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!
Van's Air Force
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Jim Smith's RV-6 wing tips
- Thread starter elippse
- Start date
n5lp
fugio ergo sum
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LifeofReiley
Well Known Member
And you can post this info here pics etc... ??
What is the purpose?
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
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
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pierre smith
Well Known Member
My concern....
....would be the added bending moment on the center spar structure. That's a lot of wing added.
Best,
....would be the added bending moment on the center spar structure. That's a lot of wing added.
Best,
WingsOnWheels
Well Known Member
While we are on the wingtip subject, has anyone tried small winglets?
I was thinking the same thing actually. Does Vans have a point of view on lengthened tips ?
My Glasair III wanst rated to 6g with the extended tips, only 3.8 if I remember correctly. 6g only with short wing.
The tips really slow up the roll rate and stall speed. Speaking from experience.
Me thinks vans should be consulted before installing these long tips......
Van does not like the wings to be lengthened
I discussed this with him briefly in October of 1996 when I was at the training session at North Plains, OR and I was going to install the 9" wide (18" added wing span) tip tanks. He was very uneasy about it and advised me to add the tankage inside the design envelope like Jon Johanson had done. I have flown the 24.5' wingspan for years with no problem but when I go to the 21.5 feet in the racing configuration the roll rate is noticably faster. I am working on a 21.08' configuration.
Bob Axsom
I discussed this with him briefly in October of 1996 when I was at the training session at North Plains, OR and I was going to install the 9" wide (18" added wing span) tip tanks. He was very uneasy about it and advised me to add the tankage inside the design envelope like Jon Johanson had done. I have flown the 24.5' wingspan for years with no problem but when I go to the 21.5 feet in the racing configuration the roll rate is noticably faster. I am working on a 21.08' configuration.
Bob Axsom
Sid Lambert
Well Known Member
It looks like a giant delta dyke from that angle.
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!
Jim is seeing much better take-off and climb performance. True, bending is higher and roll-rate is lower, so it's not the thing to do for aerobatics.
