Quickee 500 - best wing tip shape for speed?
 

What wing tip shape seems to work best for sheer speed - simple rounded, or tapering to a sharp edge? I'm not adverse to the tip shape shown in the plans but am open to changing it...

Am not into pylon racing - just looking to build a fast sport plane. I have a rear exhaust piped .60 size pattern engine for it. Am doing a little kit bashing to accomodate the bigger engine and tank. Should be a blast!

RE: Quickee 500 - best wing tip shape for speed?
 

Daryl,

I believe the best tip shape is what is called an "advancing" tip design. Look at the attachment; it should be clear and better than me trying to explain it in words.

Notice that on the front view I've included two styles--one where the top and bottom surfaces both round and meet in the middle of the chord line and the second where the bottom curves but the top remains straight. This will induce a slight dihedral effect but some people feel it reduces the tip vortex more. In my view the most important shape is the one seen in the top view.

RE: Quickee 500 - best wing tip shape for speed?
 

js3:

Your S Cat wing should be able to handle the loads of your intended airframe. Do not sharpen the leading edge or you will have one nasty flying airplane. Going to a 60 may be in reverse of what you want to do. May be better to go with a good 40-46. Power to weight do not seem to catch up to most 60' with exception of Jetts small block 60 that turns 17K or better. NOw that would be interesting!

RE: Quickee 500 - best wing tip shape for speed?
 

Thanks for the replys guys. That "advancing tip" design looks pretty close to the stock kit configuration. If that's optimal, or as close to it as makes sense for modeling purposes, I'm in! I kind of figured the Quikee 500 designs would be reasonably optimized anyway. I know the .60 isn't optimal for weight and speed, but I have it and it needs a home. This is just for sport use. I know the Nelson & Jett engines are the way to go if you're serious about going fast, but I could personally not justify paying what they're worth. I'm into cheap speed. I'm kind of excited about this project!

RE: Quickee 500 - best wing tip shape for speed?
 

The Scat Cat is a really old design, at least 25 years ago, perhaps more than 30. As such, it was developed in the era of K&B .40's of about 1 hp. A Nelson or Jett on it would blow it apart at the first turn, as the wing with the soft 1/16" sheeting just doesn't hack it anymore. If you want to up the power, you need to sheet at least the top of the wing with 3/32 balsa in the 7-8# range, and add some carbon fiber strips to the bottom skin (assuming you are going to do positive g flying at speed). On the wing, you can also add 1/8" to the leading edge to make a slightly sharper entry point without hurting the flying qualities.

The other problem you will have to solve is the balance. A K&B .40 was a very light engine, something on the order of about 12 oz (no muffler way back when). Even a very light .60 is in the low to mid 20's. So you will have to chop off much of the nose of the fuselage, we had to cut off about 1 inch with the later .40's, and mount the servos behind the wing in the tail. With the 60, I would put the tank on the CG, and cut the nose at least 2", perhaps more, depending on the servo weight.

RE: Quickee 500 - best wing tip shape for speed?
 

HighPlains - thanks for the tips. I was considering doing much of what you suggest. I made the former in front of the wing large enough to slide an 8 oz Dubro tank (on it's side) through. I was looking at locating the firewall further aft as far as I can put it - at one point the tank will begin to touch/interfere with the wing upper surface. I made cutouts and boxes for servos in the wing. I'm not comfortable with the loss of strength that imparts to the wing and will glass with Zpoxy and 3/4 oz cloth to restore strength. I've got carbon fibre strip I can glue on first to strengthen the wing, but it'll likely be overkill - I'll do it anyway because it won't weigh much extra... I'll locate the battery in the fuse aft of the wing saddle so hopefully this'll balance everything out.