If you have ever wanted to
try cutting your own foam parts and you have a battery charger
you may be half way there! The system I use is simple and easy
with no purchase of special wire or transformers. I use a Sears
2-10-50 amp self regulating battery charger (without a battery)
set to the 10 or the 50 amp setting with 55" of .032 stainless
steel safety wire stretched out on my workbench. This seems to
give around 5 and 7 amps through the wire for the two positions,
which heats the wire just about right. I put a heavy spring on
one end for tension. This means I move the part across the wire.
The more traditional method is a "bow" using the wire as the
string and leaving the part stationary as you pull the bow wire
over the part.
Aircraft Spruce & Specialties
has something that might work for you as well.
will have to play with your own charger to see if it will work.
Another method is to use a 12-volt battery with or without the
charger and/or putting a rheostat on it to regulate it. Make a
pair of templates out of something that will not burn or melt
easily. I use 1/8" ply door sheeting or aluminum sheet metal.
The edges have to be smooth and free of nicks or the wire will
jump when you go across them, which puts ridges in the part. Pin
the templates to the ends with plenty of pins making sure to
square the templates to each other. A complex wing can easily be
made using two different patterns for templates or not squaring
the templates to each other. Now clip the charger leads to the
ends of the wire and plug it in. The wire gets hot almost
immediately. On my first attempt with a different system the
wires turned red hot and melted through, falling on the bench.
Very exciting! BE CAREFUL the wire can burn you and/or your
Take some scrap foam and
run it through the wire. It should hiss slightly as it cuts the
foam and leaves "stringers" on the wire as it exits the foam. If
the wire is not pulled evenly across the templates the part will
be out of square. One method to correct this is to put station
lines and numbers along the edge of the templates and have
someone help, calling out the numbers as you get to them. Go
slow! Let the foam cut at its own pace or the wire will arc and
not make a square part. Sand the part; add spars or sheet it and
you are set!