** Kline-Fogleman (KFm) Airfoils - Building/Flying Discussion ** - Page 619 - RC Groups
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This thread is privately moderated by jackerbes, who may elect to delete unwanted replies.
Aug 29, 2017, 02:05 PM
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Bummer about the twin! Actually double bummer because it took out two ESCs instead of just one.

I was monkeying around with one of my wings and a lipo slipped out of my hand and hit the floor. Picked it up a couple minutes later and it was warm to the touch. Must have shorted out internally just a bit. I sat it on the curb waaaaaay far from the house.
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Sep 01, 2017, 12:14 AM
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davereap's Avatar
The single front motor has more than enough power on a 2s and 6x4 prop..
With a quick burst it slides into the air, no fuss...
The tough props can take a hard hit if you land heavy, but it flies well and flairs out nicely, soft landings are made easy.
The wing is ultra quiet and flies slow enough for indoors..
Maneuverability is OK but rolls are too slow, and ground handling and very slow flight is less easy without a rudder, so more mods are coming.. lol..

.
simpleV motor up front1 31aug 2017 (3 min 51 sec)
Sep 01, 2017, 09:07 AM
flyin' fool
goldguy's Avatar
for the tractor factor.....................
Sep 01, 2017, 07:33 PM
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davereap's Avatar
more mods.... added a central linked twin rudder.. removed some area from the tip fins.. strengthened up the U/C .. increase the aileron movements..
If the roll does not improve I will drastically increase the aileron size
Sep 01, 2017, 08:05 PM
looking up, down under
scruffy1's Avatar
given the aileron size already, if it won't roll i wonder if the kf airfoil is somehow too stable to co-operate with rapid axial movements ?

does that cause any limitations on other plan forms ?
Sep 01, 2017, 10:30 PM
Build straight - Fly twisty
Whiskers's Avatar
It could be a result of aileron-induced yaw which results in an opposite roll force due to the sweep-back effect.
Sep 02, 2017, 12:08 AM
flyin' fool
goldguy's Avatar
Did the same, ditched the tip fins and it made a huge difference in the roll rate. Turned it from a slow dancer to a rock n' roller.
Sep 02, 2017, 03:59 AM
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davereap's Avatar
I want a good roll rate at a minimum of forward speed.. something like that achieved by the crack yak or other similar models.. they have massive ailerons in proportion to the wings area

With its present setup its no speed machine.. indoors it will be fine , but for some extra performance on the quad motor with its 6x4 prop, it needs a 3s rather than the 2s its using..... for indoors I may change up to an 8x4 on the 2s and try that out, see if I can get better airflow over the surfaces..

.
simpleV motor up front1 2sep 2017 (6 min 26 sec)


Mods were made.... rudders added and tip fins reduced in size... however the wings stability at speed killed the effect from the rudders.. whist at slow speed the rudders do work very well.... they are not flexing, they are just overwhelmed by the wings stability at what is only a moderate speed..

More Mods.....
The tip fins are now completely removed...
and I have put a better profile on the leading edge as I think it was too square and is also acting to keep the wing flying straight.. working against turns and rolls
Bank and yank is working fine at a moderate speed.. loops are tight.. flair is good for slow gentle landings.. stall turns work well.. going downwind the turns are improved with the use of rudder
Last edited by davereap; Sep 02, 2017 at 07:25 AM.
Sep 02, 2017, 12:35 PM
flyin' fool
goldguy's Avatar
That's the trick for slow aerobatics ....... big control surfaces, big props and light weight
Sep 08, 2017, 01:04 AM
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davereap's Avatar
The latest mods have made the wing weird to say the least.. on normal cruise its fine, but bang hard on the elevons and it goes completely haywire and out of control before crashing.. lol ..
I am going to have to think on this one... but my suspicion is the forward position of the rudders is just not stabilising enough
Sep 08, 2017, 11:56 AM
flyin' fool
goldguy's Avatar
Our 'V' shaped slope wings generally have the TE of the horz stab and wing tips inline with each other.
Sep 14, 2017, 07:40 AM
Registered User
Dickeroo's Avatar

A Korean Study on the KF concept from 2014


Numerical Study on Aerodynamic Characteristics of Kline-Fogleman Airfoil and Its 3D Application at Low Reynolds Number

Nahyeon Roh* and Kwanjung Yee*†
* Dept. of Aerospace Engineering, Pusan Nat’l Univ.

(Received January 7, 2014 ; Revised March 7, 2014 ; Accepted March 14, 2014)

Abstract: In this study, analyzed the aerodynamic characteristics of Kline-Fogleman airfoils and wings with those more efficiency at low Reynolds number. It was found that lift to drag ratio is enhanced in the range of Reynolds number below ×, especially, can be improved up to 26% at Reynolds number is ×. It was confirmed that the most advantage case in terms of lift-to-drag ratio is Middle case and lift-to-drag ratio is improved to 20% at 80% of the wing area is Kline-Folgeman airfoil. At this time, endurance time increase to 12%. Also taking the structural stability of the wing and lift-to-drag improvement into account, designed to be from 50% to 80% the size of the Kline-Fogleman Airfoil would be advantageous.

†Corresponding Author, daedalus@pusan.ac.kr ; currently Seoul Nat’l Univ., kjyee@snu.ac.kr C 2014 The Korean Society of Mechanical Engineers
Sep 14, 2017, 07:54 AM
Build straight - Fly twisty
Whiskers's Avatar
Quote: It was confirmed that the most advantage case in terms of lift-to-drag ratio is Middle case and lift-to-drag ratio is improved to 20% at 80% of the wing area is Kline-Folgeman airfoil. At this time, endurance time increase to 12%. Also taking the structural stability of the wing and lift-to-drag improvement into account, designed to be from 50% to 80% the size of the Kline-Fogleman Airfoil would be advantageous.

It looks like this was written by a random word generator.
I assume it is a machine translation.
Unfortunately it is meaningless.
Sep 14, 2017, 08:52 AM
Registered User
Dickeroo's Avatar
Whiskers... I don't know if you are interested, but I could email you the PDF document if you like. It is all in Korean, however. If it is "No Thanks" I understand.

~ Dick
Sep 14, 2017, 09:14 AM
Build straight - Fly twisty
Whiskers's Avatar
As my Korean is sadly lacking that will have to be a grateful decline.
However, I would be interested in a meaningful translation of the work.


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