 | |  | |  | |  |
Rubber Band Engine Mount for the Lee Liddle designed Cobra.
When flying the cobra with its hard engine mounting system we found that
even soft hits to the engine mount would either break the engine tongue,
or damage the spar. Since moving to the soft rubber band mounting
system shown here, we have found the amount of damage done to the
airplane has been greatly reduced. In most cases, all that is required is to
slide the engine mount back into place, replace the prop and go fly again.
The engine Mount is made of 1/8” plywood laminated with 3/32” G10
fiberglass on both sides X 1 ½” X 15 ½”. These sizes may vary depending
on balance point of your airplane.
¼” O.D. X 2 ¾” Fiberglass tubing is used to attach the rubber bands to the
engine mount. I use ¼” I.D. X ¼” aluminum tubing on the outside of the
fiberglass to keep the 8 X 1/2” truss washer lath screws from splitting the
fiberglass tubing when inserted. The lath screws are used to keep the
rubber bands from slipping off in a midair. The fiberglass tubing is
attached to the motor mount with medium CA. Also, a small piece of
hardwood is used in front of the tubing to reduce the chance of breaking
the fiberglass tubing lose.
Some of my Cobras have fiberglass spars and some have plywood
spares. Since we are using rubber bands to hold the motor mount onto
the wing, the hardwood nose block is not required.
Note the photo that shows the elevator surface with (3/4” X ¾”) cutouts in
the coro for the rubber bands to pass through.
There are pictures that show the bottom of the wing with alignment
marks and 2 pieces of Velcro (loop). Velcro (hook) is also placed on the
topside of the motor mount and aligned with the Velcro on the wing. This
is done to keep the motor mount from sliding from side to side.
When flying the cobra with its hard engine mounting system we found that
even soft hits to the engine mount would either break the engine tongue,
or damage the spar. Since moving to the soft rubber band mounting
system shown here, we have found the amount of damage done to the
airplane has been greatly reduced. In most cases, all that is required is to
slide the engine mount back into place, replace the prop and go fly again.
The engine Mount is made of 1/8” plywood laminated with 3/32” G10
fiberglass on both sides X 1 ½” X 15 ½”. These sizes may vary depending
on balance point of your airplane.
¼” O.D. X 2 ¾” Fiberglass tubing is used to attach the rubber bands to the
engine mount. I use ¼” I.D. X ¼” aluminum tubing on the outside of the
fiberglass to keep the 8 X 1/2” truss washer lath screws from splitting the
fiberglass tubing when inserted. The lath screws are used to keep the
rubber bands from slipping off in a midair. The fiberglass tubing is
attached to the motor mount with medium CA. Also, a small piece of
hardwood is used in front of the tubing to reduce the chance of breaking
the fiberglass tubing lose.
Some of my Cobras have fiberglass spars and some have plywood
spares. Since we are using rubber bands to hold the motor mount onto
the wing, the hardwood nose block is not required.
Note the photo that shows the elevator surface with (3/4” X ¾”) cutouts in
the coro for the rubber bands to pass through.
There are pictures that show the bottom of the wing with alignment
marks and 2 pieces of Velcro (loop). Velcro (hook) is also placed on the
topside of the motor mount and aligned with the Velcro on the wing. This
is done to keep the motor mount from sliding from side to side.
Mark Scofield's Indiana Cobra Motor Mount System