Trim weights

[FinnMom]

I too think that experimentation or "homework" is best left for at home and maybe a checkout dive. Don't miss a vacation dive by not being able to get underwater, or have trouble holding a safety stop (esp. if there is an upward surge) after a nice, long dive with an unusually light tank.

 

[decompression]

Most manufacturers quote AL80 positive buoyancy, when empty (i.e. max) at 2.1 to 2.4lbs.

Specification tables are available online for most cylinder manufacturers.

Thanks Andy, it can be hard to find 2.1 or 2.4 lead weights so I usually round up to the ever present 4 pounder.

 

[tursiops]

Three comments on some of the posts above:
1. With only a rash guard, in a pool, it is entirely possible you won't need ANY weights. Most BCDs are nearly neutral, but the tank (if full) and the regulator will weigh a few pounds.
2. If you get your weighting right in a pool, it won't be right in salt water; you'll need more weight.
3. It really doesn't matter what the tank is made of, the important point is that the difference in weight of a full and empty tank is about 0.08 pounds/cuft. So an AL80 -- or a steel 80 -- weighs 6.4 pounds less when empty.

 

[rongoodman]

That's one nice thing about diving with a wing. I can reach back while hanging on a safety stop and feel how much air is left there.

 

[gfaith]

@flyboy08 Here is a thought, during the last couple minutes of your SS hand off a 2lb weight to your
buddy or the DM . Just exhale a little deeper and hand it to someone if you can't hold the SS take the weight back.. If you are able to hold the rest of the SS drop that 2lbs before the next dive. You could take a 2lb weight and tie a bolt snap on and clip to D-ring. No time or dive wasted at all.

 

[DevonDiver]

Thanks Andy, it can be hard to find 2.1 or 2.4 lead weights so I usually round up to the ever present 4 pounder.

Better not to round down to the ever present 2 pounder?

A small fraction of a lb is easily compensated with the lungs. Where's 4lbs is nearly double what's needed.

4lbs is my total weight requirement in an XXL 3mm full wetsuit, using twin AL80s in sidemount....but for most of the dive, no weight is necessary.

 

[flyboy08]

@flyboy08 Here is a thought, during the last couple minutes of your SS hand off a 2lb weight to your
buddy or the DM . Just exhale a little deeper and hand it to someone if you can't hold the SS take the weight back.. If you are able to hold the rest of the SS drop that 2lbs before the next dive. You could take a 2lb weight and tie a bolt snap on and clip to D-ring. No time or dive wasted at all.

Yep, this is my first test.....this will work for buoyancy, but not trim. TY.

 

[stuartv]

Most manufacturers quote AL80 positive buoyancy, when empty (i.e. max) at 2.1 to 2.4lbs.

Specification tables are available online for most cylinder manufacturers.

The specs I have (in a PDF I found on the Internet) list the Luxfer 80 at +4.4 and the Catalina S80 at +4.

Dive Gear Express sells the Luxfer AL80 and they list it as +3.4 when empty.

The Luxfer site itself lists the S080 as +4.2 empty, in salt water.

L6X® aluminium SCUBA cylinders

 

[packrat12]

The specs I have (in a PDF I found on the Internet) list the Luxfer 80 at +4.4 and the Catalina S80 at +4.

Dive Gear Express sells the Luxfer AL80 and they list it as +3.4 when empty.

The Luxfer site itself lists the S080 as +4.2 empty, in salt water.

L6X® aluminium SCUBA cylinders

They buoyancy is without a valve, typically. Add an additional -1.5 to -2 lbs for the valve.

 

[DevonDiver]

Not sure if those specs are w/valve? You can also factor in the weight of the regulator.

Also, do we need *empty* specs? Buoyancy at minimum gas (w/reserve) is what we calculate for.

Scuba Cylinder Specifications | Metric & Imperial

Why would you need to keep an empty tank that was threatening to pull you up?

In practical terms, assuming a modular valve and average regulator weight, I've always found 2lbs correct per AL80.