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View Full Version : West System 410 fairing, do I really need to coat with epoxy?



dndrich
06-11-2017, 11:29 PM
Beginning builder here. I am building a SCAMP. Going well. I am finishing the hull right now. I have it really nicely epoxied and sanded. But, while sanding I noticed some areas I felt I needed to fill and fair a bit more. So, more West Epoxy with 410. Now, the instructions for 410 say that one should coat it with epoxy after sanding it. Is this really necessary? I plan to prime with Pre-Kote, and then Rustoleum Oil based enamel.

David G
06-11-2017, 11:31 PM
Beginning builder here. I am building a SCAMP. Going well. I am finishing the hull right now. I have it really nicely epoxied and sanded. But, while sanding I noticed some areas I felt I needed to fill and fair a bit more. So, more West Epoxy with 410. Now, the instructions for 410 say that one should coat it with epoxy after sanding it. Is this really necessary? I plan to prime with Pre-Kote, and then Rustoleum Oil based enamel.

You're not intending to glass after the fairing is complete, then?

dndrich
06-11-2017, 11:46 PM
No. I glassed the bottom and the first plank. But there are some areas that already have 3 coats of epoxy and after sanding I notice some areas I would like to make a bit better. This will be a working finish, not yacht quality, in part because I am note capable of it! But, nonetheless, some obvious areas I wanted to make a bit better. So, more 410 today. Do I need to seal again with more epoxy? Or can I just prime over it and go on?

Breakaway
06-11-2017, 11:56 PM
410 is microballoons. When you sand it, you open up these, leaving tiny, "pores," too big for paint to bridge or fill. The resin overcaot fills these pinholes.

Kevin

chuckt
06-13-2017, 06:45 PM
oops. I didn't know this. I've simply painted over a lot of 410 on my hull.

dndrich
06-13-2017, 09:36 PM
oops. I didn't know this. I've simply painted over a lot of 410 on my hull.

Yeah, but how did it work out?

Paul G.
06-13-2017, 09:42 PM
Dont freak out the pores are all tiny any paint will seal them perfectly.
Plus it's dry sailed

Todd Bradshaw
06-13-2017, 10:05 PM
No, it often will not. It will bridge them, leaving tiny air pockets. When the surface later heats up from the sun, these little "bubbles" can pop, leaving a surface covered with tiny and quite visible pinholes. This is true with any filler containing microballoons, but it may or may not happen, depending on the strength of the coating. I have even seen two colors of the same brand and type of enamel (Brightside) on the same boat where one color pinholed, and the other, right next to it, did not. If you are looking for a strong coating to bridge the gaps and close them up (nothing is likely to actually fill them) then epoxy is the obvious strength champion. Some other paints and primers may also be strong enough, but it's a crap shoot with no guaranteed results.

Paul G.
06-13-2017, 11:06 PM
Maybe so, but its hardly worth worrying about. A good high build primer will do the job.

dndrich
06-13-2017, 11:11 PM
Maybe so, but its hardly worth worrying about. A good high build primer will do the job.

Would something like Pre-Kote from Interlux do it?

Todd Bradshaw
06-13-2017, 11:49 PM
Maybe so, but its hardly worth worrying about.

After you have had to sand half of a paint job off of a boat and repaint it because it looks like crap, you might change your mind about that. Then again, people have varying ideas about what constitutes an acceptable paint job and finish. Different strokes.......

Eric Hvalsoe
06-14-2017, 08:55 AM
I don't particularly trust Pre-Kote in this application. Listen to Todd and Kevin. If using 'primer' over resin, and epoxy based fillers, I have more faith in the two part products designated for that purpose. Resealing the 410 with resin is prudent.

Redeye
06-14-2017, 11:18 AM
oops. I didn't know this. I've simply painted over a lot of 410 on my hull.

Hmmm, I'd be interested to hear how this has worked out, Chuck. You're not dry sailing and you put a ton of work into that beauty. I'd hate it to go pear shaped...

chuckt
06-14-2017, 08:37 PM
Yeah, but how did it work out?

Well, fine actually. There haven't been any problems in these areas. This was on the topsides only. I used it to help fair out areas that were just a bit low. Typically this was where I sanded off topsides paint to expose bungs so I could remove screws.

A one-part paint covered it. Petit Easypox. Satin. My hull is not fair enough for gloss.

And confession time--I've even used it over the Easypoxy to continue to fair things out. (after roughing up the paint) I think where I did this I added some GFlex to the mix to make things more flexible.

Paul G.
06-15-2017, 02:42 PM
After you have had to sand half of a paint job off of a boat and repaint it because it looks like crap, you might change your mind about that. Then again, people have varying ideas about what constitutes an acceptable paint job and finish. Different strokes.......

Nice dig there Todd :) but I can only speak from experience. I have used a LOT of 410, its my go to fairing compound which I use everywhere, under the waterline, topsides, deck and interior. I have almost never overcoated with neat epoxy and when I asked the local distributors who supply West to the industry (these guys are not lightweights btw) they said and I quote "the directions are to overcoat but nobody does, you might like to under the waterline but since your'e using epoxy primer there is no need"

I have used over dozens of litres of 410 and never had pinhole issues despite using alkyd, polyurethane and 2 pot LPU systems. I also have watched a friends 60 footer being built and been amazed at how much 410 was used to fair it; by the bucket!- never over coated with epoxy and the finish was still "superyacht" five years later.

So while its probably a good thing to do, its by no means necessary especially for a dry sailed dinghy.

Todd Bradshaw
06-15-2017, 03:39 PM
No dig intended, and I'm the guy who had to sand the paint off of half a boat because one color of Brightside pinholed badly and the other did not. To me, that is not acceptable, but I can't speak for you or anyone else. I overcoat 410 and 407 fills because I was told to during a discussion I had with J.R. Watson at Gougeon Brothers, and you can't get much closer to Gougeon Tech advice than him. I'm certainly not surprised that many builders don't want to spend the extra time and labor to do it, especially those who are on the clock. On the other hand, it would be very hard to make a case for not overcoating the fills being a better option. I suspect the epoxy overcoat will also increase the abrasion resistance of those filled areas a bit as well, since 410 in particular is very soft when mixed to a non-sagging consistency. Then there is the issue that spots of sanded fill often don't have quite the same texture that surrounding, non-filled resin will. Depending on how thick your paint system is, these places can show in the final finish. I usually don't bother priming epoxy (also at the suggestion of Gougeon Brothers) so overcoating the fills really helps even out the texture. Feel free to do whatever floats your boat. Personally, I'll keep overcoating my microballoon fills. It's structurally stronger and I have the time.