DIR- GUE Appropriate wing lift capacity for steel doubles?

[Nick_Radov]

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.

You need to account for the weight of the human head in order to comfortably float with your head out of the water on the surface at the beginning of the dive. It's pretty much a direct -11 lbs (approximately) against the buoyancy of the wing while on the surface.

 

[MidOH]

10.6#. Unless its different because its frozen.

 

[PEDiver]

With double LP85s + drysuit + 2 stages I've comfortably used a 40# wing. I use a 60# wing when I switch to my bigger doubles (HP133s).

Edit: this is in freshwater. I have not dived that configuration in saltwater.

 

[PfcAJ]

This is what I was told as well.

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

There’s a point where that doesn’t hold true. A wide wing will taco up around the tanks more, and contribute to difficulty venting gas from it.

 

[SpeedyJ]

You need to account for the weight of the human head in order to comfortably float with your head out of the water on the surface at the beginning of the dive. It's pretty much a direct -11 lbs (approximately) against the buoyancy of the wing while on the surface.

Eh, understand where you’re going with that, but disagree with your allocation of where that weight sits as the buoyancy of the exposure protection is also there helping to float you on the surface.

Anyway, for a diver starting out with double LP85s / HP 100s the 40lb wing should be sufficient even with 11Lbs of head in play:
~15lbs of back gas + ~6-8 lbs of deco gas (AL80 / AL80 + AL40) + 11lbs of encased meat = +6lbs positive buoyancy.

Too many divers grab big 'ole wings to start out and have trouble as a result, failing to get the air out of their wings to descend they start adding weight to their rig, which means more air in the wing at depth, and more expansion and contraction with depth changes.

 

[Nick_Radov]

Eh, understand where you’re going with that, but disagree with your allocation of where that weight sits as the buoyancy of the exposure protection is also there helping to float you on the surface.

The buoyancy of the drysuit isn't really helping much to keep your head up out of the water when you're floating vertically at the surface. I mean you can close down the drysuit exhaust valve and add more gas to get a little extra lift but you won't get much before the neck seal burps it out.

I'm not suggesting that anyone buy an excessively large wing. It's just that we sometimes have to hang around on the surface in rough conditions for a while waiting for a buddy or whatever. So it's nice to be comfortable there and not need to put a regulator in your mouth.

 

[L13]

Eh, understand where you’re going with that, but disagree with your allocation of where that weight sits as the buoyancy of the exposure protection is also there helping to float you on the surface.

If you are properly weighted, regardless of exposure protection, you will be approximately neutral at your safety stop with empty tanks and empty BC. The BC needs to add buoyancy to compensate for full tanks and keeping your full head above water at the start of the dive.

In other words: @Nick_Radov is right.

If you are using a drysuit, you should add enough buoyancy for a flooded suit to the required BC buoyancy or have at least that much ditch-able weight. You need to be able to ditch down to a weight that is swim-able from depth with either a flooded suit or a failed BC.

 

[JoeTPhilly]

This is a good thread and I have been following closely but I have some questions as I have just started diving doubles and hopefully will do my tech upgrade in September. Please correct me if I am wrong, but I would think the wing needs to float the rig with full tanks. In the original poster's case, he is using an aluminum backplate which is about 2 pounds negative. I would estimate hardware and backup lights would be another two pounds. HP100s are about 8 pounds negative each, so -16. I would think the regulators are about -3? I don't know how negative the bands and manifold are so maybe someone could post. Anything else I am missing? I am just better when seeing numbers so thanks in advance. Also, what about a stainless steel backplate. It is only 3 pounds more than the aluminum but is a SS plate a bad idea?

 

[Nick_Radov]

This is a good thread and I have been following closely but I have some questions as I have just started diving doubles and hopefully will do my tech upgrade in September. Please correct me if I am wrong, but I would think the wing needs to float the rig with full tanks. In the original poster's case, he is using an aluminum backplate which is about 2 pounds negative. I would estimate hardware and backup lights would be another two pounds. HP100s are about 8 pounds negative each, so -16. I would think the regulators are about -3? I don't know how negative the bands and manifold are so maybe someone could post. Anything else I am missing? I am just better when seeing numbers so thanks in advance.

Yes, of course the wing needs to have enough lift to float the rig with full back tanks if you doff it at the surface. We dive from small boats sometimes so to get back on the boat you have to remove your rig, flop yourself into the boat, and then pull your rig up. In practice though any reasonable wing will have plenty of lift for that unless you have an unusually large amount of integrated weight. And you clip your rig off to a gear line anyway so even if the wing leaks it's not going to sink.

Also, what about a stainless steel backplate. It is only 3 pounds more than the aluminum but is a SS plate a bad idea?

It's not a bad idea necessarily. Most drysuit divers use SS backplates for salt water diving in order to carry less lead elsewhere. But you have to experiment to find out what gives you optimal trim. Some divers prefer to use an aluminum plate and then add extra lead as a tail weight in order to shift their center of mass lower.

For fresh water diving an SS backplate might leave you over weighted. But again that's an individual thing. You have to do a weight and trim check to know for certain.

 

[crofrog]

40lb wing for 7.25” cylinders 60lb for 8”