Mount The Booms On The Wing; Prepare The Booms & Wing - GREAT PLANES Profile 38 Instruction Manual

1. Mount the spinner backplate to the engine you are
using. Position the engine on the right boom engine mount.
The head of the engine should point to the right when
viewed from behind the plane. See the box lid if you are
confused. The backplate should be approximately 1/16" to
1/8" [1.6mm to 3mm] forward of the boom and the engine
should be centered in the mount. Trim the engine mount if
needed.
2. Mark the outline of the engine mounting lugs on the
boom. Use a sharp hobby knife to cut a recess in the balsa.
Do not cut into the plywood engine mount.
3. Position the engine in the recess and check its fit.
When satisfied, mark the location of the engine mounting
holes. A great method for marking the engine mounting
holes is to use the Great Planes Dead Center
Mounting Hole Locator.
4. Remove the engine from the boom. Drill a 7/64"
[2.8mm] diameter hole at each mark. Try to keep the drill bit
perpendicular to the engine mount.
5. Put a #4 flat washer on a 4-40 x 3/4" [19mm]
machine screw. Insert the screw through the back of the
engine mount and then through the engine mounting lugs.
Temporarily secure the engine to the mount with a #4 lock
washer and 4-40 nut. Install the other three screws, washers
and nuts.
6. Return to step 1 and install the second engine on the
left boom.
7. Once both engines have been mounted, remove them
and proceed to attaching the booms to the wing.

MOUNT THE BOOMS ON THE WING

Prepare the Booms & Wing
1. Sand a small radius along the top and bottom edges
of both booms. Fill any major dents with balsa filler.
How To Remove Annoying Dents In Balsa
Many surface blemishes on a framed model are caused
by bumps and balsa chips on the work surface. This type
of "ding" is best repaired by applying a drop or two of tap
water to the blemish, then running a hot sealing iron over
the spot to expand the wood fibers. After the surface has
dried, sand the expanded area smooth.
™ Engine
2. Finish-sand the wing, removing any surface blemishes.
Blend the wing sheeting and cap strips. Sand the shear web
at the wing tips so that it blends into the tip. Then, sand a
radius on both wing tips.
3. Test fit the left and right booms on the wing. The tabs
on the booms should fit snug in the slots in the wing. Trim
the slots slightly if they are too tight.
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