** Kline-Fogleman (KFm) Airfoils - Building/Flying Discussion ** - Page 635 - RC Groups
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Dec 06, 2017, 05:56 PM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
All very good suggestions. I have doinked this one a bunch, I did find some stuff out of alignment and think I have those fixed. Another review of the items suggested is in order...

Thanks.
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Dec 07, 2017, 03:10 AM
Registered User
davereap's Avatar
sometimes forgotten... slower models need bigger ailerons..
most of my foamies have much bigger ailerons than you might expect.. compared to my older gas powered models they are enormous...

I previously mentioned not wanting my rear step close in front of the hinge line...however there is a solution I have used, the hinge line is put in front of the step so the rear step is out on the aileron..

also note that its only the KFm3 and models with more top steps where the rear step line might get close to the hinge line... and the ailerons get left out of my calculations...
for KFm2 and KFm4 step lines are set at 50% with ailerons included...
Last edited by davereap; Dec 08, 2017 at 02:01 AM.
Dec 07, 2017, 04:04 AM
It seemed like a good idea!!!!
Hookit's Avatar
Quote:
Originally Posted by davereap
sometimes forgotten... slower models need bigger ailerons..
most of my foamies have much bigger ailerons than you might expect.. compared to my older gas powered models they are enormous...

I previously mentioned not wanting my rear step close in front of the hinge line...however there is a solution I have used, the hinge line is put in front of the step so the rear step is out on the aileron..
I concur with what Dave is saying, all my wing have been KFm2/3/4 and in standard wing forms I leave the ailerons out of the calculation and they have all performed better than I can fly them.

So far I have built upto 900mm span (6mm Depron KFm3/4) without any spars or pallet strapping. I just use 18mm leading edge stock balsa and the laminating film and they are as stiff as needed. I have used the iron edging when going bigger than that as mentioned in numerous posts by Dave.

Works very well, I have not gotten around to trying the pallet strapping yet but have no doubt it would work very well also.
Last edited by Hookit; Dec 07, 2017 at 04:09 AM.
Dec 07, 2017, 09:40 AM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
Based on the above information, I may not have enough aileron. Let me snap some pics...
Dec 07, 2017, 11:30 AM
Jack
jackerbes's Avatar
Ailerons can be wide or narrower and deep, but they have to have enough area to be effective.

On the 32" flat KFm3 wing I made for the BB 33 I used ailerons that were 11" wide and 1-1/4" deep and those worked very well. So that was 11" wide on a 15" or so span.

The ailerons had about a 45 degree deflection at full travel, and no differential was used or needed.

Used a 9 gram servo and dental flosser horn...

Jack
Last edited by jackerbes; Dec 07, 2017 at 11:35 AM.
Dec 07, 2017, 08:20 PM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
Here is what I have...

kfm2 airfoil, flat with no dihedral
Wingspan: 41.5 inches
Chord: 9.5 inches (includes ailerons)
Aileron (each)
Width: 15 inches
Length: 2 inches
Plugging in the numbers I get a 15.2 percent of the wing area for the ailerons.

I built this about 8 years ago, think I followed guidelines for the 42.

Feedback encouraged and welcome!
Dec 07, 2017, 09:13 PM
Build straight - Fly twisty
Whiskers's Avatar
I'd like to see ailerons of twice that cord.
If that is the top of the wing we're seeing that you have plenty of differential going on.
Last edited by Whiskers; Dec 08, 2017 at 02:59 AM.
Dec 08, 2017, 02:07 AM
Registered User
davereap's Avatar
they look big enough...

quote... Absolutely no dihedral on the wing, it is straight all the way out.
Separate servos for each aileron surface.
Played around with servo arm placement to get some differential dialed in.
It turns good one way but hardly the other.

Which way does it turn good...?..
Have you checked the throws on each aileron ?
Have you checked the thrust lines ?.. It may even be worth trying a clockwise CW rotating prop instead of the normal CCW and see what happens..
Last edited by davereap; Dec 08, 2017 at 02:23 AM.
Dec 08, 2017, 06:39 AM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
Quote:
Originally Posted by davereap
they look big enough...

quote... Absolutely no dihedral on the wing, it is straight all the way out.
Separate servos for each aileron surface.
Played around with servo arm placement to get some differential dialed in.
It turns good one way but hardly the other.

Which way does it turn good...?..
Have you checked the throws on each aileron ?
Have you checked the thrust lines ?.. It may even be worth trying a clockwise CW rotating prop instead of the normal CCW and see what happens..
Now you are really challenging my CRSitis!

Turns good to the left.
Let me verify the rest.
I had some very hard nose in crashes so I might have some unwanted angle changes.

One thing for sure I seem to have a lot of difficulty keeping it straight on the runway when trying to take off. I believe that is more the fault of the pilot, because when reading the recent AMA article about takeoffs I was doing several of the no-nos the author wrote about. In the early days I didn't have takeoff problems. My Hobby Zone Super Cub, which I have been flying almost exclusively is much more forgiving and I am probably more sloppy. One of my flying buddies took off this BB42 and didn't comment about any bad handling symptoms so I think this is on me.

Time for additional hard facts instead of further "I think" speculation.

My problem has been i haven't managed to get through the entire troubleshooting process and forget where I am.
Dec 08, 2017, 07:30 AM
Multirotor Enthusiast
Blacky's Boy's Avatar

Effects of CW rotating prop vs Normal CCW?


Quote:
Originally Posted by davereap
<snip>It may even be worth trying a clockwise CW rotating prop instead of the normal CCW and see what happens..
Since I've eventually going to add ailerons to my BB42 I've been following this discussion with a good deal of interest. I have a question about the statement above. Are you suggesting switching from CW to CCW prop so you get torque opposite to what is experienced with a CW prop?

The reason I ask this is I started off in the multirotor world. So I have a bunch of CW and CCW props. And during one of my first builds I didn't really pay attention to the motor rotation too much and just let it turn in whatever direction it was wired. Especially after needed to rebuild again and again after augering in. After I was done with the repair I just dug out the prop that worked with that rotation. I'm not saying that this was the reason for it being a complete failure, I'm just trying to see how much of an impact it had.
Dec 08, 2017, 07:33 AM
Build straight - Fly twisty
Whiskers's Avatar
Ruff,
Do you fly this plane reasonably fast or are you waffling around on the edge of a stall?
Perhaps you fly slowly trying to keep out of trouble.
A plane needs adequate air-speed to handle well.
Dec 08, 2017, 07:35 AM
Registered User
davereap's Avatar
yes.. on the ccw to cw switch... that will also show if the thrust lines are off
Left turns always being the easiest.. the ccw motor/prop torque tends to rotate the model in that direction..

speed and response is also linked, fly too slow and response can be poor..
bigger ailerons might help, but a rudder mix with ailerons is also a good option..
some models prefer mixed rudder on turns.. search the umx sports cub https://www.flitetest.com/articles/sport-cub-s
This small model is a lovely model to fly and has rudder mixed into the ailerons through its flight controller...
Its too fragile for our sessions, but a lot of our flyers learnt on this little gem..
When flying indoors the rudder is more often used for a quick turn around.. because we fly so slow..
When flying at slow speeds, ailerons alone can give problems with adverse yaw.. bigger ailerons can make this worse, its very much noticed on the downwind leg.. but fly fast ,bank and yank, and the yaw or poor response issue goes away..


the little fokker has been flown, crashed and bashed, its going well..
It flew well, and survived quite a lot of bashes..

the first flight was trying to get the trim sorted..
.
20inch fokker first trimming flight 7dec2017 (4 min 36 sec)


the second video has the trim better sorted but still needing some work..
please note .... some slow tight rudder turns
.
20inch fokker nearly trimmed first session 7dec2017 (7 min 24 sec)
Last edited by davereap; Dec 08, 2017 at 08:07 AM.
Dec 08, 2017, 08:07 AM
looking up, down under
scruffy1's Avatar
taking off you will almost always need to apply rudder to counteract torque, which for a normal counterclockwise rotating motor will be right rudder to keep the nose straight

once you are airborne it's less of a problem

http://www.boldmethod.com/learn-to-f...ng-tendencies/
Dec 08, 2017, 10:48 AM
flyin' fool
goldguy's Avatar
Sounds like something is out of alinement, twisted or warped.................. or all three.
Dec 08, 2017, 01:32 PM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
All of the above may apply...

Whiskers, 1047 slow fly prop on an 820 kv motor. Not a lot of speed but I don't think I'm running into stall issues.


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