Epoxy on Fully Cured Epoxy--Good Bond?

[Ken Leap]

I am building Oughtred's Caledonia Yawl (see "Reina del Llano" (http://www.3lefties.com/leap/boat.html) .) The hull is fully planked, and I am now adding the outer backbone bits, rubbing strips, gunwale, etc. I plan to coat the outer hull with CPES before applying Kirby's paint.

I am having difficulty keeping moister off of the unsealed hull. I am working under a metal roof and keep the boat covered with a tarp, but the torrential rainfalls that we have been having (and I'm not complaining because we've been in a drought for several years) seem to get things wet anyway. The moisture stains the surface of the wood and even seems to create mold if I leave the tarp on between downpours. I plan to double cover with tarps, but am still concerned about the vulnerability of the bare wood. Sanding cleans things up nicely, but I want to get the CPES on soon to protect those precious planks before I sand them away to nothing. Is it wise to brush CPES on the planks before finishing all of the bottom details? Is it then safe to just sand the CPES-covered areas before gluing on the keel sections, rubbers, and gunwales? And finally, is it ok to put one final coat of CPES on the hull after sanding everything? What I am concerned about is putting epoxy on top of cured epoxy. Ideally, I guess, these epoxy-on-epoxy layers are done before the bottom layer completely cures, but my limited working times do not permit that. I am hoping that sanding the bottom layer will be enough for good adhesion to the next layer, and I don't mean sanding down to bare wood. Any comments?

Ken

[NormMessinger]

oh, just some random thoughts:

Would it be possible to put a 100 watt light bulb or two under the boat and tarp. Just a little warmth will raise the relative humidity enough to eliminate the problem. Or not.

Is the tarp in contact with the boat. Raise it a bit so there can be a little circulation. Can't hurt.

My experience with using CPES to protect wood that might get wet prior to finishing has been unsatisfactory. Where cpes'd ocoume ply did get wet it turned black. If I were planning on coating with epoxy prior to paint or varnish I'd go ahead and coat with epoxy. Wouldn't even need CPES in that case.

Sanding a cured CPES'd surface well prior to gluing or coating with epoxy will give a satisfactory bond as will sanding cured epoxy prior to coating or bonding. Use at least 80 grit to get a good tooth for a mechanical bond.

[Ken Leap]

Norm,

Thank you for your input. I feel a little better grounded now.

In light of recent discussions in this forum about epoxy and CPES, my decision to seal the bare wood with CPES comes from a recommendation by George Kirby. In response to an inquiry that I posted on the George Kirby Jr. Paint Company website (www.kirbypaint.com) a while ago, George A. Kirby IV himself called me at home to discuss my questions about using his paint. I described my boat and its intended use. He told me to seal the bare wood with CPES before applying the paint. He then followed up our phone conversation with a hand-written letter and a color chart. What a great guy!

Ken

[Jim H]

Ken, you might want to read this thread through to the end: Repost - The Chemist on Epoxy (http://media5.hypernet.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=005831)

Take a look at his post of 8/24/01.

[Ken Leap]

Jim,

Thanks for the reference--a pretty thorough discussion on epoxy and CPES. It is difficult for me to fully understand all of the issues surrounding these adhesives and sealers. The more I read, the more complicated everything seems. I am learning to be skeptical, and that's a good thing.

My current thinking: I will put a coat of CPES on the outer hull after all of the parts are glued on. This should give me a well-sealed wooden assembly. (This assumes that sealing the wood is a good thing, of course.) If subsequent coats of paint applied to the fully-cured CPES don't stick as well as those applied to green CPES, I think I can live with that. I don't mind having to sand down to my sealed wooden shell periodically and repaint.

My biggest fear is that I will fret over this issue and never get anything done. When I began this project, I posted a question to the forum about wood selection. After getting all of the (often conflicting) advice from the "WoodenBoat Brethren", I froze. I consulted a professional boat builder who told me, "Just build it...you will know when it is right, and you will have a boat for your efforts." (Or something like that.) That was very liberating. My favorite quote (from an article in WoodenBoat Magazine) by a wise old builder warning someone who thought he finally had the right solution to a tricky problem: "Nothing solves nothing."

Into the sawdust and toxic fumes...

Ken

[ 08-26-2004, 04:22 PM: Message edited by: Ken Leap ]

[WindHawk]

Just a thought on the "fear" thing. I lost sleep; I built & rebuilt the boat almost every night. My wife likes the fact that I lost plenty of weight while working so hard, but she doesn't care for a bad attitude. In the end, I put her in the water (boat, not wife), and hit the dock a few times. What a relief! I can paint her again. Nobody besides myself notices the ding's, and all I ever hear is "Nice Boat!" Relax, take a friend for a ride.

[Jim H]

:D The CPES thing has been kicked around the block a time or two...

By all means do what you think is right I just wanted to make sure you had the information you needed. A word of advice, if you have not used CPES before, get the best vapor mask you can afford.

The Kirby people are top drawer.

[WindHawk]

I'll second the vote on Kirby paint. I haven't used oil-based enamel since the 60's, and I sweat blood for a few moments until I figured it out again. Mess it up, and a quick sanding & repaint will fix it without leaving a scar. My boats only 13' long; so, I didn't have to worry about the cost. It's about $70 US a gallon.

[NormMessinger]

Don't fret. You'll be fine. Seems to me paint will stick to cured CPES as well as or better than unsealed wood. There is such a wide range of technique used successfully by the folks that inhabit this forum it sometimes seems like anything will work just fine.

In my experince Kirby's Paint does not cure well on System Three epoxy, the traditional stuff. The deal may depend on the type of hardener used.

[WindHawk]

Whenever Norm say's something, it'd be to your advantage to listen. I put four coats of West Systems epoxy on my boat, the Kirby paint dried just fine. However, I used Interlux's Schooner varnish on the transom, after the same number of coats of epoxy, and the first coat would not dry. Varnish is a "living" finish, and the second coat got the first to dry. I owe several people on this forum a debt of gratitude on that one. I don't think I would have put a second coat on the wet one without having been told to do so. 70 some hours later, and the varnish was still not dry, I was heartbroke.