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Thrust angle on Simple cub

#1
Just finished my first build. I build the simple cub. I attempted its first flight this weekend and it went as expected, right into the ground. No worries as I am learning all this stuff. However, I did notice that every time it crashed it flew down and to the left. That got me thinking of thrust angle. My UMX timber has a very visible tilt of the motor to the right. I did not see any thrust angle on the simple cub. Should I be adding this in by shimming the motor? If so, does it need to tilt tot he right( when looked at from behind) SHould I tilt it up as well?
 

Tronglodon

Junior Member
#5
down thrust is making the motor tilt down, correct? Does this not pull the plane down? I am just learning about all this
Down thrust counteracts the tendency of a high wing plane to climb when adding power. Of course you want the plane to climb under power to some degree, so it's a bit of a balancing act. That said, my Cub flies straight and level without any change in thrust angle.
 

FastCrash45

Well-known member
#6
As a general rule, motors that are in the tractor position on smaller planes get 2-3 degrees of right thrust angles and 1-3 degrees of down thrust angle. This is for motors below the wing. Ive never built a pusher type so I don't know any info on those. The mighty mini series all seen to have right thrust and done down thrust. The larger planes don't generally need any because the size and weight negates the motor and prop torque.
 

PoorManRC

Well-known member
#9
That would be tough for my builds, the power pod has more than a couple of degrees play just picking the thing up, but it is my first build and each flight ended in a crash.
You are really going to want to shim the Fuselage, around the Power Pod...
Thrust Angle is a crucial part of controlled Flight!

Your Power Pod floating around is creating something close to uncontrollable. You can't adjust anything that's loose!!

You can use shaved down Foam Core Board, Poster Board (but it might add too much weight), or even thin sheets of Balsa...

Tighten that up though, before making any Thrust Angle adjustment. ;)
 

Merv

Well-known member
#10
I would leave the thrust angle alone for now.
You need to get the plane in the air and get it trimed out before you can evaluate the thrust angle.
My guess, the plane will fly a lot better after it is trimmed out.
 
#11
It could be that you want to add down thrust, right thrust, or both to a motor mount. I happen to have a 10" disc sander that makes the job easy. Set the table for 3° down and the miter to 3° right. Sand off just enough from the front of the power pod, then glue the firewall in place. Of course you can make these measurements to suit your needs. Just recently bought a 5" disc sander from Menards and I plan see if the smaller sander will allow me to do the same. More tips at: https://foamboardflyers.com/
 

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BATTLEAXE

Well-known member
#13
Just finished my first build. I build the simple cub. I attempted its first flight this weekend and it went as expected, right into the ground. No worries as I am learning all this stuff. However, I did notice that every time it crashed it flew down and to the left. That got me thinking of thrust angle. My UMX timber has a very visible tilt of the motor to the right. I did not see any thrust angle on the simple cub. Should I be adding this in by shimming the motor? If so, does it need to tilt tot he right( when looked at from behind) SHould I tilt it up as well?
I have had this issue with a handful of planes that I have built. The worst was with the Mini Sportster using a power pod from another Mini (I think it came from the Mini Scout). I made a new pod with the suggested thrust angle from the plans that came with the Sportster and added more throttle progressively during take off, (either hand launch or from the ground) and it helped. The wing needs to create its own lift sufficient enough to get off the ground not only fighting gravity but drag on the wing surfaces as it gains speed. This was a tip I got from other pilots with way more experience then me.