17
30% Ultimate ARF
Engine mounting
Locate the firewall, motor box cov-
ers, tri stock, and top firewall sup-
ports.
With the cowl mounted, measure
from the F1 former to the front of
the cowl ring. Write this number
down.
Measure the engine length from the
mounting plate to the thrust washer.
Subtract this number from the
length of the measurement of the
cowl from former F1. That number is
where you cut the motor box sides.
You will need to add about 1/8” to
the length of the motor box sides for
clearance between the the spinner
backplate and the cowl ring. On
most engines the cylinder will be
behind the engine mount at the bot-
tom and will hit the firewall if the
firewall is not notched out.
Use a square to draw a line on the
motor box sides. Be sure and keep it
square to the box sides as this will
adjust the up and down thrust. Mark
the left side 3/16” longer than the
right to give the desired right thrust.
