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Composite-ARF SuperXtra 330L (3.1m span)
requires about 3 - 3.5° sidethrust, and nominally 0° down-
thrust. However, due to the mould joining process it is pos-
sible that the downthrust can be off by 1/2° or so, but this
can be checked easily by setting the wing at 0° incidence
and checking the vertical face of the firewall with an inci-
dence meter if you wish.
To set the positions for the 4 mounting holes for the DA-150
engine), first accurately mark a vertical centreline on the
front of the plywood firewall, as shown. Then mark a hori-
zontal line across it 28mm (1 1/8") down from the top of the
firewall. The 1
hole (top left hole in pilot's view) is posi-
st
tioned on the horizontal line, 52mm to the left of the vertical
centreline. Drill only this hole 7.5mm Ø and fit an M6 blind
nut inside the firewall and fit the engine in place using only
one bolt to check alignment. You will need to pack the
engine mount off the firewall by about 11mm, using a stack
of large washers so that the spinner backplate has about 4
- 5mm clearance from the front edge of the cowling.
Bolt the cowling in place and put the spinner backplate
(125mm/5" Ø) on the motor. Check that the overall height
of the motor is correct, and that the top edge of the spinner
is approx in the centre of the curved radius on the top edge
Drill the 2nd hole, exactly 80mm to the right of the first
(pilots eye view). Again mount the motor temporarily,
packed off the firewall with a stack of washers about 7.5mm
thick, for the sidethrust. Re-fit the cowling and spinner
backplate. Ideally the spinner backplate should be in line
with the centre of the cowling, and the edge of it should be
in the middle of the curved radius on the top edge of the
cowling.
If the position is OK, or close enough, then remove the
cowling and drill the other top mounting hole, and fit the 2
blind nut and bolt in place. If you need to increase the
moulded in sidethrust a little, use a slightly thinner pack of
washers on the 2
bolt. Again fit the cowling and spinner
nd
backplate to check alignment.
If correct, then drill the last 2 holes and bolt the motor in
place, adjusting the thickness of the washer packing to
leave a minimum 3mm (1/8") gap between the back face of
the spinner backplate and the cowling. The centres of the 4
mounting holes of the DA-150 are 80mm horizontally, and
90mm vertically, and with the first 2 holes drilled it is easy
to mark the other 2, using a 90° square and offsetting from
the 1st two holes.
NB: In the instance that your 1st hole was not in the correct
place you can enlarge it a little with a file to correct it, and
refit the blind nut, or plug the hole with a piece of hardwood dowel, glued in with slow epoxy and
re-drill in the correct position when it is completely cured.
techsupport@composite-arf.com
(above) Vertical centreline and the
1st hole to be drilled shown here.
(below) The 4 holes for the motor
mounting, and 1 for the linkage
from the throttle servo.
nd
26
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