GWS Tiger Moth Downthrust

[PfalzPflyer]

While flying indoors last night in a large gym, my TM was struck by an IFO and busted up pretty good. One of the things damaged was the wooden "motor mount" stick. No big deal; a little epoxy, and everything was back in order. Just one question: How much downthrust should there be? I guestimated about 2 degrees. What could I expect if that's not enough? How would the plane react with insufficient downthrust?

Thanks,
Dean

[Dave Robelen]

Hi Dean,
The main characteristic you would notice with too little downthrust on a TM would be the need to trim in excessive down elevator at higher power settings, which leads to a nose down glide at low power. The tricky part is that many of these characteristics are displayed by a model that is noseheavy and needs excessive up elevator to trim level at lower speeds.
Assuming that your Moth has a good feel to the pitch control, and behaved normally before, I would watch for the nose to rise to much at full power, once you have the model trimmed for cruise setttings.
Regards, Dave

[Don Cooper]

I messed up the hole for the motor mounting stick on my Moth while trying to replace a broken stick. So I epoxied a 1/16 plywood plate on the Moth firewall, then epoxied the motor mount stick onto another 1/16 plywood plate (mount the stick in a hole the same size as the stick cut in the plywood plate). Then I attached the plate with the motor stick to the plate on the firewall with small (e.g. servo mounting) screws. That way I can use shims to adjust the thrust angle so that the plane flys the way I want it to (which is not always the way the designer wanted it to).

[PfalzPflyer]

Thanks, guys.

Dean