DIR- GUE Appropriate wing lift capacity for steel doubles?

[Ski_Lounge]

I'm primarily diving with HP-100's / LP-85's doubles and using the standard GUE setup (drysuit, jet fins, AL backplate), except a canister light. Not adding a light just yet, I will at some point, but I want to work on foundations without the additional cord management first.

I have a 40 lbs wing which floats my rig, but is this the appropriate capacity for this rig? My understanding is 60 lbs might be too much, but unclear if I should go for a 45 or 50 lbs wing.

 

[OrcasC205]

Here in the Pacific Northwest, pretty much everyone in the GUE community uses 40lb lift wings for smaller doubles (LP50s, LP85s and HP100s) and then move to a 60lb lift wing for doubled 8" diameter cylinders (and probably HP120s).

 

[Nick_Radov]

You need enough lift to float comfortably on the surface in rough conditions with your head out of the water and full tanks (including any stages). A typical human head weighs about 11 lbs. A nitrox fill in your tanks weighs about 15 lbs, and each stage will be up to 6 lbs additional gas weight. And add a little more as a safety margin because you might not get the full rated lift capacity when the wing is attached to your rig.

 

[SpeedyJ]

You need enough lift to float comfortably on the surface in rough conditions with your head out of the water and full tanks (including any stages). A typical human head weighs about 11 lbs. A nitrox fill in your tanks weighs about 15 lbs, and each stage will be up to 6 lbs additional gas weight. And add a little more as a safety margin because you might not get the full rated lift capacity when the wing is attached to your rig.

Your calculation needs to account for inherent buoyancy in exposure protection. A 40 LB wing works great for HP100s and LP85s with deco cylinders. No need to bump up to the 60lb until the tanks get wider.

 

[Ski_Lounge]

Here in the Pacific Northwest, pretty much everyone in the GUE community uses 40lb lift wings for smaller doubles (LP50s, LP85s and HP100s) and then move to a 60lb lift wing for doubled 8" diameter cylinders (and probably HP120s).

That's interesting, noted. Would it change at all if I add tail weights?

 

[SpeedyJ]

Here in the Pacific Northwest, pretty much everyone in the GUE community uses 40lb lift wings for smaller doubles (LP50s, LP85s and HP100s) and then move to a 60lb lift wing for doubled 8" diameter cylinders (and probably HP120s).

Double HP 120's are only about 1lb heavier in saltwater than HP100s, so I've used an 40Lb wing without any drama. I use the 60LB more for the width on thicker tanks vs. the lift.

That's interesting, noted. Would it change at all if I add tail weights?

You'll be fine using a tail weight, I use one that is a few lbs.

 

[Nick_Radov]

Your calculation needs to account for inherent buoyancy in exposure protection.

No, that's not how it works. The inherent buoyancy of the drysuit should be mostly balanced out by non-ditchable weight (like with a steel backplate, v-weight, and the steel tanks themselves). The buoyancy compensator (wing) is to compensate for the weight of the gas in our tanks, and to provide additional surface flotation. Whether the drysuit has 10 lbs or 30 lbs of inherent buoyancy that has zero effect on the necessary wing size calculation. With a proper shell drysuit, the buoyancy of the drysuit remains constant throughout the dive.

A 40 LB wing works great for HP100s and LP85s with deco cylinders. No need to bump up to the 60lb until the tanks get wider.

Sure, a 40 lb wing should be fine with those doubles and a single stage. With multiple stages it could be marginal depending on how much helium you have in the gas mixes. The point is to teach divers how to do the math rather than telling them specifically which wing to use.

 

[makar0n]

I'm primarily diving with HP-100's / LP-85's doubles and using the standard GUE setup (drysuit, jet fins, AL backplate), except a canister light. Not adding a light just yet, I will at some point, but I want to work on foundations without the additional cord management first.

I have a 40 lbs wing which floats my rig, but is this the appropriate capacity for this rig? My understanding is 60 lbs might be too much, but unclear if I should go for a 45 or 50 lbs wing.

There you go:

Info - Optimal Buoyancy Computer

The Optimal Buoyancy Computer A tool to help nail buoyancy and improve safety, before you splash 1) How much lead should I carry with my new wetsuit? 2) How big a wing should I buy? 3) Will my BCD support my lead, both at the surface and when my wetsuit is compressed at depth? 4) Will my BCD...

scubaboard.com

 

[MidOH]

Double HP 120's are only about 1lb heavier in saltwater than HP100s, so I've used an 40Lb wing without any drama. I use the 60LB more for the width on thicker tanks vs. the lift.


You'll be fine using a tail weight, I use one that is a few lbs.

This is what I was told as well.

Wider wing = more stable doubles. Less turtle-ing.

 

[SpeedyJ]

No, that's not how it works. The inherent buoyancy of the drysuit should be mostly balanced out by non-ditchable weight (like with a steel backplate, v-weight, and the steel tanks themselves). The buoyancy compensator (wing) is to compensate for the weight of the gas in our tanks, and to provide additional surface flotation. Whether the drysuit has 10 lbs or 30 lbs of inherent buoyancy that has zero effect on the necessary wing size calculation. With a proper shell drysuit, the buoyancy of the drysuit remains constant throughout the dive.

Sure, a 40 lb wing should be fine with those doubles and a single stage. With multiple stages it could be marginal depending on how much helium you have in the gas mixes. The point is to teach divers how to do the math rather than telling them specifically which wing to use.

Agreed in principle - my response was based on the premise that the weight of a human head isn't a direct -11 lbs against the buoyancy of the wing, though I could see if you're thinking about the diver floating on the surface.