Great Planes P-51D Mustang 40 Kit - GPMA0175 - Manual (Page 40)

D 3. By trial and error, cut openings in the cowl for the
engine head, needle valve and exhaust pipes, etc., as needed.
Allow approximately 1/8" clearance all around the engine
head for cooling air flow. While fitting, if you notice that the
cowl is a poor fit at F-1, you may sand all around the front of
the fuse, and along the sides of the upper cowl structure until
the cowl fits nicely.
IMPORTANT: If you have installed a 2-cycle engine
inverted, with the entire engine head concealed inside the
cowl, you must open up the front of the cowl to provide
plenty of cooling air flow to the engine head; and, even
more important, you must provide a large hole in the
bottom of the cowl at the firewall for the warm air to exit.
This hole should be at least twice the area of the intake
hole.
D 4. Trim the cowl to match the fuselage and the spinner
ring, as shown in the photos.
D 5. To attach the cowl to the fuselage, use the 1/4" x
1/2" x 3/4" plywood cowl mounting blocks. Glue these
blocks to the fuselage and the upper cowl structure in appro-
priate locations. Inset these blocks approximately 1/32" to
allow for the thickness of the cowl. Holding the cowl
accurately in position, drill 1/16" holes through the cowl and
blocks at the screw locations. Enlarge the holes in the cowl
to 3/32".
D 6. Reinforce the cowl at the screw locations by gluing
1" x 1" squares of fiberglass tape to the inside of the cowl.
This will help prevent stress cracks in the cowl due to
vibration.
D 7. Sand the entire outside surface of the cowl lightly
with 320-grit sandpaper.
D 8. Spray paint the cowl with paint to match your
covering material. On our prototype we used Chevron spray
aluminum and spray yellow. Be sure to allow plenty of time
for the paint to dry thoroughly.
FINISHING
ADDITIONAL FUELPROOFING
If you have not already done so, make sure the entire
engine compartment is completely fuelproof. Also fuelproof
any wood that will not be covered and which may be exposed
to glow fuel residue. Use epoxy thinned with alcohol,
polyester finishing resin or fuelproof paint.
BALANCE THE AIRPLANE LATERALLY
SPECIAL NOTE: Do not confuse this procedure with
"checking the C.G." or "balancing the airplane fore and
aft". That very important step will be covered later in the
manual.
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