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Different kinds of foam???

Old 12-06-2009, 08:53 PM
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Henry111
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Default Different kinds of foam???

Apparently there are a number of different kinds of foam used in modeling with different qualities. Some will take a certain kind of glue, but not others. Some will tolerate certain kinds of paints, but not others. Some sand well, some don't. Information on the various kinds of foams would be most appreciated.
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Old 12-07-2009, 06:21 PM
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cyclops2
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Default Me ?

I only use the Dow sheets of white & pink foam in 1" thick or thicker.
Dow Blue foam in the 12" thick X 24" wide X 72" or 96" long.

2 equal part Epoxy, sometimes thinned 30% with Acetone, Silicone Rubber or rarely White glues & fine foam mixed in for a filler of dents.

All sand VERY WELL. Blue has the finest grain. White the coursest.
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Old 12-07-2009, 07:58 PM
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crxmanpat
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Here's some more info for you:

EPS (expanded polystyrene) - This is also referred to as "beer cooler foam". Most traditional foam models are made from this. It's basically just styrofoam beads that are injected into a mold.

EPP (expanded polypropylene) - This is similar to EPS, but the beads of foam are generally bigger, and the foam is spongier and more flexible. This is the stuff that the HobbyZone Super Cub is made of.

EPO (expanded polyolefin) - Pretty much the same as EPP. All of the Multiplex models are made of what they call Elapor. Also pretty much the same as EPO and EPP.

Depron - This is a much different type of foam that is produced in sheets of either 6mm or 3mm. There may also be other sizes, but these two seem to be the most used in our hobby. This is also similar to the foam board that you can buy in most craft stores that has a paper lining.

Dow Protection Board (also known as fan fold foam or "FFF", and Blucore or blue foam) - Typically found in most hardware stores. It may or may not have a protective film on one or both sides of the foam, but it normally comes in a bundle folded like an accordion (or fan, hence "fan fold foam"). This is what Cyclops talked about above.


For all foams, contact cements like GWS glue, Ultimate RC Foam Glue from Yardbird RC and UHU Creativ for styrofoam (also called UHU Por in Eurpoe) work well when the glue is used per the instructions.

You can also use 3M Super77 spray adhesive on foam without any ill effects. This stuff is good for gluing multiple pieces of foam together that will be sanded into a certain shape (like a nose cone or canopy) as the glue does not gum up when it is sanded.

Other glues work well too. Gorilla Glue (or any equivalent like Elmer's Ultimate Glue) work well as this stuff is activated by water and expand to fill gaps. You can also use any foam-safe CA. And on the EPP/EPO/Elapor foams, regular CA works well, and is actually preferred over foam-safe CA.

And hot glue works too. Low temp works best so it won't melt the foam when you're applying it. And epoxy is good to. You can even add baby powder or microballoons to it to use as a gap filler.

All foams sand well, but the EPP/EPO is the worst of the group. Sand foam just like you do for wood. Start with a coarse paper to get your basic shape, then progress to lighter grits for finishing.

A lot of people seem to have trouble finding the right paint for foam. I have used regular old Testors spray cans without issue on all of the foams listed above. The trick is to stay at least 12" away from the surface being painted, and to spray in light coats. I believe that it is actually the propellant in the spray paint that actually eats foam, not the paint itself. By staying 12" away, you allow the propellant to evaporate before it gets on the foam.

Water-based acrylic paints also work well on foam. You can get these at most craft stores. I like these as they are available in just about any shade you want, so doing military schemes is easy.

Another useful item is water-based polyurethane, or "WBPU" (and water-based polycrylic, "WBPC"). This stuff is good for adding a protectic finish to foam models. It can also be used to do light fiberglassing with .5oz to .75oz cloth.

I hope all this info helps.
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Old 12-07-2009, 11:13 PM
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Henry111
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Thanks Crxmanpat.
Well done and very informative.
That's just the kind of information I was looking for.
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Old 12-15-2009, 05:11 AM
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Radbuster
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info How about Bazic foam board...

I stumbled across sheets of 20"x30" foam board made by "Bazic". They are the same thickness (~5mm) but much lighter than Elmer's foam boards--the paper coating is much thinner. I've had good luck with Elmers boards, but I bought some of this new stuff. I will waterproof the paper coating with craft spray, and use it in building a flat wing jet (F-22).

www. bazicproducts.com
Found at a Frye's store in California

==Radbuster

(Elmers board wings; depron fuse)
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Old 12-15-2009, 02:52 PM
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cyclops2
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Default Fan fold ??

I never have or ever will use Fan Fold.

I only use unbendable big blocks of blue foam. It is used to keep docks afloat.
1 time I used a rigid sheet of pink foam for a 6 engine Avro Vulcan bomber.

Rich
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Old 12-15-2009, 03:00 PM
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soar-ne
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Default Foamies

Here are a few of my foamy park fliers:
I use Dollar Tree and Hobby Lobby (the craft store) foam core. I mostly blow up 3 views to the size I want and tile them with a poster program and trace the parts onto the foam board. Then cut out the pieces and soak them in water for 20-30 minutes and the paper will come right off. Then assemble as a normal balsa kit. Paint them with water base craft paint and the put a couple of coats of Future or Mop and Glow vinyl floor finish on the paint to make it shine a little bit more. Good cheap airframes for soccer field flying!!!

Happy Flying
Bob
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Old 12-16-2009, 04:00 AM
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Radbuster
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Question

Bob;

Nice work. How do you put the airfoil curve in the wings? Mine are all flat.

---Radbuster
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Old 12-16-2009, 02:38 PM
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soar-ne
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Radbuster:
I'm sure that you will have to remove the paper, at least on the top side--Maybe both.
I sneak up to the kitchen when the wife is out and role it over the rounded counter top edge or roll it over a 2 inch diameter plastic pipe scrap. As you have probably noticed most of these depron types of foam have a grain like wood and they bend easier one way than the other also!!! Bend your airfoil useing the less tension way....
On some planes I will face the leading edge with balsa sticks of the right size and then round them a little with sand paper, helps to eliminate some hangar rash from weeds and my clumsiness in hauling them around, but most I just fly till they look rough and then move the controls to a new bird. To me they are all disposable after awhile...

Bob
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Old 01-08-2010, 01:45 PM
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McBlade
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I think there may be a new foam out there - a mixture of EPP and EPS - being used on planes. I'm interested in buying an ARF off Ebay made from it, but I haven't been able to find any info on it, except that it *may* be called 'styromix'?
Does anyone know anything about this foam mix? Here's the ebay url for the ARF - http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT
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Old 01-08-2010, 02:03 PM
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Another good filler for dents, closing foam cell structure and gaps is modified Red Devil Ultra-light Spackle. Easy to make, apply and sands VERY well.

First mix in just enough water to make it 'fall' then reconstitue with microballoons to desired texture. Slightly creamy for filling cell structure and thicker for gap/dent filling. Applied with an old credit card (or the fake ones that come in the mail - you do keep those don't you) it is a joy to work with.
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Old 01-08-2010, 02:45 PM
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Originally Posted by crxmanpat View Post
A lot of people seem to have trouble finding the right paint for foam. I have used regular old Testors spray cans without issue on all of the foams listed above. The trick is to stay at least 12" away from the surface being painted, and to spray in light coats. I believe that it is actually the propellant in the spray paint that actually eats foam, not the paint itself. By staying 12" away, you allow the propellant to evaporate before it gets on the foam.
.

Wish I would have found this thread earlier. I had some left over Pactra Lexan paint (nitro proof) that I used, I tested and tested on scraps to be sure it wouldnt melt the foam. I was almost done with the duster coats of paint, the last little touchup I sprayed ate the foam just a bit. This was on depron. The can was getting low so I think it picked up some residual solvent in the bottom. Dont forget to shake the can often as you paint and stay 12" back. Pactra has some nice bright colors, but you have to be ultra carefull when applying. Use plenty of between coat drying time. It worked great on a EPP model I have, didnt eat at the foam at all.
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Old 01-09-2010, 05:09 AM
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Larry,Moe,and Curly
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What's this XPS...Extruded Polystyrene.

The Great Planes Electrifly Yak-54 is made of it. How's does XPS stack up to EPP?

LMC
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Old 01-09-2010, 01:17 PM
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McBlade
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Hi LMC,

I'm a little bit familiar with these polymers, so I'd like to try to offer up a couple of properties for XPS and EPP that may be of interest:
XPS foam -
1-is the same basic plastic that plastic model kits (like Revell) and styrofoam are made from.
2-tends to be less flexible and compressible than EPP (doesn't bend readily).
3-tends to be lighter and more workable than EPP (you can sand it, paint it, and glue it more easily than EPP)
4-is soluable in certain paint propellants, glues, and solvents so you need to be careful about what chemicals are present.
5-is generally easier and cheaper to manufacture than EPP.
6-has a longer history in the RC world than EPP.
EPP foam -
1-is the same basic plastic that plastic sandwich bags, 'ethafoam', and bubble wrap are made from.
2-tends to be more flexible and compressible than XPS (bendable, squishable, and Tough).
3-tends to be heavier and less workable than XPS (imagine what happens if you try to sand & paint a sandwich bag. There are ways to shape and paint EPP, but they tend to require special tools, chemicals, and glues).
4-is generally insoluable in most paint propellants, glues, and solvents. This means that almost all paints and glues won't stick to EPP (you'll need to hunt around a bit to find the right paints and glues for EPP).
5-is somewhat more difficult to manufacture than XPS, and a little more expensive.
6-hasn't been used in the RC world very much - EPP gained a lot of notice and popularity when it was used on the Air Hogs line of toy RC airplanes.

Hope this helps -
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Old 01-09-2010, 01:22 PM
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I should have mentioned:

IMHO, the Toughness of EPP makes it Much More preferable for newbies (can take multiple HARD landings). On the other hand, the utility, workability, and low density of XPS makes it preferable for people who are more experienced at RC and rarely crash.
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Old 01-09-2010, 07:03 PM
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Larry,Moe,and Curly
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Thanks McBlade.

Some of the EPP I've ordered was too flimsy for use building planes with. Not stiff at all.

I've got very good EPP in two EPP kits-The Lightflite Bug and Mike Bailey's Midwestfoamplanes.

LMC
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Old 01-09-2010, 07:09 PM
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Good Point - you're right; sheet EPP is remarkably flexible.
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