Great Planes Extra 300S 60 Kit - GPMA0236 - Manual (Page 39)

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8. Align the cowl with the mark you made on the
fuselage, then use a felt-tip pen to transfer the hole in the
template onto the cowl. Note: The circle you marked on the
cowl may be slightly aft of the actual position of the head
of the engine due to the upward sweep of the template
when the cowl is in position. Hint: For the most accuracy,
leave the engine mounted to the fuselage but remove only
the cylinder head. Position the cowl, then install the spinner
back plate on the engine. Align the cowl with the spinner
back plate (instead of the reference line you marked on the
fuselage top), then transfer the hole in the template onto
the cowl.
❏
9. Remove the cowl and template, then remount the
engine (or the cylinder head). Cut out the hole in the cowl,
then test fit it to the fuselage (you may have to temporarily
remove the needle valve so it does not interfere with the
cowl). Adjust the position and size of the hole as needed.
The location of the hole determines the clearance between
the front of the cowl and the back plate of the spinner. Hint:
Cut the hole in the cowl undersize at first so you can make
adjustments to its position without having to oversize it.
❏ 10. Once you have made the hole in the cowl to clear
the engine, place the cowl on the fuselage and fit the back
plate of your spinner on the engine. Tape the cowl to the fuse.
❏
11. Making one hole at a time and checking to be sure
the cowl still lines up with the spinner back plate, drill one
3/32" hole through the cowl and the fuse side at one of the
locations shown on the plan. Using a #4 x 1/2" screw,
attach the cowl to the fuse. Do the same for the other three
cowl mounting screws, checking alignment before drilling
each one.
❏ 12. Remove the spinner backplate and the cowl from the
fuselage. Use a drop of thin CA to harden the screw holes
in the fuse.
❏
13. Cut four 1" x 1" pieces of fiberglass cloth. Use 30-minute
epoxy to glue one piece to the inside of the cowl at each
cowl mounting hole. After the epoxy cures, re-drill the holes
with a 1/8" drill bit.
Do not confuse this procedure with “checking the
C.G.” or “balancing the airplane fore and aft.” That very
important step will be discussed later in the manual.
❏
1. With the wing level and attached to the model (and
the engine and muffler installed), lift the model by the
propeller shaft and the fin. This may require an assistant.
Do this several times.
❏
2. The wing that consistently drops indicates the heavy side.
Balance the model by adding weight to the other wing tip.
Note: An airplane that is laterally balanced will track
better during aerobatic maneuvers than one that is not.
❏
1. If you’ve hooked up the pushrods to the servos before
you covered the model, disconnect and remove all the
pushrods and remove the hinges and control horns from
the ailerons, elevators and rudder. Remove the engine
mount and any other hardware you may have installed.
This step is optional but will enhance the scale
appearance of your Extra 300S.
❏
2. Test fit the die-cut 1/8" plywood fuselage side
stringers (part #’s 34 and 35) in the fuselage sides as
shown on the plans. Then, use medium CA to glue them
into position.
❏ 3. Most of the model should be rough-sanded by now
with all the tabs and rough edges sanded even. Fill all
dents, seams, low spots and notches with HobbyLite
™ balsa
colored filler.
❏
4. After the filler has dried, use progressively finer
grades of sandpaper to even all the edges and seams and
smooth all surfaces. Remove all balsa dust from the model
with compressed air or a vacuum with a brush and a tack cloth.
PREPARE THE MODEL
FOR COVERING
BALANCE THE MODEL LATERALLY
39