close to the engine as possible - because of the length of the HT leads that connect to the spark
plug(s). Mount it on a foam pad and secure with cable-ties, to the top surface of the motor dome
immediately behind the engine as shown on page 22. Don’t forget that the ignition unit also gets
warm during use, so it is wise to put it in a location where there is some cooling airflow. Keep the
ignition unit as far away from the receiver as possible.
Use a very small cable tie, ‘safety clip’, or a length of heat-shrink tubing to securely connect the
plug and socket from the motor pick-up to the ignition unit.
Fuel Tank
The fuel tank is held to the tank base with 2 large and 1
small able-ties. Drill a hole in the motor firewall as neces-
sary for the fuel feed tube from the tank to the carburettor,
and protect it where it passes through the hole using a rub-
ber grommet or similar.
Fit the correct stopper to the fuel tank for the fuel type used.
(If using Dubro tank the gasoline stopper has a small ‘O’
moulded in the top of it). We use the excellent ‘Tygon’ brand
of fuel tubing for all our aerobatic models. It is totally gaso-
line and kerosene-proof, and does not go hard and crack
with age. Secure the feed tube inside the tank to the clunk
with a small cable tie. If the tube is even a little loose on the
brass tubes though the stopper, you can be sure it will
come off at just the wrong moment and your engine will quit ! Therefore please solder some small
rings onto both ends of the brass tubing (easily made from the soft wire of a paperclip wrapped
around a small screwdriver, or short lengths of brass tube) and also secure with a fuel-line clamp
or cable-tie. Don’t miss this small detail - it could cost you your plane !
We use the normal 3 tube plumbing system, one from the clunk to feed the motor, one out of the
bottom of the plane (vent/overflow - leave open) and one at the top for filling (close for flight).
Final Check
Now check that you have fixed all components securely. Keep in mind that all the components
inside the aircraft are loaded with the same G’s as the wing and the wing spar during aerobatic
maneouvers. Check engine, cowling, wing and stab mounts carefully again.
-
Are all extension leads, cables & fuel tubes securely fixed to the side of the fuselage
and cannot come loose when subjected to high ‘G’ forces during flight.
-
Are all tubes and wires protected from chafing where they pass thru’ the holes in fibre
glass parts or bulkheads with rubber grommets, or short lengths of split silicone tubing?
-
Especially if you have installed the internal mini-pipe set-up, you also must make sure
that no fuel tubing or wires can come into contact the exhausts. Use the plastic spiral-
wrap to tidy up groups of cables and make sure that they cannot move around in the
plane under high ’G’ manoeuvres by fixing them to the sides with small cable ties. If using
the easily-available cable-tie plastic fixing plates, please do not trust the double-sided
tape that they usually have on them which can fail under vibrations. Peel it off, rough up
the back face with coarse sandpaper and glue to the fuselage sides with 30min. epoxy.
-
Did you fit small Tygon or silicone tube pieces over all the clevises?
-
Did you tighten the M3 locknuts against all the clevises to make sure they cannot turn?
Composite-ARF YAK 55SP
(3m span)
30
(below) Fit barbs to all brass tubes
and fuel connections for safety.
Easily made from a paper-clip, sol-
dered onto the brass tubes.
