Brant
I don't use downthrust or upthrust because if you change the angle of the prop shaft with respect to the direction that the rubber is pulling you are going to have increased friction losses in the bearing. I even have models where I've got the whole motor stick angled so that I don't have to use left thrust in the bearing for the same reason.
You can achieve whatever direction you want the prop to pull in by changing the decalage. If you're one of the many people who are convinced that indoor models should fly with their nose up you can get that by decreasing the wing incidence and then readjusting the stab incidence as necessary. If you want the prop thrust to point down for some reason you can increase the wing incidence to get that. My preference is to fly with the motor stick as level as possible to minimize friction losses in the bearing and to get the prop pulling in the direction the airplane is flying.
Others may differ on this but it's the gospel for me until Dr. Drela tells me I'm on the wrong track!
----- Original Message -----
From: Brant Fredrickson
To: Indoor_Construction_at_yahoogroups.com
Sent: Thursday, November 16, 2006 6:40 PM
Subject: [Indoor_Construction] Re: decalage
Bill,
I've done a poor job of communicating. We have set the trim and the model
will fly 2'08" in a 21 ft ceiling with a 9.5 in pitch. And we set the trim
at low power, just enough winds to cruise at shoulder height and we move the
ballast back until it just starts to stall, then move forward in small
increments until the stall disappears. However if we hit the ceiling in a
high power flight, the model doesn't recover. It is our own design so we are
without the luxury of a well thought out plan such as Little Square.
Cal Goddard,
Our wing incidence was set at 0° and stab incidence at -1°. We have reset
the wing incidence at 1.5° and the stab incidence at -2.5°, and will re-trim
the model tomorrow by moving the ballast. I was curious about your
statement, Is there a theory behind setting the wing incidence at 2° and the
stab at -1°? Also we had bent our prop hanger in a crash which induced
downthrust. The model flew ok afterwards, but we have removed the downthrust
for tomorrow's flying session. Again I am curious, what negative effects
does downthrust have? Your comments were timely.
Brant
[Non-text portions of this message have been removed]
Received on Thu Nov 16 2006 - 17:01:33 CET
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:44 CET