Right Thrust:
The eyeball method:  Put your 2 blade prop on the plane sitting horizontally and look straight down at it from above the airplane from the rear of the plane. The right blade
should be closer to the cowl, and the left blade farther away from the cowl which = right thrust.  If you don't see right thrust you may need to make some adjustments.
Adjustments can be made by relocating the motor stick (assuming its not already glued in) or by sanding and shimming the sides of the stick appropriately.  If the right blade is more than a 1/4" back and the left is more than a 1/4" forward, you have too much right thrust which could make your Beaver pull to the right during flight.  All of the above assumes the cowl is at right angles to the
centerline of the fuselage
Thrust Angles and Center of Gravity:

Thrust Angles:
One of the most popular questions for new Beaver builders is how do I set the thrust angle correctly?  The GWS instructions are critically lacking on this point. They tell you to draw a line on the stick motor mount but not what to do with it.

As a rule of thumb, you should have about 3 degrees of right thrust in the motor to overcome the torque from the spinning motor and approximately 2 degrees down thrust to help prevent the ballooning (nose of the plane pops up) when power is applied during a flight.  (Ballooning is not to be confused with porpoising which is when your planes nose pops up and then down continually during level flight.  Porpoising is caused by a plane being tail heavy)


Slightly more technical method:  Pick a fixed point on the tail, and measure to the prop tips with a 2-blade prop sitting horizontally.  When measured to the prop blade on the R/H side it should be somewhere around 1/16 -1/8 of an inch less that when measured to the L/H side.

Another more technical and accurate method:  Using a protractor make an angle template with one corner at 86 degrees (that's 4 degrees off of square) out of card stock. Use the template to set the stick in the hole at 4 degrees right and 4 degrees down thrust when you glue the motor stick into the fuselage being sure to use some masking tape to hold everything in place while it cures.   The firewall on the Beaver is square to the centerline of the plane thus making it the best reference surface to measure thrust angle.


Down Thrust
:
Can be set the same as right thrust but with the prop situated vertically and viewing from the side of the plane.  For this measurement the top blade should be 1/32 to 1/8 farther from the cowl than the lower blade


Center of Gravity:
Setting the correct center of Gravity for your Beaver is critical for good flying characteristics.  To set your C of G measure back 2" from the leading edge of the wing on both sides of the fuselage approximately an inch or so out on the wing.  Mark your measurement with small dot from a felt tip pen.  You can get more technical by taking RC 56 Canopy Glue or even regular white glue put a little dab where the mark is and let it dry overnight. These glues dry clear and will leave a little dimple on your wing so that when you slide you fingers under there to check the balance you will feel those little raised glue blobs and your balancing point.  Simply balance the plane on your index fingers at this point and see if it sits level; if not add weight to the nose or tail to balance it (more than likely you will be adding weight to the nose).


A slightly more involved (and more accurate) method to check C of G:

Use a commercial C of G machine or make your
own from some blocks of wood and finishing nails
or even my drilling some holes in a 2 x 4 and
sticking a couple of pencils in (eraser side up) to
balance on.  With the Beaver on the CG machine
at the CG position of 45-51mm (approximately 2")
from LE, measure from the table to the top of the
leading edge of the horizontal stabilizer right next
to the fuselage, then measure from the table to the
center of the spinner or gearbox shaft. The spinner
should be about 6mm (1/4") to 10mm (3/8") below
the horizontal stabilizer.

Added 05/28/07:  Here is a link to an alternative cheap to build CG machine http://iflyrc.hypermart.net/CG%20Machine.htm

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