HobbyKing.com New Products Flash Sale
Reply
Thread Tools
This thread is privately moderated by maguro, who may elect to delete unwanted replies.
Old Feb 06, 2013, 01:37 PM
Registered User
Joined Jul 2012
43 Posts
Quote:
Originally Posted by dave1993 View Post
personally in my tests there was no increase in lift. imo the biggest benefit is stall resistance. i never get tired of seeing my kf foamy float along unbelievably slow at crazy aoa. at least compared to uc w/o the strips.
Yeah, probably with thin airfoils already optimized for high efficiency, there would be no increase in L/D ratios. However with thick airfoils, there is a chance to apply the KF because the flow separates from the airfoil on a thick airfoil like a NACA0024.
g828 is offline Find More Posts by g828
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 06, 2013, 03:22 PM
KlonWarz
Joined Dec 2012
454 Posts
Interesting wind tunnel vid!
...I got nothing from it.
Suppose I need an education to know what to be looking for???

Well, here's a nice vid I just stumbled upon a few minutes ago...
These people are Flying a wing!
I'm impressed! a Lot!

BMF On Tour - GO BIG Mfk Falkens bidrag - 19. maj 2012 (13 min 16 sec)


rc
rusty case is offline Find More Posts by rusty case
Reply With Quote
Old Feb 06, 2013, 05:39 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,860 Posts
There is a thread on the plane here: http://www.rcgroups.com/forums/showthread.php?t=1655952

31feet - 9,6m
52LB - 24kg
Mats are 15 and 20mm styropor covered with tape.
Powered by Hyperion 5045 on 12S 6500mah - prop APC 22x10E
Plenty of power

Jack
jackerbes is offline Find More Posts by jackerbes
Reply With Quote
Old Feb 11, 2013, 10:16 PM
Registered User
Joined Apr 2009
122 Posts
Hey everyone, I'll be honest I'm new to this thread and have skimmed through parts of it but not in any depth. Anyways, I did a quick experiment to compare a KF airfoil to a regular airfoil and an un-profiled wing, testing lift and drag at 0 degrees and 20 degrees. It is a very basic test, but I thought it might be interesting to some of you all the same. Here is a video discussing the results:

KF Airfoil - Wind Tunnel Testing (3 min 36 sec)


I plan to come up with a better workflow for taking measurements, then test a wider variety of airfoils at increasing angle of attacks. I also want to do some airflow visualization, but am having trouble making a steady stream of smoke.
experimentalrc is offline Find More Posts by experimentalrc
Reply With Quote
Old Feb 11, 2013, 10:51 PM
KlonWarz
Joined Dec 2012
454 Posts
Nice test.
I'd like to see more variables introduced.
Thanks for posting the vid link!
rc
rusty case is offline Find More Posts by rusty case
Reply With Quote
Old Feb 11, 2013, 11:37 PM
fix-it-up chappie
tolladay's Avatar
Valley Village, CA
Joined Jan 2002
2,262 Posts
Quote:
Originally Posted by experimentalrc View Post
Hey everyone....
Nice video. I like the "simple yet effective" testing.
tolladay is offline Find More Posts by tolladay
Reply With Quote
Old Feb 12, 2013, 10:17 AM
treefinder
springer's Avatar
SE MI
Joined Oct 2004
9,576 Posts
Fascinating! Simple yet effective for sure!!!!

Have you tried any flow straightening mechanisms yet? like the soda straws or paper when you do the smoke? Love the brushless tunnel fan idea!
springer is offline Find More Posts by springer
RCG Plus Member
Old Feb 12, 2013, 10:39 AM
RC beginner
New York
Joined Oct 2008
6,048 Posts
Quote:
Originally Posted by experimentalrc View Post
I did a quick experiment to compare a KF airfoil to a regular airfoil and an un-profiled wing, testing lift and drag at 0 degrees and 20 degrees.
im unable to view videos atm. could you provide a brief summary of your conclusions regarding comparison of lift and drag?
dave1993 is offline Find More Posts by dave1993
Reply With Quote
Old Feb 12, 2013, 10:53 AM
KlonWarz
Joined Dec 2012
454 Posts
Dave, his testing confirmed all the other declarations regarding the KFm step.

a true airfoil had less drag and better lift
a KFm had a very little bit better stall at high incident AoA

The main thing here is that the KFm is ez to build for the hobbyist and will get respectable results.

I'm sure someone will come along and give a more technical critique!
:-)
rc
rusty case is offline Find More Posts by rusty case
Reply With Quote
Old Feb 12, 2013, 11:12 AM
RC beginner
New York
Joined Oct 2008
6,048 Posts
thanks rusty. that was very helpful and agrees with results from my own tests couple years back. i also like the improved stiffness with the kf strip. allows higher aspect ratio wings which sorta compensates for the slight reduction in lift..
dave1993 is offline Find More Posts by dave1993
Reply With Quote
Old Feb 17, 2013, 07:01 PM
Registered User
Dickeroo's Avatar
Joined Dec 2006
1,185 Posts
For those of you who haven't seen this but might be interested...

Here is a weight-lifting test between a KFm3 and a conventional airfoil.

weight lifting part 2 (11 min 40 sec)


The final tally.

KFm3 79 oz. / Conventional 71oz.

weight lifting part 3 (6 min 10 sec)
Dickeroo is online now Find More Posts by Dickeroo
Last edited by Dickeroo; Feb 17, 2013 at 07:16 PM.
Reply With Quote
Old Feb 22, 2013, 02:59 PM
Must not buy more planes!
mclarkson's Avatar
USA, KS, Wichita
Joined Jul 2010
2,289 Posts
Is there a recommended relationship between wing chord and step height? Might I make my steps too shallow or too tall?
mclarkson is offline Find More Posts by mclarkson
Reply With Quote
Old Feb 22, 2013, 03:38 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,860 Posts
Quote:
Originally Posted by mclarkson View Post
Is there a recommended relationship between wing chord and step height? Might I make my steps too shallow or too tall?
Not really, just the percentages in the figure in post #2 and how that happens to work out for various materials. If you have a 10" KFm4 wing the recommended thickness at the thickest point would be 6-9% or 0.6-0.9".

If there was three layers of material there and we used 0.25" FFF it would make the steps about 0.25" high and the wing would be just slightly over the 7%.

If you did the same build with 1/2" foam and the chord was scaled up and the other numbers all scaled about the same (20" chord, 0.5" steps, 1.5" thick wing) I would expect it to work as well.

Jack
jackerbes is offline Find More Posts by jackerbes
Reply With Quote
Old Feb 22, 2013, 05:29 PM
Must not buy more planes!
mclarkson's Avatar
USA, KS, Wichita
Joined Jul 2010
2,289 Posts
I was never entirely sure, reading those diagrams, just what the 7-12% referred to. The chord? The span? Something else?

I have a wing with a 12" chord, for example. So a KFm4 would need to be around 1.25" to 1.50"? So, were I making it from 1/4" FFF, I'd want to use multiple layers? (Otherwise, I'd only be 0.75" thick, correct?)
mclarkson is offline Find More Posts by mclarkson
Reply With Quote
Old Feb 22, 2013, 05:47 PM
Build straight - Fly twisty
Whiskers's Avatar
Australia, QLD, Little Mountain
Joined Feb 2010
4,217 Posts
Go for a KFm6 with steps at around 40 and 60% (or whatever takes your fancy)
At 1 1/4 inch it will be right on the money.
Whiskers is offline Find More Posts by Whiskers
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) 7177 Today 12:33 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