My Dad and I are building a Glider, and when it came time to install the engine firewall it says that it is supposed to be at an angle, so the engine would be cockeyed. Could someone please tell me why this is? I would just like to know.

Thank you!

It's called side thrust...to counteract the torque of the engine and prop..
The firewall of the butterfly is set to the right and down...looks awful, but it flies great..

hi if youre meaning right , and down thrust angles
these keep you from having to constantly having to trim plane
whenever you change throttle setting
if you putting a decent sized engine on it- 20 -25 range
whithout down thrust you can epext it to try to go straight up on a full throttle[not req]
takeoff ,requires a lot of down to keep it stalling,
you can add lots of down trim for takeoff but will need to retrim when powered back
full down trim probablywont be enough .but it will be upstairs fast
smaller engines req lots of skill and time to get plane up high enough to were it
starts to climb decent whithout stalling though,
good luck
mike

I have seen one with a OS 40LA on it..wing didn't come off...but waaayyy too much power..

I've been flying a Butterfly for quite a while now and in my opinion a .20 to .25 is more than adequate. I've had both on mine. A .15 would probably do it but in the wind it's nice to have some reserve!! The Butterfly isn't a sport or pattern plane thus you don't ever run it full throttle very often or for very long duration. I wrecked mine once and tore the firewall off and simply glued it back together - I have no idea if it's got the recommended thrust angle, I'm not sure if I care, what I'm trying to say is on this model is dosen't make a lot of difference. Once your airborne just set your trims, fly figure 8's and relax.

Oh I know....

A 25 is a good average..and better than 15 with some wind gust...
The club member just didn't have a smaller motor to put on it...and used the throttle real gently...