decalage

From: <Warthodson_at_aol.com>
Date: Tue, 27 Jun 2006 12:59:52 EDT

I had a very enjoyable conversation with Rex Hinson (NFFS president) at the
USIC recently. One of the things we discussed was Rex's approach to decalage. I
will try to describe it, briefly. Keep in mind we were discussing indoor free
flight scale models. Assume an airplane that requires 3 degrees of decalage
(angular difference between wing & stab). Rex recommends that the entire three
degrees be in the wing's angle of attach relative to the thrust line & the
stab be set at zero relative to the thrust line. Assume for the moment that the
thrust line is drawn from the prop hook thru the rear peg & the prop is
perpendicular to this line. The benefit of this is that the prop thrust is in line
with the stab & therefore the prop wash does not strike one side of the stab,
especially during the power burst causing a pitching moment. If the wing were
set at zero & the stab at negative 3 degrees, the prop wash would strike the
stab causing a nose up pitching moment which would require down thrust to offset
it. In addition, if set up as Rex recommends there is effectively 3 degrees of
down thrust relative to the wing without any shimming of the nose block. I
hope I have explained it clearly enough for you scale flyers to comment on this
theory/trimming method. I would appreciate simple (minded) explanations or at
least a simple summary if lengthy aerodynamic/mathamatical formulas are
required to discuss this.
Thanks,
Gary Hodson


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Received on Tue Jun 27 2006 - 10:06:04 CEST