HobbyKing.com New Products Flash Sale
Reply
Thread Tools
This thread is privately moderated by maguro, who may elect to delete unwanted replies.
Old Sep 07, 2011, 07:03 AM
Registered User
Dickeroo's Avatar
Joined Dec 2006
1,180 Posts
Bill Sharpe of Texas, has made a number of KFm4 airfoils with a different twist.
He created a saw-toothed pattern which increases the step area on his Horten flying wing. He told me that this pattern channels the airflow and doesn't allow it to spill off the wing tips. This looks more like a bird's wing to me.

Here is a video that he just posted. Very artfully done.

http://www.youtube.com/watch?v=L1EZeEe64DQ

Take a look at some of his other videos of his KFm4 Horten in flight. They fly beautifully.
Dickeroo is offline Find More Posts by Dickeroo
Reply With Quote
Sign up now
to remove ads between posts
Old Sep 07, 2011, 05:43 PM
Build straight - Fly twisty
Whiskers's Avatar
Australia, QLD, Little Mountain
Joined Feb 2010
4,176 Posts
Quote:
Take a look at some of his other videos of his KFm4 Horten in flight. They fly beautifully.
They certainly do fly beautifully, but then so do many other planes with different airfoils.
I am completely open minded here. When I turned up at the field with a KF plane I was told that it would be no good. And I was given all the reasons it would be no good.
But it did fly very well and continues to do so after a huge amount of flight time.
But my other planes, using a variety on sections, also fly very well.
When the Micks' did all that testing I think the KF skeptics were amazed that the KF wing was not a complete dog, and the KF believers were amazed that the KF wing did not far outshine its competitor.
It was an earlier test, by a father and son team, that got me into KF wings. They liked the way they flew, but found that the flat plate was the fastest and the conventional symmetrical wing had the best glide.
My 3 main aerobatic planes have a KFm4, thin sharp-nose symmetrical and medium thick round-nosed symmetrical sections. Of these 3 the Kfm4 has far the worst glide but that could well be due to other factors and I'm not offering that as a finding, just an observation.
I think the main virtue of the KF concept is in the ease of construction with foam, rather than any magical aerodynamic properties. Others, who I respect, think otherwise. All I can say is that they have observed things that I have not.
P.S. There was an earlier version of the KFm4 wing plane with a flat plate wing. That one had a worse glide than the KF version though it flew OK under power.
Whiskers is offline Find More Posts by Whiskers
Last edited by Whiskers; Sep 07, 2011 at 06:38 PM. Reason: Added the PS
Reply With Quote
Old Sep 08, 2011, 05:21 PM
Build straight - Fly twisty
Whiskers's Avatar
Australia, QLD, Little Mountain
Joined Feb 2010
4,176 Posts
Interesting footage of a stalling wing here.
Zenair Zodiac 601HDS Exper. with Vortex Generators installed (0 min 38 sec)

I seems to me that a KF step could stop the "reverse flow" shown here.
It's a lot like Springer showed us in his excellent work where the tuft tucked in behind the step.
Whiskers is offline Find More Posts by Whiskers
Reply With Quote
Old Sep 09, 2011, 12:45 AM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Aberdeen
Joined Mar 2006
11,233 Posts
Quote:
Originally Posted by Whiskers View Post
I seems to me that a KF step could stop the "reverse flow" shown here.
It's a lot like Springer showed us in his excellent work where the tuft tucked in behind the step.
It's possible but it's also possible that the step only stops the tuft itself from reversing, not the airflow?

If you look at Roger's video: http://www.rcgroups.com/forums/showp...&postcount=495

he has added tufts to the top of the step also.. Look 2min 40seconds into the video; Roger does some high alpha flight.. Notice that the tufts on top of the step bend forward and upward much like the tufts behind the step.

Steve
JetPlaneFlyer is online now Find More Posts by JetPlaneFlyer
Last edited by JetPlaneFlyer; Sep 09, 2011 at 12:53 AM.
Reply With Quote
Old Sep 09, 2011, 12:55 AM
Build straight - Fly twisty
Whiskers's Avatar
Australia, QLD, Little Mountain
Joined Feb 2010
4,176 Posts
Quote:
It's possible but it's also possible that the step only stops the tuft itself from reversing, not the airflow?
Indeed, although the reverse flow must be interrupted to some extent. But would that be a Good Thing? I don't know.
The other interesting thing about that video in that the wing has small vortex generators on the outer part of the wing. It demonstrates how they dramatically delay the stall.
Whiskers is offline Find More Posts by Whiskers
Reply With Quote
Old Sep 09, 2011, 06:48 AM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Aberdeen
Joined Mar 2006
11,233 Posts
I didnt see any vortex generators

The stall progression in the video is what you would expect from a wing with slight or zero taper. i.e. stall starts near the root. The wing may well have some washout built in which would also delay stall near the tip.
JetPlaneFlyer is online now Find More Posts by JetPlaneFlyer
Reply With Quote
Old Sep 09, 2011, 07:34 AM
Build straight - Fly twisty
Whiskers's Avatar
Australia, QLD, Little Mountain
Joined Feb 2010
4,176 Posts
You didn't see the vortex generators because they are very hard to see. But they are there. It's what that video is actually showing.
Have a look here: http://www.stolspeed.com/
Whiskers is offline Find More Posts by Whiskers
Reply With Quote
Old Sep 09, 2011, 12:30 PM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Aberdeen
Joined Mar 2006
11,233 Posts
Ahhh.. 'stealth' vortex generators!
JetPlaneFlyer is online now Find More Posts by JetPlaneFlyer
Reply With Quote
Old Sep 15, 2011, 09:29 PM
Registered User
Dickeroo's Avatar
Joined Dec 2006
1,180 Posts
The KFm4 David really kicks air!

Just saw this posting of the David KFm4 in the RC Flying Wings section where it went over 146 mph. That is probably the fastest KFm4 to date... looks like it has the potential to go even fastest.

http://www.youtube.com/watch?v=zm58pwXye9o

Here's the maiden flight of the KFm4 David...

http://www.youtube.com/watch?v=8hlGx...eature=related
Dickeroo is offline Find More Posts by Dickeroo
Last edited by Dickeroo; Sep 15, 2011 at 09:51 PM.
Reply With Quote
Old Sep 16, 2011, 12:45 AM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Aberdeen
Joined Mar 2006
11,233 Posts
That's zipping right along

The two videos look like different planes to me. The speed test video is a pink foam model and the maiden flight vid is a white foam model with a red painted leading edge. The maiden flight model looks smaller too
JetPlaneFlyer is online now Find More Posts by JetPlaneFlyer
Reply With Quote
Old Sep 16, 2011, 12:59 AM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Aberdeen
Joined Mar 2006
11,233 Posts
Perhaps there may be some error in the speed estimate? Here's what the guy who made the model in the speed test video said:
Quote:
It is just a 3s. Theoretical top speed should be ~125. Static pitch speed is 89. Either I am gaining a lot of speed in the dive, or RCSpeedo is wrong. I have the app on my phone and I backed it up by running the file on my computer. The phone actually said the passes were a bit faster. I went with the lower numbers.
So the maximum theoretical speed for the motor/prop/battery is 125mph based on pitch speed x kv x voltage.. So unless the model is effectively gliding during those speed runs (the prop is contributing only drag at any speed above 125mph) then there must be a problem in the way the speed is measured by 'RCSpeedo'. Or the guy got the pitch speed calculation wrong?

Something is amiss anyway.

Steve
JetPlaneFlyer is online now Find More Posts by JetPlaneFlyer
Reply With Quote
Old Sep 16, 2011, 01:03 AM
Registered User
United Kingdom, England, Portsmouth
Joined Jan 2009
686 Posts
Quote:
Originally Posted by Dickeroo View Post
Bill Sharpe of Texas, has made a number of KFm4 airfoils with a different twist.
He created a saw-toothed pattern which increases the step area on his Horten flying wing. He told me that this pattern channels the airflow and doesn't allow it to spill off the wing tips. This looks more like a bird's wing to me.

Here is a video that he just posted. Very artfully done.

http://www.youtube.com/watch?v=L1EZeEe64DQ

Take a look at some of his other videos of his KFm4 Horten in flight. They fly beautifully.
is there any plans for this Horten IX (KFm4) Flying Wing?
would like to have a go at that wing please.
many thanks RCT
rcta15 is offline Find More Posts by rcta15
Reply With Quote
Old Sep 16, 2011, 12:38 PM
Registered User
Joined Mar 2008
627 Posts
JPF, you may appreciate this video.
Cap_n_Dave is offline Find More Posts by Cap_n_Dave
Reply With Quote
Old Sep 16, 2011, 03:05 PM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Aberdeen
Joined Mar 2006
11,233 Posts
Quote:
Originally Posted by Cap_n_Dave View Post
JPF, you may appreciate this video.
Now THAT'S a flying machine.. thanks for the link.
JetPlaneFlyer is online now Find More Posts by JetPlaneFlyer
Reply With Quote
Old Sep 17, 2011, 08:11 AM
Registered User
maguro's Avatar
United States, DE, Bear
Joined Apr 2007
1,570 Posts
Those under wing feathers make great flow indicators. Did you notice how the airflow reversed under the wing when approached stall? That's what happened on the top of the KFM2 in my tests.

Roger
maguro is offline Find More Posts by maguro
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion ** Kline-Fogleman (KFm) Airfoils - Building/Flying Discussion ** jackerbes Foamies (Scratchbuilt) 7153 Jul 22, 2014 04:20 PM
Cool Here is my KFm-5 DLG GLider (Kline-Fogleman) dougmontgomery Foamies (Scratchbuilt) 151 Apr 21, 2014 09:08 AM
Discussion ** Kline-Fogleman Airfoiled Flying Wing ** Tony65x55 Foamies (Scratchbuilt) 3945 Apr 08, 2014 10:40 AM
Video Kline Fogleman Airfoil on a flying wing Tony65x55 Electric Plane Talk 3 Jan 30, 2009 07:37 PM
Idea Per Dick Kline, Kline-Fogleman test dougmontgomery Hand Launch 49 Apr 13, 2007 02:13 AM