Re: decalage

From: calgoddard <calgoddard_at_yahoo.com>
Date: Fri, 17 Nov 2006 05:41:08 -0000

Brant:

Decalage is defined as the angular difference between incidence of the
wing and the stab.

Don Ross (he wrote a great book called Rubber Powered Airplanes) says
that for stable flight decalage should be somewhere between 2 and 4
degrees. I learned the hard way to take the advice of the experts -
like Lew Gitlow (and lately Bill Gowen), who have a lot of
experience. Out where I live we have several top notch flyers with
decades of experience, including John Hutchison and Cezar Banks. I
always take their advice at indoor flying sessions. Sometimes there is
a good scientific explanation for what works best, sometimes not.

Let's face it, its difficult to translate such small degrees into wing
post adjustments on a stick model, but if you do the geometry you will
find out that for each inch of chord a degree amounts to about 1/64
inch of tilt.

Your main wing should never be at a negative angle of incidence. So
the above relationship (2 - 4 degrees decalage) usually results in a
small, e.g. 1 degree, negative incidence for the stab.

I defer to Bill Gowen's explanation of why you don't want downthrust
in a stick duration model.

Thanks Bill for your answer on wrinkling the film. Ray Harlan says
its great. I think I recall John and Cezar saying they are not sure
it adds any duration.

Calgoddard
Received on Thu Nov 16 2006 - 21:45:38 CET