Are the Super Wings too much?

[jagfish]

I could be wrong,but that doesn't happen often

I think this might be one of those times...

At 6ATA, the air inside the bladder is also at 6ATA. If you fill it up at that depth, it will fully inflate and a bag rated at 55 lbs of at or near the surface will also have the same lift if fully inflated at depth by my reconing.

Maybe you were confusing teh fact that someone who is marginally bouyant (or even slightly negative) at the surface with a thick wetsuit could become dangerously heavy at depth when the suit compresses.

 

[novadiver]

I think this might be one of those times...

At 6ATA, the air inside the bladder is also at 6ATA. If you fill it up at that depth, it will fully inflate and a bag rated at 55 lbs of at or near the surface will also have the same lift if fully inflated at depth by my reconing.

Maybe you were confusing teh fact that someone who is marginally bouyant (or even slightly negative) at the surface with a thick wetsuit could become dangerously heavy at depth when the suit compresses.

air compresses at depth. that compressed air now weighs more. ( just like a full tank weighs more than a empty tank) and there is less volume.

lets ask this question? is the 100 lb rating of the wing, rated to hold 100 lbs at the surface or at depth? Because the max volume is still the same. It's the volume under presure that changes. have you ever taken a tennis ball to 100 feet, It will be crushed yet return to normal at the surface.

 

[-hh]

At 6 ata (6 x 33=198 ) ( 198 - 33=165 fsw) ( 6 x 14.7= 88.2 lbs psi) that's a whole lot of water pushing down . now lets take into account that the air in the bladder is now 1/6 the volume it was on the surface, and my guess would be - the diver needs more lift to stay neutral.

I could be wrong,but that doesn't happen often

I think its in how you're trying to phrase your answer: yes, if we descend, the air in a BC will produce less lift if we don't add more air to a BC as it compressed with depth...but that's because the air occupies less volume, not because water becomes denser with depth.

IMO, the intended question was to ask if a BC that produces "55lbs" of lift when full at the surface, will or will not continue to provide "55lbs" of lift when full at some depth?

First, we know that 1 cubic foot of seawater's roughly 64lbs (mass), and while water isn't technically incompressible, its close enough to for us to ignore depth as a factor here.

Next, we know that a "55 lb" wing basically means that it displaces 55lbs worth of water, or 55/64ths of a cubic foot of seawater.

Since we use air to displace the water, we have to take into account the mass of the air being used. 1 cubic foot of air @ STP weighs ~0.081 lbs, so technically a "55lb" wing would need to actually displace 55.081lbs of water (55.081 - 0.081 = 55.000 lbs) at the surface in order to account for the mass of the air.

If we now take this "55.081lb" BC down to 6 ATM, it takes roughly ~6x more air mass to fill it because we're at 6x the pressure. So instead of needing 0.081lbs of air, we need 6x that: ~0.486 lbs.

And the 55.081 lb BC @ 1 ATM would provide (55.081 - 0.486 =) ~54.6 lbs of lift @ 6 ATM.

This is roughly a half pound reduction in lift: a ~1% reduction. We should be able to ignore this decrease because we would have built in a larger safety margin than this...plus many BC manufacturers' actual lift capabilities don't match their claimed performace this closely to begin with.

So the answer is that its close enough to being unchanged to consider it unchanged. The bigger question IMO is to verify that a BC actually provides the amount of lift that the manufacturer claims.


-hh

 

[cool_hardware52]

The bigger question IMO is to verify that a BC actually provides the amount of lift that the manufacturer claims.


-hh

hh, good point, many claims are off. It is also important to consider if the wing can inflate fully as used. In other words rigged as you intended to use it, positioned on the plate, and with the tank or tanks secured is the wing constrained from inflating fully? Often this is the case. If you want to test just rig up your unit, and fill the wing with water. Remove the wing and weight it full and empty. Might be surprised.

Another point to consider is water in the BC. As you vent, or orally inflate, water enters the bladder, this further reduces the available lift.



Regards,




Tobin

 

[northcoast_diver]

OMS 60# wings (no bungy) and a dry suit.( redundancy)

I agree. I would think the 60s are enough.

The only reason for a large wing is to float yourself better on the surface. It all depends on how high out of the water you want to be when you inflate the wings on the surface.

Underwater, you only need to be able to offset about 35 lbs max, consisting of the weight of your gas in your twin tanks (0.08 lbs per cu ft x 260 cu ft max) plus your deco mixes in their stages (0.08 lbs per cu ft x 160 cu ft max) , and camera or metal detector.

 

[northcoast_diver]

air compresses at depth. that compressed air now weighs more. ( just like a full tank weighs more than a empty tank) and there is less volume.

lets ask this question? is the 100 lb rating of the wing, rated to hold 100 lbs at the surface or at depth? Because the max volume is still the same. It's the volume under presure that changes. have you ever taken a tennis ball to 100 feet, It will be crushed yet return to normal at the surface.

Very, very small insignificant difference in the buoyancy of air near the surface compared to ... say ... 400 fsw.

 

[northcoast_diver]

SS plates will make you so top heavy that you will be fighting your trim. The AL plate is better for 104s.

My AL plate is very sturdy. I would bet the bolt on the bands would break before it would/

I really like my OMS aluminum plate too!

 

[northcoast_diver]

Lets see if he comes back to read his own thread. So far, it doesn't seem so.

 

[novadiver]

I think its in how you're trying to phrase your answer: yes, if we descend, the air in a BC will produce less lift if we don't add more air to a BC as it compressed with depth...but that's because the air occupies less volume, not because water becomes denser with depth.

IMO, the intended question was to ask if a BC that produces "55lbs" of lift when full at the surface, will or will not continue to provide "55lbs" of lift when full at some depth?

First, we know that 1 cubic foot of seawater's roughly 64lbs (mass), and while water isn't technically incompressible, its close enough to for us to ignore depth as a factor here.

Next, we know that a "55 lb" wing basically means that it displaces 55lbs worth of water, or 55/64ths of a cubic foot of seawater.

Since we use air to displace the water, we have to take into account the mass of the air being used. 1 cubic foot of air @ STP weighs ~0.081 lbs, so technically a "55lb" wing would need to actually displace 55.081lbs of water (55.081 - 0.081 = 55.000 lbs) at the surface in order to account for the mass of the air.

If we now take this "55.081lb" BC down to 6 ATM, it takes roughly ~6x more air mass to fill it because we're at 6x the pressure. So instead of needing 0.081lbs of air, we need 6x that: ~0.486 lbs.

And the 55.081 lb BC @ 1 ATM would provide (55.081 - 0.486 =) ~54.6 lbs of lift @ 6 ATM.

This is roughly a half pound reduction in lift: a ~1% reduction. We should be able to ignore this decrease because we would have built in a larger safety margin than this...plus many BC manufacturers' actual lift capabilities don't match their claimed performace this closely to begin with.

So the answer is that its close enough to being unchanged to consider it unchanged. The bigger question IMO is to verify that a BC actually provides the amount of lift that the manufacturer claims.


-hh

the 100 lb wing is rated for heavy doubles. I don't own one, ( mine are 60 lb oms)but I see alot of divers with them, there must be something they can be used for?

 

[decoeric]

Well geez, that makes all the difference bud. I had no idea I was in the presence of greatness. I have a special place I keep special divers like you...

And what place would that be?