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Re: planes flying abreast: the Newtonian solution



As we point out in our article, the efficiency of a wing is proportional
to the length. Also, for an isolated wing the lift must go to zero at the
tip (which is a simple boundry value problem) because the higher pressure
below the wing communicates around the tip of the wing with the lower
pressure on top. Winglets are put on wings to prevent this communication
so that the lift can extend farther out on the wing. This increases the
effective length of the wing and thus its efficiency. Denker's planes
flying tip to tip are just doing the same.

Some believe that winglets are there to reduce the strength in the wingtip
vortices. In fact they strengthen them because they cause the gradient in
the lift at the tip of the wing to be even stronger.

David Anderson
dfa@fnal.gov