Bob Hunt suggests using Z-Poxy Finishing Resin to
adhere balsa LEs and sheeting to foam-core wings. The
procedure is referenced in this column. Hunt photo.
A578: Former MA aeromodeling
editor, Bob Hunt, is the master of
foam-wing sheeting. Bob still offers
CDs containing his foam-core balsa-sheeting techniques. He has a website
that describes the process and includes
many detailed photos.
The title of the PDF file is, “How
to Sheet a Foam Wing.” It then breaks
down into Part 1: “Molding a Leading
Edge Balsa Cap” and Part 2:
“Sheeting the Actual Wing.” Bob
lists contact information in this
PDF if you have any questions.
Converting Old Ignition
Engines to Electric Power
Q579: I’ve heard that old
ignition engines can be
converted so that an electric
motor actually turns the
crankshaft, but it still has the
appearance of the old engine.
Can you provide any details
about how this is done?
A579: The expert in this area
conversion is Ralph Bradley (brother of
Paul Bradley, who writes MA’s “
Small-Field Flying” column).
Ralph took an old Brown Jr. engine
that was no longer in working order. He
adapted an Atlas AM2915/10 brushless
motor that was originally available from
Hobby Lobby. Any equivalent .40-size
electric motor will work. The motor
should be roughly the same diameter as
the engine backplate.
Ralph extended the shaft with a
4mm x 4mm shaft coupler and short
extension. The shaft coupler came
from an old Graupner folding-propeller
drive set. He removed the Brown Jr.
crankshaft and piston.
The crankshaft diameter was 0.374
inches so he was able to buy a pair of
3/8-inch diameter flanged ball bearings
that were a light press fit into the
factory-installed bronze crankshaft
bearing in the Brown Jr. This provides
support for the drive shaft at the
front of the engine directly behind
the propeller and at the rear of the
The ball bearing ID was 5/16 inches, so
he needed to machine a couple of bore
reducers to fit the 4mm output shaft.
He also machined a set of standoffs
that mount the motor to the Brown Jr.
The only non-reversible modification
to the Brown Jr. was the holes drilled in
90 Model Aviation OCTOBER2013 www.ModelAviation.com
frequently asked questions