HOW TO CUT PERFECT CHANNELS IN FOAM

by Ironsides

Revision 3 dated 27 Mar 2001
 
The easiest way to cut channels in foam is to melt them with a soldering gun similar to the Weller ® model 8200 shown opposite (see below). The normal soldering tip has been removed and a custom "melting form" substituted.

The copper wire used came from ordinary household 110 volt wire with the code CSA AWG 12 CU. The sheathing was stripped from the black or white wires - the lighter gauge ground core was not used. The heavier wire retains its shape better when heated.

The copper wire is shaped to the depth and width of channel desired, with shoulders bent to act as a depth limiter. Measure the depth from the bottom of the depth limiting shoulder to the bottom of the wire.

Any covering over the foam is removed with a sharp blade to the exact dimensions of the foam channel.

A balsa template is made from 3/32 inch stock and it is tacked into place using masking tape.

Starting at one end, the heated wire is allowed to sink down to the depth stop. Then the iron is slowly drawn horizontally along the balsa template. Move only as quickly as the foam melts - do not try to go too quickly or you will deform the hot wire. Try to keep a constant speed and do not stop at any one place - the wire will melt a deeper ridge if allowed to stay in one place too long.

When you reach the stop at the far end, withdraw the hot wire vertically.

If all has gone well, you will have removed a perfect block of foam. The trench will be nicely cauterized!

In this case, the channel was created to insert a Futaba® S148 servo and mounting box in a wing.

This technique can be used to cut channels in foam for wing spars, to route long runs of servo extensions, or to create channels for dorsal stiffeners on the top rears of foam float cores.

Remember that you must add the thickness of your balsa template to the depth desired.

Always test on a piece of scrap foam!!!!!!!

 (*) Note 1: The Weller® model is 8200, 1.2 amps, duty cycle 1 minute ON, 4 minutes OFF, 100/140 watts.

Note 2: "Lee" reports [I've used 12 gauge wire wrapped around a Weller® 25 watt iron as a "carving" tool]