Sling AL40/ weight offset?

[Gravybird]

I currently dive a Bp/w setup with single lp95's. I am going to start slinging an AL40, and just wondering how much weight to ditch on the side where the full AL40 (3,000psi) will be. I currently use 6 pounds per side when I have all my undergarments on under my drusuit. Thank you

 

[tkdgodess]

You want enough weight to keep you at a safety stop with both tanks near-empty. I wouldn't drop weight first, I would drain my tanks with my current weight and see if I can hold my safety stop. If I can then then I would evaluate dropping lead. I need all my lead with all my tanks empty. Plan for worst case scenerio IMO.

 

[spectrum]

Do you wish to preserve the option of handing the pony off to another diver? That would preclude dropping any lead.

 

[fdog]

I do not bias my weight (removing weight from one side as you describe). My lead is evenly distributed, even when carrying 3 or 4 stages/deco cylinders.

Also, I don't carry stages on both sides. They're all either on the left, or a combination of on the left/leashed between the legs, as you can see here:

For this, I don't remove any weight; I actually add weight. The more bottles, the more weight. For a typical 3-bottle dive like the above photo (a trip to Twin Peaks at Point Lobos) I'll add about 6 lbs. (evenly distributed, of course)

When full, these bottles are negative because of gas weight. This is commonly offset by differential of air in the wing. We'll put more air in the left side to counteract the additional weight on that side.

As the bottles empty, they become positive; this is why the additional weight. In this case, we will bias the air in the wing to the right, making the left side "heavy" which compensates for the floaty bottles.

Keeping trim by skillful distribution of air in the wing does not just apply to feet heavy/feet light, it also applies to controlling roll.


All the best, James

 

[Gravybird]

Ok thank you. Very good info. Ya my main concern was rolling. But I see how I wouldn't be able to hand it off if necessary. I'm not at the point for staging yet. I'm just getting used to redundancy, which is needed for the ice diving I plan on doing this winter. For now I'll try with out dropping any weight.

 

[decompression]

As mentioned above, the Al40 will actually require weight added due to its positive characteristics when empty. Do a balanced rig calculation of your gear ( subtract all the positive from the negative and ensure you are at least a few lbs neg), this will ensure you are neutral all the way to the end of the dive. Cheers!

 

[ianr33]

Does an Al40 really get positive with a reg on it? An 80stage will float once below about 500psi, but I don't believe a 40 ever will.

To the OP: Don't change your weighting at all. You won't even notice a 40.

 

[decompression]

Does an Al40 really get positive with a reg on it? An 80stage will float once below about 500psi, but I don't believe a 40 ever will.

To the OP: Don't change your weighting at all. You won't even notice a 40.

If I may, do not use the AL40 as a negative weight, so in your op you ask how much weight should you ditch.As above, you will hardly notice a difference, so don't lose any. My sidemount 80s do like to float, I've never drained my 40 but it is positive when low psi.

 

[ianr33]

When you say a 40 is positive do you mean the tail floats up ,or the entire tank and reg will float to the surface? A near empty 80 will float on the surface even with a reg on it. I believe an empty 40 will sink (but if I'm wrong let me know! )

 

[PfcAJ]

Guys... its an al40.

A pound left or right at that point doesn't matter. Eating a bean burrito before the dive will make more of a difference than a single...aluminum...40...

Fwiw, empty luxfer al40s (with a reg) will float a little.