N2EC

Guys, I wanted to paint a fuselage in the mold...i have tried the epoxy paint and it works well...i was wondering whether I could use high quality enamel automative paint...will the paint get transferred well to the composite and are there any other issues which I should be aware of.

Thanks.

Mike James

Since I'm an amateur on this subject, let me be the first to kick things off...

I've painted a fair number of parts in molds, but only one color, or two-color "fake airbrush" looks with soft seams...no fancy schemes. Most of the time, I was limited by budget or time issues, and simply used what was on hand. Here's what I've found.

The chemical composition of the paint only seems to matter if it will actually be the outside layer, meaning that you would be spraying right against the PVA. If you're using a clear coat of any kind, (presumably fuel proof) then you have a lot more flexibility with the paint, because the clear coat protects it, and epoxy on the inside will stick to almost any paint.

I recently did a test, intentionally using bad technique, to see just how far we could push sloppiness with the paint. (in case production people got in a hurry) That test involved two intentional mistakes. The first one was starting to spray the paint (automotive engine enamel) before the PVA had dried. This produce very bad results, where the paint and PVA blended together, and in one small case, stuck to the mold. The second intentional mistake was starting to apply the epoxy after the paint had only sat for about 30 minutes... not even close to cured. This mistake worked fine, and I didn't see any visible problems.

We've started a "painting in the mold" thread several times here on RCU, and we have yet to see really intricate, spectacular schemes in the mold. (like say, Composite-ARF) When a good method is finally disclosed and proved here with photos, I will be thrilled. Obviously, doing this really well is not easy, or we'd see more examples of it.

N2EC

Mike, one school of thought suggests that when painting in the mold, PVA should not be applied and the wax should be the only release agent as the PVA tends to dull the finish on the part. What has been your exprience..also do you spray the PVA or apply it with a cloth...

daven

My Feedback: (1)

When the mold is new, PVA is the way to go, but you will not be able to mask or stripe hard lines over PVA. The pylon guys have been painting some pretty intricate wings and tails in the mold. Check this web page and see a whole lot of airplanes that were all painted in the mold (wax only) with sing stage Eurathane paints without a clear coat (a few of mine are in there). I believe he uses a paint called "Utech"??


http://www.flyfastcomposites.com/photo.htm

If you contact the owner of Fly Fast Composites, he will tell you everything you need to know about painting in the mold. I have been experimenting with this myself, and have done 4 wings now, all with very simple paint schemes. I hope to do some striping and stenciling on my next wing. With Epoxy paints you can paint the mold and let it sit for a while (I've waited over a week) before laying up the mold. With some of the Auto paints, I'm not sure you can get away with this, and need to lay up withing 24 hours of painting.

Here is a picture of one of my favorite wings painted in the mold.

Mike James

N2EC,

I've sprayed the PVA, and I've also simply applied it with a (PVA-soaked) piece or ordinary paper towel. When you first put PVA in the mold, you can quickly wipe it around into all the corners pretty agressively, since it's very wet. From then on, I move it around very gently, just barely touching the PVA. With good light, that method has been fine.

In my case (and as I said, with one or two-color schemes only) I've sprayed against the PVA. I may investigate the method Daven mentions though, since I do admire these great in-the-mold paint jobs.

Thanks for the link.

TT2

My Feedback: (13)

Just curious...how come you guys using PVA don't use one of the 'wipe-on and forget' mold releases like Safelease? I found PVA to be tricky to work with but I'm sure my flawed spray setup / technique contributed to this. I haven't opened a bottle of PVA since trying the Safelease.

These newer mold releases may aid in painting in the mold since they may allow 'worry-free' masking. I haven't tried it but it should work with the Safelease provided you're not using an 'aggressive' masking tape.

-Tom

daven

My Feedback: (1)

I hated PVA the first few times I tried it, untill I finally figured it out. I watered it down roughly 1:1 with water and put in my HVLP spray gun. The only way I could get it down smooth was too put down an EXTREMELY light mist coat. It looks rough initially, but after about 10 minutes it wets out smooth. Then I repeat with another EXTREMELY light mist coat which looks rough again (initially) but will smooth out. I put down 4 coats like this, and let dry for about an hour before painting. I was able to get a quite smooth part out by doing it this way, and it released a bit better than wax only.

Heres a picture of my PVA only wing.

ptxman

My Feedback: (2)

Most of the wipe-on wipe-off release agent work well as an alternative to PVA but they have a few pros & cons to consider too.

- they are quick to apply, but are not really 'forget'. You still have to maintain the coating to some degree in between layups. Some products like Zyvax further requires base sealers & they also have special removal potions. Some recommend re-conditioning the mold every so often. The good news is water based chemistries are improving all the time.

- they are not quite as forgiving as wax based systems. The wax fills & buffs out microscratches & imperfections. You may find over time that composite molds will degrade a bit with successive pulls especially around the sharp corners of the mold flange for example. May of these wipe-on type suystems are intended for industrial type molds; cnc'd metal & high polish state.

- they do not accept pre-painting in the mold without a lot of ugly beading, at least any of the systems Ive used. If you are having good results in this regard, please tell us. Furthermore, soeme of teh water based systems do not like petroleum based paints. Experiment first.

- the best compromise system IMO is Dolphin wax, no PVA. From start to finish it takes the same time as wipe-on chemistries, but it has a proven track record of readily accepting paint finishes. Because it is a wax it really helps with mold protection & releases every bit as good as the wipe-ons Ive used.

ptxman

My Feedback: (2)

Heres are some visual results I was referring to. I tried a new wipe-on release system ACP was offerring a while back. It release parts lickety split, no problem there. But this is the typical result I hav eexperinced with trying to pre-paint on it. The other shows H&M Dolphin wax. You can see it stays put. The test coupons are mylar, the paint is high end catalysed auto urethane.

Mike James

Thanks, Peter!

Nothing like a little emperical evidence. I've been using Partall for years, but may try Dolphin Wax next.

TT2

My Feedback: (13)

I finally had a chance to experiment with the Safelease / masking / painting (been OOT on business). I used 0.010" clear mylar for the test coupons. I first waxed them with Meguiar's Deep Crystal carnauba paste wax and buffed. The first is wax only, the second is wax / Safelease 20L (wax-based release liquid), the third is wax / Safelease 30 (PTFE-based release liquid). Neither formula contains any silicones or silanes that can 'play' with the paint's surface tension.

After allowing the Safelease to dry for about 30 minutes (overkill) I shot a tack coat from a pre-heated can of good (debatable) old (5+ years) Krylon gloss Blue on the three samples. Nothing odd occurred. The second coat was quite a bit heavier, the third coat was heavier still. The paint flowed nicely on coupons 1 and 2 and fisheyed a very tiny bit on coupon 3...probably due to too heavy of a coat or maybe a fingerprint. There was only a tiny difference between 1 and 2 and a slightly greater difference between 2 and 3. All results were comparable to Peter's Dolphin Wax test coupon (the 'good' one). I believe that the wipe-on release that Peter had used may have contained silicone...that would explain the horrible beading.

Next (currently drying) I decided to mask a test coupon. This coupon was carnauba wax and Safelease 20L. I used 3M fine-line tape AND the cheapest tape I had in my shop (some $0.25 / roll Walmart junk...of which I use copious amounts...but NEVER for painting) and masked a line and a small pattern. My work was quick and sloppy and I'm sure the results will reflect this! After painting the dark color (blue) the masking was removed. The cheap tape left behind a slight amount of adhesive on the Safelease...which was easily removed by sticking more tape to it an pulling. The Safelease, as predicted, was totally undisturbed. I then shot a mist coat of 'cold' Krylon gloss White followed quickly by a very heavy coat. I was trying to get it to fisheye but it didn't.

I'm going to let the paint cure overnight then hit it with some glass / epoxy / balsa tomorrow. I'll edit this post as I go...pictures will be posted soon.

I will get some Dolphin wax. What's the consistency like? I sure hope that it's not as 'sticky' as Partall wax during application. I seem to have problems with laying down WAY too much Partall wax...so I stopped using it years ago and went back to carnauba.

BTW, what kind of spray guns do you guys use? I just picked up two mini HVLP gravity-feed guns (Astro Pneumatic's version of the renowned SATA minijet) for cheap. One with a 0.8mm tip (for clearcoats) and one with a 1mm tip...I might get the 1.2mm tip version for primer/surfacers. I've never used HVLP equipment since I simply don't paint that much. Any tips from the pros?

-Tom

ptxman

My Feedback: (2)

Good info, keep up the testing. The coupon I did that showed severe beading was an ACP water based wipe-on product. Actually it was a product sample George offerred, they didnt have it for sale yet at that time although they may have now. I dont know for sure what chemistry it was but Im pretty sure it contained no silicones. I have tried other similar wipe-on products with very similar results, I just didnt post the pics. They drop off parts like crazy but the painting aspect is pretty similar. So apparently the absence of silicones still doesnt mean you get pre-paint results, there is obviously some other chemistry in there causing "silicone-like" painting issues. The mist on paint ritual is usually what has to be done, but it its more time consuming, usually requires more paint (=weight) & can have masking problems even if the paint gets down.

Its kind of asking opposite characteristics of the release agent when you think about it: dont let epoxy stick, but let this epoxy-like paint stick with perfect opaque coverage. But Safelease & a specific Frekote product keep coming up as having potential. I just find with the wipe-ons in general are thin & you have to be extra careful, especially on sharp corners like mold flanges, otherwise degradation can occur.

FYI the consistency of Dolphin wax is pretty soft relative to others Ive used. It tacks up more quickly & you have to be on the ball to buff it otherwise its tough sledding. But it does build up a lustrous coat & enhances/protects a mold as good as any. I have not tried pva over it, it could be hit 'n miss in that regard as it was not intended to work with it like other systems.