Wing lift?

[Bob DBF]

I calculated for my wing backwards. I e-mailed the mfg of my old jacket and found it had 40# of lift and then ordered my Oxycheq Mach V to match. I figured that since the jacket worked well for me over the years, there was no need to change size. It has worked out well, I dive wet, in cold water with various tanks from old steel 72's to HP 120's. I have a different wing for doubles. For AL80's in warm water I would have opted for a smaller wing, although this one has worked OK.



Bob
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Always use the right tool for the job. A hammer is the right tool for any job. Anything can be used as a hammer.

 

[Lorenzoid]

Can someone point him to that fancy Excel weight calculator that someone developed a while back? He'll love that.

 

[eelnoraa]

For single tank diver, and assume the diver is weighted properly, a 40lb wing is usually used by diver wearing thick exposure suit. The wing needs to compensate for thing that change buoyancy. In this case, it is dominated by the exposuresuit. A thick wetsuit can lose 25+ lb at depth during to compression. A drysuit can flood. The wing should be able to handle these cases.

Take a drysuit diver with HP120 for example, a 25lb drysuit is not uncommon in cold places. 9lb for full HP100. At worse case, you have drysuit completed flood with full HP120. You are -34lb. A 40lb wing isn't unreasonable.

 

[Lorenzoid]

Can someone point him to that fancy Excel weight calculator that someone developed a while back? He'll love that.

Look here: http://www.scubaboard.com/forums/bu...imate-wing-lift-calculator-3.html#post7032051

 

[Roman_66]

In other thread (#34) I did some simple calculation for correct weighted diver.
Looks 30lb is enough for any recreational dive up to one pony and it included HP120 with wet suit up to 5mm.
I am very confused about "wetsuit can lose 25+". In all my checking different between 5mm and 1mm suits is about 4lb.
For thicker suits it can be more. How much, I don't know, never check as I don't have wet suit thicker than 5mm.

 

[Storker]

30lb is enough for any recreational dive up to one pony and it included HP120 with wet suit up to 5mm.

You're quoting your specific results in a way that makes them seem more general than they are.

For thicker suits it can be more.

It is. See upthread for real-world experience with thicker wetsuits or a drysuit.



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[stuartv]

In other thread (#34) I did some simple calculation for correct weighted diver.
Looks 30lb is enough for any recreational dive up to one pony and it included HP120 with wet suit up to 5mm.
I am very confused about "wetsuit can lose 25+". In all my checking different between 5mm and 1mm suits is about 4lb.
For thicker suits it can be more. How much, I don't know, never check as I don't have wet suit thicker than 5mm.

You're talking about the weight of the suit. Losing 25 # is talking about the buoyant force from the suit. A 4 # suit can have a lot more than 4 # of lift, when under water.

I reckon the comment you refer to is suggesting that a 7mm suit could have 40 # (made up number) of lift when you're just under the surface, and compress enough at depth to only have 15# of lift.

 

[Roman_66]

Correct, I did this calculation for me, who is not use more than 5mm suit and it is applied, like I wrote, "for any recreational dive up to one pony and it included HP120 with wet suit up to 5mm "
I wear dry suit if water temperature doesn't allowed to use 5mm.
I don't understand what is issue with wind size with dry suite.
I thought that dry suite itself buoyancy doesn't change during a dive.
Actually I need to think about buoyancy change of underwear of flooded dry suit.
It might add other 10 lb of negative buoyancy.
It should be pretty big hole that dry suit will be flooded completely very fast.

You're talking about the weight of the suit. Losing 25 # is talking about the buoyant force from the suit. A 4 # suit can have a lot more than 4 # of lift, when under water.
I reckon the comment you refer to is suggesting that a 7mm suit could have 40 # (made up number) of lift when you're just under the surface, and compress enough at depth to only have 15# of lift.

No, I never spoke about weight, only about buoyant. Different between my (less than 70 dives) 5mm and 1mm wet suite is about 4lb. It maybe was 6lb, when it was new.
About 7mm suite buoyancy change I don't, as, like I wrote, I don't have it.

 

[eelnoraa]

I am very confused about "wetsuit can lose 25+". In all my checking different between 5mm and 1mm suits is about 4lb.
For thicker suits it can be more. How much, I don't know, never check as I don't have wet suit thicker than 5mm.

25 maybe a bit exergerate, but a new wetsuit like a Aqualung SoAflex 8/7mm can easily be 20lb positive on surface. I can have a 10lb weight belt on me and still float with head above water.

 

[Storker]

I don't understand what is issue with wind size with dry suite.
I thought that dry suite itself buoyancy doesn't change during a dive.

It's not the normal buoyancy change during the dive which is my concern. It's what happens if you've put on enough weight to be able to descend at all with the air that's trapped in your undergarments, and you then have a catastophic loss of buoyancy, say if your zipper breaks. Yes, I know it isn't likely, but I like to know that I won't do a good anchor imitation if fit hits the shan.

Actually I need to think about buoyancy change of underwear of flooded dry suit.
It might add other 10 lb of negative buoyancy.

As I said, the issue is the weight you put on to counter the buoyancy of your undergarment.

On my last dive, I used my 15L 200 bar tank, which is close to neutral when empty. I carried some 18kg of weight distributed between my BP, my weight pockets and my belt. I still had to pick up a rock to hold on to towards the end of my dive. Only a part of those 18 kilos was easily ditchable.

I prefer to be sure that my wing can keep me afloat on the surface in a worst case scenario, without too much hassle. YMMV.


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