Droop Wing Tip Mod...

[rv9ralph]

I have a mode 3. The problem with the droop wing tips is restriction of visibility to the side. I have thought of modifying the shapes of these to improve visibility. However, what do you loose in performance and handling. I just wanted to tap the braintrust of TeamKitfox.

Here is an annotated picture showing about where I would cut it off. Filling the gap with foam, shaping and covering with glass.

Any thoughts?

16290
Ralph

[avidflyer]

Probably wouldn't make much difference. I remember reading an old study that was done on the different types of wingtips, and it wasn't a whole lot from one to the next. Wish I could find that again. It was kind of interesting. Some government agency did the work. One good thing about the drooped tips is they probably make a good ski for the wing tip to ride on in a good ground loop. :-) Maybe the flaperon gets some protection then and the end rib tail doesn't get broke off. :-( JImChuk

[rv9ralph]

One good thing about the drooped tips is they probably make a good ski for the wing tip to ride on in a good ground loop. :-)

Right you are. My tips are ground down from previous bad handling.

Ralph

[Bud Davidson]

I recall the mentioned study of droop tips, in addition there was a pacer flown with droop tip on one wing. Just to see what happens. No significant effect.
Some of you are familiar with Harry Riblett's work with airfoils. He also had strong opinions about wing tips. Rounded Cub like tips he considered inefficient. He suggested they created drag too far inboard He advised me to square off the tip and consider a slope upward from the bottom of the last rib and flat to the tip from the top of the last rib.. mine was 5 inches out to the squared tip from the last rib. No wind tunnel studies to confirm the effectiveness of this, but I am a strong believer in his work. As I have indicated in the past, Harry was a fellow chapter 240 member (Wilmington, Del)

[sturdee]

Old bungee gear on a friends failed plus the wire strap, the droop tip saved the wing,
as for vizability just lift That wing takes a twitch of the stick in flight, and the roof is excellent too see through during a turn!

[Dave S]

...........Harry Riblett's work with airfoils. He also had strong opinions about wing tips. Rounded Cub like tips he considered inefficient. He suggested they created drag too far inboard He advised me to square off the tip and consider a slope upward from the bottom of the last rib and flat to the tip from the top of the last rib.. ...........(Wilmington, Del)

Sounds a little like a hint of what we call the Hoerner wingtip.

I recall about 30+ some years ago there was a lot of talk and experiments and brew-ha-ha with droop tips on more than one type of aircraft.....one of my pals at a local 'port flew a 152 known as "droopy".

[buckchop]

I took mine off my model 1, and made my own stall fences at mid wing and at the end of wing instead of drooptip, the droop tip is around 3.5lbs each is y i took them off.

[alexM]

Man, all these years I've been calling the drooped tips "Hoerner". As indicated by a previous poster, they are definitely not.

http://buyplaneparts.com/the-hoerner-wing-tip-design-story/

I've built a bunch of r/c planes with tips that do match the description.

Hoerner's resume is not something that can be dismissed.

[Delta Whisky]

My experience matched Bud's. A glider pilot friend taught aero at Texas A&M and after studying and testing he pined that the best wing tip was as if the wing was built too long and someone cut it parallel to the relative wind and at 45 degrees to the longitudinal axis.

[rv9ralph]

If you do some research on Dr. Hoerner, he did design the wing tip from the earlier Kitfox, in that era the design was used by Piper and several other aircraft designers. However, he designed many different types of wing tips. The current Hoerner tips that Kitfox offers are very different from the earlier designs. All were considered advanced for their time

Ralph