Advice On Building A Set Of Doubles

[Bob S]

I recenlty purchased a real nice pair of in hydro circa 1978 71.2 c.f. galvanized tanks. I am planning on purchasing a 200 DIN Sea Elite Manifold. My questions is will Piranna's 6.9" SS bands be the right size? Secondly I tested the tanks last weekend and found them >1 pound positve with a K valve and no air. Consequently, I am leaning toward purchasing one of Dive Rites new style REC EP wings (50# lift). Any comment on my wing choice? I do dive both a wet suit and dry suit. Thanks for your replies. I am amazed at everyones knowledge!
Bob S

 

[cool_hardware52]

I recenlty purchased a real nice pair of in hydro circa 1978 71.2 c.f. galvanized tanks. I am planning on purchasing a 200 DIN Sea Elite Manifold. My questions is will Piranna's 6.9" SS bands be the right size? Secondly I tested the tanks last weekend and found them >1 pound positve with a K valve and no air. Consequently, I am leaning toward purchasing one of Dive Rites new style REC EP wings (50# lift). Any comment on my wing choice? I do dive both a wet suit and dry suit. Thanks for your replies. I am amazed at everyones knowledge!
Bob S

If your tanks are 6.9 inches in diameter the 6.9 inch bands will fit.

72's are commonly 6.9 and 7.0.

If you don't have calipers lay the tanks down on nice flat surface and place a yard stick across both, on edge. Measure from the bottom of the yard stick to the surface and bingo you have the diameter.


Regarding wings:

The minimum wing size should be The weight of the gas + the buoyancy of your exposure suit +~2-3 lbs.

2 X 72's will hold about 12 lbs of gas with a good fill.

The typical drysuit, (medium undies in a shell suit on an average sized person) will be 22 ~26 lbs positive with minimum gas.

That 12 + 26 + 2 = 40 lbs. Unless you have a very buoyant suit a 50 is more than you need.

Tobin

 

[TSandM]

That's a huge wing for those little tanks. I dive my 72s with a 40 lb wing, and it's plenty.

A wing has to be able to float the gear at the surface -- and those tanks are about -13 when full with a manifold (add a V-weight and a SS BP, and you're still at -24) so 40 lbs of lift is more than you need, even when you consider a canister light and other gadgets.

In my drysuit, with my Puget Sound undergarments, it takes 28 lbs to sink me, so that's the total lift that I can lose with a complete suit flood. Still 40 lbs is enough.

I think you'll find a 50 lb wing tacos around the tanks.

 

[DA Aquamaster]

It depends on the width of the wing. I have not seen the new DR Rec EP wing, but the old one had a fairly narrow profile that while ideal for steel 72's could be problematic with larger 8" diameter tanks when used with a back plate. When pinched between tank and plate it could not inflate to anywhere near it's full lift.

Double Steel 72's are fine for mild deco dives down to depths around 140-150 ft, but for deeper dives or longer shallow dives, (FL caves, etc) you will end up using larger doubles.

I use a 55 lb halcyon wing for larger doubles with stage, deco bottle etc, and while I still own a rec wing and still on occasion dive double steel 72's, I don't bother swapping out the Halycon wing. I don't notice any excessive tacoing with the skinnier tanks.

A set of double steel 72's with bands and manifold attached will be neutral to a pound or so buoyant when empty and about 11-12 pounds negative when full. A huge wing is consequently not required as you'll need only about 5 to 7 pounds more lift than you'd need with a single Steel 72 or a mildly negative steel tank like an X7-100.

You still need a wing wide enough to accomodate the double tanks and going smaller than 40 pounds in a double wing makes little sense. In the other extreme, going 10 pounds larger is not going to present any serious issues either, at least based on my experience.

Consequently my view is that it makes sense to buy a wing that will work well with the 7.25" and/or 8" tanks you will eventually use rather than to go with a narrow wing oprimized for 6.9" tanks and don't get too hung up on an extra 10 pounds of lift. Depending on the tanks you eventually end up with and whether you dive with deco bottles stages, etc, the extra lift may be needed and may prevent having to replace the wing (says the owner of a rec wing he no longer uses for exactly that reason).

 

[NorthWoodsDiver]

I have used my 32lb OMS wing with double 72's with success but I didn't have stage/deco cylinders or a canister light either.

 

[halocline]

I use the piranha 7.0" bands on my 72s and they work fine, I'm sure the 6.9 ones will also work well. In fact, I had to trim one of the bolts just a little, so if the 6.9" bands are in fact a little smaller, not just sold as smaller, then the plates should be a little further apart and the bolts should fit a little better.

I found a new rec wing with a slight silkscreening blem for $160, I think it might have been at caveadventurers. It's PLENTY of wing, smaller would be ideal but it's manageable. If the new style is any bigger I'd really look around for one of the older ones. Dive rite markets this wing as a hybrid, but personally I think you'd be nuts to use it with a single tank.

A year or so ago DR came out with a humongous travel wing, before they went back to the 30lb square and then on to the EXP. I'll bet there are a few of those big travel wings around, everyone hated them. Ironically, they might be perfect for small doubles, I don't know about 72s, but it's worth a look.

 

[SparticleBrane]

I use a DSS Torus 38lbs doubles wing for double 72s and it is fantastic. Rock-solid, stable, easy to dump gas, doesn't really taco around the tanks, and a good amount of lift.

I've also used my Agir 38lbs doubles wing for double 72s and it works nicely as well. Not as easy to transfer gas from one side to the other (horseshoe rather than donut) but still great.

 

[Bob S]

Matt, Is your Rec wing the new EXP donut style or the 2008 with 47#'s of lift? Also can you give me the site where you found your wings for $160. Thanks, Bob S

 

[Bob S]

Everyone, thanks for your advice. Other than the Dive Rite what other wings in the 40-45# lift should I look at? I will check out the DSS and Agir. Any comments on the horseshoe versus donut configuration with my 72's? Again thanks! Bob

 

[halocline]

Mine is about a year old, horseshoe. I don't know the rated lift. Try caveadenturers.com or NESS.

There are lots of nice small doubles wings out there. It's not hard to find a deal.