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Thread: Using West epoxy over CPES in a repair

  1. #1
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    Default Using West epoxy over CPES in a repair

    We are tuning up a 40' wooden schooner built in 1979-80 and re-boring the shaft hole through the planking and lining it with a copper sleeve. At the outside end of this sleeve the original hole through the mahogany planking has been worn away and shows some rot. Our plan so far is to CPES the worn places that show some rot and then fill in around the copper sleeve with West epoxy with 406 filler.

    Since we have never used the two products together and there appears to be a certain tension between the manufacturers, we thought perhaps a forum member who has done this could advise based on his/her experience. We were thinking of applying the West epoxy while the CPES is still curing so as to ensure the best bond for the West - before the CPES is hard and impervious. Does this make sense or has someone tried it and run into problems?

    Thanks in advance for any insights or expertise.

  2. #2
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    Default Re: Using West epoxy over CPES in a repair

    I'd be a bit leery of hotcoating neat epoxy over CPES. Only because there are a lot of solvents in CPES that will need to escape. But that may just be me being over-cautious. A question for West's tech folks, though, for sure.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  3. #3
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    Default Re: Using West epoxy over CPES in a repair

    I'd be a lot more than a little leery. Leaving rotten wood in a boat is usually a bad idea. Making it hard with snake oil does not turn it back into wood that you would use in a boat, and compromising the strength and bond of your real epoxy with said snake oil's evaporating solvents (which is a very high percentage of what it contains) is another bad idea.

  4. #4
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    Default Re: Using West epoxy over CPES in a repair

    So you propose using epoxy over CPES that is embedded in rot. Nah.

    I think your best bet will be to replace a section of the plank with a highly rot resistant species.

  5. #5
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    Default Re: Using West epoxy over CPES in a repair

    +1 ALL of the above.

    CPES is (and I am not a fan) a decent primer. Let it dry before applying the resin. As David G. said, you don't want to trap the solvents. Nor do you want to bury the rot, live fungus, under a plastic shell. It will continue to grow and the plug will fall off.

    I will suggest the possibility that a pressure washer might be able to erode rotten wood to the extent that you might be able to effect a repair. I have not seen anyone make this recommendation. I have recently gotten a pressure washer and it does cut away punky wood around knots, but I have not found a rot pocket to test the idea yet. If you do blow away any softened wood. let it dry for a long time and treat with Tim-Bor or borax and antifreeze. Let the flames begin.

    West 406 is the most expensive way to buy silica and silica alone is a waste of epoxy. Fillers should be inexpensive and provide more volume to the mix, reducing the cost per unit volume. West fillers are expensive, so the savings are not there.
    http://www.duckworksbbs.com/supplies...ives/index.htm
    http://raka.com/fillers.html
    http://www.douglasandsturgess.com/mm...e=FILLERSTHICK
    http://www.sculpt.com/catalog_98/mol...es/fillers.htm

    Dave
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  6. #6
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    Default Re: Using West epoxy over CPES in a repair

    Yep, you are proposing a bodge job.
    Cut out the rot and glue scarf in new wood, a dutchman if you can, a length of plank if you must.
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
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  7. #7
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    Default Re: Using West epoxy over CPES in a repair

    I agree with most of what's been said here, but must offer a perspective. As one of those guys who works doing such repairs, I have to point out that sometimes the client's budget has to be stretched, compromises made, and full repairs put off until later. I answered with the assumption that the OP was a professional - who had has such discussions with his client, and was prepared to make the best of a temporary solution... with as much demo as can be accomplished on a budget, as much borax treatment as can easily be managed, as much CPES as can be injected quickly. As much epoxy sludge as it took to infill the voids, and a new sleeve to help obviate the resulting fragility. Otherwise he would have opened a different kettle of fish by asking about the whole approach, instead of one detail he doesn't happen to be familiar with regarding a specialty product (CPES).

    But I could have read that all wrong. In which case, the OP maybe shouldn't be tackling this particular job. Even if he's located near me, and will be creating future work for us. Fixing someone else's muck-ups - esp. when they involve inaccessible epoxy - is not my favorite type of work.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  8. #8
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    Default Re: Using West epoxy over CPES in a repair

    The point that you must not encapsulate rot is well taken. CPES is used to solidify rotten structures that are for some reason impossible to repair or where the high cost of great quantities of CPES is lower than tearing out the rot but it's always a desperation choice. And it results in a structure that has perfectly fine compression strength but has very poor flex strength.

    The real argument against just solidifying rot with the weasel pssss (our local affectionate name for CPES - sniff once and you'll know) is the great difficulty in getting it into the wood past the rot. Gravity can do some if you bore a few hundred very fine long holes and inject. But it takes real skill and a correct understanding of the exact dimensions of the rot to pull this off, with in practice more failures than successes.

    This is a hard rebuild and in practice you'll end up replacing much of the deadwood, horn timber, and frame hood ends. You'll likely find it easier to replace lengths of planking than to spread them.

    Not to say I'd not be tempted to "do it wrong" if I were satisfied that the frame ends and horn were fully sound and the only problem was some rot in the shaft alley. I'd start by over-boring the shaft hole to see if a tube of surrounding sound wood can be found. If so, you could then insert a wooden pipe (make in two halves so you can make the hole by router - drilling that long through endgrain is no fun) into the hole that's been slathered with CPES and then epoxy.

    I have routinely used CPES to treat areas where I have removed rot and will insert a dutchman. I do this as a prophilactic even though I try to remove all rot. I have had no glue failures putting WEST (my glue of choice) on right after the CPES and buttoning it all up. I don't know if it's really needed but I allow such joints a week to cure before subjecting them to a real strain. An all WEST joint seems to be cured and strong in a day though even there I give it two or three days. Been a while since I really read up on this and before I do another job, I think I'll do some reading. Never hurts to check for bad habits that have only accidentally been working.

    Finally, there's nothing like a powerful pressure washer for finding planking rot in the hull. Most rot follows fastenings so it gets near enough to the surface that even 1/4" good wood will, under pressure, collapse into subsurface rot and if you're good with the pressure wand you can give that much pressure without damaging the surface where the whole depth is sound. Once the spot is exposed, I hydro-enlarge it a bit but I'll be going out past the rot by chisel to get to the sound wood and to regularize the shape for a dutchman so I don't worry the hole too much. The pressure washer is more to find the rot than to get rid of it all.

    G'luck

  9. #9
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    Default Re: Using West epoxy over CPES in a repair

    If memory serves, CPES was developed to restore rotten architectural molding and the like. Not an application where structural strength is very important.
    The Gougeon experimentation indicates that solvented epoxy (Think CPES) does not penetrate to any great depth and does not show meaningful structural properties.

    Until I see credible lab results, I won't consider CPES useful in a structural load path. CPES'd mush is still mush.
    Last edited by JimConlin; 05-02-2017 at 08:28 PM.

  10. #10
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    Default Re: Using West epoxy over CPES in a repair

    Thanks for the quick responses. We should clarify that the place that may be rotted is only around the outside opening of the shaft hole. We did rebore it last week and watched what came out the hole and other than at the outer part of the plank it looked good. It may be worm damage rather than rot as the boat's previous owner had it in San Diego at a marina. We have already refastened, recaulked and gone over the whole hull checking every suspicious spot and replaced planking where needed. We have checked and sistered any frames needing attention. This is just the abraded outside edge of the hole. The plan is to swab the 2 foot length of the hole with cpes as a precaution and then fit the Schedule K copper sleeve, filling gaps outside it with West epoxy. The copper sleeve and other treatment for the shaft hole are really to keep shipworms out if the boat goes back to the west coast and for cosmetics. Everything we can see or assess in the hole and around it are sound or we would have replaced the wood.

    We have the 406 around for other work, not a cost issue, but thanks for the heads up.

    So we hear the possible concerns about rot and how CPES works, but are really mostly interested people's experience in how using West over CPES will work in terms of cure. It sounds like the consensus is to wait for the CPES to dry for at least a day so that the solvents can evaporate? That makes sense.

    Thanks for the input - much appreciated.

  11. #11
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    Default Re: Using West epoxy over CPES in a repair

    West epoxy doesn't stick to CPES treated wood. I don't know how I know this.

  12. #12
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    Default Re: Using West epoxy over CPES in a repair

    I used CPES under MAS brand epoxy resin for the construction of an exterior wood railing and mailbox bracket for my home. I had never used CPES but was interested in trying it in preparation for a boat project. I applied the CPES to Douglas fir, cedar, and mahogany. That was followed by the epoxy resin. I followed the manufacturers recommendations for hot coating. Some pieces were then primed with System 3 water based epoxy primer. After the primer, I applied two coats of Petit Easypoxy polyurethane paint. The parts that were not primed received the Easypoxy on top of the epoxy resin. The railing is now ten years old and is ready for another coat of paint, but structurally everything is still 100%
    While the solvent content is very high in CPES, I have seen no signs of blistering. The mailbox bracket looks new, but it is not as old as the railing. I would think the solvent flashes off rather quickly. When my Beg Meil hull is ready I may very well use CPES.
    Good luck

  13. #13
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    Default Re: Using West epoxy over CPES in a repair

    Seems to be one of those gray areas. Proceed at your own risk.

  14. #14
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    Default Re: Using West epoxy over CPES in a repair

    Be good to see a photo.

    Without really understanding the situation, for lack of photos, I wonder if you could maybe push a cork some distance into the boring then fill the problem area with straight epoxy and re-bore once it's cured.

    If it's just the outer surface of a plank perhaps you can route out the plank for half of it's thickness and add a Dutchman?

  15. #15
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    Default Re: Using West epoxy over CPES in a repair

    Quote Originally Posted by Jim Ledger View Post
    West epoxy doesn't stick to CPES treated wood. I don't know how I know this.
    Does this need a smiley?

    I don't use CPES, but I've been around when it was being applied. Nasty stuff to wade thru a cloud of. But I did have a client for a tender - glued plywood lapstrake - who was initially pretty gung-ho about a finish schedule of: CPES; Epoxy; 2-part Polyurethane.

    I had no question about the compatibility of 2-part poly over epoxy, but wondered about the epoxy over CPES deal. West System had some things to say about CPES, but they did say they had never heard of any compatibility/adhesion issues. As long as (like I mentioned earlier) the solvents in the CPES were allowed to fully flash off.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  16. #16
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    Default Re: Using West epoxy over CPES in a repair

    I do use CPES.

    I've no problems with soaking CPES into the endgrain slope where a dutchman will then go, then using WEST as a bonding epoxy with the dutchman right away. Perhaps some of the CPES solvents perk out through the curing epoxy but, judging by the smell deep in the wood discovered six years later in a different repair, they end up going deeply into the wood and just sitting there as silent rot killers.

    This is different from painting a hull with anything other than plain epoxy. When using CPES as a sealer before painting, I for sure let it cure a week and then wash to remove the amine blush. I have not used WEST as a coating since the early eighties. For me it's too hard - too hard to apply and too hard for marine use as it withstands minor damage but after a goodly ding it's too hard to repair. And that was before I ever even heard of CPES so I've no idea how my scarfing experience might or might not apply to surface coating.

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