DROOP TIP VS SPEEDSTER HOERNER TIPS

[EDMO 1078]

I have been discussing with SuberAvid about the differences in wingtips - I know that the Avids have permanent tips - There are a lot of conflicting opinions on the lift and drag of the drooped Kitfox tips compared to the later Hoerner-type tips that Kitfox uses. The Hoerner is supposed to have less drag, and the drooped is rumored to have more lift.

As a rational way of comparison, someone who has removeable tips could use each type and make valid notes about how each type affected takeoff, cruise, stall, etc., on the same plane.

I cant do this with my extended wing chords since I use Cessna wingtips, and I don't have the Cessna droop tips.

Has anyone ever flown a plane with both wingtips? Maybe Cessnas with a droop tip change?

Does anyone have any info on this?

EDMo

I guess that none of this probably matters, unless you are in the Reno Air Races!

Edited 11 Mar 2015 by Ed In Missouri

[TJay 1041]

I would like to know too, My kit has the 2 piece drooped tips. when I install them I would like to cut them down a bit, I really dont care for the drooped look.

[Cropduster13 11]

FWIW  I changed out the droop tips on a KF4 , and saw no difference in performance, but did get a better view and quit banging my head ,when I walked around the plane.

[EDMO 1078]

FWIW  I changed out the droop tips on a KF4 , and saw no difference in performance, but did get a better view and quit banging my head ,when I walked around the plane.

Thanks,

That's the best, and only information, that anyone has posted.

EDMO

[1avidflyer 1983]

There was a study done on the different types of wingtips that I found on the net a year or two ago.  It was done quite a few years back, don't remember if it was by a gov. agency or collage.  In comparing the different types of tips, figures showed not a lot of difference from one to the other.  I do remember that the drooped tips had a slightly better lift.  I looked for the study last night and didn't find it, that's why I didn't say anything already.  I was searching drooped tips when I ran across the study.  Pictures were all in black and white, so it was fairly old.  Jim Chuk

[dholly 718]

I recall John McBean and some of the Desert Squadron builders discussing this topic years ago. IIRC, they said there was no appreciable increase in top speed when swapping to Hoerner tips from drooped, nor any great decrease in stall speeds when swapping from Hoerner to droop tips. Boiled down to aesthetics for most.

[SuberAvid 617]

Thanks for the discussion.  I like the look of the stock Avid tips so at this point plan to use them on my new wings.  The Avid tips are better than 12" addition to the length of the wing each side.  I plan to use 1/2" washout like the later KF and Magnums.  Wondering if the added length of the Avid tip vs a short Hoerner or flat end makes any difference with the lessened washout???

[wolves200 31]

I have some friends here in Sweden that are building a new aircraft and as far as I heard; wing tips are only a tangible advantage; when you are flying more than 200kt or 10000ft and above; somewhere there can´t recall the exact numbers, basically top end airplanes and airliners are really making use of these advantage. Rest is just cosmetic.

 

Their original design didn´t have wing tips because it wasn´t necessary, but they got hold of a Rotax turbo engine 150Hp and the airplane performs just within that range, now the plane is suited with wing tips.

 

http://eco1aircraft.com/

 

Edited 26 Mar 2015 by Wolverine

[TJay 1041]

cruise at 150 to 200 knots and stall at 35 knots? sounds almost to good to be true.

[akflyer 1427]

cruise at 150 to 200 knots and stall at 35 knots? sounds almost to good to be true.

The sherpa does.. well it will 175+ and stalls around 36.. that plane has been my wet dream since it was introduced.

[dholly 718]

Randy - Why not use Finch tips? According to Steve Winder, it was the only tip that showed more than negligible benefit in testing at our speeds, although only at top end with no real low speed or stall benefits. Along with your 1/2" twist, might really help you cruise. An easy install... Magnum wing chord and installation with standoffs the same as Mk-IV. If you don't mind fixed tips, this would be one the easiest of all Avid/KF tips to do and, hey, if you get pissed at the 'eye pokers' as Ed calls them, it would be a pretty quick job to remove them and replace the short piece of trailing edge material with straight and only minimal fabric patch/paint work.

[edit] P.S. - I can go measure but, IIRC, the KF Hoerner tips I have for my A+ added ~3"-4" per side over the stock Mk-IV fixed tips.

Edited 26 Mar 2015 by dholly

[KFfan 151]

Finchtip.pdf

[EDMO 1078]

Randy,

My KF Hoerner (Speedster) tips measured 16" long - I just measured them to box and mail to the buyer.

If you are looking at lift, try Catalina wings.

Optimum for speed, if you can make them, is winglets that stick straight up and give a theoretical increase in span, increasing aspect ratio and reducing drag - Just look at the modern Boeing Jets wings.

I just noticed that the Airbus 320 has triangles on the tips, like up and down winglets, but I think the Boeing engineers have them beat with the up winglets.

EDmO

Edited 26 Mar 2015 by Ed In Missouri

[dholly 718]

16" wide I presume? Keep in mind the tip is trimmed length/chord wise by each builder. I know one guy who left his tips wider than the factory scribe line and another who cut his quite a bit narrower, so the plane would fit in his garage with wings folded.

 

[edit] Randy - I just measured the width of my KF Hoerner tips. I had cut them to 13.75" wide. So add 144" spar length and I have 157.75" L.O.A. per wing. I need to find my calculations for the wing area of my A+ vs. my KF4 w/ droops.

Edited 26 Mar 2015 by dholly

[wolves200 31]

cruise at 150 to 200 knots and stall at 35 knots? sounds almost to good to be true.

 

Dynaero MCR airplane is performing near the same, nothing new, there are other examples, blackwing is not pioneer in this technology, it´s just another all carbon composite down to the control stick and it came out lighter than anticipated.

 

I also want to mention that the only one who I ever heard had any type of effect by modifying the wing tip is John Miller placing Vortex generator there; he has a full report over the other side of the river (the dark side) I believe Randy also installed VG on the wing tips...

 

for those curious about 150hp Rotax; there is a Norwegian company who thought, regular 80hp rotax was over complicated and overkill NICE little ENGINE, so they began removing useless systems and parts to make it nicer and cleaner they came up with a pretty nice upgrade to that engine.

 

https://www.facebook.com/edgeperformance.no/photos_stream

 

Regards

Dimi3

[Jfquebec 2]

I think the drop wing tip have better control at slow speed...because the vortex at the tip stop down on the side of wing tip..and whitout the vortex it under the wing...?? That is the result of my reserch.....

[EDMO 1078]

One pilot used both kinds of tips on his Kitfox, and reported no differences in performance.

EDMO