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Sep 16, 2018, 12:38 PM
Out Standing In The Field
RexGalore's Avatar
LOL - you fooled me at 1:50! I thought you were landing, not making a 6" inverted pass!

Great flying!
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Sep 16, 2018, 09:30 PM
flyin' fool
goldguy's Avatar
Nice!!
Sep 17, 2018, 06:10 AM
I Look, Listen, and Learn
Timbo383's Avatar

Where to place the KFM?


I'm building a larger 40 inch ws version of this boxwing plane pictured and want some opinions on kfm placement. I've built several conventional wing planes with kfm but I am wondering if I should just put a kfm strip on the top wing only, or should I add one on the bottom wing also. I've added more chord to the upper wing in the larger version. Also should it be kfm 1 or 2.
The small one flew ok but it was somewhat of a handful and I still want it to be an simple build for the bigger one, so kfm is the logical choice to add lift and strength to the wing (wings?).
And the top wing has ailerons, bottom one has the elevator if that makes a difference in the deciding factor.
Last edited by Timbo383; Sep 17, 2018 at 06:24 AM.
Sep 17, 2018, 07:13 AM
Jack
jackerbes's Avatar
Thread OP
Adding a step at the red line (50% of the chord, parallel with the leading edge) will work and give you a KFm2, if you add them to both top and bottom it would be KFm4. Either one should work.

Jack
Sep 17, 2018, 07:45 AM
It seemed like a good idea!!!!
Hookit's Avatar
Really interesting shape there Timbo!

Where are going to put the motor?

Will be watching progress with great interest
Sep 17, 2018, 09:38 AM
I Look, Listen, and Learn
Timbo383's Avatar
Quote:
Originally Posted by Hookit
Really interesting shape there Timbo!

Where are going to put the motor?

Will be watching progress with great interest
Already built and flew it, but the small size and adjustments made during the testing phases has prompted me to make a larger one....aka the crash test dummy can only take so many poundings and repairs then it needs to be replaced.
Motor was up front on the nose looking section, I posted some of the build and videos on nutebox's thread.
https://www.rcgroups.com/forums/show...ox-Joined-Wing
Sep 17, 2018, 10:22 AM
Planes are for trix
tiretrax's Avatar
Timbo, super cool looking plane! More pics?
Sep 17, 2018, 10:42 AM
I Look, Listen, and Learn
Timbo383's Avatar
Thanks Jack, yeah I pretty much know where and how much to put on, just not sure what difference it will make if I add one on the bottom wing....also since it is a single servo elevator design on the lower wing, the kfm crosses over the elevator which I prefer not having to change unless it's better to do so.
Sep 17, 2018, 10:51 AM
I Look, Listen, and Learn
Timbo383's Avatar
Quote:
Originally Posted by tiretrax
Timbo, super cool looking plane! More pics?
Only pics I have are the ones on the thread posted above, the plane has been recycled, that's what why I love making planes out of one sheet of dtf...cost effective....
Sep 17, 2018, 06:00 PM
Jack
jackerbes's Avatar
Thread OP
Quote:
Originally Posted by Timbo383
Thanks Jack, yeah I pretty much know where and how much to put on, just not sure what difference it will make if I add one on the bottom wing....also since it is a single servo elevator design on the lower wing, the kfm crosses over the elevator which I prefer not having to change unless it's better to do so.
If you put the strip or strips on and then cut the elevator out the portion of the step that is on the elevator will move with it and that will work fine. You'll have to bevel the edges of the elevator and KF strip where they meet so the elevator can swing up and down.

If you use the method I show in the (using tape as a hinge on the top surface) image to make the hinge you only need to bevel the bottom of the meeting edges. If you use a centerline hinge you'll have to bevel both top and bottom to the center line.

Jack
Sep 17, 2018, 08:31 PM
I Look, Listen, and Learn
Timbo383's Avatar
Any thoughts on using a kfm 2 on the upper wing and kfm 1 on the lower?
Sep 17, 2018, 09:22 PM
Jack
jackerbes's Avatar
Thread OP
It has not been done as far as I know but I don't see any contradiction in it. Taken alone, both fly well and I think they would do that together...

Jack
Sep 18, 2018, 01:15 PM
scratchbuilder
Thomas B.'s Avatar
I did it and it worked fine.
Sep 18, 2018, 04:32 PM
I Look, Listen, and Learn
Timbo383's Avatar
Well, that's two yes and zero no, majority wins....off topic question, since this is a canard type plane does anyone know if I should I add some incedence to the bottom front wing?
Sep 18, 2018, 05:48 PM
Jack
jackerbes's Avatar
Thread OP
I think you want them both at zero incidence since you are using wings that have lift.

Incidence generally goes with undercambered wings and it's primary purpose is to expose the undercambered bottom of the to the airflow and generate lift.

Another consideration is that having incidence on one of the two wings sets up a conflict of sorts and on a canard the front wing is usually the elevator, isn't it?

A lot of interesting discussion on it here:

https://en.wikipedia.org/wiki/Canard_(aeronautics)

Use of canards falls into two categories, either lift or control. Are you going to use it for control? If it is not the elevator but there to contribute lift and hold the nose up it would be for lift, if it is the elevator it is for control.

Jack


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