Trimming

[s.vannostrand at kodak.com]

Greg,
I have to make some assumptions here, like that you are flying a pattern 
style plane and that it is not a flying brick.  If so, then you are on the 
right track.  It sounds as if you might need some positive incidence in 
the wing and a more rearward CG, but if your wings are not adjustable, you 
can't test this.  I'd do some more tests to see if moving the CG back is 
OK.  Do this first.  Then try downthrust.  The problem with testing 
downthrust is more mechanical than aerodynamic.  Increasing downthrust and 
keeping the spinner in place requires you to move the engine mount.  This 
is tough, but can be accomplished by wallowing out the holes where you 
bolt the engine mount to the firewall, and then making large nuts out of 
tee nuts and 1/8" ply squares that allow you to tighten the screws down 
and lock the mount in a new location.

--Lance





"Gregory Morris" <greg_morris at email.msn.com>
Sent by: discussion-request at nsrca.org
09/09/2002 05:23 PM
Please respond to discussion

 
        To:     <discussion at nsrca.org>
        cc: 
        Subject:        Trimming


I have a newbie plane trimming question.

On my new plane if I trim for straight and level flight at full throttle,
then reduce the throttle to say half I need to put up trim in to maintain
level flight. I know a slight amount of up trim may be required, but I 
think
in my case it might be excessive. Also, when the plane is trimmed for
straight and level flight, the elevator has a few degrees of down  instead
of  neutral. Up and down lines are relatively straight. The wing and stab
incidences are fixed, and can't be changed. The plane hunts a little in
pitch, but I think it is due to trimming the elevator at one speed, and
flying at another. Inverted flight takes just a breath of down pressure to
maintain level flight.

Question is.. will a CG change(move back more, or forward), or the 
addition
of down thrust help this condition, or do I just adjust the elevator trim
for a happy medium, and live with it. Does anybody have any ideas?

Thanks
Greg Morris


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