Replies to This Discussion

Permalink Reply by Reto on April 4, 2009 at 4:49pm

You may also check out this study by Rich Thompson
Or the RCgroup thread
There's also a nice test video of 4 different KF airfoils on youtube (by RCpowers.com)

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ModeratorPermalink Reply by Howard Gordon on April 5, 2009 at 12:21pm

Interesting reading and viewing. I followed the links to rcpowers.com, and greatly enjoyed the interview with Dick Kline (the 'K' in KF). The interview is in 4 consecutive YouTube clips starting about 25% down the page ...
http://www.rcpowers.com/forum/blog.php?u=27&page=3 . Definitely worth the time !

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Permalink Reply by bGatti on April 5, 2009 at 7:27am

I found the linked article interesting, but merely subjective - and note that an autopilot may be an excellent tool for evaluating wings empirically, since the results can be directly reduced to numbers. This would requite a ground link or data-logger of course.

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Permalink Reply by jpace on April 5, 2009 at 7:44am

bGatta,

Way to bring the conversation back around to autopilots, since that is what this site is for! I was a little off-topic in posting this, but I found the KF airfoils pretty interesting because they look like a pretty quick and easy way to build up a wing for a scratch built project.

Given that we are building airplanes to haul radios, autopilots, sensors, and cameras I think the KFm3 airfoil has special application where this group is concerned in that it is a "heavy lift" design. This may be why user jaron selected it for the scratch-built wing he designed which got me interested in this whole KF thing in the first place.

I believe the study referred to in this thread by Reto is probably more interesting than the original article I linked to.

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Permalink Reply by bGatti on April 5, 2009 at 11:23am

Right (I was referring to 'The Study" which I think is a spreadsheet of subjective observations. Certainly a world in which "5" means "As fast as the other planes" doesn't come across as the most scientific. That said - and I'm quick to say - the FogelKline wing - presents an interesting challenge to the general view of smooth lines - ie, that they are aerodynamic.

I think we must include in this page a mention of "coke bottle shapes" - which were discovered to solve a problem with smoother fuselage shapes. I suspect the advantages of both, and the physics of both are the same - by upsetting the laminar flow, particularly on the later half of the body, the tendency of the fluid to latch on to the body and hold it from moving forward may be useful.

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Permalink Reply by jaron on April 5, 2009 at 1:49pm

Unlike the example from above the KFm3 airfoil of my flying wing is built without spars (except for the root section). The rigidity results from the overlapping foam sheets.
Have a look at the PDF plan for a cross-section of the wing.

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Permalink Reply by Reto on April 6, 2009 at 8:32am

It is a similar layering that makes some other foam flying wings and deltas rigid enough. an example of such construct, though not a KF airfoil, is the Pibros delta using decreasing triangle layers in a folded foam sheet envelope.

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Permalink Reply by Dick Kline on May 25, 2009 at 5:33am

For those of you interested in the Kline Fogleman airfoil concept, you might want to check out this thread which discusses why people chose the airfoil they use. It is only four pages long and a number of people seem to prefer the KFm airfoils and they state the reasons why they use them.

http://www.rcgroups.com/forums/showthread.php?t=1051573

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Permalink Reply by Edo McGowan on September 6, 2010 at 7:57am

I'm building up a long thin KFm3 but want a Hoerner curved tip. Any thoughts on how to step this down with the KFm3? The dimensions are 12 foot span by 13 inch cord. Input would be appreciated.

If the wing tip is cut at 45-degrees with a small radius at the bottom and a relatively sharp top corner, the air from the secondary flow travels around the rounded bottom but can’t go around the sharp top corner and is thus pushed outward.


The performance of the aircraft depends on the distance from the right to the left tip vortices (the effective wing span), and not the actual measured geometric span. Hoerner wing tips provide the largest effective span for a given geometric span or a given wing weight.

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