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Foam confusuion

Frank Day

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Can anyone clarify what Depron is. I'm planning a few mods to a model it is old school polystyrene essentially -  Robbe Concorde. Last time I did anything it was balsa, ply and tissue.


Is depron the slightly shiny rubbery, bendy stuff rather than little bobbles stuck together. I believe these are the technical terms!

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To add to Dons info

Depron is very flat expanded polystyrene, so no bobbles as you say.

But it is very stiff and not rubbery, so maintains its airfoil, but will crack with sufficient impact.

Remember your last fish and chip tray, very stiff, for lightweight flight construction.

Edited by Denis Watkins
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10 minutes ago, Frank Day said:

Many thanks guys,  the sheets I have are EPP, I was told they are Depron but I had my doubts. I'll try a couple of the outlets suggested.


Converting my Robbe Concorde to EDF, fan mounts from balsa/ply and the main visible structure/panels from Depron

EPP is still useful

Slightly heavier, but for example, indoor models are more likely to survive as EPP is more resilient/ bouncy

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I've been building a model for a few months now, using a combination of 'depron' I bought about 15 years ago and some bought by a club member more recently.  Part way through the build I realised that one of them is slightly rubbery while the other (the older one, I think, though I'm not 100% sure) is harder and crystalline.  The harder one is easier to sand down to shape without tearing.

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In fact the original Depron (it is a trade name) is no longer made. It was actually extruded expanded polystyrene. Not only was the sheet surface smooth and flat but it also had a top and bottom denser 'skin' which gave it properties not unlike softer balsa but at 1/4 the weight. Originally intended as insulation for the construction industry it proved uneconomical to produce despite its popularity in the modelling world. The original Depron was white in big 1200x800mm sheets either 3 or 6 mm thick. Later grey was added but it was not as stiff and finally 2mm thick in white.


The current expanded foam sheet (it is also made by Depron) eliminated the process that created the denser skin so as a result it is a bit lighter but considerably more flexible.

Being polystyrene it is very sensitive to the solvents in glues and paints so requires true 'foam safe' versions.  

Edited by Simon Chaddock
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