Steel vs Alum. in relation to trim

[EdC]

I have a question about the differences between steel and aluminum tanks as it relates to trim. Specifically how it relates to a back inflate BCD at the surface. I have a SP Knighthawk and I am completely happy with it, especially in comparison to the jacket style I was wearing the first couple of dives. The one nit pick I have is that it wants to flip me face down on the surface, which I know is a common complaint.

So far I have used aluminum for all my training dives as well as a trip to Bonaire. I have been splitting the weight I am carrying between the trim pockets and the integrated weight pockets; its a little better but not a complete fix. My question is would a steel tank by virtue of its negative buoyancy help this issue by moving weight to the back?

 

[kelemvor]

The problem is most likely that you have too much air in the bladder. Get with an instructor and do a buoyancy class. I'm guessing you'll be able to reduce a ton of lead from your configuration. When you reduce the lead, you need less air in that bladder to stay at the surface. You also need less when you're underwater, and (you'll see what I mean if you give it a shot) this makes things vastly easier and therefore more fun.

Also, keep your legs out in front of you when you're floating if you can, so that you're kind of resting on your back slightly. It becomes very easy and natural to float in back inflate once you get used to it.

It may also be that you're wanting to stay too far above the water line.

Jackets do have an advantage on the surface in that they have buoyancy 360 degrees. That's the only place where it's an advantage. I prefer to configure my gear so my time under the surface will be the most enjoyable.

Back to your original question about steel vs aluminum. It really depends on what specific tank you go with. As you know, an aluminum 80 is positively buoyant when it nears empty (it floats). Some steel tanks are negatively buoyant (sink) even when empty. I use low pressure steel 108cuft tanks most of the time. They don't float. In a wetsuit, it means I don't have to use any lead at all! There are many steel tanks that get floaty when empty.

While I do love my steel tanks, and they can be a benefit weight wise... you can solve your buoyancy/trim issues without spending tons of cash buying steel tanks if you want to.

 

[DiverDownD3]

^ What he said.

 

[tbone1004]

you should not notice a significant difference. Most issues relate to operator error when at the surface, largely due to lack of a crotch strap. Without one, you have to keep the waist strap incredibly tight to keep it from riding up and when it rides up, it flips you forward. If you put a crotch strap on it, you are able to "sit" on the bc and it keeps the lift where you want it.

When at the surface, try to imagine you are sitting in a seat on an airplane with the seat back reclined. You want your legs mostly bent and pulled up and you want to lean back a little bit. This will put the lift in a better spot and allow you to hang out at the surface without fighting it.

should look something like this. Obviously in sidemount, but all of the lift is on your back and the tanks are farther forward than they would be in backmount, so same principal applies.

 

[The Chairman]

The one nit pick I have is that it wants to flip me face down on the surface, which I know is a common complaint.

The question!

The problem is most likely that you have too much air in the bladder.

The most likely answer.

I love big steel tanks: I cannot lie. They are a bit harder to balance while prone, but the learning curve is easy. On the surface, they love to become the keel, so staying on your back is far, far easier. I rarely have to add lead which is another benefit for me.

 

[Tug]

I'll second or third everything kelemvor said, but wanted to focus on this:

The problem is most likely that you have too much air in the bladder. Get with an instructor and do a buoyancy class. I'm guessing you'll be able to reduce a ton of lead from your configuration. When you reduce the lead, you need less air in that bladder to stay at the surface. You also need less when you're underwater, and (you'll see what I mean if you give it a shot) this makes things vastly easier and therefore more fun.

Depending on where you are in CT, I'd check out the buoyancy class that Scuba Shack in Rocky Hill runs. The shop owner Ed is a GUE Instructor and I've heard great things about this class.

Core Principles - Scuba Shack - Connecticut

--EDIT--

it appears as if Ed and Gina recently sold the store to other long term instructors and store staff

 

[EdC]

Thanks all for the tips, I had put a bouyancy class on the to-do list now that im getting comfortable with the basics.