Have any of you seen Jim Smith's new wing tips on his RV-6? They've upped his AR from 4.8 to 5.8, increased his span to 26' and his area to 116 sq. You can contact him at [email protected], and ask him for some pix and performance data!
I haven't. Is it possible? There must be a photo somewhere on the Interweb.Have any of you seen Jim Smith's new wing tips on his RV-6?...
....would be the added bending moment on the center spar structure. That's a lot of wing added.
Best,
When I was doing data reduction from his initial flight tests with my two-blade prop, I noticed how much his speed dropped off with altitude, much more than with my Lancair. Using the parasite drag area of 2.2 sq.ft. I got from the testing, and using his wing span and area, and flight weight I computed his total drag, What I found is that at higher altitude his induced drag was quite high. I remarked that he must see a much higher nose angle at higher altitude to which he agreed. I talked him into trying these triangular tips which shape increases span faster than area, and since induced drag is proportional to span-squared whereas parasite drag increases with area, the crossover point for a speed increase is about 6000' to 7000' dalt. Below that altitude, decrease area to increase speed; above it, increase span. This span increase really shows up on a trip at higher density altitude and high weight!I met Jim Smith in Wichita a while back and he seemed like a reasonable guy. He was flying in the cross country air race with a prop that you designed I believe - it looked like the one in the previous post photograph. I am currently working on molds for wingtips that will reduce the total wingspan to approximately 21' 1" for speed improvement. Why is Jim increasing the span to 26 feet? I assume he is looking for better performance at high altitude or some STOL performance. Has he changed the gross weight? Is he adding fuel out there? Just idle curiosity - I'm going the opposite direction.
Bob Axsom