model and therefore affect the safety during flight.
When satisfied, drill for the 4 mounting bolts and
glue the T-nuts to the top surface of the fibreglass
flanges with the spikes pointing upwards, using
epoxy and micro-balloons mixture. Follow turbine
manufacturers recommendations for the spacing be-
tween the back of the turbine nozzle and the front of
the bellmouth. Final small adjustments to turbine
alignment can be made by inserting washers be-
tween the turbine bracket and ply mounts.
Thrust Tube
No thrust tube (exhaust duct) is provided in the kit,
as there are so many different sizes and shapes to
suit the many different turbines that can be fitted.
The back end of the outer (or ejector) tube should
extend approx. 6mm out of the back of the fuselage,
and should just be a sliding fit in the bulkhead - to
allow for heat expansion. The rear bulkhead has a
circular hole in it of Ø 75mm (3”), but you can sand
the 4 small tabs on it if needed for an Ø 80mm pipe.
The total length (for 54-sized turbine) from the front
of the bellmouth to the back of the outer tube will
need to be approx. 535mm (21”).
In the prototype we used a dual-walled tube from
PST (Thailand) which performed well. Total weight
of the tube is 240 grams.
Many of our customers are using the tubes from
Wren Turbines (UK), and they seem to be very light-
weight have excellent performance. They manufac-
ture a couple of ‘standard’ tubes, which could be trimmed to fit the Hawk.
Be very careful to keep the extension leads for the elevator and rudder servos as far away from
the thrust tube as possible, and it is wise to protect them with a layer of self-adhesive aluminium
tape, or ceramic quilt, as well.
Fuel Tanks
The tanks included in the kit each hold about 875cc,
and fit into the fuselage very close to the CG, giving
no noticeable trim change during flight.
A fibreglass tube (17mm I.D) is bonded into the front
of each tank, which accepts standard sized stoppers
(eg: Dubro or Sullivan). The nylon end plates, and
connecting screw, for the stoppers are included in
the kit, but you need to provide the brass tubes (1/8”
dia.), kerosene compatible stoppers (eg: Dubro pt.
#400), Tygon tubing and clunks.
Fox Composites Co., Ltd.
23
(above) View of left fuel tank, with com-
pleted stopper and vent/feed tubes.
5 - 6mm
(above) Outer thrust tube should project
out of fuselage 5 - 6mm. Back end of
inner tube should be at least 6mm in
front of back end of outer tube.
(below) Trim the 4 tabs in the rear bulk-
head as needed to give a sliding fit of the
outer thrust tube.
