lakeside1000

HI ALL, I have just built two flying wings, I intend to fit the motors at the back with pusher props, but I have a dilema, they are both foamies, built from the blue builders foam, its all I can get here in spain, no model shops for miles, its a while since ive flown and back then it was all engines that needed a glow plug and a fuel tank, I have fitted pylon style foam mounts on each of the flying wings to get the prop up clear of the ground, but I am wondering if the high thrust line will affect the flight and control, any advice would be much appreciated,before I get to the stage of mounting the motors, im new to electric systems and to pusher motors, but not to flying, thanks for your time, alan.

Larry3215

A hi thrust line on a pusher flying wing is going to be a real challenge to control.


Your going to get wild pitch changes with throttle on/off unless you can angle the motor WAY down so the thrust line goes through the CG of the model. Thats going to make the prop very in-efficient because your thrust line will be off from your flight path to a very large degree.

Thats why no one does flying wings with raised props - its almost impossible to make work well at all

Larry3215

By the way - welcome to WattFlyer!!

mclarkson

People generally mount their pusher motors like this.

Larry3215

Exactly.

If that motor had a really long prop shaft extending forward, you would see that it passes through the center of the wing pretty darn close to where the CG point falls on the cord line.

In that picture, it looks like the motor is mounted more or less on the top of the wing, so the motor shaft tilts down as it points forward just slightly.

The higher you raise the motor, the greater that tip down would have to be to avoid drastic pitch/throttle coupling.

Larry3215

Actually, to be exact, you really want the motor thrust line to intersect the cord line just a hair in front of the cg to get some slight down thrust - needed to offset the reflex in the wing TE.

lakeside1000

hi all, many thanks for all your comments, brilliant, its a good job i thought to ask before i finished the build, looks like ive got some foamcutting to do, looks like i also have some challenging flights ahead, muchas gracias to all from alan in spain.

Larry3215

Good luck and let us know how it goes, post some build pics etc.

Thats why we are all here