> OK Jerry here is the BD4 version. I like the rear
         > beam better. Also I added shims so the downthrust
         > angle can be adjusted.
         > --
         > Paul Lamar ...No rotor no motor.
         >



        Question,  in general is the thrust of an aircraft engine either
        level or down?   Is it ever up?    What about pushers?    Jerry

        Tractors are usually down. Pushers are up. Usually less than 3
        degrees. Spacer or shims would be +/- .75 inch in case you were
        asking? :) In general the thrust line passes through the CG.
        Does not work for Coots and their cohorts in crime :)
        No matter what you do they are going to pitch down when
        power is applied and pitch up when it is reduced.

        Paul Lamar ...No rotor no motor.


   Expanding on  what Paul said..  Most tractor airplanes have nose
   pitch-up response to increased power setting.  Part of that is increased
   air flow over the stabilizer - increasing the pitch response of the
   trim
   setting.

   The other part of the picture is where the thrust line is in relation to
   the center of drag.  If the the thrust line is below the center of drag,
   increasing power causes pitch up, if thrustline is above, pitch down to
   increasing power.

   I am pretty sure the Varieze and LongEZ don't have any thrustline offset
   (up, down, left, right).  Increasing power causes very slow pitch up
   because of trimmed airspeed, plus a slight roll effect (but no yaw)
   because of torque..


   Regards,

   Matt-

   Excellent explanation Matt. The Questair had an adjustment. You could
   tweak it for top speed. That is why I was so in love with the Questair
   rear mount for so long. People did not like to modify their
   firewall to accommodate it so that is why we went to the new rear
   beam mount. "Don't confuse me with the facts I don't like the look
   of it" :) Also it was hard to implement when you moved the engine
   forward a few inches.
   --
   Paul Lamar ...No rotor no motor.


Thanks Paul..

I forgot to mention one thing about the Varieze/LongEZ.  They are able
to run without thrust offsets because the center of drag is very close
to the center of thrust.  Interestingly, if you take one of these planes
and and go from no wheel fairings to a pair of Klaus or Hertzler
pressure recovery wheel fairings, most planes nearly run out of nose
down trim when at low altitude.  Not only is the plane lower drag
allowing higher speeds, but the drag centerline moves up significantly,
causing a pitch up effect..  I have heard similar stories about RV's..


Matt-

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