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Composite-ARF Extra 300L (2.12m/84")
techsupport@composite-arf.com
glass bulkhead sandwiched in between them,
using the M6 bolts and T-nuts included in the kit,
while the glue cures. This ensures that there are
no air pockets in the firewall - especially where
the standoffs will be positioned. Use a slow (at
least 30 minute) epoxy and microballoons mix-
ture and make a nice smooth fillet all around as
shown in the photos.
The stand-offs are mounted to the firewall with
the M6 bolts and large diameter washers provid-
ed, or whatever bolt size is needed for your
standoffs. Use an Incidence meter on the wing
root, and against the prop-driver or spinner
backplate of the motor to set the upthrust to
about +0.5 to +0.7 degrees for the first flight.
Add washers behind the (pilots view) left side
standoffs and the front firewall the set the side-
thrust to approx. 3.5 degrees, which will require
a stack of washers about 4mm thick.
Fit the spinner backplate to the motor and check
that the outside edge of the spinner aligns with
the middle of the radiused curve on the top of
the fuselage. The thrustline can easily be adjust-
ed after trimming flights by adding or removing
washers.
You will need to make a cut-out in the bottom of
the cowl as the DA-50 cylinder head sticks out,
but this gives excellent cooling and no internal
baffles are needed in the cowling. You will see a
very fine line molded into the to bottom surface
of the cowl which can be used as a guide for
cylinder cutout. Also open up the small cooling
vent in the front lower surface of the cowl, as
seen in the photo above, to approx. 30 x 30mm
(1.25" x 1.25").
Mini-Pipe
A TD75 mini-pipe (Ø55 x 355mm long) and spe-
cially manufactured header from MTW is shown
fitted, and these are available as an option from
Composite-ARF (product #910060), as well as
the DA-50. This set-up gives the engine a nice
throttle response, a perfect mid-range, and also
increases top end power slightly.
Now mill the large cutout in the bottom of the
fuselage for the pipe cooling air exit. For the
MTW TD75 mini-pipe the front of the cutout
should be 230mm (9") from the front of the fuse-
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