stefusa:
As far as I know (i am still a newbie) Aluminium tank are butt light !!!
So is there really a reason to choose a donuts wing instead of an horseshoe wing because we don't need to add lift on the bottom of an AL tank ???
Am I right ????
Thanks
A circular bladder, by itself does not add lift at the base of a wing, in normal use.
Consider a diver in horizontal trim, with 50% or less of his wing filled, i.e. a 30 lbs wing filled to displace 15 lbs. Except on the surface wings are almost never filled to capacity, usually 0-50% in normal use. If you have your wing fully inflated at depth something is wrong.
Where is the gas in that 50% filled wing? It's in two bubbles, one running down each side of the tank. There is no gas in lower arc of the wing. Why? because gas naturally moves to the highest point in the wing. The lower arc of a donut singles wing is trapped below the bottom of the tank and your rear end. That's alot lower than the bubbles on each side of the tank, where the partially inflated wing wraps up the side of the tank a bit.
It's possible to build a donut wing with more lift near the lower end of the tank. That's achieved by making the wing wider at that location. We do exactly that on our Torus 35. Why? because if you are wearing enough exposure suit to need a 35 lbs singles wing you are also using more ballast. If that ballast is in a weight belt you need more lift near your hips.
Our Torus 26 has much less "flare" near the bottom of the wing. In conditions that permit using a smaller wing the exposure suits are typically less buoyant, and weight belts are either not used or are only a few lbs. If you have little or no weight belt you don't need lift at the hips.
Tobin
