Foam Core Elevators

[Casey]

Hi Guys

After I used a jigsaw to cut the elevators to it's intended length, I noticed that the surface of the elevators is not straight as light can be seen under the ruler. Anyone have a solution to this problem?

[SteveMoon]

Water with ammonia. Mix water with a small amount of ammonia
(enough that you can easily smell it) then use a spray bottle to
spray it onto the balsa surface. Weigh it down on a flat surface and
let dry overnight. Be sure to leave some areas if the balsa surface
uncovered as this will promote drying. This should yield a flat, straight
elevator.

Steve