Question 40 or 50 lb wing for doubles? And what about (future) stage tanks?

[Sebs]

Sorry to revive this but from my googling and researching I've noticed that there are distinct differences in recommendations between European divers and American divers regarding wing sizes. Are the tanks' characteristics that different to warrant this? Or something else?

For instance basically everyone in Europe says a 40-45lbs wing is more than enough for D12 + 1 or even 2 stages. Meanwhile Americans say that a 40lbs wing is cutting it close for just HP100s (which I assumed were the rough equivalent to D12s), let alone additional stages. They therefore recommend getting 55-50lbs wings. So what is "correct"? I'm looking at getting a D12-equivalent twinset when I move to Canada later this year and am hoping my OMS45 wing is big enough for that + 1 stage.

All of this is assuming a trilam drysuit and exposure protection for 6-10°C (42 - 50°F) waters .

Edit: From googling, it appears that a Faber FX100 is -0.27kg when empty, while a Euro 12L is +0.51kg when empty. That's already a pretty big difference across two cylinders and could account for at least some of the discrepancy.

 

[Imla]

For anecdotal evidence.... I tried a full suitflood in the baltic (brackish) sea with a D12 and 3 stages after a T2 dive there. My Halcyon Evolve 40 worked like a charm. (The full suit flood came at maximum bottomtime, just before planned ascent. So with no less 1/3 gas in tanks (probably more, I used less gas than my guy teammates), and 1 empty bottom stage, and 2 full deco stages.

 

[NothingClever]

Wetsuit. I’m comfortable diving an LP85 twinset wet. Any cylinder above that I acknowledge needs to be in DS.

Just took the Doubles Primer with Jon @kierentec .

Not diving LP85s wet anymore. AL80 twinset - yes - but anything more than that and I’ll be happier (more confident) in a DS.

Also, I still like the material and quality construction of XDeep wings but Jon laid out my XDeep wing on top of a more traditional wing and that sorta ended my love affair with the XDeep design. It became instantly clear why on my previous technical dives I was struggling with miserable positive trim. And the solution I had (tail bag weight on lower twinset post) is a solution but not an optimized one. I’ve been diving light fins (DR XT) so as soon as I added two deco bottles to the XDeep wing (that minimizes air volume around the nipple line and higher), it’s no wonder I was working harder than necessary.

So, future AL80 TS dives in the ocean? Yes, and I feel good about doing them in a wetsuit.

Mo’ gas necessary? DS, different wing and heavier fins and NOT with a tail weight or cam bands with a weight threaded on around the bottom of my cylinders like XDeep has advertised.

 

[Badger7]

Meanwhile Americans say that a 40lbs wing is cutting it close for just HP100s (which I assumed were the rough equivalent to D12s), let alone additional stages. They therefore recommend getting 55-50lbs wings.

Just the opinion of 1 American here, but likely shared by a few of the people I dive here with in the Midwest in freshwater. A 40lb wing is perfect in both size, shape, and lift for a pair of HP100 tanks, even a stage or two. You do need to be willing to select the rest of your kit to offset the extra weight of the bands, manifolds and regs. For instance, a steel plate is perfect for a single tank, but an aluminum plate pairs much better with steel doubles. That switch fixes about 4 pounds of the 9 pound increase of the extra metal required to mount and plumb doubles. You can continue on down the line if you wish, getting yourself darn close to neutral with empty doubles. Then your wing just needs to be able to float the 16pounds of gas at the start of the dive, and/or offset the same amount of lost bouyancy lost in case of a total suit flood. An AL40 stage bottle, full of gas, fully rigged with a big brass reg is only 4 pounds negative, half that by the time you breath some gas out of it.

Of course the calculus changes in the extremes, like carrying a lot of gear for a working dive, lots of bigger stage bottles, thick undergarments requiring a lot of lead, bigger/longer/heavier tanks, etc - but for me and my homies dropping down to check out a wreck at 110' at 42 degrees for less than an hour - 40 pound wing for a pair of HP100s is more than enough lift.

 

[inquis]

Meanwhile Americans say that a 40lbs wing is cutting it close for just HP100s (which I assumed were the rough equivalent to D12s), let alone additional stages.

HP100 is 12.9L. Short answer: not a problem.

This American weights for a neutral with empty primary tanks, so the only thing that matters is the gas weight. Considering Nx32 (since Trimix is lighter), 2x HP100 holds 8.2 kg (18 lb) when nicely overfilled to 250 bar (3600 psi). Clearly a 18 kg (40 lb) wing is plenty for that. Adding two AL80 (11.1 L) stages at 206 bar (3000 psi) adds 4.6 kg (slightly less than the gas weight because it's positive when empty), for a total of 12.8 kg (28 lb). That 40-45 lb wing is still good.

Additionally, I use a drysuit for redundant buoyancy. I have tested it's ability to compensate with an empty wing and full tanks. No problem whatsoever.

All that said, it could be insufficient for warm water where you might be negative with empty tanks. With an AL plate, I'm about neutral with Xerotherm underlayers (+13 lb buoyancy alone) and double LP85s (13L) in fresh water. If I went with just a wicking layer, I'd be -31 lb with just doubles (so still OK) but -41 lb with doubles+stages. In that case, I'd probably run AL80 doubles and come in at -31 lb.

 

[inquis]

@Imla raises a good point I didn't mention above about a suit flood. I use a 44 lb wing, which would support a complete suit flood with my light (Xerotherm) undergarments (no lead to drop). Buoyancy would be -41 lb with full doubles & stages and flooded suit.

With my Arctics, I would switch to a steel plate and add 5 lb of lead, and a complete suit flood would take me to -51 lb, but dropping the lead goes to -46 lb. I dive Arctic+Xerotherms down to high 30s F with 10 lbs of ditchable lead, again taking me to -46 lb in the worst possible case.

I'm just not worried about that: +44 from the wing and +6 lb from lungs gets me to the surface without even kicking. In a pinch, I can handoff the stages to a buddy (or flat out ditch them if SHTF) taking me to -36 lb, easily handled by the wing. And honestly, this worst-case is fairly contrived (zero gas used and complete suit flood).

 

[Badger7]

Another thing maybe worth considering - if carrying a little extra gas is almost always better, is carrying a little extra lift always better? I think what you might find is that the way 50-60 pound wing would wrap farther up the sides of a pair of 7.25" doubles, its less efficient to dump gas from the larger wing, requiring getting a little closer to vertical one way or the other when dumping gas on ascent using either the hose or hip dump.

 

[Eric Sedletzky]

Hmmm. Plenty of technical dives are done using double Luxfer Al 80's (2 x 77.4 cu ft @ 3,000 psig). So, "pumped" old school 72's (2 x 86.3 cu ft @ 3,000 psig) should have enough capacity for some technical dives--not that I would ever recommend overfilling a 72.

rx7diver

Oh no, we should never overfill a steel 72, wink, nod

 

[Eric Sedletzky]

Not to throw a rock into the dryer, but I hear a lot of talk about what a felony it is to wear a wetsuit diving steel tanks.
Do you realize that some of the earliest technical dives on the Andrea Doria involved the use of double steel tanks, wetsuits, double hose regulators, no SPG's, no wings of any kind, and using air, yes air! Oh the horror!
Sorry to give you heartburn and make you lose a night of sleep, but it's true.
Many don't know how good they have it now.

 

[happy-diver]

Yeah did it today, and still diving manifolded steel tanks with farmer john and jacket wetsuit thing
then the various offshoots come along with their weird ideas, and want to help us by fixing things
not why I got into diving to be encapsulated as one with the ocean not in a sack of my own sweat

But this wing thing, swimming your gear up when an alien chews your bladder out, some baloney

Really all I want is to be able to empty it when I want without too much extra fabric flapping about


So current manifolded twins setup is steel Faber 55s oms 32lb wing with a wetsuit it's just beautiful


When you can't get back up then it must be time