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Droop tips

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d(at)cfisher.com
Guest

Posted: Sat Mar 03, 2007 5:29 am Post subject: Droop tips

I am looking for anyone that has changed from Droop  tips to the more current  hoerner style tip on a IV.

  

 What was gained  or lost  if anything ?  

  

 I have mixed thoughts on Droop tips.    Personally would a winglet tip  ( invested tip) now give better STOL  ?

  

  

 Open for comments.

  

  

 Dave 

  

  

   [quote][b]

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat Mar 03, 2007 9:28 am Post subject: Droop tips

At the speed my 'Fox flies I  doubt the droop tips make any difference to flight dynamics.  I don't think  winglets will make any difference either.  They do look distinctive  though.

  

  

 

Noel [quote]   

   --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Sat Mar 03, 2007 12:35 pm Post subject: Droop tips

Here is a place I think the droop winglets may help: It will protect 

the flaperons in case of a ground loop where the wing tip touches the 

ground. I never tried it so I have no idea if I am right, just a hunch.



Cheers,

Michel

_________________
Kitfox 3 - Jabiru 2200

d(at)cfisher.com
Guest

Posted: Sat Mar 03, 2007 1:17 pm Post subject: Droop tips

Michel,  Funny  -- let's hope that not the only reason  



I would like to think that they might help in ground effect but I cannot see 

what gain they are otherwise .

They would tend to hold the vortice in longer and I think for better STOL 

perhaps if they were inverted  they would hold the low pressure in better on 

top and possibly create more lift ?   Simular to a STOL fence on a 185.



What was reason for newer Kitfoxes to have the differnt tip anyone ?

Lessening Adverse yaw  would be my thought.

Speed ?  I am not sure as mine runs 86 to 90mph  on wheels with a 582 .



Dave



---

Glenn Horne

Joined: 10 Jan 2006
Posts: 96

Posted: Sun Mar 04, 2007 5:12 am Post subject: Droop tips

You are right. Been there done that.

Glenn

---

mclayton(at)rochester.rr.
Guest

Posted: Sun Mar 04, 2007 5:57 am Post subject: Droop tips

Dave,



I have done some digging on the effects of various wingtip designs on performance.  Here is what I remember....

Winglets effectively increase the span of the wing by keeping the tip vortices outboard of the wing.  Hoerner tips and tips that droop or the reverse (stick up) also have the effect of pushing the vortices further outboard on the wing.  However, in order of effectiveness (as I recall) they are: 1. Hoerner tips, and 2. Droop tips.  However, published experimental data from wind tunnel tests, as well as mathematical modeling indicate that the differences between these are relatively small.



I am rebuilding a KF2, and spent time looking into this issue to see if a change would be worthwhile, and concluded that the differences were not large enough to consider.  However, there is another technology that will help improve the stall performance of the aircraft, and that is vortex generators.  These are small devices that are usually attached to the wing, near the leading edge, and they help to prevent boundary layer separation at steep angles of attack, and thus improve the lift coefficient and reduce the stall speed.  They are very inexpensive, and John McBean sells a kit that can be used to install these on a Kitfox.  



There is lots of good information on the web, you just have to go digging a bit.  If I can resurrect the URL's for some of the web sites I looked at, I'll post them.



Mike

On Mar 3, 2007, at 8:29 AM, D. Fisher wrote:

 	  Quote: 	
		  I am looking for anyone that has changed from Droop tips to the more current  hoerner style tip on a IV.

 

What was gained  or lost  if anything ?

 

I have mixed thoughts on Droop tips.   Personally would a winglet tip  ( invested tip) now give better STOL ?

 

 

Open for comments.

 

 

Dave

 

 

 	  Quote: 	
		           - The Kitfox-List Email Forum class="Apple-converted-space"> --> http://www.matronics.com/Navigator?Kitfox-List              - NEW MATRONICS WEB FORUMS -  class="Apple-converted-space">   --> http://forums.matronics.com

Bob

Joined: 24 Oct 2006
Posts: 89
Location: Damascus, Maryland, USA

Posted: Sun Mar 04, 2007 6:45 am Post subject: Re: Droop tips

Hi Dave



First off, you've got a great web-site! 



I don't have personal experience with the droop tips on the IV, but did have them on a Cessna 150 that I resurrected and flew for a year.  The "batman tips" (I think they were the Madras STC) became a magnet for talking such things with other droop-tip owners.  In short, they maybe-possibly-perhaps lowered the stall speed by a smidge (2mph?) in the Cessnas.  It sure wasn't the 5+ mph was advertised.  The Piper owners reported more pronounced effects, especially when in ground effect, which makes a lot of sense.  When the stall developed in the 150, the droop tips did seem to make things a bit more squirrely and I liked the stall less than in similar planes with hoerners or the old round tips. For how low and slow you seem to like flying around the mud-patch, that may be something to consider.



The hard aerodynamics and common-sense perspectives agree with what Mike Clayton mentioned.  The big-3 in determining stall speed are your weight, wing area, and CL (coefficient of lift).  Your plane's weight is pretty well established and while the tips sorta kinda make a small change in effective area, it is relatively small.  However, the VGs change the CL for the entire wing.  The change can be enough that the size of the horizontal tail can become an issue, so if you go this route put a set on the bottom of the horizontal stab, as well.



Bob

Aero Eng, A&P

Vixen in work

_________________
Remember that internet advice may only be worth what you pay.

d(at)cfisher.com
Guest

Posted: Sun Mar 04, 2007 4:21 pm Post subject: Droop tips

Bob,



Yup the site is a great way to share info with others.



I agree with all you say...  and  VG's  I have afew sets from differnent 

companies here  and I might try them in the spring......



Personally I think that  the fundamentals of the hoerner style give me the 

more interest. Droops tips I have mixed feelings on.

A slight winglet like these are interesting 

http://www.crosswindsstol.com/prod01.htm

Or these more hoerner style ......... 

http://www.stewartshangar21.aero/wingtip.htm



Food for thought for anyone who thinks they can tweak a bit more outta 

Kitfox.



I think a the big hole in the round cowl is way to big for the needs of the 

582 and possibly a bit of drag there as well. ?

Dave



---

rexjan(at)bigpond.com
Guest

Posted: Sun Mar 04, 2007 7:09 pm Post subject: Droop Tips

Here is a place I think the droop winglets may help: It will protect

the flaperons in case of a ground loop where the wing tip touches the

ground. I never tried it so I have no idea if I am right, just a hunch.



Cheers,

Michel



I agree but  although I have looped nothing touched the ground. In  fact  I

just held the wing up with the stick. I also used rudder but I thought that

was wasted effort. I thing holding the wing up was worthwhile though. I do

feel the droop tip may be helpfull too.

                  Rex..

rexjan(at)bigpond.com

trevorkebb(at)earthlink.n
Guest

Posted: Mon Mar 05, 2007 6:01 am Post subject: Droop Tips

Nah, ground looped my Model IV with Hoerner tips once and scraped the tip 

only. No damage to the flaperon.



This was with standard, not Speedster, length wings.



Droop tips were a fad that came and quickly went.



RB



Do not archive



 	  Quote: 	
		  

 Here is a place I think the droop winglets may help: It will protect

 the flaperons in case of a ground loop where the wing tip touches the

 ground. I never tried it so I have no idea if I am right, just a hunch.

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