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Old Mar 04, 2002, 11:40 AM
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How to mold styrofoam?


I saw something on Mr. Wizard once where he had some small round 'plastic looking thingies' that he put inside a mold then submerged in boilding water. After a minute he had a nice styrofoam character or whatever it was. Can this stuff be used to mold your own parts and if anyone is familiar with it do you know where I can get it (and some more instructions)?

I'd like to carve a plane out of something easy to work with (balsa) then make a clay/fiberglass mold. Wonder if EPP can be molded the same way?
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Old Mar 04, 2002, 06:18 PM
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The plastic looking thingees are unexpanded polydtyrene. SOmeone here should know where to get some. It is normally injected into the mold with steam and then they expand.
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Old Mar 05, 2002, 12:14 AM
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How about using that spray insulation "triple expanding" foam stuff into a mold? I played with a hunk that was sticking out the wall at a construction site and it looks like it might have potential. The surface had a kinda glaze and was very flexible yet held it's shape. Best of all the stuff was extremely light. Have to tape and/or use a spar for a wing, but even if it only worked for fuses, I'd be happy.

Anyone tried it?
Old Mar 05, 2002, 02:14 AM
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A lot of the combat guys use the expanding foam inside their balsa structure wings to make them tens times stronger and less susceptible to damage. I can't see why you could not make a female mold of a part and use this stuff to create molded parts... The only problem I could think of would be getting the weight and density down to a usable point. This stuff expands like you would not believe and inside a mold it could create a part that is too dense and too heavy.
Old Mar 05, 2002, 11:08 PM
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My observations of the 3x foam.


I agree that it could cause a blowout in a mold and that a spar would be necessary. Maybe a carefully designed mold w/ pressure reliefs would work? Maybe make two molds, an LE half and a TE half, that are open where you'd glue the two halves to the spar.

The surface glaze seems to form only when in contact with the air; where it is touching a surface there is no glaze. The size of the bubbles tend to show a range of sizes from small (good) to large (bad) - maybe careful application could control this.

The stuff does seem to work well -it sands and razor-cuts nicely and it appears that it could be hot-wire cut.

And the stuff is billed as an adhesive and seems to be very similar to the polyurethane glues we use on foamies (Pro-Bond) -it will surely stick well to a mold.

Let us know how you make out
Old Mar 07, 2002, 02:47 AM
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Evenly make a block out of the stuff and hot wire some wings out of it...


I have seen a book in which they used unexpanded polystyrene beads to make coffe cups, you can buy the beads from plastics/foam suppliers apparently.
Old Oct 29, 2006, 01:05 AM
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A lot of the Byron Origionals planes used molded foam EPS flying surfaces they included the spar tubes in the molding process if I remember right. Very efficent use of polystyrene when that was considered strange. Saved a whole lot of dust you went right into fiberglassing. Most other planes made that way didn't get glassed and would blow away in the wing after impact (Sprit of 76)


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