This baffling is usually made from a
corrosion- and crack-resistant alloy of
aluminum, usually 6061. Do not use
the 2024 aluminum that you probably
used for the aircraft structure. The
heat and vibration environment of
the engine compartment will rapidly
cause 2024-T3 to corrode and crack.
Most of our engine installations
bring cooling air in through the
cowling above the engine and then
direct it down over the cylinders. This
is known as downdraft cooling. It can
be theoretically argued that running
the cooling air in the opposite
direction, from the bottom up, would
provide more even cooling, since the
exhaust port is on the bottom, but
the mechanics of bringing the air
in below the cylinder, up through
the cylinder fins, and then back out
the bottom create a lot of sealing
problems, and so it’s usually not
done. The Piper Turbo Lance and the
Globe Swift use this system, but it is
complicated and a high-maintenance
item, so most of us use downdraft
cooling. The baffling system creates
an air plenum, sealing all the edges as
much as possible, directing all the air
possible around the cylinders, ideally
in the closest possible contact with
the fins.
To maximize cooling and to cool
the cylinder evenly, the cylinder
baffles must wrap around the bottom
of the front and back cylinders
to keep the cooling air moving
through all of the fins. To keep these
wraparound baffles from opening
under high airflow, some sort of
connecting device is usually installed
between the front and back cylinder
baffles. There are actually two baffles
for each side, one of smaller radius
for the portion of the cylinder
barrel that is steel and one of larger
HOW HAS A TECH COUNSELOR
HELPED YOU?
;E-mail your TC success stories to editorial@EAA.org with TC
as the subject.
