What is "Fan-Fold Foam"?
BlueCor, Fan-Fold, Foam-Core, Sturdy Board, Depron, Meat Trays. Are these all the same? What's the deal?
Here's what it is: These are all names for different lightweight sheets of Extruded PolyStyrene foam. Most of them are used for insulation.
Depron is a Brand name, and is only widely available in Europe. (Something about not meeting firecode here in the U.S., not that it matters for airplanes.)
BlueCor is also a brand name. It is manufactured by DOW and Georgia Pacific, and is primarily used as insulation under vinyl or aluminum siding.
Fan-Fold, is a generic term. The Dow product (which is Blue), one made by Owens Corning (Which is Pink), and Amocor (Green), and a few others fall under this category. The foam is sold in 3/16" (or 3/8") thick sheets that are 4 feet tall, and 50 feet long. It is then "fan-folded" back and forth into 25 4'x2' sheets.
A bundle that size usually sells for about $25, and will build 10-20 planes depending on how much foam you waste, and how big your planes are. The foam sandwiched between the poster board, which goes by the names Foam-Core, and Sturdy Board, can be used as a substitute, but you have to peel off the paper, and it gets pricey. Still, it has its uses...
Then why are all these planes blue?
My favorite of all these by far, is the Dow/Georgia Pacific BlueCor. It is about 25% lighter than the others, is among the brands that have a thin plastic skin attached to both sides of the foam. This skin add tremendous strength to the foam, and can be easily peeled away where you want to do heavy duty bending or glueing. The foam is MUCH lighter than Coroplast (a corrugated sheet plastic, commonly used to build gas powered airplanes.) . A carefully built foam model will probably end up with a weight very similar to its balsa counterpart, but is much more likely to be made up of about 5 big pieces instead of 36 ribs, 12 formers, etc.... Plus, foam bounces a heck of a lot better than balsa.
Here's how they stack up:
White Foam-Core with the paper peeled off:
0.6 Oz/SqFt
Georgia Pacific BlueCor with the skin:
0.75 Oz/SqFt
Black Foam-Core with the paper peeled off:
0.8 Oz/SqFt
Amocor Green Foam with the skin:
0.95 Oz/SqFt
Owens Corning Pink, has no skin:
1.0 Oz/SqFt
White SturdyBoard with the Paper on:
2.0 Oz/SqFt

Note: They are different thicknesses, but I weigh them in Square area instead of volume, because cutting it the thin way removes all the convenience of using sheet foam.
I wonder why they call it "Fan-Fold"?
Fan-Fold of a different color. I've found Blue, Pink, and Green. There may be more!
Can't find it? Click on this picture. Print it out and take it to your local Lowe's. They can order it for you.
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