How to work with Depron foam for model airplanes

Your Source for Depron Foam Information

"Foamies" are model foam planes made from Depron foam, in this case radio control planes. It's proving to be a very popular item with my model airpane customers because of it's superior strength and appearance compared with BlueCore or fan-fold foam. Developed in Europe, its primary use is for thermal insulation under wallpaper and as a flooring underlayment. Depron isnt very common in North America except for use as meat trays, quite useful themselves if you can find some large unused ones to make snow skis, struts, etc.It's actually polystyrene (EPS/XPS) plastic and the (EPS) means expanded while (XPS) means extruded. For our purposes, were only interested in the stronger, denser XPS foam which also happens to be a closed-cell foam. Open or Closed cell refers to its structure and because open cell foam soaks up all fluids (water & glue) its just not suitable for a foamie plane. The superior closed cell foam takes much less glue and is easier to waterproof. It's one sealed surface adds considerable strength as well as making it very easy to apply paint finishes. To summarize, here are its advantages:You don't have to worry about grain direction and splitting like with balsa woodEach sheet is is consistently identical to every other pieceCan easily be curved into airfoil shapesColors come out nice and bright compared to painting over pink, blue or gray foam that needs to be primed firstDoesn't absorb moisture and you don't have to spend time sealing it to prevent warping in summerThe 3, 5 & 6mm thicknesses are primarily used for building large scale models, indoor flyers, 3D foam flyers, gliders, etc. Its great for structural supports and one piece foam plane fuselages because of its strength. The thinner Depron makes excellent skins for covering models instead of using expensive balsa wood. For extra strengthening requirements (wings, fuselage, struts, pushrods, etc), use carbon fiber rods, tubes and strips It's quite easy to work with and no special cutting tools are required. A common #11 Exacto blade or single edged razor blade is all you need. It cuts very nicely with these tools but to ensure straight cuts be sure to use a long metal ruler.Depron foam cannot be heated without losing shape and in fact will shrink in width and length too. It also becomes brittle and thickens with heat because of the numerous tiny gas filled cells in it. So in order to overcome those handicaps while shaping it with heat, heres what we need to do:pre-heat a wooden mould of the desired shape in an oven for 20-30 min at 80-90 deg.C (176-194deg.F)form the piece around the heated wooden core or mould by first carefully cold-crushing it without cracking it.wrap clear packing tape tight around the whole outside. This forces the foam to follow the shape of the mould, and prevents increasing in thickness. place it in an electric oven for 15 minutes at 80-90 deg.C (176-194deg.F) remove from oven and let cool for at least 1 hour. This will fix the shape of the mould into the depron, and retain its strength too.To assemble your models, I recommend you use 5 min. or 30 min. epoxy. Be sure to use it very sparingly because it's a heavy glue. Foam-safe CA glue can also be used but its quite expensive AND you need to spray on an accelerator otherwise it will take overnight to dry. Be aware that many solvents and paints will destroy this foam so be sure to use only water-based latex paints commonly found in craft stores.