Wayne and Bob,
I took a picture of the flat racing tips, and Wayne, hope you don't mind me posting some closeups, to help answer Bob's questions and then ask a couple of my own, as I would like to make a set as well. Here are the pics, cropped to show the full length, and then just the aft portion, by the aileron:
I wish I'd have taken more, including pics of the inside before they were installed. I'd describe them as a fairly narrow endcap glassed onto a flange (poor word) that is match drilled to fit the nutplates in the wing (like the regular wingtip is) and then is fitted over the wing, and screwed into place. Seemed like they added almost nothing to the span (Maybe a quater inch Wayne?).
Wayne, I didn't notice the inside of the section that runs next to the aileron...was that just flat layered glass, thick enough to stay put and not interfere with the aileron (as you described above)? Or did you embed any stiffener into that section?
The second pic is a little closer of the aft section, and you can see the neat little fairing that Wayne added to next to the outside of the aileron hinge. Nice little touch.
OK, here's a couple questions:
1. Bob, why the bevel? Sounds like if viewed from the front, the upper portion of the tip would be wider than the lower, and the outer surface would be beveled about 45 degrees toward the ground. Is that what you are thinking? Just wondering what you are trying to acheive aerodynamically...not questioning you at all, just scratching my aero 101 brain to think of what that would do...very interested!
2. A VAF buddy and I were talking about the tips the other day, and he came up with a thought to make the tips in a way that would end up making little winglets out of them. His idea was to make the bottom follow the contour of the wing, just as Wayne's do, but to have the upper edge (outboard of the flange/nutplates, of course) go straight back, parallel to the chord line. That would make a sort of triangular shaped section that was perpendicular to the ground, that was the thickness of the endcap (maybe 1/4" to 3/8" thick...maybe even 1/2"). His point was that slowing the spanwise flow near the tip might delay separation near the tip, perhaps impede vortex development, and decrease induced drag a bit. My first reaction was skeptical, but the thoughts might have merit, if the vertical extension could be made strong enough without adding too much weight. It would definitely need to be strong enough not to fail and get tangled up in the aileron...my biggest source of skepticism. Perhaps if the endcap was built as a solid piece, and the shape of the extension was just made in final trimming.
Not sure if I'm 'splainin' that very well Lucy
, so here's a (poor) little drawing to illustrate the basic idea. The blue is the wing and the tip endcap would be the blue and the white triangle all made as one piece:
Not trying to start a winglet debate, as these would not be full blown winglets, but just be very small extensions, tapering from nothing near mid-chord to perhaps 3" at the trailing edge. Not sure whether they should be pure vertical, or slightly canted out, as real winglets often are (hmmm, could that be the source of your bevel idea Bob?)
Anywho..whattya guys think? Is stopping or slowing spanwise flow worth the effort at glassing up tips such as this? Think a small extension would be effective at doing this, or would just reducing the wing area with basic flat tips provide the most bang for the buck, speed-wise? Comments from anyone welcome!
Cheers,
Bob
