Wing Question

[nimoh]

not the first time, and not even remotely close to the last time

 

[j2s]

PM sent

 

[DevonDiver]

wow, I never would have guessed that this was possible.

I apologize for being reluctant to accept your word on it, but it seemed sort of ridiculous to me that a wing could bend a stainless steel plate

It's freakish and unanticipated. Forgive me for making up words, we should give the phenomenon a name...something like 'pneumatic'.

 

[Slmason.72]

Just for reference, fire / rescue services use LOW pressure lift bags to lift cars at accident scenes. 10psi over 576 square inches (that's a 2 foot square bag) will lift even the largest pick up truck with the 5760 lbs of lift generated. That's almost 3 tons with 10psi.
Granted your wing may only have 40 or so square inches of surface area, but even at 5 psi, that's 200 lbs. That's like the average size man standing on your BP, and using the attachment point of the doubles set up as a fulcrum.

Air pressure has some freakish strength when applied over a large surface.

 

[Doc Harry]

Me bongo

Me hate tacos

Me have 3 wings

 

[sgl308]

Hi all, I am fairly new to tech diving. Trying to come up with a new setup where I can switch between singles and doubles fairly easily. I dive single steel 100s and was thinking of banding together some AL 80s I have sittin around. now I was hoping to find a wing that will accommodate both so I dont have to keep changing it out everytime and not spend a ton. I came across this online Hollis X37 Wing discounts on sale Hollis and was wondering if I can dive both singles and doubles with it or if anyone has any other recommendations
thanks!

When I started diving doubles, I got a Dive Rite Rec EXP wing because the website said it is good for single tanks and doubles. I now use a Trek wing for singles and a Classic wing for doubles. The Rec EXP could not provide enough lift for me with LP 85's and a dry suit to float on the surface. I couldn't tell you if that was because the wing was sandwiched between the tanks and backplate or not... It was the last time that wing hit the water.

That being said, I have a Dive Rite Rec EXP wing for sale if that is the route you choose to go.

---------- Post Merged at 07:09 PM ---------- Previous Post was at 07:05 PM ----------

Just for reference, fire / rescue services use LOW pressure lift bags to lift cars at accident scenes. 10psi over 576 square inches (that's a 2 foot square bag) will lift even the largest pick up truck with the 5760 lbs of lift generated. That's almost 3 tons with 10psi.
Granted your wing may only have 40 or so square inches of surface area, but even at 5 psi, that's 200 lbs. That's like the average size man standing on your BP, and using the attachment point of the doubles set up as a fulcrum.

Air pressure has some freakish strength when applied over a large surface.

That is a very confusing statement. It's not just about pressure, it's about weight vs. displacement in the water.

If the fire department is lifting a car at the bottom of a retention pond, there may be 5-10 psi of air in the lift bag. If you are lifting a 25 pound brick at 100 ft, there will be about 44 psi of air pressure in the lift bag. That's basic physics.

 

[Slmason.72]

That is a very confusing statement. It's not just about pressure, it's about weight vs. displacement in the water.

If the fire department is lifting a car at the bottom of a retention pond, there may be 5-10 psi of air in the lift bag. If you are lifting a 25 pound brick at 100 ft, there will be about 44 psi of air pressure in the lift bag. That's basic physics.

Sorry for the confusion. I'll admit it took me a minute to see where I lost you. I guess on a scuba website I should have indicated the hypothetical wreck the fire department was working was on the side of the road, not in a pond or quarry.

I was addressing the discussion of single tank wings bending a backplate when placed under doubles. In this case, it has nothing to do with water displacement, rather with the force applied by the air pressure over surface area between the two objects, BP and Tank.

As to lift bags, I think you meant the discussion to center around volumetric displacement of water. Pressure will always be ambient at depth in a non compressible container such as a lift bag. To whit, your 44 lbs at 100 feet will be 0 lbs at 0 feet (which cannot happen with a lift bag as the object will remain below the surface by a few feet causing the bag to retain a small measure of pressure) To lift a 25 lb brick from 100 feet, you would need to displace 25 lbs of water, very roughly, 12 liters. As the bag lifted, the air would remain at ambient pressure, with the pressure reduced as the bag lifts through the water column. From there, Boyle's Law takes over and you'd have 3x the volume (4ata - 1ata). Also the reason a SMB only needs to be partially inflated at depth for full surface deployment.

Or should that read 4x the volume... My brain is not processing basic math this evening.

 

[sgl308]

Sorry for the confusion. I'll admit it took me a minute to see where I lost you. I guess on a scuba website I should have indicated the hypothetical wreck the fire department was working was on the side of the road, not in a pond or quarry.

I was addressing the discussion of single tank wings bending a backplate when placed under doubles. In this case, it has nothing to do with water displacement, rather with the force applied by the air pressure over surface area between the two objects, BP and Tank.

As to lift bags, I think you meant the discussion to center around volumetric displacement of water. Pressure will always be ambient at depth in a non compressible container such as a lift bag. To whit, your 44 lbs at 100 feet will be 0 lbs at 0 feet (which cannot happen with a lift bag as the object will remain below the surface by a few feet causing the bag to retain a small measure of pressure) To lift a 25 lb brick from 100 feet, you would need to displace 25 lbs of water, very roughly, 12 liters. As the bag lifted, the air would remain at ambient pressure, with the pressure reduced as the bag lifts through the water column. From there, Boyle's Law takes over and you'd have 3x the volume (4ata - 1ata). Also the reason a SMB only needs to be partially inflated at depth for full surface deployment.

Or should that read 4x the volume... My brain is not processing basic math this evening.

Let's just agree to agree here. We both know how to calculate displacement in our own ways. Now back to the topic... I don't think it matters how big or small the wing is, if it's for singles or doubles, 25 lb lift or 90 lb lift, a bladder will not be able to hold enough pressure to generate enough force to bend a backplate. All the bcd's/wings I have have overpressure dump valves that let air out before pressure gets too high in the bladder.

 

[PfcAJ]

lel how many pieces of evidence do you have to be shown? People tested it, and it bent the plate. Go read the TDS thread I posted.

 

[nimoh]

lel how many pieces of evidence do you have to be shown? People tested it, and it bent the plate. Go read the TDS thread I posted.

time to science another non-believer