Dow foam question

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plncraze

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May 11, 2006
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I am interested in getting my foam locally in southern Ohio (and hopefully cheaper) rather than going to the usual aircraft kit suppliers. I was reading Andy Marshall's "Composite Basics"(1994 Edition) and he warned that there were two types of Dow Sytrofoam. One was the type used on the Varieze, Longez, etc. The other was what he called "bead foam" which is made by exposing the styrene beads to steam. This foam is weaker than the other Dow Styrofoam and so should not be used on aircraft. Does anyone here have a way to tell the difference in the two foams? Also when you go to the insulation store do you just ask for the Dow blue 2 pound per cubic foot foam and see what sizes they have?
 

orion

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Mar 2, 2003
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Conventional Styrofoam is easy to spot - it's the same as what you get any time you buy any electronics. If you look close, the white stuff is made up of thousands of small spheres which if you break the piece, will go just about everywhere you don't want them.

The blue stuff is extruded in a continuous process and so it does not have this ball type structure. Generally it's made in big blocks, which are then cut to various sizes as per the distributors' needs. If your hardware store carries board type insulation foam it will most likely be this type of extruded product. I don't think I've ever seen bead foam used for insulation in this manner.

But you also want to watch out for Urethane foam. Generally this is a sort of yellow product, often faced with an aluminum foil. It's easy to spot since if you run your hand over an exposed foam face you'll have a thin coating on your hand of a fine but gritty foam dust. You don't want this type of foam either since it will not hot-wire cut. As a matter of fact, if you do try to hot wire it, it will release a rather noxious and poisonous gas.

Stick with the blue extruded stuff and you'll be OK. In some areas of the country it's apparently also available in pink.
 

DaveK

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Apr 21, 2007
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Northern California
I was about to post about this same issue, because the bead foam seems to be the only kind available at the big hardware stores in California. Or that has been the case in both areas I've live in since moving here from Virginia. In Virginia the blue stuff was at all the hardware stores, I wonder why the difference?

If anyone knows were to find the blue or pink stuff in NorCal let me know. Hate to spend the money on shipping for something I could previously buy down the street.
 

Dust

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Feb 9, 2004
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Troy, Michigan
Perfect timing

I'm a cozy builder and have cut 3 planes worth of wings and 4 of vert stabs.

i was just doing research on the extruded polystyrene and found that the foam specced for the rutan planes is "pipe insulation" by dow chemical. It comes in 108 inch lengths.

I could not find it locally, but i also found "dock flotation billet", it comes in 96 inch lengths, by Dow. It is also extruded polystyrene and it is just a little denser than the pipe insulation. I have a buddy that reviewed the specs for both materials and found that the "dock billet" is just a tad better in all categories. makes sense as it is the same material just a tad denser, like from memory, pipe insulation is 1.8 lbs a cu foot and the dock floatation billet is 2 lbs a cu foot.

you can call dow 800 number and ask for the nearest distributor for the dock floatation billet, but be warned - if you mention airplanes, they will politely hang up on you, so - go build them docks
 
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