The open structure of the wing mold is designed to provide room for clamping the pieces together (above). While the mold may not close completely at first, the tension from the clips will bring it together as the foam softens in the oven. Molded foam is an efficient way to make multiple models. Seen here (at right) are the wings of four S.E.5a models. Fresh from the mold, this upper wing panel just needs to be trimmed to shape.
The wing mold for Cassidy’s Bristol F.2 Fighter (above left) is skinned with laser-etched plywood to create the desired surface detail. Cassidy's 1:19 scale S.E.5a (above right) weighs 53 grams and spans 17 inches, yet is detailed to
minutes for small thin parts, or up to 12 minutes for 1mm Depron on larger parts. Since you can watch the foam forming, keep an eye on it while it’s in the oven. This will help you adjust your time.
Once cooled, trim your parts on the mold. Anything you can’t trim, you can sand using 220-grit sandpaper. To finish your fuselage, you can dry-sand the surface using high qual- ity 400–600 grit wet-dry paper. Join your fuse halves and fill in any gaps using lightweight spackle as filler or a mixture of Polycrylic and microballoons. Paint your fuselage with at
the same level as his larger Bristol F.2. Even the turtle deck stringers were molded in place. Both feature functional aileron cables that give full control to these diminutive models.
least one light coat of Polycrylic before your color coats or before you mask off your trim.
Foam sources
Depron foam sheet is available in 1, 2, 3 and 6mm two-faced sheets from RCFoam
www.rcfoam.com, 404-556-9117. The thin - nest Depron foam at 1mm can be used to mold fuselages on larger models up to 30- inch spans or so where slight compound curves are present. Thicker sheets at 2mm and 3mm are well suited to molding wings and tail surfaces.
What You’ll Need Depron or Cellfoam — several sheets
Your household oven (convection type) set to a temperature of 250°F
An accurate temperature gauge (don’t trust your oven) 1⁄32, 1⁄16, & 1⁄8-inch balsa wood — Look for hard density wood for mold ribs and other tooling, soft density for mold faces or any sheeting. 1⁄32, 1⁄16, & 1⁄8-inch ply and light ply — for mold bases or the faces of larger molds
Soft density balsa block — various sizes to suit your needs
Various sizes of paper clamps — get a lot! FLYING MODELS
Wood glue Thin Pro CA Medium Pro CA+ Thin Foam-Safe CA Medium Foam-Safe CA Formula 560 canopy glue 12cc glue syringe Single-edge razor blade Hobby knife with #11 blades
Minwax Polycrylic water-based clear finish Microballoons filler
Cellfoam produced by Midwest Products Co. has properties similar to Depron and is available in 3, 5, and 10mm sheets at your lo- cal hobby shop or through Tower Hobbies at
www.towerhobbies.com/.
Give it a try
Just like gluing and sanding wood or iron- ing on covering material, working with foam will be a new technique until you try it out. Give it a chance though. Once you do I think you will agree that it is the right way to go for many models.
Tips and Techniques
Ovens with dials should be set by turn- ing the temp dial in one direction (going from cold towards hot) whenever you are fine tuning.
Do not overshoot your temp range! 260°F is the limit for this material.
Don’t open your closed-face mold until the foam is cooled.
During clamp-up, work with the natural curvature of the foam (1mm Depron).
Clamp from the center outward and pull the foam to shape.
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