ORIGINAL: Randy Etken
Michael thanks for answering on my post.
The all red wing tip #3 is the one that I designed using Hoerner and adding concave curve to the tip. Saw a picture of a Reno Mustang # 69 using this method.
The though behind this shape is, air flow is diverted for less educed drag in high speed turns, helps hold a knife edge from pylon one to two and from pylon three back to one, also acts as wash out to help in slow speed landings.
Also thanks for listing my R140 Quickee 500 airfoil on UIUC airfoil data site. I try to read every thing you publish.
Pictures are top front bottom and back of wing tip.
You know ... we tested your R140. I did not know who designed it, so it's just called the R140. It's in Vol 1 of our airfoil data:
http://www.ae.uiuc.edu/m-selig/uiuc_...ilsTested.html
Bill Friedlander made the wind tunnel model.
My favorite approach to carving tips is the taper the sharp edge to the camber line of the tip airfoil. There's really no proof that this kind of sharp tip is any better than another type of sharp tip. However, I do think the merits of THE Hoerner tip (drooped down) are iffy relative to any other (I agree w/ what HighPlains wrote above). I've not seen any specific data on Hoerner tips. I had one plane that had interchangeable tips - sharp, round, and squared off. What I found was that the squared off and sharp tips produced more max lift (I could pull tighter). This is pretty consistent w/ what Hoerner shows in his Fig 10 - more max lift. The lower drag part was not something I could confirm by flying feel. So I think your "sort-of" sqaured-off tips are going to behave pretty much like squared-off tips proper and also a sharp edge tip.
Michael