Author: J. Beshar
Edition: Model Aviation - 1999/07
Page Numbers: 48, 49
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Foam Carver

By Joe Beshar

Since day one I used balsa, plywood, and basswood selectively when building models; only recently did I become interested in using foam. I learned to work it with a band saw, the hot-wire method, and sanding by hand or power.

All of those methods worked well for straight lines, but curves could only be cut in a straight-line fashion. When it came to carving, I could not find a way to shape foam satisfactorily because the foam pellets dislodged.

To solve that I conceived and designed the Carver. It is a simple, inexpensive device that employs the hot-wire process in a form that allows carving foam and leaving a nice surface finish that can be final-sized with fine sandpaper.

Description

  • Power source: step-down transformer, 115V to 24V.
  • In the 115V line a standard lighting dimmer switch is wired to vary resistance.
  • In the 24V line a three-amp fuse and nichrome wire are wired in the circuit.
  • The nichrome wire is strung in a U over the ends of a crosspiece notched at both ends, and down through slits in the handle, held snugly in place with strips of plywood.
  • Tension is kept on the nichrome wire by an expansion spring. The spring is compressed with the nichrome wire assembled. Two 3/32" collars are tightened to pinch the nichrome wire and the wires to the 24V power supply.

Operation

  1. Plug in the 115V power.
  2. Turn on the dimmer switch and adjust on a piece of scrap foam until the proper cutting temperature is reached.
  3. Carve the desired foam shape. Wingtips, nose blocks, and any compound-curve foam surface can be shaped with this tool.

Note: If increased throat depth is desired, use a larger-diameter handle dowel and increase the length of the crosspiece accordingly.

Materials / Parts

  • CYA (cyanoacrylate) glue
  • Crosspiece: 1/4" dowel, 1-1/2" long
  • Nichrome wire (see fig.)
  • 1/4" dowel, 8" long
  • Handle: 1/2" dowel, 4" long
  • "F" drill to 1/4" from bottom
  • Expansion spring: 7/32" O.D. x 2" long (Servastar Hardware #2)
  • 3/32" collar (2)
  • 24V lead-in wires (2)
  • 3/32" x 3/16" plywood strips, 4" long (2)
  • Wide razor saw or band saw: slit 1/3" deep

Contact

Joe Beshar 198 Merritt Dr. Oradell, NJ 07649

Transcribed from original scans by AI. Minor OCR errors may remain.