finishing bright mahogany classic runabout

Discussion in 'Materials' started by H A van Nes, Feb 15, 2015.

  1. H A van Nes
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    H A van Nes designer builder sailor

    I could use some help two main questions so far.

    1 - Can one use a ceps (clear epoxy penetrating sealer) before staining? I'ld like to use a heavy paste stain to even out blotching and fill the grain.

    2 - Is there a better way (esker - but efficient) to fair this 30 foot runabout than by hand with a long flexible board and belt paper?
     
  2. pauloman
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    pauloman Epoxy Vendor

    stain - let sit week plus for oils in stain to evaporate
    then good quality epoxy sealer and primer - (not cpes!!)
    then several coats of traditional marine spar varnish
    optional coats of clear LPU with uv blockers ($$ stuff) best sprayed

    contact me for specifc recommendations if you like

    paul oman
    progressive epoxy polymers inc - epoxyproducts.com
     
  3. PAR
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    It might be best to contain your questions about fairing and stuff on your Chris Craft to one thread, so to keep the focus.

    CPES isn't going to help you with staining, as it'll partly seal (not completely) the wood fibers, preventing the wood from accepting the stain. In fact, there's no reason for CPES under any type of clear coating. Stain is best put on raw wood.

    This said you can tint epoxy, as you seal the wood, though this does take some experience to do well and not get a blotchy look.

    There's no easy way to fair wood that will be brightly finished. This is why most boats are painted. Fairing is a pain in the butt, tedious and difficult to do well, even under paint. Brightly finished surfaces, just makes this more so, as you can't make mistakes.

    As to your denting and other damage/defects issues, you have a few options, but it all depends on how extensive and wide spread the damage is. At some point most will have to decide if it's worth the bother: re-sheathing with veneer, grinding down below the worst of it and re-fairing, using localized heat to pop up bad spots, partial or wholesale plank replacement, etc. Without a bunch of pictures, it's a tough call from here. Most brightly finished boats get painted once the hull gets battered enough to warrant it.
     
  4. H A van Nes
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    H A van Nes designer builder sailor

    This may be a repeat. I'm not sure I actually posted. But thanks to both of you Pauloman and Par. You confirmed my own opinion. I will start another thread for the fairing issue. Can I use my MAS low viscosity epoxy thinned with alcohol, xylene or methyl ethyl keytone? Or can you recommend a sealer/primer. Or should I just stain, seal with a non epoxy sealer and varnish? I've just finished wooding the deck and topsides and the wood is in very good condition. thanks again for your help.
     
  5. PAR
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    PAR Yacht Designer/Builder

    Why are you looking to dilute epoxy? Do you know what happens to the physical properties of epoxy when diluted with solvents? We use epoxy to stabilize wood's moisture content. A modest 5% dilution will make epoxy non-water proof and degrade it's compressive and tensile modulus by 30%, a 10% dilution will degrade it below 50%, so . . .

    If you "play" with these chemical concoctions, you really need to have a pretty good idea of what you're fooling with, particularly if you plan on using that (listed above) particular combination of solvents.
     
  6. H A van Nes
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    H A van Nes designer builder sailor

    The only reason I thought of thinning was to help the varnish grip the wood. Thinning was my idea to make my own penetrating epoxy. I was never intending to use all the mentioned chemicals at once. I was told by the owner of MAS Epoxy that it could be thinned 10% with acetone without making it non-water proof. Pauloman apparently does not like CEPES. I know, for myself anyway, its much easier to condemn particular method or suggestion than to come up with a solution. But what do you suggest?
     
  7. H A van Nes
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    H A van Nes designer builder sailor

    BTW What is LPU mentioned by Pauloman?
     
  8. PAR
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    PAR Yacht Designer/Builder

    Epoxy under varnish or polyurethane tends to make maintenance more difficult. A very marginal improvement in "grip" can be had with a thinned epoxy base, though the few percent difference this adds, doesn't out weigh the increase in care and upkeep in my opinion. Varnish gets a fine grip on raw wood if it's thinned, for the first few coats. Most use a quite diluted mix initially on raw wood, say anywhere between 30% to 50%. I use about 30% on the first coat, reducing it to 20% on the next and 10% on the next if applying by hand. If spraying I use a slightly higher dilution rate, mostly to get it through the gun without stippling.

    A 10% acetone dilution will decrease epoxy's waterproofing, below that of sufficient moisture vapor penetration, that wood can tolerate before you get issues. Simply put at 10%, the coating is not even as good as polyester resin and we all know how poor this is, at resisting moisture vapor. The way many get around this is, eventually putting enough coats of 100% epoxy, over the diluted coats to make a film thickness that can resit what the base coats can't. My point is, why bother, as the penetration issues aren't as important, as the ability of the coating to resist moisture vapor penetration (the real thing you're trying to avoid).

    Paul O., as well as anyone that's performed the tests on waterproof coatings don't like CPES, because it's a marketing tool and really not good for much and nothing under coatings (paint, varnish, etc.). It's a 40% dilution, using both hydrophobic and hydroscopic solvents in the mix, which is self defeating in nature (one fights the affects of the other). I suspect they use this combination, to toss off others attempting to make their own mixtures, but it can't be justified chemically and tests have proved this out repeatedly over the last couple of decades.

    In the end, if you want a varnished surface, use typical varnishing practice. Rebecca Wittman's book "Brightwork" is the bible for many and it'll offer the same advise I have - skip the epoxy under varnish, to save maintenance issues and employ well practiced techniques that boat builders and furniture makers have been using for a very long time.

    [​IMG]

    This book has a resent revision, including dealing with epoxy. Anyone doing a bunch of varnish work should read this book. Steinway piano's don't have any epoxy under their finishes BTW, nor do any high end brightly finished products, known for the quality of their finishes.
     
  9. H A van Nes
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    H A van Nes designer builder sailor

    Thanks Par. Although I must admit that I am a bit cocky about my woodworking and finishing skills. I did build this 30 footer from scratch. I recognize that this attitude can come close to arrogance and there's too much of that going around. I will humbly take your suggestion and read the book.
     
  10. PAR
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    PAR Yacht Designer/Builder

    Even though I'm very experienced at finishing wood, repairing and building boats and other stuff (several decades), I still manage to find I learn things. For example, I was once a strong advocate of the use of penetrating epoxy products, even coming up with my own formulations, to save the gouging the Smith brothers where inflicting, with their CPES stuff (huge markup on raw materials). After running into Jan Gougeon on the west coast, while he was enjoying some of our weather, the conversation came up and some enlightening points made. I took the challenge and performed the appropriate tests, since a number of times and he was right, as were subsequent tests and documented (published) reports about the physical qualities of these formulations. So, I changed my mind and now argue the exact opposite of what I once defended. Classic first amendment stuff really, though not much more then an evolution, based on study, tests and observation.
     
  11. SukiSolo
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    SukiSolo Senior Member

    Good varnish finishes last well if applied properly. I know of at least one dinghy with most of her 1958 2k varnish intact, and she is no mothballed museum piece even if kept in a boathouse when not used. Said boathouse is no super dry haven but flooded by tide occassionally. That particular boat was specially varnished for the 1958 Boat Show, and they (Cerrux) must have done a good job as most of it is still there. A clinker (lapstrake) type with fore and stern deck and clear inside and out.

    My own experience of finishes ref epoxy/varnish has led to preferring the all high quality varnish route on brightwork. When you have to repair the epoxy covered with varnish it is much harder to get sweet. It must be said that long term UV exposure is detrimental to most finishes and timber colours change with it, some darkening, some lightening.
     
  12. PAR
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    I got 22 years from one of my varnish jobs. I built and varnished (real varnish) her in 1988 and she was sold to a guy with a boat house. When he got in financial trouble, I bought her back from him and stored her in my barn. Neither location was ideal, but both did keep direct sunlight off her flanks, except in use, which is the key. In 2010 I stripped her top coats and re-varnished her. She was in a pretty serious need, but no gray or burned wood was on her. I had to grind through about half of the film thickness to get down to good finish, before recoating.

    It's all about care and exposure to UV. Most finishes can tolerate normal environmental movement, but not prolonged UV. If the finish is kept clean, relatively dry and out of the sunlight, it'll last, though don't expect to get a half of century, like Suki's example. I've repaired and refinished 50 year old varnished surfaces and they're almost always crazed, cracked, checked and dramatically darkened over this long. It's nice to know some can survive, but it's the care they receive that is the only reason.
     
  13. H A van Nes
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    H A van Nes designer builder sailor

    Another problem with this boat is that some cracks have formed between the carvel planks (maybe 10 to 20% of the matgins between planks. These crake are right between the planks and not big enough to fill with an inlay or Dutchman. I was planning to clean them mechanically and fill with epoxy before starting to varnish. I would appreciate your suggestions.
     
  14. SukiSolo
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    SukiSolo Senior Member

    I assume you are referring to solid plank 'checking' as we call it in the UK. Yup, I would fill this with epoxy at the driest state/humidity you can achieve. I have done some paint finishes on solid timbers which have rewarded this treatment and finished fine afterwards, some clear and some painted but the 'checking' has not shown through later at least over 5-6 years.

    The dinghy (prevoius post) I referrred to was 6mm (1/4") 5 core ply so checking was not an issue. Well done PAR, I've had stuff last about 20 + years with light touch up, but generally, find roughly 10-12 about time for a thorough refurb. If the original is good though, leave as a sound base. I'm really pleased to find some one else so similar in thought about varnish finishes, maybe the real world and experience teaches us....;)

    My own little 'baby' is going to need a touch up this year at 5 years old and several Championships as well as a lot of use. 98% perfectly sound, just rubbing strake damage etc. as per normal useage.

    Don't forget the odd touch with Oxalic acid, if parts are black or discoloured either. Just remember to let it dry properly (not a real problem) beore applying first coat.
     

  15. H A van Nes
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    H A van Nes designer builder sailor

    Thanks for the comment Suki. Actually the cracks that concern me are between the planks. The are a few checks but I plan to treat them just the same way. I used to use Oxalic acid to clean raw teak decks. It worked very well. Is there a trick to using it on wood that has turned dark? Do you have to avoid the light wood next to the dark spots?
     
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