Primer for plugs

General Composites Discussions Composites Talk
#1

So today I was showing a paint and body man my progress (building plugs) and he asked my why I used duratec PE primer vs regular epoxy high build primer to spray my plugs. I didnt have a good answer other than “the duratec PE primer is what a lot of the guys on composites central recommend”.

Question: Will any expoxy primer work on plugs or is there a good reason I should stick to the duratec PE primer vs Dupont’s Ecolar 13580S, [SIZE=5][SIZE=2]Non-Chromate Epoxy Primer-High Build that I have on hand?[/SIZE][/SIZE]
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#2

I don’t use a primer unless I need to cover/fill blemishes. Otherwise I go straight to PPG Deltron DBC black base coat followed by PPG Deltron DC3000 clearcoat. The clear coat can be polished within 3 hours after spraying. I like the clear-coat and black base coat because I see the spray blemished better sanding/polishing and the coating is less porous than a primer. This combination also works very well with the Frekote FMS sealer and the Frekote 770-nc semi-perm. release.

#3

When I made plugs I only used Duratec and have never heard of the Dupont product. IMO if you have the Duratec on hand like I thought you said in the other thread, use it.

#4

Re wyowindworks comment about painting with black base coat then clear coat: Am I okay applying the Frekote FMS sealer and 770-NC semi perm directly over polished primer (Duratec PE) or do I need to paint/clear first?

#5

Here are some pics of the plugs after two coats of Duratec PE primer mixed with Duratec High Gloss additive at 2:1. The glossy finish revealed a few flaws (minor) that will need to be addressed but they turned out pretty well all considered.

http://www.flickr.com/photos/81745619@N08/7518241576/in/photostream
http://www.flickr.com/photos/81745619@N08/7518241934/in/photostream

#6

I’ve never used Frekote on Duratec so I can’t comment. You could do a simple test though. Next time you have Duratec mixed up just shoot a scrap, prep it just like you will the plug, apply the release, and then apply your gel-coat with a piece of fabric over the top. If you have a good release then you are good to go.

#7

Jbocek, nice landing gear door fairing there. Well, we use duratec, its been good so far. However, you’ll find it does not mix well with epoxy, we’ve gone the whole cycle, cleaning the epoxy/micro’d plug with water and scotch brite, then alcohol, many times over, and still there could be some amine’s left on the micro surface that can cause issues with duratec.

That said, duratec, indeed gives great finish. I don’t think that you’ve wet sanded the orange peel. From the looks of it you’ll need to sand from 320, 400, 600, 800, 1000, 1200 then polish it with acquabuff and you’ll see how pretty it turns out.

all the best.

#8

Thanks Nash! So you just mold straight off the polished Duratec finish?

FYI, the plugs were shaped from 2 part expanding foam, then glassed over with five layers of 9oz cloth/VE resin, then body filled w/auto body filler, then primed with Duratec PE surfacing primer. The molds will be layed up with PE Gelcoat, veil w/VE resin, then bulked w/PE resin CSM (no epoxy)… Re your comments above: Does this make a difference?

The actual gear doors will be infused with epoxy.

PS… You are correct, this images are of the Duratec finish before any wet sanding. I still have a few imperfections that I want to correct, then re-prime if necessary, then wet sand & polish.

#9

We polish the duratec high gloss VE topcoat with upto 64000 product. The finish is like a mirror. Then we do deep cleaning of the surface using marbo-cleaner, followed by sealing of the surface using marbo-sealer, then we polish it with wax, at least 6 coats, with 4 hours to 6 hours between coats and then we pull off the molds from the plug surface. Even the slightest defect in the surface gets magnified as you increase the level of polishing. We use VE tooling gelcoat, sprayed on the waxed and polished surface (no PVA), then we wait for 1-2 hours and do the skin coat using VE resin and 225gm CSM followed by 450gm csm. Let this stay over 24 hours or more and then we infuse the mold with zero shrink tooling resin.

The parts are of course made in aero-grade (EASA certified epoxy), using infusion. Hope this helps.

#10

Thanks for all the great advice/tips guys! I’ll post some pics after I lay up the molds…

#11

I polished the plugs today. There are still a few areas that I want to hit with he polisher again before sealing/waxing but overall I’m pretty happy with the results. Click links to see pics:

http://www.flickr.com/photos/81745619@N08/7570298406/in/photostream
http://www.flickr.com/photos/81745619@N08/7570294750/in/photostream
http://www.flickr.com/photos/81745619@N08/7570296710/in/photostream

Next I plan to seal the plugs with Frekote FMS sealer (3 coats) and then apply 8 coats of a good release wax waiting an hour between coats. I decided to use wax on the plugs vs Frekote’s semi perm release (700-NC) on the plugs after one of the reps at PTM&W said some have had trouble with gel coat fish eyeing when sprayed onto a surfact treated with Frekote 700-NC. I will use the FMS and 700-NC on the molds when making the actual parts.

Do you guys agree with this advice (and my action plan below)?

Again, the plugs were sprayed with Duratec PE primer. I then wet sanded to 2000 grit and polished with 3M polishing compound. Next I will seal with Frekote FMS (3 coats). Then wax (8+ coats - 1hr between coats). Next tooling PE gel coat will be sprayed on the plugs followed by a two layer veil with VE resin, then up to 8 layers of 1.5oz CSM w/PE tooling resin. Finally a wood frame will be laminated to the molds around the edge on the flange.

#12

…I have to ask something. Why go to all the expense/trouble of polishing the plug? I know the mold surface is a direct reflection of the plug but don’t you finesse the mold surface as well after that’s done? Just curious…

#13

Why “finesse” the mold surface if it’s perfect?

Polishing a plug is much easier and faster than polishing a mold surface…especially if the mold is concave.

Adam
Who hasn’t had to polish a mold in 4 years.

#14

We only used semi-permanents for mold production, much more reliable than wax IMO. There are semi-permanent release agents designed for gelcoat applications. Using Frekote 770nc or similiar high slip release products you may have a problem with fish eyeing depending on your technique. In these cases you usually can just do a light mist layer first, let it tack off for a minute then put coats on as usual after.