Wingtips discussion

[SuberAvid 617]

Did you all notice that the new KF STOL wing has squared off wingtips with fences plus mid wing fences?  It doesn't took like they lengthened the wings, just increased the chord.  I wonder if they did much performance testing of the wingtips to decide the best for short field performance since KF has used drooped tips and Horner style tips before.  Anyone have insight on this?

[Av8r3400 1178]

They are very tight lipped on the details of testing and R&D.

The STi wing is the same span, a very slight increase in chord and quite a bit thicker than the standard Riblett profile. 

I seem to remember someone saying this was another Ribblett design, but I can't say that for sure. 

[EDMO 1078]

They are very tight lipped on the details of testing and R&D.

The STi wing is the same span, a very slight increase in chord and quite a bit thicker than the standard Riblett profile. 

I seem to remember someone saying this was another Ribblett design, but I can't say that for sure. 

If I remember from reading the Riblett letter long ago, I think he said the chord should be about 1.5" or 3" longer, but could be mistaken on that?  Thicker could give more lift, but slower cruise - maybe?  Look at Zenith.   

I don't think that tips mean as much for STOL as they do for decreasing drag for cruise, although squared tips add more wing area / lift than rounded tips, such as Kitfox tips compared to Avid tips - the Short-wing Pipers have proved that with their aftermarket Hoerner style squared chord tips. 

Not to sound at all like picking favorites, but I think that Dean made the rounded Avid tips like the Pipers as an economical way for the homebuilder to make them without having to buy fiberglass tips.  The Kitfox tips can be put on any Avid and should improve STOL a little by adding wing area and lift, but is it worth the expense and weight?  The droop tips are heavy - The Hoerner tips are lighter.

  EDMO

Edited 22 Nov 2017 by EDMO

[Neloner 46]

I liked the fences on the STI wing and am fabbing up a set for my model 3 rebuild to replace the crack prone (and HEAVY) droop tips. Ill have to weigh them and get the difference, Im sure that savings alone will make up for any performance loss from eliminating the droops. 

[SuberAvid 617]

I'm thinking about using the stock Avid wingtips but building a fence from the marker light back.  I'll make it so I can add it and remove it pretty easily so I can tell if it adds any benefit.  I may have to try a build a mid wing fence like KF did as well; there must be some benefit to that since they added it to their STi.