How much lift for doubles wing?

[Guy Alcala]

I'm getting myself geared up to do Fundies in doubles, trying for a tech pass (but not expecting one). I'm probably going to double up my heavy Asahi 100s because I can't afford to get some lighter tanks at the moment. I've been estimating the negative buoyancy of my gear, and it comes out like this:

2 x HP100s -12.5/-10 lb.
Al BP -2 lb.
2 x regs/hoses -5 lb.
bands/crossbar -4 lb.
Can & B.U. lights -3 lb.

Total -39/-24 lb.


I figure I need another 3 lb. or so for my head and a soaked undergarment, or somewhere around 42-45 lb. If I figure that I'll be adding two or three stage/deco bottles once I start tech diving, I probably need 45-50 lb. I'm considering something like the DSS 49 lb. Torus, if I can't find something used. I've asked Rob Lee if he thought that's enough, as I'll likely be taking Fundies from him, or if I should be looking at 55-60 lb. instead. I thought I'd ask it more generally to see what local divers are using, and why. So feel free to recommend what you use/would like.

Thanks,

Guy

 

[Anti-Hero]

I use the DSS 49 Taurus wing for double Worthington (XS scuba) LP85's, AL BP, etc. I really like it, and it's been plenty adequate for me.

 

[andrewy]

i find that dive rite classic wing does em all you can buy it new for 149

 

[Gombessa]

55-60 sounds like a lot more than what most people need (my buddies and I use 38-40lb wings with doubles and a stage). 9lb allocation for regs + bands/manifold seems a bit much for most calculations, and I'm not sure I understand where the -12.5/-10 means for the tanks. Is this including gas, or empty (I'm not familiar with the Asahis)?

 

[Indian Valley Scuba]

Anything in the 50 to 60 pound range should be more than adequate, and there are so many choices. OMS wings are first rate and cost effective.

 

[alwaingold]

Personally I would not recommend using those tanks for doubles, since, as you pointed out, they are heavy. A lot of people have trouble with doubles making them head-heavy, and if the doubles are relatively light (buoyancy-wise), then you have the freedom to move weight around on v-weights, weight belts, etc. to the appropriate position on your body. If you start out with heavy tanks, then all of that weight is fixed on the tanks, and you don't have that freedom to balance things out. There are a lot of other tank options in the same size range but that are less negative.

Also, since you mentioned it, you probably don't need to worry about 2 to 3 stage bottles in this calculation, as any dive (locally) where you have that many bottles, you will almost certainly have (a lot of) helium in your backgas. So you will have more weight from the stage bottles, but less weight on your back.

I dive both Faber LP85s and PST HP120s with a 40 pound Halcyon evolve wing. The heaviest configuration that I dive is LP85s (over)filled with nitrox and a stage bottle of nitrox. This is a bit heavy with the 40 pound wing, and feels a little uncomfortable on the surface for a long swim in big water. But I find it adequate. The HP120s always have mix in them, so it's not an issue with them, even with bottles.

Allison

 

[kathydee]

I'm getting myself geared up to do Fundies in doubles, trying for a tech pass (but not expecting one).

Sounds like an excellent plan!

Good luck Guy! I know you will love the class!

 

[cool_hardware52]

I'm getting myself geared up to do Fundies in doubles, trying for a tech pass (but not expecting one). I'm probably going to double up my heavy Asahi 100s because I can't afford to get some lighter tanks at the moment. I've been estimating the negative buoyancy of my gear, and it comes out like this:

2 x HP100s -12.5/-10 lb.
Al BP -2 lb.
2 x regs/hoses -5 lb.
bands/crossbar -4 lb.
Can & B.U. lights -3 lb.

Total -39/-24 lb.


I figure I need another 3 lb. or so for my head and a soaked undergarment, or somewhere around 42-45 lb. If I figure that I'll be adding two or three stage/deco bottles once I start tech diving, I probably need 45-50 lb. I'm considering something like the DSS 49 lb. Torus, if I can't find something used. I've asked Rob Lee if he thought that's enough, as I'll likely be taking Fundies from him, or if I should be looking at 55-60 lb. instead. I thought I'd ask it more generally to see what local divers are using, and why. So feel free to recommend what you use/would like.

Thanks,

Guy

A bigger wing is never the solution to being over weighted. Changing / swapping components like plates and cylinders is.

Being over weighted multiplies the problems associated with any buoyancy failure.

Minimum ballast = the buoyancy of your exposure suit at your shallow stop with empty tanks.

If your empty cylinders + back plate + regs + bands and manifold + can light exceed this value you need different gear. Not what you wanted to hear perhaps, but still the best approach.

BTW massively negative cylinders will limit your choices in *where* you mount your ballast, and that can make horizontal trim more difficult to achieve.

Good Luck

Tobin

 

[dannobee]

Guy, we can probably loan you some tanks for your class if needed. I also have a couple of different doubles wings that you can borrow.

Those Asahi's are just too heavy for doubling up. For single tank diving they're great. Not so much for doubles though.

 

[Guy Alcala]

55-60 sounds like a lot more than what most people need (my buddies and I use 38-40lb wings with doubles and a stage). 9lb allocation for regs + bands/manifold seems a bit much for most calculations, and I'm not sure I understand where the -12.5/-10 means for the tanks. Is this including gas, or empty (I'm not familiar with the Asahis)?

Brain fart. Should read -25/-10, as the Asahis are -12.5/-5 lb. each. As to the rest, I'm figuring dual regs and hoses at 4 to 5 lb.; I've seen both estimates used, so went with the higher one. I've seen a figure of 4 lb. for the cross bar (1.5 lb.) and bands/bolts (2.5 lb.). Since I have no personal experience with doubles I'm guesstimating based on the best info I could find, but GIGO.

Guy