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Composite-ARF YAK 55SP (3m span)
tal hole centres of 80mm and vertical centres of
90mm, so mark these offsets either side of the
motor centreline as shown. Drill the 4 fixing
holes Ø 6mm, and secure the motor to the fire-
wall using the M6 x 55mm bolts, and the T-nuts
against the inside face of the firewall. Add
washers as needed behind the standoffs to set
the correct thrustline, and then fit your spinner
backplate to check that it will be centrally posi-
tioned in front of the cowling.
Don't forget to add a drop of Loctite to all the
engine mounting bolts during final assembly.
Fuel-proofing
We highly recommend that you fuel-proof the
plywood firewall, and all bare wood inside the
motordome/tank base area with a thin coat of
laminating resin, to protect your investment in
the case of a fuel leak. It's wise to do this now,
before the motor is finally installed.
Canister and Header Installation
Included in the wood pack is a milled plywood
bulkhead designed to suit the excellent MTW
TD110 mufflers (or similar Ø70 cans), and this
must be glued into the muffler compartment
approx. 440mm (17.5") back from the front of
the fuselage. No other support is needed.
Cut eight 20mm lengths of the hard silicone
tube provided, and insert into the milled slots in
the corners to make the isolation mounts (see
photos on next page).
Sand the outside edges of the plywood support
a little to fit (if necessary) so that it does not
deform the fuselage of muffler compartment,
sand the gluing areas very well, clean off the
dust and tack-glue in glue in position with a few
drops of thick CA. Now trial fit your headers and
the 70mm canisters to your motor and carefully
push them into the muffler support to check that
the position is correct.
Check that there is at least 8mm (3/8") between
the canisters and the fuselage/muffler compart-
ment/landing gear support tubes in all positions
so that there can be no heat damage, and if
necessary bend the headers a little to set the
cans exactly in the required position.
techsupport@composite-arf.com
(above) Throttle linkage goes directly back-
wards through a slot in the firewall, to the
servo which is mounted on the milled plywood
assembly included in the kit.
(below) 2 views of the compact 3W 157cc Xi
installed. The venturi for the carburettor clears
the fuselage by about 6mm (1/4")
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