge but something as simple as heavier fins may solve your problem.

 

[Dive Right In Scuba 2]

I'll echo what tbone said. also, what awap stated....since it's at the end of your dive the only hard variable that would exist is the weight of the air consumed in the tank which also leads me to believe that its a small difference.

 

[Michael Guerrero]

I use a tail weight in my LP85s to keep me in trim. You could also strap a weight to the bottom of your tank using a cam band to keep your lower half down.

If you only slowly come out of trim you might only need a pound or two down toward the bottom of the tank.

 

[KeithG]

end of dive... i claim that points to tank buoyancy effects. maybe... how much gas left in your tank?

I have seen multiple divers "swimming down" near the end of the dive due to the buoyancy of the nearly empty tank pulling them up to the surface.

These divers were (mostly) able to maintain okay horizontal trim until they drained their tank. They then assumed a heads down position as they tried to kick themselves deeper.

Just a thought. This may not apply to your problem.

 

[NAM001]

By the op i would think that as the dive ends and the tank empties he should become head light and not head heavy.

 

[tbone1004]

lowering the tanks actually won't really help on this because as the butts get floaty and their CoG is shifted lower it makes the moment larger so you are actually more prone to pivoting, moving the wing up does help, but we do need to get the rest of the gear story before we can help you.

 

[The Chairman]

That's true on an aluminum tank, but not so much on a steel. To get your head up on a steel, slide the tank down. Even when empty, the entire steel tank is negative so you are simply shifting the load on a fulcrum. To get your head up on an AL, slide the tank up. On an AL, the butt is buoyant and pulls your backside up with it. By moving it up, you are reducing the lever arm affect of the buoyant butt (moment of inertia) by shifting the AL tank forward.

One of the ways I get my student's feet up while in the Scuba position is to push their AL tank all the way down. We work from that position to get them horizontal.