jackhammer

So, everything I've ever read says never put poly on epoxy. Here comes Awlgrip 545 Epoxy Primer and Awlgrip Polyester Urethane topcoat. This combo seems to work just fine.

So can I also use poly glazing compound over the epoxy primer?

FIXX

iTrader: (2)

i think you mean polyurethane ? yes thats what you want to use.. poly glazing compound over the epoxy primer?????? why if your going to paint over it..just prime then paint.make sure you scuff up the area your going tot paint first..

jackhammer

"Type: Two Component Linear Aliphatic Polyester Polyurethane" <- from their website. Keyword being Polyester. I'm no chemist but to me a polyester is a polyester.

If i'm blocking an area and notice some small stuff that I didn't notice before. Again I can only go on what Awlgrip says to do because I'm no painter. They say prime your work, then fair your work (optional), then high build primer (optional), then finally 545 primer before applying topcoat. So I have some work that's fairly straight which I primer according to instructions. Then blocking it I notice some stuff that still needs work... I could apply some of their high build primer and block the area again, or if it was more than I expected actually put down some fairing compound. The problem with the epoxy fairing compound is that it takes forever to dry. So for these areas I would like to use something faster like dolphin glaze (or something compatible). Maybe the thickness of a fingernail or so. I suppose the pros have a detailed enough eye to notice this type of thing before actually applying primer, but I do not. So instead of learning I'm a loser of a painter and my terminology is all wrong, I would rather learn if I can put a poly based glazing compound over epoxy primer. My thoughts are "why couldn't I, if I'm going to put a poly based topcoat on anyway?"

jackhammer

Looks like I got my answer from the Corvette resto guys (who also deal with old bare fiberglass). Some swear by it and say they do it on every job with great success, some swear against it and guarantee it will fail, lol! Typical.

So I guess to answer my own question... what's the hurry, no sense cutting corners and risking a fail. It's only for the portholes and deck hatches I filled and the windscreen I built... the rest of the boat is straight.

ren3

When you are fairing before putting on the epoxy primer just mist the suspect areas with some spray can black lacquer. Then when you sand the low spots will show as the black mist will not be sanded off in the low areas. Fill those and proceed.

jackhammer

Omg! I've been using a guide coat on the rest of the boat, why it never occurred to me to do the same thing on the glass work is beyond me lol! (no one needs to answer that)

On the windscreen I started using different color fairing compound to try to help me keep track of what was going on. It got so convoluted that I couldn't tell up from down. So I shot it with some primer to see it better. It really didn't help me because I was struggling to get it flat. I couldn't tell if I was dealing with a valley or two humps lol! I could get the hatches and port holes flat because they are surrounded by a basically flat surface... but the curved windscreen kicked my ass. I actually asked the body guy that helps me with my car resto work to come help me get it flat. Hence the reason for my original question about glazing compound.

Black Baja

iTrader: (2)

Make sure you don't put anything on top of cured epoxy primer it will not stick scuffed or not only epoxy will stick to cured epoxy. The epoxy I use has a 1 week cure time and does not need to be scuffed to do work on top of it. It is a great product but you have to know how to use it. I learned the hard way and painted half the boat on top of cured epoxy that I scuffed with 400. The paint didnt even think about sticking to it I peeled it off in sheets...

1OLDSALT2B

^^^^^^^^ Not true with US Paint 545 epoxy primer,,,it can be top coated after it has cured...Will need to be sanded again to assure a mechanical bond

jackhammer

Reply from Awlgrip about using Dolphin Glaze -

"Awlgrip does not recommend use of polyester-based filers, except in very thin applications (less than 1/16th“). If they are used, they must be applied to the gel coat before application of the 545. Trying to sandwich them between applications of 545 will inhibit their cure."

The also said that my weathered 545 should be removed. Cured is fine after sanding, but sitting in the elements for a year or so like i did is no bueno Oh well... it will come off fast and it's a hell of a lot cheaper to reapply than the topcoat!

jackhammer

Oh, they did recommend a product from Interlux called Watertight. But to me it's no different than any fast curing epoxy if you have to wait 4 hours to sand.