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Old Mar 04, 2002, 11:40 AM
Joe B is offline
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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.
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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