16
Mount the Cowl
Decide whether you wish to attach the cowl to the fuselage
with four sheet metal screws through the sides, or with a
cowl ring and internal screws. Some pilots may prefer a cowl
ring because the cowl mounting screws will not be visible,
but a cowl ring takes a little more skill and patience to install.
Follow the instructions for the method you prefer:
Mount the Cowl with Sheet Metal Screws
❏
1. The cowl mounting screws are to be centered over the
edge of the front former, or slightly aft so they are anchored
in the hardwood triangle stock inside. Mark a line on masking
tape applied to both sides of the fuselage 2-1/8" [54mm] aft
of the front surface of the front former.
❏
2. Install the cockpit hatch. Fit the cowl and mount
a propeller.
❏
3. Accurately position and hold the cowl so the crankshaft
will be centered in the hole in the front of the cowl and so
you will have adequate propeller clearance (masking tape
may be used to hold the cowl if necessary). Mark two screw
holes on both sides of the cowl 2" [50mm] forward of the
lines on the tape (centering the screw holes in the edge of
the front former).
❏
4. Drill 1/16" [1.6mm] holes through the marks in the cowl
into the fuselage sides. As you drill each hole, partially thread
in a M2.5 x 10 washer-head Phillips wood screw through the
cowl into the hole before drilling the next hole.
❏
5. After all four holes have been drilled, remove the cowl.
Enlarge the holes in the cowl with a 3/32" [2.4mm] drill.
❏
6. Test-mount the cowl with the screws. Remove the cowl
and screws. Add a few drops of thin CA to each screw hole
and allow to harden.
Proceed to
Finish Cutting the Cowl
.
Mount the Cowl with the Cowl Ring
❏
1. Press 4-40 blind nuts
into the four holes in the
cowl ring. This side will be
the front.
Option:
Press the bottom two blind nuts into the back of the
front former instead of into the cowl ring. Then, the screws
may be accessed through the cowl. This requires a “clear shot”
to the screws from the front of the cowl (not concealed by
the engine muffl er, etc.) and a hex driver that is long enough.
❏
2. Mount the cowl ring to the fuselage with four 4-40 x
1/2" [13mm] socket-head cap screws and #4 lock washers
and fl at washers.
❏
3. If you’ve installed a glow engine, refer back to the cowl
cutting procedure on page 14 to fi t the cowl to the fuselage
over the engine.
❏
4. Fit the cowl and a propeller. Be certain the cowl goes
on far enough so there will be enough clearance between
