Model Forum / Radio Controlled / Air Models / June 2009

On Wed, 03 Jun 2009 19:38:48 -0700, dan.hoffard wrote:

How much pull?  When it's going slow?  When it's going fast?  Only after
hand launch, or when you take off from the ground?

Any warps or inaccuracies in the airframe will make it pull one way or
another.  Check that the wings aren't twisted, with the left wingtip
pointing up or the right wingtip pointing down.  Check that when the wing
is on it isn't canted with the left tip farther forward than the right.  
Check to make sure that the horizontal stabilizer really is horizontal
with respect to the wings.  Check to make sure that the vertical
stabilizer is straight in line with the fuselage, and not giving it right
"rudder" all he time.  Make sure that you don't have _too_ much right
thrust on the motor (up to 5 degrees of right thrust is desired -- check
the assembly manual to see what it has to say).  Finally, check the
balance from side to side, to make sure that the right wing isn't heavy,
making the thing drop at low airspeeds.

HTH

Ted shuffled out of his cave and grunted these great (and sometimes not
so great) words of knowledge:

Did you do a lateral balance ?  Support the plane by it's prop and the
end of the plane (if necessary insert a pin in the end of the fuselage).

The wings should be level.  If a wing dips (drops) add some weight to
the opposite wing.

If the wings are level, make sure you do not have a warp in the wings or
tailfeathers.  If you have a warp, depending on what the plane is made
from you can do the following to get rid of the warp.

1.  Shim the offending surface in the opposite direction and weight it
down overnight.  This may have to be done several times as the surface
will "spring back" to a certain degree.

2.  Using a heat gun for modelers (NOT A HAIR DRYER - too hot),
CAREFULLY heat the offending surface and twist in the opposite direction
of the warp.

#1 and 2 normally work very well on conventional (balsa) airplanes.

#1 may work on the foam planes.

If the plane is foam and #1 doesn't do the trick, you will need to
fashion a brace from balsa/lite ply and while holding the surface in the
correct position (shims and weight come in hamdy here) CA the brace in
place using FOAM SAFE CA.  Remember to do a lateral balance afterwards.

Tape a stick onto each wingtip, in exactly the same manner on each side.
Try to make it from the point at the front to the point at the back of the
wing, then sight the sticks looking at one tip along the length of the wing
to the second stick.  They should be at the same angle, and if not, they
will cause the plane to bank.