Hi, Floyd-
>...I have never liked those swept-back wing tips. In the latest SN, there is something that seems
>to favor that wing tip shape. Do they actually reduce the dreaded wing-tip vortices?,...
One violinist to another...
The raked tip should reduce vortices, but the amount at our low Reynolds Numbers may be less than trustworthy NACA test results indicate for larger sections (sorry, mine are 'misplaced' at the moment). As posted on the current "tip" thread, I remember that the amount of rake on most designs (F.S., Imitation, T.P., P-Force, etc.) is a lot less than specified in the report I examined. Unfortunately, all I remember is that my current flapless design employed less rake than data suggested, but quite a bit more than these models. Still, I think some of the air rounding the tips to form vortices must be intercepted by the widening span, as the wing moves forward.
As I stated in the other thread, John Kilsdonk apparently told my HS/college buddy that he felt that he had overstated the case for raked tips on his rat racers in his M.A.N. article - i.e., that he thought the effect to be quite small and perhaps barely statistically valid against his experimental error margin. I think that we can use whatever is aesthetically pleasing, without fear of weakening a design much, especially if it's flapped.
SK
