Problems painting new Waterproof Foam

[hack-o-holic]

So I was excited to buy a handful of sheets of the new foamboard at FliteFest this year to try out on my next scratch build. All my previous planes have been scratch built with the DTFB and waterproofed using paper tape for the edges and Minwax. From there I typically airbrush with craft acrylics but have also used a rattle can. These planes are all still flying with no delamination or paint failures several years later.

I read about the new foam and how to paint it so I sanded the model first with 220 grit and then painted a base coat of white using Krylon ColorMaster (Paint+primer). I also found that the initial act of sanding paper created so much fuzz and debris that I ended up sanding with 600 grit between coats just to keep a smooth surface.

So lots more detail I can give but the end results were a plane that is chipping and peeling paint before it even was done being painted! I'll attach a pic that shows all the blemishes (if you zoom in). I've not read of too many people complaining so wondering what others are experiencing. I really liked this Krylon for the coverage and super fast dry time but maybe that is my problem? I'm already thinking I'll go back to regular DTFB.

Anyone else care to share their experiences painting the new foam?

 

[localfiend]

Sounds like you sanded it way too heavily if there was a bunch of fuzz and dust.

Always when trying out new paints on an unfamiliar surface, make a few tests before painting the whole thing.

 

[Jugsy]

It works great for me!

I'm gonna second localfiend, I think you're sanding too much. In Peter's video on painting the WR foam, he says to just take the shine off it, and I find that gives the best results. Find somewhere to stand/sit where you can see it reflecting and sand til it doesn't, then stop.

I use Rustoleum (I live in Australia but IIRC I've seen it in a few FT videos) Ultracover paint+primer spraycans, not only looks good but from experience with multiple FT arrows, it probably quadruples the durability of airframes. I put down really light coats, probably about 8 all up, with some extra forward of the CG to balance out the inevitable tail heaviness, and give the nose/leading edge more strength.

 

[CrashRecovery]

Like local said I think you sanded too heavily but also you didn't sand evenly. With paint pulling up that tells me it did not get a good bond. I had that happen to my bronco. When I painted my bushwhacker I made sure I sanded every surface evenly so there was not a single bit of the original shine. By doing that I made sure the paint had the best base to bond to. This time I was able to tape things off and make designs without pulling the paint off.

 

[localfiend]

You also don't want to push hard against the foam or anything. Let the sandpaper do it'so job. You're just trying to evenly scratch the very top surface, not digoing into the paper.

 

[hack-o-holic]

Crash, I just saw your http://forum.flitetest.com/showthread.php?29538-Painting-foam-board thread and your pics look exactly like my bad areas except much larger. I barely sanded if you ask me (just a couple minutes for whole plane).

I used 220 for taking the shine off. What grit are you guys having success with?

 

[johanjonker]

I just use vinyl stickers to decorate my WP foam board.. I cant get a proper coat of paint sticking to it without added tons of weight with layers of paint.

also.. there other options.. like having stickers printed and peel the paper off, and replace it with the stickers. I found some cheap china quality vinyl rolls that's super thin but in this application its a good thing.

 

[PsyBorg]

Faster drying paints as well as the ones that are primer/ paint tend to dry too fast and have a huge tendency to shrink. They work great on prepped metal but other surfaces not so much. Thinner coats as well will help and it dries almost instantly. Try a separate primer and use different brand if need be. Also make sure the paint is not latex based that stuff always peeled no matter what it was used on.

 

[CrashRecovery]

Crash, I just saw your http://forum.flitetest.com/showthread.php?29538-Painting-foam-board thread and your pics look exactly like my bad areas except much larger. I barely sanded if you ask me (just a couple minutes for whole plane).

I used 220 for taking the shine off. What grit are you guys having success with?

I used one of those foam blocks with sandpaper on it. I think its like 80 or 120. I dont press hard i let the block do the work. just takes a little longer.

 

[The-One-Who-Never-Crashes]

I use steel wool to lightly scuff the surface. Works great!

 

[hack-o-holic]

I appreciate hearing from more people regarding their suggestions and what works for them. I really like the idea of the foam sanding block or better yet the steel wool since both will get into cracks and crevices.

Then it just hit me... next time I'm going to sand the entire 20x30 sheets both sides BEFORE I even cut the first piece! Has to be WAY easier than trying to sand a finished plane!

 

[The-One-Who-Never-Crashes]

I appreciate hearing from more people regarding their suggestions and what works for them. I really like the idea of the foam sanding block or better yet the steel wool since both will get into cracks and crevices.

Then it just hit me... next time I'm going to sand the entire 20x30 sheets both sides BEFORE I even cut the first piece! Has to be WAY easier than trying to sand a finished plane!

BRILLIANT idea!

 

[localfiend]

Then it just hit me... next time I'm going to sand the entire 20x30 sheets both sides BEFORE I even cut the first piece! Has to be WAY easier than trying to sand a finished plane!

That's how I do it. Just make sure you paint before exposing it to water if you sand first. Sanding without painting takes away a lot of the water resistance.

 

[Gryf]

Good thread... I recently built a Sea Duck, and have sprayed most of it with a Navy seaplane blue (Krylon).

Now I want to brush-paint the lower surfaces in white, and have tested with different types of paint, both pre-sanded and not... Results pending, but note that water-based acrylic craft paint fails the tape test, regardless of sanding first. I just tried some white enamel, which is still curing.

Have any of you done any testing with brush painting on the waterproof DTFB? If so, what works best for you?

Cheers,

Gryf

 

[Closecall20]

I had issues with acrylic (water based) paints even after sanding. I had the great results with enamel (oil based) paints. they take a little longer to dry but have a beautiful shine. I am also using an airbrush and not rattle cans so that may be a factor to my success. Good Luck.

 

[hack-o-holic]

While I used acrylics, it was ONLY on top of the Krylon Paint/Primer base. The acrylics stick extremely well to the base coat but I noticed another very strange property. Blue painters tape WILL NOT stick to any area that has the rattle can paint/primer base covered in acrylics. The acrylic is typical flat paint with lots of tooth but there was literally nothing I could do to get the blue painters tape to stick. It felt as if I was trying to mask over Teflon. I don't recall this ever being a problem on all the Minwaxed DTFB planes I painted prior.

 

[AkimboGlueGuns]

I've been using 400 grit paper which works pretty well. Make sure you're giving the paint enough time to fully try between coats, and do multiple coats.

 

[fliteadmin]

Hey guys,
Just for reference and ease of use... HERE is the Video that Peter did on painting WR foam! Enjoy!
https://www.youtube.com/watch?v=ucYGbGHE0Mw

S.O.