Twin Motor glider

[Jameskibler]

I've had a Phoenix 2000 glider from hobby king sat in my shed for about  a year now and after seeing the release of the new sky mule i had an idea  ;)

Equipment:

BL Motor A2826(2212) 1400Kv (x2)
Robotbirds Basic-20A Brushless ESC (x2)
SERVO - EMAX METAL GEAR ES08MA
RB UBEC 5A With Filter
EzUHF Lite
Battery - 2200-3000 mah 3s

FPV Equipment:
Lawmate 2.4GHz 500mw (if i can find one in stock!)
FPV-25CE 1/3 Inch Exview HAD II CCD Camera 650 Line Sony Effio-E

The fuse is blow moulded so its stupidly strong and has loads of room inside for FPV gear and the like.

I started the build with the motor mounts, I used 2mm balsa sheets, doubled up for the motor firewall to give a bit more strength. I adjusted the angle so the motors are facing down a couple of degrees. I forgot to take pictures actually building them but here are the finished mounts glued to the wings (unpainted):



Whilst i was waiting for the gorilla glue to dry I set about fixing the pan and tilt mechanism for the camera onto the canopy. I could have gone for the more streamlined approach and only been able to pan the camera but I'll be using a trinity head tracker with it so i went for the full works  :P (roll axis might be added in the future).
Pretty simple, drilled a 2.5cm hole in the canopy and fixed the mechanism base to the underside with screws:

[Coyote]

Looking good :)

[Dizzy]

Thats going to be different for sure looking forward to seeing how it flies  :)

dizzy :)

[skyscraper]

looking good! Will watch with interest

regards
Andy

[Jameskibler]

Got a bit done on the wing electronics tonight, used a soldering iron to run larger channels for the ESC power wires, Just a test fit of the esc's for now. I'm also mounting the ESC in the Flap servo cut out (had to extend it a bit). Should get some good cooling out on the wing and in the prop wash  :)

[rob.thomson]

I like the look of this mod.   Very nice

Sent from my GT-I9300 using Tapatalk

[Jameskibler]

Finished this build this afternoon after the servo extension cables, receiver, props etc arrived this morning.

Ive had to put 40g of lead in the nose with a 2200mah 3s behind that. Happy with that as I've got loads of room for either a bigger battery or if I'm wanting to keep it light i can move the battery forward 2/3" .

There are 5 cables connecting the wing to the fuse (servos, esc power/signal) so its a bit cluttered with all that and the XT-60 plug enabling me to remove the wing but like i said, the fuse is pretty big inside and it all fits in quite well :)

Took it down the field for the maiden. Very un-eventful  ;D

triple checked all connections and control surfaces, 3/4 throttle with a gentle throw and it was away. a few clicks of rudder trim and it was dead on  :)

Cruises beautifully at 1/4 throttle and it still glides like it should. Overall I'm VERY happy with how it turned out  :) just need another Vtx to arrive from canada and then I can have some proper fun  :P might make it look a bit nicer whilst I wait  ;)

Will get some pictures and videos of it flying as soon as i can

[skyscraper]

congrats on the maiden. looking forward to pictures!

regards
Andy

[Dizzy]

Well done sounds like you got her spot on first time  :D

dizzy :)

[Jameskibler]

[iwan_canobi]

This looks great, thinking of doing something similar with my walrus since it's sat doing nothing at the moment.

Any advice for the build? Was the down thrust required?

[Paul881]

Please excuse my ignorance but why does a push motor have down thrust but a front pull motor doesn't?

[Jameskibler]

I'll be honest with you lads, I know little about the physics of flight and I did absolutely no calculations when building this. I just looked at a multiplex twin star and went from that.

I did angle the motors down ever so slightly, looked like the right thing to do  :laugh: in practice it flies perfectly throughout the throttle range. On full throttle it doesn't pitch up or down, just maintains the same pitch.

"If it looks right, it'll fly right"

[mrwilljackson]

Please excuse my ignorance but why does a push motor have down thrust but a front pull motor doesn't?

Pull motors do usually have down thrust, but just far less than a pusher, typically only a couple of degrees down thrust. I think it also depends on where the moot is in relation to the centre of the main airfoil / wing.... Like James says, if it looks right....  ;D

Edit; Wikipedia to the rescue... http://en.wikipedia.org/wiki/P-factor

[Paul881]

So that explains why a single pull prop is offset to the right or left depending on prop rotation, but I'm still not sure why push motors on/behind the wing have such a sharp angle compared to a front mounted motor.