9
MOUNTING THE COWL
Before mounting the cowl, carefully inspect its inside rear edges.
Use sandpaper to smooth the inside rear surface of the cowl,
making it free of any bumps or ragged edges that may scratch or
dent the fuselage when pressed in place. Also make sure the four
mounting holes are open and free of any debris.
❑
1) Slide the fiberglass cowl in place over the engine and back
onto the fuselage. Watch carefully to see if the cowling is going to
clear your engine installation. Engines at the larger end of the
recommended size range (like the Irvine 1.50 shown here) will
need to have an opening made in the side of the cowl to clear the
head of the engine. As a general rule, you should have at least
3/16" clearance from the cowl to any engine part. This is largely a
matter of carefully observing where the engine part is contacting
the cowl and then marking that location on the cowl with a felt
marker.
Remove the cowl, and use a Dremel
®
Tool to make
a small hole in the cowl at the point of contact. Refit the cowl,
checking the hole location and size, adjust as needed and again
use the Dremel
®
Tool to work on the opening. This method is
referred to as "sneaking up" on the opening, to make a perfect
clearance hole. A handy tool for this job is a small penlight. The
penlight can be used from the inside or outside of the cowl to
highlight and spot required hole locations.
❑
5) Use a 3/16" dia. bit to drill the four holes in the firewall for
the motor mounts. After all four holes are drilled, change drill bits
to a 1/4" dia. and redrill the four holes to allow clearance for the
10-32 blind nuts.
❑
6) Bolt the engine mounts in place on the front of the firewall
using the four 10-32 x 1” Socket-Head Bolts, four 10-32 Blind Nuts,
and four #10 Flat Metal Washers provided. Tighten the bolts until
the prongs of the blind nuts are sunk securely into the back of the
firewall. Apply some epoxy glue around the flanges of the blind
nuts to keep the nuts from coming loose. Be careful not to get any
glue in the threads of the blind nuts.
❑
7) With the engine mounts bolted on the firewall, place your
engine on the mounts.
Move the engine forward or backward
on the mounts until you measure exactly 6" from the front face of
the prop drive washer to the front of the firewall.
This is the
distance your engine needs to be from the firewall for proper cowl
alignment and prop clearance purposes.
Accurately mark the
engine's mounting bolt hole locations onto the engine mounts and
then remove the engine.
❑
8) This kit does NOT contain bolts for mounting the engine to
the engine mounts. That is because not all 1.20-1.50 size engines
use the same size. The diameter of the bolts you need depends
on the size of the holes in your engine's mounting lugs. Some
engines may need 8-32 size bolts, while others may need 10-32.
You will need to go to the hobby shop to obtain the correct size for
your engine.
Drill the four mounting holes in the engine mounts, being very
careful to drill them perpendicular to the mount. Use a drill press
if available. These holes must be clearance holes, which allow the
bolts to slip through. In the case of 8-32 bolts, an 11/64" dia. drill
bit will provide clearance holes. For 10-32 bolts use a 13/64” bit.
After drilling the holes, mount the engine in place to the engine
mounts.
We suggest using a little thread locking compound
(Loctite
®
) on the bolt threads to keep them from coming loose.
IMPORTANT SAFETY ISSUE!
Use only steel Socket-Head Bolts with Aircraft Lock Nuts and
Flat Metal Washers to fasten your engine to the glass-filled
engine mounts. The holes you drill through the mounts must
be big enough for the bolts to pass freely through. They
should not go in tight.
DO NOT DRILL AND TAP THE GLASS-FILLED MOUNTS
FOR BOLTS, OR USE SELF-TAPPING SCREWS OR WOOD
SCREWS.
THOSE METHODS WILL WEAKEN THE
MOUNTS AND CAN LEAD TO MOUNT FAILURE!