Depron Blues
Editor's note
In his February "Flying for Fun" column, D.B. Mathews wrote about the increasingly popular SPAD (Simple Plastic Airplane Designs)-type models and the use of Depron and fan-fold foam in fabricating them. D.B. innocently received erroneous information about the Depron material's properties and usage from his sources, and we have received two letters, which follow, from authorities on this material that set the record straight. The first letter is from Scott McKie, who was a former partner in DepronUSA, a company that imports Depron foam products. The second letter is from Tim Hart (incorrectly identified in the column as Tim Holt), who designs the models for the Foamy Factory and hosts its web site (http://www.foamyfactory.com/airplanes.htm).
Letter from Scott McKie
I am writing to you about the February column "Flying for Fun" by D.B. Mathews. What I am writing about is the totally incorrect comparison Mr. Mathews makes between the product Depron and fan-fold foam. Depron is not a blue polyurethane foam core material that is covered with a thin layer of semitransparent plastic. This statement is totally incorrect and has no basis in fact.
Depron, as used in the modeling field here in the U.S., is a closed-cell polystyrene foam product that gets its surfacing qualities only after it is drawn through a compression/heat process at the factory. It isn't "sheeted" with anything.
I know of which I speak because I, after collecting all of the relevant information about Depron, formed a company named DepronUSA with Mr. Carl Crabb, my then next-door neighbor, to import Depron in quantity to be retailed over the internet predominantly for the RC modeling hobby field. We were the first in the U.S., and I understand that Mr. Crabb still successfully operates DepronUSA, as I have gone on to form another company that will be kitting a number of RC kit airplanes—specifically including Tim Hart's (Foamy Factory) Ultimate biplane as shown in the column. We are also negotiating to kit the 3DX for Tim, along with his future designs.
I am writing to ask that a correction as to the properties of Depron be made in your magazine so that your readers are not given incorrect information. Other than the fact that they both are "foam," there are no comparisons that can honestly be made between the two foams mentioned together. Depron is only available in either processed sheets of varying millimeter thickness or, elsewhere in the world, in the form of unprocessed rolls, whereas "blue foam" has to be hot-wire cut from larger thickness blocks to get pieces as thin as Depron.
Also, there is absolutely no comparison in structural sheet strength between a sheet of standard processed Depron and a piece of comparable thickness "blue foam." Try it and you will see what I mean.
Scott McKie Chairman, Gamma Star International (GSI) [email protected]
Letter from Tim Hart
I'll try to clear up some of the "foam issues" that have been brought up. We (Scott and I) are in the negotiating process of his kitting some of my designs. In Scott's letter, he mentions that blue foam needs to be hot wired to get the correct thicknesses. This is true; however, BlueCor, or fan-fold foam, comes in 3/16-inch-thick sheets and has the clear plastic coating on both sides and does not need to be hot wired. Depron and BlueCor are, in fact, two different types of foam.
With that said, here we go on the foam explanation. Blue foam is an expanded-bead polystyrene foam (similar to white "wing core" foam), typically used in hot-wire-cut foam-core wings, which are then sheeted with balsa and fiberglassed. Depron is a brand name, and is only widely available in Europe (something about not meeting fire code here in the U.S., not that it matters for airplanes). All of the Depron that is used in modeling here in the U.S. is imported from Europe. We have no source here in the U.S. that manufactures Depron. Depron is superior to fan-fold in many ways: it is more rigid, stronger, and lighter. Depron comes in 2 mm, 4 mm, and 6 mm thicknesses for modeling use.
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. This is the stuff that is referred to as fan-fold, BlueCor, FRF, etc., and has the clear plastic coating on both sides of the sheet.
Fan-fold is a generic term. The Dow product (which is blue), one made by Owens Corning (which is pink), Amcor (green), and a few others fall under this category. The foam is sold in 3/16-inch (or 3/8-inch) thick sheets that are 4 feet tall and 50 feet long. It is often "fan-folded" back and forth into 25 4-foot x 2-foot sheets.
A bundle that size usually sells for about $25 and will build 10–20 airplanes, depending on how much foam you waste and how big your airplanes are. The foam sandwiched between the poster board, which goes by the names Cor-Cell 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.
Both types of foam work well and have their advantages and disadvantages. Depron is superior, in my opinion. However, because it is imported, it is much more expensive.
Hope this clears some things up for you. By the way, I thought the article was great as is (other than that my name was misspelled!).
Tim Hart
Transcribed from original scans by AI. Minor OCR errors may remain.
