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Thrust Tube Assembly
The thrust tube is manufactured from an aluminium
outer “cool” tube and a stainless steel inner pipe
rolled and spot welded for you at the factory.
This tube is designed to work with the sizes of turbine
intended for the BAE Hawk. Turbines in the 22-35lb
thrust class are perfect.
The tail pipe is mounted in the fuselage between the
rear fuselage cut-out opening and aluminium
mounting brackets provided that fix to the carbon
bellmouth and turbine mounting rails.
The first job is to fix the carbon bellmouth to the
stainless inner tube. The bellmouth is designed to go
inside the tail pipe and be fixed by M3 cap head
screws or pop rivets if available to you.
The thrust tube can be fitted in any orientation, but
the neatest look is with the joint seam at the top
when the aeroplane is on its wheels.
For simplicity the Hawk was designed without full
ducting, hundreds of test flights in various conditions
have shown perfect operation and normal turbine
temperatures.
A trial fit of the carbon bellmouth should show any
areas that need sanding to allow a snug fit. The
carbon moulding process will undoubtedly lead to a
variation in thickness of the material. Some early tail
tubes show a reduction in diameter where the lip is
formed in the tail pipe tube, this needs to be worked
out before the carbon bellmouth will fit. Later pipes
have no lip.
Once the bellmouth can be inserted at least 12mm
drill four holes to suit the fixing you have chosen.
If using M3 x 8 Socket head cap screws use washers
under the screw heads on the inside (carbon)
Fitting the aluminium mounting angles to the bellmouth at approximately 3 and 9
o’clock is best done after the turbine has been mounted so that the inner tube is fixed
centrally on the turbine cone. This is important to avoid “hot Spots” in the pipe that can
lead to tube failures. Note that on early kits the tail pipe outer “cool” tube will get very
close to the elevator servo mounting plate restricting how high the pipe can be mounted
at the front. Later kits will have more clearance.
Alignment by eye is accurate enough when fitting the carbon cone.
The outer tube should protrude through the fuselage rear between 3 and 5mm. This sets
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CONSTRUCTION
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