Carf-Models Ultra Lightning Instruction Manual page 14

over the back of the bypass duct to check lengths. The
fixing tabs on the exhaust duct should be about 10 -
12mm in front of the rear bulkhead. You might find that
about 5 - 6mm needs cutting off the back of the bypass.
When satisfied, fit the carbon rear cone over the back
edge of the upper bypass, and drill 3 holes of 3mm Ø for
the supplied M3 bolts and T-nuts to hold it in place to the
upper bypass only, approximately in line with the 3 bolts
that secure the bypass to the aluminium angles. (The red
arrows in photo P13 show positions). Note that the T-nuts
are fitted upside-down, with the flat face against the out-
side of the carbon cone, and the 'spikes' sticking up -
which get covered by the epoxy/micro mixture (photo right)
Trial mount your turbine using the manufacturers brack-
ets, with the supplied M4 bolts and T-nuts glued under-
neath the carbon side rails (fitted upside down), with a
thick epoxy/microballoons mixture. Make sure the turbine
is exactly straight and in-line with the flying axis of the
model (photo P12). The optimum distance between the
back of the turbine exhaust nozzle and the front edge of
the 45 degree angled 'bellmouth' on the inner tube varies
for different turbines, but a good starting point for a JetCat
P160 or AMT NL Pegasus is 12 - 15mm. A little adjust-
ment may be needed for lowest turbine EGT's, and
exhaust tube cooling, especially after long periods at 'idle'.
Important: Whatever make of turbine you install, please
read, and follow, the manufacturers instructions and recom-
mendations before installing your motor.
Some brands of turbine have slightly offset mounting
brackets (eg: JetCat), and in this case you should pack
them off the ply mounting rails with 3mm plywood spacers
to get the turbine in the vertical centre of the bypass, which
is very important for the best performance and cooling of
the motor and exhaust tube.
Now you can fit the lower bypass (bypass cover) and cut any clearance slots around your tur-
bine mounting bracket, and to clear the cables and fuel/gas tubes to your turbine. The lower
bypass is held in place using 2 sheet-metal screws 2.9Ø x 13mm into plywood plates glued
under the front flange, and a pair of M3 bolts and T-nuts in the middle.
Note: Remember that carbon-fibre composite is extremely abrasive and all tubes or wires that
pass thru' it must be protected, either by fitting rubber grommets in the holes, or wrapping the
tubes/wires in plastic 'spiral-wrap' or similar (see photos P14 and P15).
Exhaust Duct/Thrust tube
This is a 'generic' twin-walled system,consisting of lightweight aluminium outer tube, and a
0.25mm thick stainless steel inner tube, spotwelded together. It is designed to work with a wide
The T-nuts that secure the carbon
cone to the bypass (above) and
the engine mounting bolts
(below) are glued on inverted,
and then secured with a thick mix-
ture of epoxy and micro-balloons.
3mm ply packing on Jetcat P160
mount to centre it in bypass duct.
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