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May 28, 2013, 01:35 PM
aerodynamics is just a theory
uses kfm2 airfoil(:
https://www.rcgroups.com/forums/show...2#post25106172
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May 29, 2013, 08:58 PM
just Some Useless Geek
MPF from Model Plane Foam in Michigan is RL Adams precision foam. Adams decided they wanted to play in the modeling foam market and the Model Plane Foam boys formed a new corp to be Adams' distributor. This is the best thing to happen to scratch building since the invention of the X-acto #11 blade. I kid you not.
Last edited by A Useless Geek; May 30, 2013 at 10:23 AM. Reason: Oops! Missing end quote
May 29, 2013, 09:15 PM
Jack
jackerbes's Avatar
Bad link on that geek, must be your excitement...

"http://www.modelplanefoam.com

does not work and takiing the quote mark off didn't fix it for me... ???

Jack
May 29, 2013, 09:42 PM
ancora imparo
jj604's Avatar
Jack

http://www.modelplanefoam.com

works for me.

Quote:
Originally Posted by jackerbes View Post
Bad link on that geek, must be your excitement...

"http://www.modelplanefoam.com

does not work and takiing the quote mark off didn't fix it for me... ???

Jack
May 29, 2013, 09:58 PM
Jack
jackerbes's Avatar
Yep, that's working. Geek had an extraneous quotation mark on his or something but yours is working fine.

Jack
May 30, 2013, 10:24 AM
just Some Useless Geek
Sorry, folk. Yeah, I left off the closing quote on the URI. Sad, how these technoweenies can't even mark up a URI properly...
May 31, 2013, 03:15 AM
Must not buy more planes!
mclarkson's Avatar
Is MPF stiffer than Dollar Tree foam w/o paper? Or ...?
May 31, 2013, 08:01 PM
just Some Useless Geek
No. There is a great deal of discussion on this material over on the MPF thread.
Jun 16, 2013, 10:32 PM
Registered User
Dickeroo's Avatar

Testing of a KF prop against a conventional prop.


I dug into my old files and came up with a note from George Leu from 2007.
Here is what he said about the prop test that he conducted many years ago... sadly, George died several years ago.


"The experimental blades were eleven inches long and had a seven-degree angle of pitch, the engine used was a Webra Speed .60 cubic inch.
George Leu conducted a simple static test with a radio-controlled plane anchored to the ground. A spring-loaded fish scale was used o determine the amount of pull or thrust produced by both a conventional blade and the Kline-Fogleman prop. The results were striking. The conventional blade pulled a maximum of ten pounds. But when Leu put the Kline-Fogleman prop on, he got eleven pounds of thrust, or a 10-percent increase in thrust with slightly fewer RPMs (a 200 RPM drop in a 13,500 RPM run). The test was repeated a second time, and the results remained the same. Then Leu put the Kline-Fogleman prop on his radio-controlled plane and flew it. He noticed that it climbed vertically with much more power than with the conventional prop that he had flown before. Furthermore, the plane needed less correction than usual to do the standard maneuvers, such as rolling or looping. Obviously, something was happening that was rather hard to explain."
Jun 16, 2013, 11:14 PM
aerodynamics is just a theory
That's very interesting... Why aren't there props made like that?
Jun 16, 2013, 11:19 PM
ancora imparo
jj604's Avatar
Possibly because, unlike a straight model wing, machining/moulding a step in an airfoil that has a continuously changing shape and twist is fairly difficult?

You also have to sell "weird" looking props to disbelieving customers.
Quote:
Originally Posted by corsair2014 View Post
That's very interesting... Why aren't there props made like that?
Jun 17, 2013, 05:01 AM
(pr zedsumo)

KF step props


Quote:
Originally Posted by Dickeroo View Post
I dug into my old files and came up with a note from George Leu from 2007.
Here is what he said about the prop test that he conducted many years ago... sadly, George died several years ago.

"The experimental blades were eleven inches long and had a seven-degree angle of pitch, ... ..."
I recall seeing this report some time ago. It included a photo of the prop, (unfortunately can't find a link, perhaps Dickeroo can) - a critical fact missing from this post is that the "KF step" adaptation to the prop was applied to only the outer fifth or sixth of the prop blades, by carving/filing/machining an existing wood prop, obviously then rebalanced.

This is interesting as this is the high-speed business end of the prop. Perhaps if the step were applied to the length of the blade a different result may be had, or perhaps the efficiency gain from the slower moving portion may be a diminishing return not worth the (one-off hand) manufacturing complexity. With solid modelling in CAD and CNC of casting molds for production run, this would not be an issue.

For adapting existing props, obviously the profile of the prop would need to be "fat" enough to accommodate the "KF step" cut-out, meaning it would have to be a wooden prop. The typical RC plastic/nylon/CF APC/GWS/SF/E type props don't have thickness to spare.

I don't recall mention of whether the noise levels changed at all. The tip of the prop is the noise generator end and turbulence=NOISE.

Also, no mention of whether the static-thrust efficiency gain came at an increase or reduction of power draw - something probably more easily quantified with an e-power analyser / watt-meter setup.
Last edited by zsumo; Jun 17, 2013 at 05:26 AM.
Jun 17, 2013, 09:50 AM
Registered User
Dickeroo's Avatar
[QUOTE=zsumo;25290804]I recall seeing this report some time ago. It included a photo of the prop, (unfortunately can't find a link, perhaps Dickeroo can) - a critical fact missing from this post is that the "KF step" adaptation to the prop was applied to only the outer fifth or sixth of the prop blades, by carving/filing/machining an existing wood prop, obviously then rebalanced.

Okay, I went back into my old files and found another document. It is from a man named Paul Wheeler, who used the KF concept on a powered glider. He tells a man named Ivo what he had learned from his experiment of applying the KF to the tip of his propeller blades.

> Dick
Last edited by Dickeroo; Jun 17, 2013 at 10:14 AM.
Jun 17, 2013, 09:59 AM
Registered User
Dickeroo's Avatar

Stumbled across old KF Prop pictures.


This is the wooden prop that George Leu tested.
Last edited by Dickeroo; Jun 17, 2013 at 10:15 AM.
Jun 17, 2013, 11:06 AM
just Some Useless Geek
It seems to me that such a profile would require a minimum of changes to a mold to make it out of plastic, Dick. I wonder if any prop manufacturers have the fortitude to attempt a test of this shape? And would the prop benefit from a tip plate winglet, I further wonder?

-- Marty, scratching head and looking askance at APC and Windsor --


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