Doubles w/Stage on a 30# wing

I was talking with a technical instructor for ANDI/TDI earlier today and he mentioned having used doubles (AL 80s) with an Al 80 stage bottle on a 35 lb wing. The more I thought about it, I thought, why not? A full Al 80 is negative by what, about 2 lbs? Three of them is 6 and if you're using a SS plate, that's another 5-6 lbs. Then 14 lbs of lead to offset the bouyancy those three tanks would have when empty and you're at 26 lbs.

Am I missing something here? Sure, not every 30 lb wing is really 30 lbs you need to expect +/- 1-2 lbs. but the total is still under the fudge value. Is there some reason I'm missing why this wouldn't work, especially if some of that lead was ditchable?

Why this wouldn't work? Shape of the wing? Every doubles wing I've seen has at least "40 lbs" capacity.

A couple of things spring to mind (since I've done this).

Depending on manufacturer, the AL80s are more negative than 2 pounds, closer to 3 -5. With the manifold, bands, regs, and SS plate, factor in another 8-9 pounds. Add lead to keep the system neutral after buoyancy swing, and you're now sitting at 18-20# negative before we factor in gear or accessories.

The 30 pound wing is going to be very narrow. The pull dump will be blocked by the left tank. Been there, done that. Since the wing is narrow the lift will all be between you and the tanks, instead of wrapping the tanks a bit where they can provide some roll stability, so you will be fighting the tanks the entire dive. Especially as you begin to empty the wing and the tanks press down on the edges of the wing.

If you want to dive doubles, even AL80s, I'd suggest you get a doubles wing if for nothing else but the lift. I am using an Oxy 40# wing at the moment for this, and am looking at some other options as well. Not because I don't like the Oxycheq, but because it's borrowed.

Best of luck.

Shape comes to mind for me as well.

In terms of capacity and lift, I've been so surprised at how versatile my 40 lb doubles wing is.

Diving dry, I dove twin 130s with two stages and a canister light. No problems w/ buoyancy at the surface with suit empty.

remarkable...

The shape of the wing is what matters. If it's not a wing made for dual cylinders, you will not be able to inflate it fully, decreasing your lift an even greater amount.

What wing is it?

It will work. (Or at least it will with an Oxycheq 30 wing) Might be a problem with a thick wetsuit though.

Not optimal,a proper doubles wing is to be preferred but in a pinch, if you bring the wrong wing on a boat trip it sure beats not diving.

Suspect it is not DIR though.........................

It depends a lot on your total system. As indicated above, the wing can get pinched between the tanks and backplate and not be able to fully inflate. Whether this is a problem for you will depned on your particular wing, plate, tanks and bands.

I'll also second the concern that you are on the edge already with tanks, bands, regulators and stage bottle and have little if any margin to compensate for wetsuit compression at depth.

The words "doubles", "stage bottle", and "ditching lead" used in the same paragraph also make me extremely nervous. Ditching lead should always be a last resort as it will in most circumstances result in an ascent all the way to the surface - something that is just not an option on a deco dive. This would certainly be the case if you dropped lead on the bottom to offset wetsuit compression.

Personally, I don't think it should even be a question of whether you CAN do it, but rather the question should be WHY do want to do it, since you are using the wrong tool for the job which is never a very good idea.

And then there are always those other factors like:

Extra weight of.....

1. Valve
2. 1st stage
3. Accessories
a) knife
b) light
c) camera
d) emergency equipment
e) redundant air source (spare air?)
f) Camera equipment
g) surface buoy line and reel
h) Speargun or pole spear
i) goody bag (of fish or our favorite..lobsters!!)

4. Fresh or salt water?

This all might sound really obvious but it all adds up to negative weight. It all adds up quick.

I agree...dumping weight should not be the option to make the system work

Could it work in the right circumstance? Maybe, but it could also compromise you in the wrong one. You'd need to test it out in a safe situation first.

I tried this rig out on a couple recreational dives, MOD 132fsw, just to see how much floataion I really needed.

Full twin HP100s, 2mm shorty, zero weights, 24 lbs. lift bladder, 52" double freeshaft speargun and hoop stringer.

On the surface at the start of the first dive it was barely enough, I kept a high lung volume. During the dives it was fine, no problems, even at max depth. Surface floatation got better as the gas was consumed.

I never used it again, because it was too close to the edge. I use my Ranger LTD cell, with 44 lbs lift.

Chad

fwiw - OMS makes a 35# doubles wing, and AGIR makes one that is 39#... so smaller doubles wings are available...