Hi Guys, I'm scratch building a semi-symetrical wing using a NACA 2415 airfoil and have been wondering what to do as far as wing tips on it. It'll have a 11.5" chord, 72" span, and will be used on a high wing sport trainer. Any suggestions on what type of tips I should make if any? Thanks, Tim

If you look up the shape of the Avistar wing tips, they are probably something you want to emulate, since that is considered a high wing sport type trainer. They are actually chopped at a bevel on the underside of them. I imagine they do this for two reasons, first, they shape helps tame it down during potential tip stalls, second, it's more forgiving when landing since you can bump one into the ground and it will not catch into the surface, it actually deflects from it to help autocorrect it back onto it's tripod landing gear.

Another direction to go if you really want to make this even more stable are to add Zagi style winglets.

And yet another direction to think of is simply rounding them off to decrease drag caused by the vortexing of the air around the outer edge of the wing.

they are ez to make -
real benifit-
you can on an aerobatic model , actually change roll couple by slicing tips at different angles - dun it
on the trainer - if you can find any real difference by doing different shapes I would be VERY surprised . theory is one thing
practical experience is another and on stuf this size - changes often are not as "theory" might suggest.

There was some discussion on another board in regards to how people are experiementing with the humpback whale's forward fins, that their shape has some advantages which can be used for increased capacity for wings as well.

For a model of the sort you're talking about the wingtip shape isn't a big deal. You'll have a big fan on the front to make up for any sort of inefficiencies you find. Just about any simple and pleasing shape to your senses will do fine.

Thanks for the advice Guys! I guess I'll just go with some rounded up block and hollow them out to save weight.

Keep in mind, your tips are going to get pulled in after you cover it, that's an area you want to make sure there is some reinforcement. I've never heard of hollowing out a block for them, but what ever floats your boat. :0) Have fun with the build!