Prop Balancing
BY FRED KEIP, EAA 93236, MEMBER OF THE HOMEBUILT AIRCRAFT COUNCIL
NO MATTER WHAT ENGINE you use on your
Sonerai, there’s an almost 100 percent
probability that you will use a custom-built
wooden propeller to provide the thrust. To
make the production of this thrust as smooth
and vibration free as possible, it will be
necessary to occasionally check and adjust
the balance of your propeller, since
temperature and humidity changes will
affect it over time. This is not a difficult task
and can be easily accomplished using a
knife-edge balancer.
Its manufacture is really simple. It is
made up of two 1-by- 8 pine boards 12 inches
long, spaced 4 inches apart, and held by two
pieces of 1/2-inch plywood, 2-1/2 inches
wide by 5-1/2 inches long, glued and nailed
in place. The knife-edges are made from
0.025-inch by 2-inch by 5-inch 2024-T3 alu-
minum. The back knife-edge is attached to
the pine board with two small screws so that
it is in a fixed position. The front knife-edge
is also held with two screws, but the holes
are slotted vertically to allow it to be leveled
relative to the other knife-edge.
Reprinted from the Jan-Feb March 2001 issue of
the Sonerai Newsletter. To see EAA’s collection of Hints
for Homebuilders videos visit www.SportAviation.org.
After positioning the prop and tubing on the prop balancer
the prop should not rotate on the tube if it is in balance.
If the prop is out of balance the heavy blade will slowly
rotate downward.
