Hey All..... I'm rebuilding a nose damaged Hobbico Superstar OS 40 LA for a neighbor and since it was a RTF I do not have the specs on Downthrust or right thrust, since the firewall was removed by the landing gear in the crash ( common I know) I have replaced it with a new fabricated one, repaired the top front and bottom front of the fuse, now I am wondering about down thrust and right thrust, my usual rule of thumb is 1/2 inch difference from prop tips to wall measurement for right thrust..... however does it need down thrust???? Waddya think???????
Thanks....... Captain Crash...

If you can see where the old firewall was, use those locations for the new one.

If there is no indication of where the old firewall was, install the new firewall at 90 degrees to the fuselage (no side or down thrust ).

Make sure your wing incidence is correct as it will affect the flying tests. The incidence should be 0 degrees on the horizontal stab and 0 degrees on the main wing.

When you fly the plane, if the plane consistantly pulls to the left, put a thin washer under the left side of the motor mount (when looking forward ).

Now fly the plane at about 2/3 throttle. Suddenly cut the throttle to idle. If the plane suddenly jumps up you need some down thrust, if the plane suddenly drops down you need up thrust. For down thrust you can either put a thin washer between the motor mount lug on the engin and the motor mount or a thin washer under the top of the motor mount.

Repeat the above flying/washer tests until the plane flies level when you cut the throttle and does not pull to the left.

A variety of thickness of washers is available in the fastner section of your local hardware store (Ace, True Value )

Thanks Campy for the feedback......... I am a little confused on your explination of how to correct up/down thrust..... I thought it was the other way around.........
I was wondering if anyone knew if there was a pre-determined amount of down or right thrust as the RTF comes from the factory......... I can do the trial by error, that worrks as well..........
Thanks.... Captain Crash...

Yes, it's the other way around.

The rule of thumb for many years has been 2 degrees.

Enjoy,

Jim

Jim.....
Thanks for the imput, I will start out with the 2 degrees, I have been flying long enough to know how to tweek the settings, its just that I wanted to start out as close as possible...... I appreciate it, Thanks........... Captain Crash...

Sorry about reversing the directions for up/down thrust . Rampant senility must be setting in.

hey not a problem......... it all works out in the end hahahahaha............ Captn Crash...