Bouyancy characteristics of double AL80's

[mksmith713]

What are the bouyancy characteristics of diving double AL80's?

I need 16lbs to get down with a single.

Also wondering how much lift I'll need to insure I get back up again.

Too lazy to do the math right now....

 

[Blackwood]

A single 80 swings about 6#, so I'd start by adding that. You'll need a little less given the added weight of the manifold (unless diving independent doubles) and additional first stage (unless diving with a connector bar).

 

[mksmith713]

I'm thinking of adding a manifold connecting the tanks so I only need my primary, octo and pony regs.
Any changes to my weight for adding two tank bands and hardware?

I'm using an 30# wing now but rarely need it other than adding a little air at depth to keep me off the bottom.
Ya think this wing will be OK for doubles?

Trying to avoid buying another wing...

 

[Blackwood]

Yah, I neglected the bands. They weigh probably a couple of pounds.

No, I don't think a singles wing is appropriate for doubles. 30# may be enough, but that's not the only consideration.
1) The wing isn't wide enough for the tanks, and thus its capacity may be severely compromised.
2) How do you attach it?
3) etc.

I suggest getting in touch with Tobin of Deep Sea Supply (cool_hardware52). Even if you don't eventually buy a DSS wing, he's very helpful and will be able to address all of your questions.

 

[UCFKnightDiver]

If using a singles wing with double tanks, you can bend aluminum, and stainless steel backplates, get a doubles wing for doubles

 

[Blackwood]

To be blunt, I think this is one of those do it right or not at all moments. If you are on a budget, wait a while. When you jump off the boat for the first time in doubles with a singles wing that is either too small or can't fully inflate because its bladder is clamped between the cylinders and the backplate, as you desperately try to ditch your gear while sinking towards the bottom, you'll really regret not spending that 200 bucks. You may regret it literally for the rest of your life.

 

[TSandM]

Well, two Al80s are +8 when empty -- the bands and manifold add two or three pounds, and the regulators a bit more, so I suspect the whole kit is close to neutral when empty (maybe slightly positive). If you are using 16 lbs to sink a single Al80, you will probably need 10 to 12 to be properly weighted in doubles. But remember that means you are about 10 lbs negative when you start the dive. Then you have to add the possible loss of buoyancy from suit compressing or flooding. In reality, a 40 lb doubles wing might be slightly larger than you need for double 80's, but I don't think there are many smaller doubles wings made. As already said, you really need a doubles wing, because singles wings don't have a wide enough center panel for the two tanks, which means they'll squish the bladders and reduce/compromise the lift.

 

[Rainer]

Forget reduced lift using a singles wing, as rox notes, you will straight up bend the plate (AL or SS) if you fully inflate it.

I have both AL80s and LP85 doubles. The buoyancy difference between them is handled with an 11# v-weight.

 

[mksmith713]

I added 6# to my AL plate in the channel. I stick 5# each in weight pockets.
Contemplating switching to SS plate but it's a hassle when I travel.
Much easier to haul an AL plate and use the dive ops weights when travelling

 

[Blackwood]

Forget reduced lift using a singles wing, as rox notes, you will straight up bend the plate (AL or SS) if you fully inflate it.

I missed his point. Interesting. Guess that wouldn't feel too good if you were in the rig at the time