Carf-Models Extra 330SC Instructions Manual page 21

CARF-Models Extra 330SC (3.1m)
We use the excellent 'Tygon' brand of fuel tubing for all our
models. It is totally gasoline 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 small rings or short lengths of larger
brass tube onto the brass tubing (easily made from the soft
wire of a paperclip wrapped around a small screwdriver) and
also secure with a fuel-line clamp or cable-tie (see photo).
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) and one at the top for filling (close for flight).
If you install a 4zyl engine with two carburetors, it'll be
recommendable to install two clunks. You have the choice to
install two fuel tanks (one for each carburetor) or two clunks
in one fuel tank. So, the two carburetors won't influence each
other!
Drill a hole in the motor firewall where necessary for the fuel
feed tube from the tank, and protect it where it passes
through the hole using a rubber grommet. Fix the tubing
securely to the underside of the top of the motor dome with a
couple of cable-ties or equivalent, to make sure that it cannot
touch the hot exhaust.
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The two clunks in one tank
extended with a long brass
tube to make sure that the
clunks aren't able to fall to the
front of the fuel tank.