If fitting the switches into the outside surface of the fuse-
lage, as shown, you should reinforce the area inside with
a small patch of 3mm thick plywood to reduce vibration
transmissions to the switches. The Powerbox switches
all come with card templates for cutting the slots.
NB:
Please double-check the manual for your R/C sys-
tem if the use of 5-cell battery packs is recommended.
Motor ignition system
The ignition unit can be secured onto the back surface
of the firewall, as previously mentioned, using 2 or 3
small cable-ties. We advise that you mount it either on a
foam pad to protect from vibration. At C-ARF we recom-
mend a 800 - 1200 NiCd pack for ignition, and we use a
Powerswitch for the ignition cut-off. Add a very small
cable tie around the plug/socket connectors from the
motor pick-up to the ignition unit for extra security.
Servo extension leads etc.
We advise you to use good quality twisted-cable exten-
sion leads, of heavy gauge wire with gold-contact con-
nectors. Secure all loose wires and extension leads -
remember that when you are pulling those 10G manoeu-
vres everything in the plane has 10 times more force
than usual! Be very careful to fix all your batteries
securely.Make extra sure that no fuel tubes or cables
can come in contact with hot exhausts.
Fuel proofing
If fitting a gas or glow motor we highly recommend that
you protect both sides of the plywood firewall, and all the
bare wood parts and edges inside the front of the plane
with one thin coat of 24 hr laminating epoxy, or similar,
brushed on. Be careful not to add excess weight here -
it only needs about 25 - 30 grams (1 oz.) of epoxy to fuel
proof all the wood in the whole area in the front of the
plane.
Final check
Check that you have fixed all components securely.
Keep in mind that everything inside the aircraft is loaded
with the same G’s as the wing and the wing spar during
aerobatic manoeuvres. Check engine, cowling, wing and
stab mounts carefully again.
-
Are all extension leads, cables and fuel tubes securely fixed to the side of the fuselage ?
-
Are all tubes/wires protected from chafing where they pass thru’ the holes in fibreglass
parts or bulkheads with rubber grommets, or short lengths of split silicone tubing?
-
Make sure that no fuel tubing or wires can come into contact the hot exhaust.
Composite-ARF Yak 55
(2.1m/83”)
29
PowerBox ‘Sensor’ switch
(above) Motor ignition system is fas-
tened to back of firewall with 3
cable-ties. Powerswitch for Ignition
is on the right of fuselage, seen here.
