Fairing & Primer Q

[scot]

Guys,

I am using epoxy fairing compounds, I have used Awlfair and some Fasco. On certain sections of the cap there is some Interlux primer that remains is small sections. The question is; assuming the primer is clean, roughed up (180 grit finish), etc.. can I go directly over the primer with the fairing compound, or does all the primer need to come off?

I know if this were polyester filler I could go directly over the primer. Shouldn't the higher quality epoxy be able to do the same thing?

Thanks

[Navatech]

I am using epoxy fairing compounds, I have used Awlfair and some Fasco. On certain sections of the cap there is some Interlux primer that remains is small sections. The question is; assuming the primer is clean, roughed up (180 grit finish), etc.. can I go directly over the primer with the fairing compound, or does all the primer need to come off?

I know if this were polyester filler I could go directly over the primer. Shouldn't the higher quality epoxy be able to do the same thing?

Whereas polyester on epoxy often results in problems epoxy on polyester is hardly if ever a problem so my guess is that you'll be fine... If you want to absolutely sure consult with the tech support of your top coat brand... That's why the keep those people on staff (and on a salary)...

[CamB25]

Scot,

Per the Awlgrip manual, you should first prime with 545 or hull guard or awlquik to seal the substrate, then apply Awlfair, then seal with 545 and repeat until your arms fall off. But...I don't think it's a big deal to fair over the interlux. You are relying on a mechanical bond, hit it with 80 grit before fairing. Block sand fair to 150 grit, then prime with 545.

Cam

[scot]

Thanks Cam,

That's what I was thinking. You almost have to get some primer on it to actually see the shape and imperfections. I had to completely remove ALL the gelcoat on the cap due to severe crazing and I'm starting from green Bertram glass and sand, sand, sand and sand some more. I typically don't pay the "AWL-Whatever" price, but I do have some of the fairing compound and I like it :-) I had some FASCO products show up in the little brown truck this week, so I am going to see how I like their stuff as well. The Capt spoke well of FASCO epoxies and they match my budget much better.

[CamB25]

Scot,

I know exactly what you mean. When you make it white, all the bumps and dimples show up. I did major amounts of shaping and fairing before priming. It may have been easier to seal the surface first, then try to make it smooth.

If you are down to Bertram green glass on the cap, then you are probably looking at the surface of the moon - lots and lots of craters, air bubble voids,etc. under that gel coat. Based on my experience (at least on my boat) you'll want to seal the surface first with a superduty epoxy primer before fairing. Two reasons - you'll see the imperfects easier and, probably most important, the epoxy will fill most of the craters and bubble voids. The result will be fewer pinholes to fill after finish priming. I did not do the "superduty" epoxy in all places on the boat and now I have 1 billion pinholes to fill. On the sections I did use the epoxy primer, only one or two pinholes - easy.

Here's my rough recipe for your green glass:
1. grind 40 - 80 grit
2. Awlgrip Hullgard Extra (3 coats - brush/roll) - this stuff is like iron. Tough to sand but works and fills.
3. Sand to 80 - 180
4. Awlfair or other epoxy fairing compound
5. Sand, sand, sand - 180
6. 545 primer ( I would shoot one coat in the grey first, then multiple coats in white. Grey will be your telltale layer)
7. block sand, fairing - repeat 545, or sand to 320
8. top coat

Huge work...but you know that already!

[scot]

then you are probably looking at the surface of the moon - lots and lots of craters, air bubble voids,etc

Nope. This isn't my first boat to completely restore and rebuild and I have been extremely impressed with the quality of workmanship from Bertram. Almost no voids, pockets, bubbles etc.. just smooth fresh green glass. A few tiny pin holes is about it. I can't find ANY evidence that they even owned a chopper gun, 100% of this hull and cap appear to be hand laid. "IF" they used a gun at all, it would have been in the first layer, next to the gelcoat, as this is mat on the cap. The hull sides and bottom appear to be woven directly to the gelcoat.

It's impressive glass work throughout. 95% of the 47 year old plywood was in great shape. That's why I don't mind using plywood in the restore.. I won't be around in 47 more years.

[CamB25]

Even around the raised edges? Pretty amazing. Maybe the boat didn't sit out the sun for extended periods. Mine has all sorts of mini craters along that edge from gel coat voids, etc..

Hit it with 3 or 4 coats of 545 and see what you get. If you can skip the Hull gard step you'll save a bunch of work.