How to get the best finish on a foam model - RC Groups
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Jun 26, 2003, 09:35 AM
Registered User

How to get the best finish on a foam model

I have built a TwinStar (which is currently about 25 foot high stuck in a tree!!!) and now am thinking of building a Cargo. I would really like to get a nice smooth finish on these models. I was thinking of applying some paint (not sure which one??) mixed with some talcum powder (not sure what ratio??) - sand and repeat as often as is necessary to get a smooth finish. Then I want to paint the models gloss white with some gloss red markings (again not sure what paint to use here??). Has anybody got a magical recipe for this? If possible I would like the exact makes of the paints to use and where I can get it - I live in the UK.

Thanks a lot.

Let me now go and retrieve my broken TwinStar!!
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Jun 26, 2003, 09:52 AM
Flying Free
erashby's Avatar
For non-EPP foams, I have used lightweight spackling. It works great! It is a bit brittle, so I mix it 1:1 with foam beads. It fills in all the gaps and allows yu to sand to a smooth surface. Then a spray a couple of light coats of minwax polycrylic and fine sand again. Then you can put any paint on it without melting the foam. I usually use Krylon. I have used this on SkyScooter, Mini Sped wing, and Twinjet. I haven't tried it on EPP because I usually tape them for added strength. Also, EPP flexes so much that I think that it would just "pop" the filler out of the little defects.

What airframe are you doing this on?
Jun 26, 2003, 10:00 AM
Registered User
I am wanting to do it on my doomed TwinStar and a Multiplex Cargo. Do you know of a website where I can buy the products you refer to?
Jun 26, 2003, 04:15 PM
Registered User
any local home improvement store carries these products, just find where the wood stains are located, and the water based poly is located right there with them,

Then walk over to the wall spackle section, and look for the one that say light weight spackle, it's really cheap and pretty much the same as you buy at the hobby shop.

hope this helps

ryan d.
Jun 26, 2003, 04:22 PM
Registered User

You can get smaller quantities of this stuff, this price is for a gallon

ryan d.
Jun 26, 2003, 07:36 PM
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Ray Lowinski's Avatar
erashby, is the Krylon you're using the new "plastic friendly" type or the original?
Jun 26, 2003, 08:08 PM
Flying Free
erashby's Avatar
Originally posted by Ray Lowinski
erashby, is the Krylon you're using the new "plastic friendly" type or the original?
I don't know of any foam friendly Krylon. Once I have an even coat of Minwax polycrylic the paint doesn;t attack the foam. I think that this would be the same for all foams, but I would do a test on a foam scrap first. I did have a model that when sanding down the polycrylic I sanded through it in some places and then the paint did attack the foam.
Jun 26, 2003, 10:50 PM
Registered User

Foam safe Krylon

I don't know of any foam friendly Krylon.
This works ...

Krylon Short Cuts

I just tried it on some scrap fan-fold foam yesterday with no problems.
Jun 27, 2003, 08:56 AM
Registered User
tekochip's Avatar
I found paint to be hit or miss, so to speak. One paint was good on one type of foam, and ate the heck out of another. Sometimes polycrylic helped, sometimes it still ate the plane.

For me, the best all around solution was to cover the model in low temp (I used Oracover) covering, or even clear covering that was painted.
Jul 14, 2003, 07:25 AM
Registered User
joeygoose's Avatar
I've safely used Minwax Polycrylic on both EPP and pink foam, it seems to protect the foam from just about every paint I've tried. On my last project, an JKA E-Plane, I even used Rustoleum (automotive primer) over a coat of poly to paint the canopy (with no issues).

I've also had some pretty good luck using the Polycrylic to laminate 10 gram carbon fiber veil directly to foam - after a few layers you have and extremely strong and light outer skin that may be lightly sanded to a reasonably smooth finish.

Just my two cents.
Jul 14, 2003, 07:52 AM
Aging Busdriver
Captain Ed's Avatar
I use Oracover also. A side benefit of covering is added stiffness and strength. The next time you whack a tree it might keep it from breaking into multiple pieces. Ed
Jul 14, 2003, 12:06 PM
Registered User
whichwazup?'s Avatar
My $.02- I have used Krylon "Fusion" spray on EPP with fine results without any surface pre-treatment. The Krylon Tech guy didn't recommend it for EPP but it seemed like he wasn't too sure what EPP even was.
Jul 14, 2003, 03:11 PM
What goes up, will CRASH!

Finishing Foam

I don't know yet if this going to work, but I am going to try it and that is thinning light weight spackle with water and painting it on, that I know works. Then some light sanding. Then I am going to try mixing some poster paint pigments into both the spackle and into polycrylic and see what happens. I also have different dyes both liquid and powders that I use for finishing speakers. I am going to try mixing these with polycrylc. I have enough chunks of different types of foam that I should find out what it will work with and what it won't. If polycrylic will hold the pigments in solution it should work.