Top heavy problem

[pelagic_one]

Hi submariners,

This is a tank question but it concerns weight and trim. I usually dive warm water and use a thin wetsuit top with hood, soft backplate Dive Rite Transpact and AL80 tank. I only need two 2# weights on the belt with 1.5# on tank valve. Good weight and trim.

To extend my diving season, I tried a 2/3 top wetsuit (mid-thigh to neck, long sleeves), no hood, SS backplate, Dive Rite donut wing with Steel 100 tank, 3442 psi present. The wetsuit and mask need 18# lead, the dive pack produces -18# in water, weight balances out, trim good enough.

Problem is, the steel tank always wants to roll me over. It requires full attention to stay upright in flat diving position. All I can figure is if I add 4 or more pounds of weight, to make up for air used by end of dive, at the center of my belt, this will help the roll some.

Any advice about this? Thanks!

 

[MB NZ]

I haven't experienced this myself, but saw it in a female diver when I was guiding. She was very petite and a 12L steel tank was rolling her over as you describe. Possible solutions:

1. Ensure the tank is centralised and stable. Do you use an STA?
2. Ensure harness is snug, but not too tight.
3. Some weight on your belt at your front, balanced left and right. You should be weighted for 50 bar or less anyway. I prefer to be weighted for an empty tank, but not everyone agrees.

 

[pelagic_one]

I did not use an STA.

 

[ChrisMBC]

Is that 18lbs of weight in addition to a steel backplate and a steel tank, for a 2-3mm wetsuit? To me, that sounds like quite a lot - about what I use diving a drysuit with fairly thick undergarments.

To your point about trim, where on your rig is the weight?

 

[MarkA]

I used to dive with a tippy steel cylinder (15l Heiser)

Although it was before backplate and wing, diving in a drysuit and horse collar BC. The improvements were basically what @MB NZ Said.

3. All my lead was either side of the weight belt buckle (2x7lbs). This acted a bit like a keel.
2. The harness was not loose, especially the waist strap. Any slack would allow movement and accentuate the tipping.
1. The cylinder was held to the backpack with steel bands and bolts, allowing no movement between the cylinder and backpack.

This did not fully solve the tippyness but helped. That was solved by changing to 2x10l Fabers.


Does the 18lbs negative bouyancy of the backplate & wing + cylinder + regulator etc, include lead or a full cylinder with its 7-8lbs of air?

 

[happy-diver]

at the center of my belt.

A very good idea

 

[pelagic_one]

I weighed the scuba pack (full steel 100 tank, wing deflated, SS backplate, harness valve, regulators) submerged in water and it had -18 pounds weight. Myself, wetsuit, mask and fins required 18 pounds to sink. So I put on the pack and was neutral submerged. I did not figure the loss of air as the dive would continue. For a 100 ft3 tank, it could be a 6-8 pound loss. So I guess I should have at least 6 pounds of lead on my belt at the front. I'll try that, hoping this keeps the steel tank more on top than making me roll over.

 

[happy-diver]

Unless you want to swim on your back which is good if you want to and can and have a reg that works that way