Cowling
The 1 piece cowling is already cut and trimmed at the fac-
tory, and should need almost no adjustment for a perfect fit.
With the main undercarriage legs bolted into place, install
the wing tube in the fuselage sleeve and place a small spir-
it or incidence meter level on top of it to set the plane exact-
ly level (side to side). Pack under one undercarriage leg as
necessary to get it level on your building table.
If necessary, sand the fibreglass joining tapes inside the
back edge of the cowl slightly to get a perfectly flush fit
between the cowling and the fuselage sides. Trial fit the
cowling, and use the spirit level or an incidence meter on
the lower (flat) part of the cutout at the front of the cowl to
make sure that it is level and properly centred. Tape the
cowl firmly into position, and mark a centreline on the top of
the cowl and the fuselage, on masking tape.
The cowling is held in place with 9 bolts (M3 x 12mm),
washers and blind nuts. Drill one 3mm diameter hole at the
top/centreline of the cowl, approx. 8mm (5/16”) in front of
the back edge of the cowling, and insert an M3 x 12mm
bolt. Thread a T-nut onto the bolt inside the fuselage, and
secure it to the fuselage with one small drop of thick CA.
Note that the blind nuts are fitted
reversed
, with the spikes
pointing inwards! Check alignment again, and then drill and
fit the other 8 bolts in the same way, securing the blind nuts
to the inside of the fuselage with a single drop of thick CA.
Space the 9 bolts 105mm (4.2”) apart, so that the lowest 2
bolts will be quite close to the edges of the square cutout in
the bottom of the cowling, which retains it properly.
Don’t forget to wax, or oil, the M3 bolts first, to make sure
that you don’t accidentally glue any of the bolts to the cowl-
ing or into the blind nuts! Finally remove all the bolts and
cowling, and glue the 9 blind nuts in place properly using a
medium-thick mixture of 30 minute epoxy and micro-bal-
loons, as shown. During final assembly, add the supplied
M3 washers under the heads of all the M3 bolts.
Composite-ARF Extra 300SX
(2.6m span)
13
(above) Cowling is secured with
nine M3 bolts, into T-nuts fitted in
reverse, glued inside fuselage with
a thick micro-balloons mixture.
(above & below) Tack glue the T-
nuts in position with a small drop
of thick CA first. When cowling is
correct, secure all the T-nuts with
a drop of, fairly wet, epoxy and
microballoons mixture as shown.
M3 T-nut
M3 bolt
cowl/fuselage
Epoxy
& micro
mixture.
