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 sys-
tem as needed, within the
overall size of the molded
exhaust tunnel.
The mini-pipe is only sup-
ported in the exhaust tunnel
in a ‘U-shaped’ milled ply-
wood part which has 3 sili-
cone buffers fitted into the
slots in it, and no other support is necessary.
Assemble the header and mini-pipe with the
teflon joiner and clamps, and trial fit it into the
fuselage. You will need to mill an ’L-shaped’ hole
in the fuselage as shown, between the LG legs
for the pipe outlet - which can be cut a little
shorter to ease installation without affecting the
performance noticeably.
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. The
hard silicone tube ‘isolation’ buffers on the pipe
supports give some flexibility for the pipe mount-
ing, and also reduce the vibrations transferred to
the airframe.
Glue the 2 small ply doublers to the ends of the
pipe support, which will take the 2 sheetmetal
screws for the spring that secures the pipe.
Screw in the sheetmetal screws now, as it is
more difficult when this part is finally glued into
the pipe tunnel. 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 110mm (4.25”) from the back of the cutout
in the fuselage, and temporarily tack in place
with a drop of CA. Test fit the header and mini-
pipe and adjust the position of the pipe support
if needed, checking carefully that the mini-pipe
clears all fibreglass parts by at least 6mm to pre-
vent scorching.
When the fit is Ok, sand and clean 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 anoth-
er length of the Ø 10mm hard silicone tube. Bend a small hook in each end of the spring, and
Composite-ARF Yak 55
(2.1m/83”)
25
