30 lbs or 40 lbs wing?

[chrpai]

Starting simple...

I can wear an AL plate and AL tank in fresh water with no additional weight and be neutrally buoyant at 500psi (13cf of gas). That means at the beginning of the dive I only need enough air in my wing to compensate for the additional 2500psi of gas (66cf of gas) that I have at the beginning of the dive. That's 5lbs of gas.

If I put on a 7mm wetsuit I switch to a steel plate (+3lbs) and put 6lbs on my belt. This is what I need to still be neutral at 500psi. So I still need 5lbs for the gas. For the wetsuit, assuming 100% suit compression which is impossible, I need 9lbs for max depth. Add in the 5lbs and that's 14lbs. In all reality that's probably much closer to 10lbs - 12lbs since the suit can't fully compress.

Now let's say I switch out my AL tank with an LP95 steel tank and keep the steel plate. The tank is about 6lbs negative compared to my AL tank so the 6lbs so I get to lose the 6lbs on my belt. But now instead of compensating for 66cf of gas I need to compensate for about 85cf of gas which is about 7lbs.

So now I need 9lb for the 7mm suit and 7lbs for the gas in the tank. That's about 16lbs.

So hopefully this shows you the math and that a 30lb wing is pretty big. I'm very happy in my 27lb wing.

The next question then becomes..... can you swim it up? If you were at you max depth and had a wing failure could you swim to the surface without ditching weight? If the answer is no, then you need to have some ditchable weight.

 

[Griffo]

I too would be worried not with the size of the wing, but about the weight of that tank when diving wet. Assuming you are using Fabers, a full 15L cylinder is 11.6# negative.
If we do some sums, and assume a worst case of a wing failure at the beginning of the dive, you are gonna have some serious weight to swim up - even with an Ali plate.

I've made some assumptions of a well used 3mm suit which at 30M will provide almost no buoyancy. I hope these sums are right as I'm a metric guy and imperial makes my head hurt

Beginning of Dive on Surface:
Regs -3
Tank -11.6
Backplate -1.3 (-6 Steel)
Light -3
Wetsuit +9
Weightbelt -2

Total: -11.9 (-16.6 Steel)

At Depth with Loss of Wing:

Regs -3
Tank -11.6
Backplate -1.3 (-6 Steel)
Light -3
Wetsuit 2
Weightbelt -2

Total: -18.9 (-23.6 Steel)

Ditch the Light and Weight:

Total: -13.9 (-18.6 Steel)

That's still a LOT of weight to be swimming up.

 

[Nasser]

I too would be worried not with the size of the wing, but about the weight of that tank when diving wet. Assuming you are using Fabers, a full 15L cylinder is 11.6# negative.
If we do some sums, and assume a worst case of a wing failure at the beginning of the dive, you are gonna have some serious weight to swim up - even with an Ali plate.

I've made some assumptions of a well used 3mm suit which at 30M will provide almost no buoyancy. I hope these sums are right as I'm a metric guy and imperial makes my head hurt

Beginning of Dive on Surface:
Regs -3
Tank -11.6
Backplate -1.3 (-6 Steel)
Light -3
Wetsuit +9
Weightbelt -2

Total: -11.9 (-16.6 Steel)

At Depth with Loss of Wing:

Regs -3
Tank -11.6
Backplate -1.3 (-6 Steel)
Light -3
Wetsuit 2
Weightbelt -2

Total: -18.9 (-23.6 Steel)

Ditch the Light and Weight:

Total: -13.9 (-18.6 Steel)

That's still a LOT of weight to be swimming up.

Thanks for that - actually I'm a metric guy too so I'm also trying to decipher some of the info kindly posted by everyone and convert to metric!

I'm still not quite sure though what the general consensus is.... go with the 30 or 40 lbs. wing ? It seems evenly split at this point. Again, I'm not overweighting myself (4-5kg in 3mm and around 6-7kg w/5 mm suite in a very salty sea) With the 15 liter steel tank - deco at 3m with 50 bar and empty BCD jacket is fine. But I want to transfer some of the weight from my waist to a steel backplate, STA, and possible integrated ditchable weights.

I guess part of the challenge is to try to transfer the weighting scheme of my current Jacket style BCD setup w/ weight belt to a steel BP & Wing configuration... at least in theory. Unfortunately no one here was a configuration I can try and dealers are in other countries so I have to try and take an educated guess as to what might work best.

 

[chrpai]

This is more a weighting question then a wing lift question.

A lot of jacket BCD's have a substantial amount of "inherent buoyancy". This is caused by the plastic / ABS hard pieces and all the various padding and other stuff.

A BP/W has much less of this. Plus it has a metal plate that might weight 3 - 6 lbs or more. ( 1 1/2 - 3kg). When you combine this, my BP/W allowed me to take about 10lbs (5kg) off my belt. I also have an AL backplate that weights 3lbs (1 1/2kg) less.

Between my AL tanks and Steel tanks and my AL and Steel backplates I can set my relative weighting at:

0 (baseline - AL plate, AL tank) - Swimsuit fresh water
-3lb (SS plate, AL tank) 3mm fresh water
-6lb (AL plate and steel tank) 5mm fresh water or swim suit salt water
-9lb (SS plate and steel tank) 7mm fresh water or 3mm salt water

Each of these configurations result in me being properly weighted at 500psi.

If you are following me, I think you would be fine with a 30 or smaller wing.

 

[ams511]

I'm still not quite sure though what the general consensus is.... go with the 30 or 40 lbs. wing ?

What brand of wing are you looking to purchase? The reason I ask is narrow wings such as the oxycheq and DSS are only slightly wider and a bit longer. I am not convinced that there will be a noticeable difference under water. They will still vent well and the additional drag will be negligible. Wider wings will cause problems with both venting and drag.

 

[Peter_C]

I dive an HP130 which is 16L, and would have no problem floating it and my stainless back plate with a 30lb wing...if I didn't have a 5lb lead weight in the rail, two sets of regs attached, and a heavy can light, so I use a 40lb wing. If I was diving what the OP described as a basic kit without heavy additions I would rely on a 30lb wing, but I would always carry an SMB anyhow which can be used for added buoyancy in case of a wing failure. Of course it wouldn't matter what the wing size is if it fails.

 

[Nasser]

This is more a weighting question then a wing lift question.

A lot of jacket BCD's have a substantial amount of "inherent buoyancy". This is caused by the plastic / ABS hard pieces and all the various padding and other stuff.

A BP/W has much less of this. Plus it has a metal plate that might weight 3 - 6 lbs or more. ( 1 1/2 - 3kg). When you combine this, my BP/W allowed me to take about 10lbs (5kg) off my belt. I also have an AL backplate that weights 3lbs (1 1/2kg) less.

Between my AL tanks and Steel tanks and my AL and Steel backplates I can set my relative weighting at:

0 (baseline - AL plate, AL tank) - Swimsuit fresh water
-3lb (SS plate, AL tank) 3mm fresh water
-6lb (AL plate and steel tank) 5mm fresh water or swim suit salt water
-9lb (SS plate and steel tank) 7mm fresh water or 3mm salt water

Each of these configurations result in me being properly weighted at 500psi.

If you are following me, I think you would be fine with a 30 or smaller wing.

Yes I do follow you - thanks for the explanation it makes a lot of sense.

What brand of wing are you looking to purchase? The reason I ask is narrow wings such as the oxycheq and DSS are only slightly wider and a bit longer. I am not convinced that there will be a noticeable difference under water. They will still vent well and the additional drag will be negligible. Wider wings will cause problems with both venting and drag.

I'm considering the Halcyon Eclipse which is a very streamlined design... either the 30 lbs or 40 lbs wing

---------- Post added June 15th, 2013 at 08:26 PM ----------

I dive an HP130 which is 16L, and would have no problem floating it and my stainless back plate with a 30lb wing...if I didn't have a 5lb lead weight in the rail, two sets of regs attached, and a heavy can light, so I use a 40lb wing. If I was diving what the OP described as a basic kit without heavy additions I would rely on a 30lb wing, but I would always carry an SMB anyhow which can be used for added buoyancy in case of a wing failure. Of course it wouldn't matter what the wing size is if it fails.

which brings up a good point - it makes sense to consider not only what one is currently diving but also what kind of diving and additions may be added in the future. Diving doubles with a deco bottle and two regs will most definitely require a different wing and weighting considerations but going from the very basic setup I describe in my earlier posts to perhaps a few additions on a single tank (light, reel, knife, camera, etc..) does bring this consideration more into focus.

 

[Peter_C]

Diving doubles with a deco bottle and two regs will most definitely require a different wing and weighting considerations but going from the very basic setup I describe in my earlier posts to perhaps a few additions on a single tank (light, reel, knife, camera, etc..) does bring this consideration more into focus.

I have a 40lb wing for doubles too I was talking single 16L tank diving. In the past I used a 30lb wing with the same setup and at the beginning of the dive my rig was slightly negative. If I took it off it would sink so I changed to a 40lb wing.

 

[ams511]

In my non scientific test, eclipse 30lb float me higher above water than Oxycheq 40lb with every other piece of equipment remained the same.

Only the part of the wing that is submerged will generate lift so how high you float is not a good test of lift because you cannot control the submerged part of the wing.

 

[Nasser]

I have a 40lb wing for doubles too I was talking single 16L tank diving. In the past I used a 30lb wing with the same setup and at the beginning of the dive my rig was slightly negative. If I took it off it would sink so I changed to a 40lb wing.

Yes I know you were referring to single tank diving. My reference to doubles was more to point out that sometimes you need separate setups for different circumstances and there are limits to what one setup can achieve... but additionally that one should also consider what add-ons may come down the line as an aid to help decide for each rig.