Smaller Wing Tips for Speed

[David Shelton]

Jim Smith's tips:

[Christopher Murphy]

Sorry Jim Smith, That is too ugly to be on an RV. Those tips and the spars and attachment weight surely has to offset any performance gain. Can you say double tapered wing?

Chris M

[Bob Axsom]

Originally Posted by elippse

...A flat tip with sharp edges top and bottom trips the flow around the tip from bottom to top and keeps the vortex near the tip. ...

This would be fairly simple to implement with sheet metal, angle brackets and floating platenuts. I am thinking about it but not now - schedule crunch.

Bob Axsom

[hevansrv7a]

Wouldn't it be easier to just attach with fixed platenuts inside the new, flat tips? I don't see what the angle brackets would do.

Originally Posted by Bob Axsom

This would be fairly simple to implement with sheet metal, angle brackets and floating platenuts. I am thinking about it but not now - schedule crunch.

Bob Axsom

[elippse]

Let me give you a few equations so you can play around with the numbers to see what performance increase you can see at different weights and density altitudes.
Parasite drag, lb., = Q X AP; Induced drag = W^2/ Q X S^2 X PI X e, where:
Q=rho X V^2 / 2, AP=equivalent parasite drag area, sq. ft. W=weight, lb., S=span, ft., PI=3.1416, e=Oswald efficiency factor, V=TAS,mph X 22/15, rho=.00237689(1-6.88E-6 X dalt)^4.256.

Add the two drags, multiply by V, and divide by 550. That will give you the total drag power required.
Now let me show you the resulting HP required from increasing the span by 13% to 26' and reducing the area by 13% to 97 sq. ft., using 200 mph TAS at 1400 lb and 1600 lb at three different density altitudes. It also shows the HP difference and the speed increase that could be seen.

1400 lb 1600 lb
dalt 23/110 26/97 23/110 29/97
1000' 130.7 124.9 4.7% 203.1 133.1 126.7 5.0% 203.3
7500' 110.5 105.0 5.2% 203.4 113.4 107.3 5.7% 203.7
14,000' 93.9 88.6 6.0% 203.9 97.5 91.4 6.7% 204.3

You can use these values to check your own calculations and a spreadsheet program to see if you've set it up right.

[Bob Axsom]

Originally Posted by hevansrv7a

Wouldn't it be easier to just attach with fixed platenuts inside the new, flat tips? I don't see what the angle brackets would do.

The old semi-flat tips with the rounded edges are considered offerings to the God of Speed - N_G. If I do this I will start with a flat 0.016" aluminum tip plate butted right up against the end of the wing skin. The angle brackets will be riveted to the inside of the tip plates and will extend inside the wing skin aligned with the existing tip mounting holes. The floating platenuts will be riveted to the angle brackets and pick up the #8 flathead tip mounting screws. After I have the 3/32" platenut mounting holes drilled in the angle brackets using a non-floating platenut as a drill guide I will open the center hole to 3/8" to clear the wing skin dimples. I hope that clarifies the approach. I may start with an oversized tip plate (anyone remember Ron St Jean's Ram Rod 750?) then test and trim and test and trim ... until the edge of the tip plate conforms exactly to the size of the end of the wing.

Bob Axsom

[elippse]

[quote=Christopher Murphy;407451]Sorry Jim Smith, That is too ugly to be on an RV.Chris M
Chris; you forgot to write IMHO! You probably wouldn't like the triangular extensions on my Lancair, or those on the Diamond Katana and the latest Boeing jets.

[C-FAH Q]

Originally Posted by Bob Axsom

If I do this I will start with a flat 0.016" aluminum tip plate butted right up against the end of the wing skin. The angle brackets will be riveted to the inside of the tip plates and will extend inside the wing skin aligned with the existing tip mounting holes.

Bob,
did you guys get that space camera going on my hanger? I was sure the lead sheild would prevent it !!

You are thinking what i have started to do. quick and easy and no fibreglass.

[Christopher Murphy]

[quote=elippse;407657]

Originally Posted by Christopher Murphy

Sorry Jim Smith, That is too ugly to be on an RV.Chris M
Chris; you forgot to write IMHO! You probably wouldn't like the triangular extensions on my Lancair, or those on the Diamond Katana and the latest Boeing jets.

To each his own I guess.. I was just being sarcastic. The legacy's wing doesn't look bad and I don't know about the Diamond. I am pretty familiar with the Boeing planes and I don't recall seeing anything like that on a Boeing.

I saw a 4 blade prop somewhere that had that type of tip on it. It was pretty ugly too....IMHO.

Chris M

[Mike S]

Originally Posted by Christopher Murphy

I saw a 4 blade prop somewhere that had that type of tip on it. It was pretty ugly too....IMHO.

Chris M

I saw that prop too, on a race plane at Reno-------kicked but t on the rest of the field big time----like 30 mph IIRC