Foam Types - RC Groups
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Dec 23, 2005, 08:38 PM
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The Fonz's Avatar

Foam Types


I'm new here and I have probably a silly question but are there any links to an explanation of the different foams used for these planes. It seems very confusing for me as I have never used it before.

Blue cor, depron, epp etc ?????????

Thanks for the help

The Fonz--------Ayyyyyyyyyyyy
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Dec 23, 2005, 11:23 PM
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Theres tons of info on foam here. Just put in the foam type in the search and it will pull it up for you. Butch
Dec 23, 2005, 11:38 PM
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LBMiller5's Avatar
There are 5 or 6 types of foam used in airplane construction. Most of them were originally designed to be used in the building industry as insulation in one form or another.

BlueCor is made by Dow Chemical Company. It is an extruded polystyrene type foam. It is 6mm thick, and has a thin plastic skin on each side, similar to onion skin. The skin really stiffens up the foam, and prevents it from flexing. The down side to BlueCor is the fact that it has waves in the surface that are about 3 inches apart that protrude up about 1/8" from peak to valley. It also has a pinhole diamond shaped pattern to it with small 1/32" holes on a 3/4" size grid pattern. It is designed to be used as an underlayment for aluminum siding, and comed in 4 foot by 50 foot pieces that are accordian folded into 25 sheets that are 2' x 4' each. At around $35.00 per bundle, the cost per square foot is 17.5 cents.

Owens Corning makes a very similar product that is pink in color, it is also about 6mm thick and has just about the same properties as BlueCor, but is a little heavier. The price is similar to BlueCor

Another foam of this type is called GreenGuard PB4. It is designed to be a waterproofing barrier on concrete foundations. It has properties very similar to BlueCor as well, and comes in 1/4" and 3/8" thicknesses. Again, the price is similar to BlueCor.

Depron is a type of white foam that is similar to the meat trays you get at the supermarket. It has no skin, so it is more brittle that BlueCor, but it is perfectly flat, and has a very smooth surface without any pinholes. It is designed to be an underlayment insulation that is used under hardwood floors. The product is mainly used in Europe as an insulation, because it does not meet US fire code ratings for house construction. It is imported into the US for building models. Depron is considered to be the "premier" material to build planes from, and is by far the most expensive. Normally it is found in sheets that are 13" x 39". This is because it is a metric product that comes in 1 meter square sheets, and these are cut into 3 pieces that are 1 meter by 1/3 meter (39" x 13") to make shipping them easier. Prices vary depending on the quantity purchased, and can range from 90 cents per square foot to over $2.00 per square foot depending on the supplier for 6mm thickness. Depron is also available in 2mm and 3mm thicknesses as well.

All of the foams listed thus far are "Extruded" type of foam. They are shot out of an extrusion die at high temperature and rolled into thin sheets.

The next family of foam pruducts are "Expanded" type foams. The 2 main types are EPS and EPP. EPS is Expanded Poly-Styrene. Styrene plastic is a hard, brittle plastic that is used to make many products. CD Cases, Cassette Cases, and plastic model car and plane kits are made from Styrene plastic. Expanded Poly-Styrene foam is made by shooting little pellets of styrene plastic, about the size of salt grains, into a mold under high temperature, usually with steam. Under these conditions, the little pellets Pop up like popcorn and fuse together into a lightweight solid that fills the mold. You can recognize EPS foam by it's beaded texture. The common name of EPS foam is "Styrofoam". This type of foam is used as insulation in houses, and for making things like styrofoam coolers, and corner padding for things like TV's, Stereos and VCR's. EPS foam is very light, but it is not very strong, and is usually covered with a wood veneer or fiberglass to give it a strong surface.

EPP foam is Expanded Poly-Propylene. EPP foam is very similar to EPS, in that it is an Expanded bead type foam, but it is made from Poly-Propylene pellets instead of Poly-Styrene pellets. Poly-Propylene plastic is very strong and somewhat rubbery. Some common products made from poly-propylene plastics are black plastic DVD cases, plastic 55 gallon drums and plastic tool boxes. EPP foam is heavier that EPS foam, but it is very tough, and can be bent to extreme amounts without breaking or tearing. It is rather flexible and flimsy on it's own in thin sheets, so it needs to be reinforced with carbon fiber or fiberglass spars when used in building planes. It is a good material for building foamy planes from, because you can litteraly crash the plane over and over again without really damaging it.

Well there you go, a short tour of the "World of Foam". There are other types of foam used in aircraft construction, but these are the most common.

Hope that helps sort things out a little bit.

Last edited by LBMiller5; Dec 24, 2005 at 10:02 AM.
Dec 24, 2005, 08:42 AM
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The Fonz's Avatar
THANKS LUCIEN, (great name by the way, My oldest's name also)

That was exactly what I was looking for especially the points you added about strenghth and different uses. I am in Canada and I think that some of it may be hard to get especially the depron.

I will be asking some more questions as I want to start building with this material. It seems that I am in the minority by not using it as of yet in any model....Strictly balsa and ply you know

Thanks again

The Fonz
Dec 24, 2005, 04:16 PM
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Lucien! I think your thread should be a sticky in the foam forum. I've read alot and just learned more. Thanks for the info!!! Butch
Dec 24, 2005, 04:50 PM
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scratchandbash's Avatar
There is a book "Building with Foam" which shows a large British sea plane on the cover. I've heard it is good, and would like to get it.
Dec 24, 2005, 05:35 PM
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DregsFan's Avatar
What about foam-core sheet? Ala Bordens, etc. Can be bought at Target, OfficeMax, craft stores, etc.
Dec 24, 2005, 08:37 PM
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LBMiller5's Avatar
I forgot to include that in my list. The central core of that foam board is very similar to Depron. Some people use it as is for durable planes, but it is about 3-4 times heavier that Depron when you leave the paper facings on. The central core is about 5mm thick, and the foam is a little more flexible that Depron. Most people cut out the parts with the paper skins on the parts, then soak them in a bathtub full of hot water to soften the paper skins and remove them. It is a fair amount of work to pull off the paper, since little bits seem to stay stuck to the foam, and these need to be carefully removed so you do not dent or scratch the foam.

For many people that live on the outskirts on modern civilization, the Elmers board is the only thing locally available since most WalMart stores carry it now. And as we all know, there are WalMart stores everywhere!

Dec 24, 2005, 09:31 PM
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scratchandbash's Avatar
What about good old cheap white packing foam. Sculpted all these planes from one HUGE block, and sheeted them.
Dec 24, 2005, 10:17 PM
zagnutz fiend
stirlingnut's Avatar
WOW! scratch,great job!
Dec 25, 2005, 04:45 AM
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most of that foam is EPS. now if you put a dent in it and it comes back out that is EPP.

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