Carf-Models Composite-ARF Extra 300L Instruction Manual page 23

Composite-ARF Extra 300L (2.12m/84")
techsupport@composite-arf.com
a horizontal line, 25mm from the bottom of the firewall,
which is the centreline for the lower 2 bolts of the 2.5"
(65mm) long standoffs. The DA-50 has vertical mount-
ing centres of 66mm, and horizontal centres of 78mm,
so mark another line 66mm above and parallel to the
1st line.
To give the correct sidethrust, and still have the spin-
ner centred on the nose of the fuselage, the motor
needs to be offset from the centreline by approx. 6mm,
therefore the (pilots view) left standoff bolts are posi-
tioned 42mm from the centreline, and the right bolts
36mm the other side. The photos here should make
this clear.
If you use a different diameter spinner you will need to
adjust the vertical position of the motor - so that the
spinner is central and aligns with the small radiused
shape on the top of the fuselage.
Note: When the firewalls are finally glued into the
fuselage you should leave a 3 - 4mm gap between
them and the top of the fuselage and fill this with
a nice glue fillet.
Place the 2 firewalls exactly on top of each other
and drill thru' Ø 6mm for the 4 holes for the
standoffs. With the fuselage upside down, mark
the centerline of the fuselage just in front of the
firewall position. Tack glue the front firewall
(only) to the fibreglass firewall with 1 or 2 small
drops of CA, not forgetting to leave 3 - 4mm
space around the top edge, and drill thru' all 4
holes to set the alignment.
Tip:
If you wish, at this point you can temporari-
ly bolt your motor and standoffs to the firewalls,
fitted either side of the fibreglass firewall, insert
washers to set the sidethrust/upthrust and check
for correct alignment of the spinner backplate
with the fuselage. Small adjustments to the
alignment can be made now by slightly moving
the position of the plywood firewalls on the fibre-
glass bulkhead, and redrilling the holes in it,
without having to redrill the holes in the ply fire-
walls.
When satisfied, remove the front firewall from
the fibreglass bulkhead and rough up and clean
the gluing surfaces of both ply firewalls, and
both surfaces of the black fibreglass.
Glue both plywood firewalls into position and temporarily bolt them tightly together, with the fibre-
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