Trim issues - Rolling over bp/w + heavy tank

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

Depending on the type of STA, if it looks like a piece of channel steel, that will set the tank farther away from your body then you are probably used to. And that will give you that rolly feeling.

Even if it is a low profile STA, that tank will still be a bit higher than you may be used to, just based on the design of the back plate.

Dont forget, the back plate was specifically designed for doubles, and a very low profile, not for singles.

A stainless steel back plate will sometimes cure that because it counters the weight of the tank.
 
As a point of discussion, IF you still have air in your wing at reserve tank pressure, you might be able to ditch the tank adapter. This moves the weight closer to your central axis yielding a reduced tendency to roll. There are soft (low profile) stabilizers available, and some people find their tank stable just with the pressure of the bands against the backplate alone. This does require your backplate have slots for the bands, of course, but most do these days.

ETA: if you ditch the STA but are then underweighted at reserve pressure, putting the needed weight in trim pockets on your belt will further reduce the tendency to roll.
 
Hi @andrethediver

Others have also asked, are you rolling side to side or is the BP&W with cylinder rolling/moving on your body?

I had the former problem when diving with an Aqua Lung Outlaw. Aqualung Outlaw The releasable weights for this BC are located far back and vertical, essentially next to the cylinder. I was fine with a 3 mm wetsuit and 8 lbs of weight. I started feeling rolly with my 5 mm wetsuit and 14 lbs. With my 7 mm wetsuit and 20 lbs, I felt that I was always fighting a roll to one side or the other, whichever might be a little down. The problem was even worse when I shifted some of the weight to tank band pockets, placing the weight even farther back. All these dives were with an AL80. I dive all three wetsuits every year. This problem was so annoying, I quit diving the Outlaw.

I have been diving a Scubapro Knighthawk for 15 years and have never had this problem, with the same weighting. Perhaps this is because the weight pockets are horizontal, on the side, more forward, similar to a weight belt distribution. I often put a little weight in the trim pockets, no problem. Did you ever have this problem when you were diving your Knighthawk?

If you are actually rolling from side to side, try what @Rukkian suggested and add a little forward weight. If you don't want to be over weighted, try it with some exposure protection and balance that with some forward weight. You could try diving an AL80 with a little forward weight, the AL 80 is something like 4 lbs more buoyant than an AL100

I look forward to follow up.
 
With an aluminum tank, aluminum plate and no lead, you don't have the option of moving much ballast around. I think that if the steel sta is at all heavy, you might benefit by replacing it with something lighter and then moving the weight differential to your belly on a belt or weightbelt or pocket....placing weight below you is going to act like a keel and improve stability simply due to physics - or just get used to it.

If you were diving a heavy steel tank, the situation would be worse, you should be able to make it work with an aluminum tank.
 
Are you saying the kit rolls off your back, or you are being turtled? If you are just getting rolled over, you may need to add a bit of weight (just a lb or 2) in front and add a bit of air to the wing. I have a ss bp and al80, so a bit different. Having a small amount of air in the wing helps to keep you in trim.
With 15l tank i have to add quite a bit if air into wing and adjust as i go. Ultimately i feel overweighted by the tank already so i feel like adding weight may not work.
 
i started diving a bp/w as well. tried using the sta. only used it a couple of times. feels much better without it.
 
I am with Boulderjohn. All your weight is behind you. You are going to roll. There are scuba ninjas who are going to give great advice about moving weights to adjust trim. Unless it interferes with normal swimming, you will stop thinking about it and never notice it again.
It does sort if interfere as i fin to move forward and fight to stay in trim.
 
A 15 litre tank's somewhat fatter than a 12 litre tank. Would mean the centre of gravity's a little further out from your centre of buoyancy, so would be more "tippy".

Assume the wing's free to roll around and that the gas is distributed to both sides (years ago I hated a horseshoe because the gas tends to sit in one side).
 
https://www.shearwater.com/products/teric/

Back
Top Bottom