Av8er Tim

I need some advice on wing/stab incedence and control coupling etc. I am working on an "own design" 3D electric airplane called the 3Demon. The first prototype is done and flying (pic below). It flys very well, but knife edge is not where I want it to be. It pulls toward the canopy.

The wing is mounted at 0 degrees incedence to the thrustline, and on the thrustline. The horiz. stab is mounted at 0 degrees also, and is also on the thrustline. Wing airfoil is an Eppler 169 15% tapered root to tip. Stab profile is a flat plate. I would like to design out as much coupling as I can on the next proto.

Here is the 64 dollar question. should I mount the wing with a positive angle in relation to the thrustline, and if I raise the stab position above the thrustline what would the "theoretical" result be? What are the basic aerodynamic results of stab placement vs. thrustline? Like I said, I would like to design out as much coupling as I can but obviously I can't get rid of all of it. Suggestions please...

Here are some basic specs:

Wingspan 42"
Motor Hacker B20-12L 3.8:1 gearbox, APC 11x4.7 SF
AUW 21 oz.

It hovers at about 1/2 throttle and it is very fun so far. I just want to improve on the design. Here is a link to a short video too: www.jetworksmodels.com/videos/3demon.wmv The video was shot on a VERY windy day, and on the second flight, so I really wasn't wringing it out, and hovering was almost impossible.

Thanks in advance,

Tim H.

bryan bateman

My Feedback: (1)

I dont know how the thrustline on the wing affects it bu you ca move the stab, as long as it pitches up in knife edge with left as well as right. If it pitches up wit right rudder and down with left rudder, and vice versa, i cant help you. But if it pitches toward the canopy both left and right, then raise the stab a little at a time until you get it right. This could change the snappyness (is that a word?) of the plane, but you cant worry about little things like that. Good luck

Jleyland

My Feedback: (1)

Hey Tim - Awesome video - thanks for sharing - I like the music - who is it?
thanks,
Jon

da king

My Feedback: (5)

Tim......Great video ! The plane is bad as h*** too !!! Do you have plan's for it?

How does it hover? Do you have to hold down elevator in a hover? Sounds like all you need to do is move the cg back some more. I would play with cg and thrust angles before i made any changes. I am willing to bet you could fix it like that.

Try rolling to inverted and seeing what it does. It should fly pretty level. If the nose drops pretty hard you are way to foward on the cg.

Av8er Tim

Jon - Thanks! The music is the intro sequence from "Eye In The Sky" by The Alan Parsons Project.

da king - No plans yet. I'm still tweaking it. It hovers well, although the wind here lately has realy kept me from testing it's true potential. It's so light (21oz) that the wind throws it around pretty good. I need some calmer days to test. I am hoping for some better WX soon, then I will start messing with the thrust angles and such. As it is right now, I'm a little dissapointed in it's knife edge. I am going to increase the side area on the next one.

Tim H.