Confirm wing lift?

[cool_hardware52]

Cliff Notes:
Floats above water line with 40 lbs of lead in bathtub
Description on web says 35lb/18L of lift, 18L=39.66lbs if my math is not fubar
Wondering about giving vendor crap


Trial #1 was interesting - I could not dig up a scale at the moment and the pool deal fell through tonight so I ended up going with the old bathtub trial. All I had was 40lbs of hard/soft weight, so I started with 35 lbs. No problem, so I put the last 5lbs on and it was still quite buoyant with a fair amount of material still above the water line.

I inflated the wing by mouth and the relief valve never opened. I know there must be some tolerance in the manufacturing process, but I would not expect 5+ pounds over the rated lift to be normal (if it really was a 35lb wing). So now I need more weight just to find out how much it takes to drop it below the water line.

Tobin, can you comment on the tolerance of your wings compared to rated lift? I figured that you would have more knowledge on the subject than myself.

I just looked at their site and noticed that it states 35lb/18L of lift. If I converted right 18L = 39.66 lbs and 35lbs would be 15.86L. So I will assume it is a 40lb wing. Now I am tempted to go back and call BS.

What is the lift when tested as I recommended? Lift in the "free state" is often greater than when tested in the "as dived" condition.

There's a reason why I recommended filling the wing when it was attached to a plate with a cylinder in place.

Tobin

 

[Spg01]

What is the lift when tested as I recommended? Lift in the "free state" is often greater than when tested in the "as dived" condition.

There's a reason why I recommended filling the wing when it was attached to a plate with a cylinder in place.

Tobin

As soon as I can get a scale I will try your recommended method.

 

[Spg01]

Trial #2 - "The Tobin recommended method"

I set up the wing/plate and weighed it, then I strapped it on to my PST HP 100 and filled it with water. The OPV was not as difficult to open as I thought it would be. I double checked that there was as little air as possible.

Getting it off the tank was interesting to say the least, but back to the scale. It turned out to weigh 44.4 lbs. That is with a digital bathroom scale weighing me and the bp/wing both times. The bp/w itself weighs 10.8 lbs dry.

Quite a bit over the 35 lb wing I thought I ordered. It is a nice wing, just way more lift than I need/wanted.

 

[Insta-Gator]

44.4 - 10.8 = 33.6 pounds of NET lift available with your rig. If the dry weight of your rig were less, the net lift available would be more, etc. Not that far off from 35#

 

[bane51031]

You wanna sell it cheap, I do not know how you could dive such a wing lol.

 

[Spg01]

I know I could dive it, the wing on my Ranger is "supposed to be" 44 lb of lift. But when the vendor says it is a 35# wing it is just marked wrong, I now know he is full of ****.

Insta-Gator, I think it is kind of cheating to add the backplate weight to the wing just to bring it back down to near 35# of lift.

Bane, not quite ready to sell it yet. But I do have to decide weather to just live with it or try to have them get me a smaller wing.

 

[cool_hardware52]

Insta-Gator, I think it is kind of cheating to add the backplate weight to the wing just to bring it back down to near 35# of lift.

Wing lift / displacement stands alone. It's not calculated as wing lift less the negative buoyancy of the plate / harness.

If the net difference in the dry weight and the water filled weight of your wing was ~45 lbs then that's the effective lift.

Tobin

 

[Spg01]

How much variation in lift would be typical on a 40lb wing? I would guess +1 or +2 lbs at most and -0.

 

[cool_hardware52]

How much variation in lift would be typical on a 40lb wing? I would guess +1 or +2 lbs at most and -0.

That largely depends on who is fabricating the wing.

Tobin

 

[Spg01]

They offered a full refund, but not a 35lb replacement. Now to search for another wing.....Dam, I was hoping this would have turned out better.