Deco Tank Trim

[Beau640]

Just an update

I moved the top bolt snap up as high as possible/snug against the valve (since I have such a large bolt snap up there) which brought the tank nice and close to the upper D ring without requiring a bungee. Then I moved the hip D ring a little forward instead of back towards the plate, which was a little counter intuitive but looking at pictures of how the tank sits on you and how the harness runs, for non bungee set ups having the waist hip D ring a little forward and not snug against the back plate actually will help trim the tank out.

The results are that the tank is trimmed out much better. So for future reference, if having issues and want to still use a standard DIR rig, get the top bolt snap up as snug/close as you can to the shoulder D ring and move the hip D ring a little forward rather than moving it back against the plate if trying to trim the tank out.

 

[Beau640]

For the visual people, I attached a picture which helped me trim the tank out (this is the old picture with the tank untrimmed).

Purple line: body's axis
Red line: path the harness takes on the body
X1, X2: places where the D ring can be on the hip/where the tank can attach
Green line: where the tank needs to move to to be in line with the body's axis
Blue line: tanks axis

Looking at the picture we want to align the blue and purple lines. Moving the bolt snap from X2 to X1 allowed the snap to connect in the body's axis and the tank to trim out better. Also moving the valve up as close as possible to the shoulder D ring did the same. Seem much simpler to conceptualize when I drew it out.

 

[MegDiver792]

why not hang a 2pd weight on the ass end? Been doing that for years. 1 pd on a 40, 2pd for an AL 80

 

[Beau640]

I thought about doing that but I got it fixed without adding any extra weight to my kit which i felt was better.

 

[lv2dive]

Sheesh oh Pete

Compared to the guy that went in before us with his CCR, a bailout CCR, and an AL 40 of oxygen..

 

[lv2dive]

I agree with you about not adding weights! Btw, Do you still have 1000 psi in it? I imagine it would sit more horizontal with 2500. Just a thought.

I thought about doing that but I got it fixed without adding any extra weight to my kit which i felt was better.

 

[Beau640]

It's like completely horizontal when full now. The problem is it's not uncommon to get an O2 fill around here without a booster so it caps around 2k psi. I wanted to make sure I could keep it horizontal even when around 2k so that it's trim most of the dive.

I'll be diving again this weekend I'll try to remember to take a picture to post how it looks now with the adjustments. It made a big difference.

 

[MegDiver792]

I thought about doing that but I got it fixed without adding any extra weight to my kit which i felt was better.

You arent "adding" any weight, just re-distributing it

 

[DevonDiver]

Some pics of properly trimmed deco cylinders on backmount. The aluminium cylinder don't change trim at any pressure.

Achieved through the simple application of sidemount principles.

 

[Patoux01]

You arent "adding" any weight, just re-distributing it

You're making heavy tanks even heavier, making it more complicated to move them around, don/doff, ... Just the same thing we argue about when people try to trim sidemount Al80s by adding weights on them, it's a poor solution to a lack of skills.