Daddy, the centerboard is blushing!

[Thorne]

I'm used to Smith's fine line of epoxy products, and have never had any issues with their 1:1 slow-cure epoxy -- but I have a solid wood boat and only use it as a glue, not a coating.

To build my new marine ply centerboard in time for this weekend's boating event up the coast, last week I picked up some marine epoxy with a fast-cure hardner at Tap Plastics, and it worked OK for wetting out the glass fabric. I was letting it cure until it got hard enough to trim -- maybe 8 hours in our warm climate.

But once I got a few coats of epoxy over the glass, it began to 'puddle up' like rainwater on the surface, rather than spreading smoothly. I've been sanding it to shape, then rinsing with cold water while scrubbing with a sponge-backed scrubbie.

So if several rinses with a hose and some scrubbing won't remove the blush, what will? I know that blush isn't supposed to be cleaned with solvents, but I tried MEK with no luck anyway.

Do I need to leave it longer between coats, for more of a full cure? Or do I need to scrub/wetsand it more heavily and rinse it a lot more? I read that blush is caused by the hardener, and the faster the cure, the more blush *some* hardners create.

The epoxy site that Todd listed has lots of good info and links, but other than purchasing a no-blush epoxy next time, what are my options with the Tap marine epoxy?

http://www.epoxyproducts.com/blush4u.html

[JimD]

I don't quite follow. Are you sanding and rinsing before a full cure? Shouldn't be doing that. And cold water on uncured epoxy sounds like a bad idea. A good way to promote the creation of blush though. What I do whenever possible is pick a warm, sunny day and apply a very thin coat of epoxy every four hours or so until by evening I have three or four thin coats, none of it fully cured. The thin layers prevent pooling and waiting until the epoxy is just barely touch dry before applying the next coat prevents any blush from forming. By nightfall the job is done and the result is a near perfectly even buildup of epoxy that requires only a quick and painless few minutes with the random orbital sander a couple days later after a full cure and a wash. When letting the last layer cure overnight it is very important to keep the surface protected from any condensation that might form dew if the temp drops over night. The worst case of blush you can get is leaving epoxy to fully cure overnight exposed to damp cool air. The blush turns white and is almost impossible to get off. My appologies for rambling if i have misunderstood and you already know all this, buddy.

[Thorne]

Nah, I'm a relative neophyte regarding epoxy issues, particularly blush which I've not had to deal with before.

Yes, I'm sanding and rinsing before a full cure, because the additional coats are puddling on the surface instead of spreading smoothly -- and I can feel the waxy blush on my hands when I touch the surface.

At this point I'm unsure whether I should be recoating with epoxy as soon as possible, or waiting for a full cure. But since no matter what I do the epoxy puddles on the surface, I guess that I need to wait for a full cure, sand and wash, and see if I can get subsequent coats of epoxy to spread evenly.

This isn't desperate, as I've got enough coats on to seal the CB very well -- and don't really need to paint it because it will be fully protected from UV (unless stored upside down outside which is wildly unlikely). And of course it is my own fault for buying cheap epoxy from a non-chandlery source...

;0 (

[JimD]

Blush forms only at the last stage of cure which is why you can apply successive coats without worry as long as the cure is not complete. At this point it probably would be better to just leave it for a couple days, then give it a warm water wash and scrub, then sand fair, and apply one or two very thin finish coats. What are you applying the epoxy with? I use almost exclusively a plastic spreader such as bondo makes. The spreader allows for very thin, smooth coats which when built up to thickness ends up being very fair and requiring very little final sanding.


...I need to wait for a full cure, sand and wash... Actually, wash first, then sand or your sandpaper will gum up with the blush.

[Thorne]

I'm using a commercial epoxy spreader, and mixing the stuff by weight on my grandfather's photo chemical scale, so that part should be good.

I can wash first and then sand, but probably should wash again to make sure that no blush forms on the "new" surface before I apply epoxy again...

...but at this stage its goin' in the boat as-is for this weekend's sailing at Stone Lagoon -- can paint the lower part of it later up on the cradle.

http://www.luckhardt.com/stnlgn2/stnlgn2-Images/0.jpg

http://www.luckhardt.com/stnlgn2/stnlgn2-Images/11.jpg

[JimD]

but probably should wash again to make sure that no blush forms on the "new" surface before I apply epoxy again...


No blush will form once the cure is finished. That's it. Chemical reaction complete. You might have oily fingerprints to wash off but not blush.

And wow! Stone lagoon looks beautiful. Where is it? Got more pics?

[Thorne]

Stone, Big, Dry and a few others are part of the Lagoons State Park above Trinidad (near Eureka) on the coast.

Lovely indeed! And do I ever have pictures...

http://www.luckhardt.com/stnlgn06-4.jpg

http://www.luckhardt.com/stnlgn2/stnlgn2.html
http://www.luckhardt.com/stonelagoon04.mov

http://www.luckhardt.com/stonelagoon05sm.mov

http://www.luckhardt.com/biglagoon9-06/biglagoon9-06.html

http://www.luckhardt.com/big-lagoon-06/

[wwaterman]

Oh man, I can't wait to finish my Wineglass Wherry so I can embark on trips like this.

My neighbor, three blocks down from my house, also built a WGW and is converting his back to just a row boat (taking out the centerboard, which he said REALLY detracted from its rowing capabilities).

He said he'd sell me the sailing setup that he took off. Speaking of centerboards, I need to figure out how to put a leeboard on my WGW so I don't run into this issue.

Back to the point, awesome pictures! I want! I want!

Will

[Dave Gray]

I was just in that area - we drove down to do a 'preview' of Humboldt State - it is really a wonderfully scenic area but gas prices are astronomical! I paid $3.45 a gallon in that area, and about that much at Crescent City. Twenty miles north in Brookings gas was $2.93. But this shouldn't dissuade anyone from visiting the Lost Coast.