lage, the length is 175 - 180mm (7”) and the
width should be 70mm (2.75”). Radius both
ends of the cutout as shown. The dimensions of
this slot can be adjusted to fit your chosen
exhaust system as needed, within the overall
size of the molded exhaust tunnel.
The mini-pipe is supported at the back of the
exhaust tunnel in a ‘U-shaped’ milled plywood
part which has 3 silicone buffers fitted into the
slots in it, and an additional small plywood sup-
port under it at the front. Assemble the header
and mini-pipe with the teflon joiner and clamps,
and trial fit it in the fuselage. You will need to drill
a hole of approx.18mm (3/4”) diameter just
behind the front flange of the fuselage for the
exhaust outlet (see photos). Cut three 15mm
lengths of the hard Ø10mm clear silicone tube
provided, and fit them into the slots in the rear
pipe support as shown. Glue the 2 small ply dou-
blers to the ends of the pipe support, which will
take the 2 sheetmetal screws for the spring that
secures the pipe. You may need to sand the
inside of the pipe support a little, in the area of
the ply doublers, for a good fit of the TD75 pipe.
Trial fit the pipe support in the tunnel, positioned
about 75mm (3”) from the back of the cutout in
the fuselage, and tack in place with a drop of
CA. Test fit the header and mini-pipe and adust
the position of the pipe support if needed. When
the fit is Ok, sand the gluing position inside the
pipe tunnel carefully, and glue it permanently in
place with slow epoxy. The pipe is secured to the
support using a short length of Ø 4mm spring
(included), covered in another length of the Ø
10mm hard silicone tube. Bend a small hook in
each end of the spring, and screw 2 of the Ø 2.9
x 13mm sheetmetal screws into the pre-milled
holes in the pipe support doublers to hook the
spring over - as shown in the photos.
Fit the additional milled plywood pipe support under the front of the mini-pipe (with a 20mm
length of the silicone tube in the slot for isolation) glued to the bottom of the fuselage and on to
the front of the plywood landing gear mount, using slow epoxy and micro-balloons mixture as
shown.
The hard silicone tube ‘isolation’ buffers on the pipe supports give some flexibility for the pipe
mounting, and also reduce the vibrations transferred to the airframe.
Composite-ARF Extra 300L
(2.12m/84”)
25
