one could possibly want ... and it has
lots
of ver-
tical performance! There are many other gas
engines that would be suitable, for example the
Zenoah 38 or ZDZ 40, and ready-to-fly weight
with these will be in the range of 6.7 - 7kg (15.5
LBS)
You could also use a powerful 2 or 4-stroke glow
engine, like the OS140/160 or YS140/160 -
which will give excellent, and quiet, flight per-
formance and a very lightweight airframe.
DA-50 (gas engine installation)
Installation of gas or methanol engines will vary
considerably, depending on your motor and
exhaust system choice, but here we show a typ-
ical set-up of a DA-50 and MTW TD75 mini-pipe.
The method shown here can be modified to suit
your preferred set-up.
The integral black fibreglass firewall and
exhaust tunnel is factory installed in the fuselage
and jig aligned, so that the front face the front
face of the firewall has, nominally, 0 degrees
side thrust.
However the manufacturing process does not
allow us to set the up/down thrust exactly, and
this could be as much as +/- 1 or 2 degrees from
the wing incidence. Of course when you install
the engine the upthrust required is easily adjust-
ed by using a stack of washers between the
back face of the motor stand-offs and the front of
the plywood firewall.
The firewall consists of 2 identical milled 3mm
plywood sheets. One of these must be glued to
the front of the fibreglass firewall, and the other
to the back face, with the black fibreglass part
sandwiched in between them. With the DA-50
and carbon Mejzlik 23 x 8 prop the correct thrust
line is approx. 3.5 degrees right thrust, and
between 0.5 and 0.75 degrees ‘upthrust’, but
this will vary a little depending on your
motor/prop combination.
We recommend that you accurately mark and drill the engine mounting holes in the 2 plywood
firewalls
before
they are glued in to the fuselage. The dimensions shown here suit the DA-50 with
a 88mm (3.5”) diameter spinner. Cover the front plywood firewall with masking tape and mark
the vertical centreline on it, exactly at 90 degrees to the straight bottom edge of the firewall. Mark
Composite-ARF Extra 300L
(2.12m/84”)
22
(above) The dimensions shown here suit the
standoffs for a DA-50 with Ø 3.5” spinner.
(below) The firewalls are glued into the fuse-
lage, and temporarily secured with the bolts
and T-nuts. Fill the 3 - 4mm gap between the
firewall and the top surface of the fuselage
with a glue fillet. Use slow epoxy and micro-
balloons to glue the firewalls in the fuselage.
