The Age Old Question: Seal cabinetry or not?

Discussion in 'Materials' started by snowbirder, Mar 26, 2015.

  1. snowbirder

    snowbirder Previous Member

    I've had several boats in my time. Inside, there were raw wood bulkheads, raw wood cabin sole supports,raw wood cabinets.

    20 and 30 years in from creation, none of these items, located inside large boats, ever had a problem with rot.

    Also, a mega yacht I worked on had 100% home appliances and furnishings inside.

    So in the spirit of being lazy, do I have to seal up interior cabinets with epoxy or can I just paint and clear polyurethane the wood where each looks best?

    The cabin area is in a catamaran, literally inside the boat under 2 roofs. There is the main roof of the boat, then inside, indoors, under the main roof in the main salon, is another roof enclosing the space. Add to this that I live aboard full time and maintain things meticulously. Bilges are always dry. All leaks instantly fixed.

    Can i just leave the wood without epoxy?

    Interested in what wooden boat purists think. Hull is foam/glass/epoxy.
  2. rasorinc
    Joined: Nov 2007
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    rasorinc Senior Member

    Is your boat a saltwater boat? Is it trailered to and from water?
  3. snowbirder

    snowbirder Previous Member

    It is.

    My understanding is actual salt water in contact with wood preserves it compared to fresh, which causes the nasties to grow. ie: wooden boats usually rot from the inside out when in salt water, due to fresh water leaks.

    Saw your edit. The boat is the width of 2+ highway lanes. It will never be trailered. It's a 50' x 25' fully enclosed bridgedeck catamaran.

    Inside the main salon at bridge deck level, indoors, is yet another roof (looks like a shelf when you are inside the main area), under which is the cabinetry in question. Unless the boat sinks, these things will never get water on them.
  4. alan white
    Joined: Mar 2007
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    alan white Senior Member

    There are good reasons to seal wood interiors. An interior will experience a huge range of humidity levels. Wood is reactive to humidity and it will warp if a rapid change in humidity has better access to one side of a given piece of wood than the opposite side.
    However, if well sealed, the same water that might enter a given area of unsealed wood in a few hours of high humidity would take as much as weeks to enter the wood if it is well sealed, and far longer if epoxy encapsulated.
    If the interior wood is to be protected from warping, seal it equally on all sides to slow transfer of moisture in or out. Choose solid wood pieces with grain that is made up of lines (quarter-sawn) instead of whorls (plain-sawn). It costs more but it is about twice as resistant to expansion/contraction and therefore is not as likely to warp.
    Unsealed wood can survive against warping in many cases if the wood species is soft like cedar, for example, as opposed to white oak.
    It's not practical to build with raw, unsealed wood unless you aren't concerned with looks or fit and tolerances of drawers, cabinet doors, etc..
    Polyurethane is fine. Cheap and easy to use, available matte or glossy, found at any box store, three coats are plenty.
  5. snowbirder

    snowbirder Previous Member

    Alan, thank you. I'm glad to hear I don't need to go through the trouble and expense of epoxy. I'll use the polyurethane.

    What got me wondering was all the fiberglass production boats I've owned. To a boat, they all had various items made of untreated wood, were all 20 or 30 years old.. and none of the wood had any signs of rot.

    It's funny you mention the various humidity changes. Whe thinking worst case scenarios for untreated wood, MAINE was exactly what came to mind! ha ha ha

    A nice, sunny start to the morning, dry, then a fog bank rolls in. Soaked! Then it passes... Dry! Then an afternoon thunderstorm.

    If your advice works in Maine, it'll work anywhere! :)
  6. philSweet
    Joined: May 2008
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    philSweet Senior Member

    I like the breathable option for interior wood. Wood needs even exposure to moisture changes - Be that sealed, or just wiped with tung oil. It is the differential moisture across the panel that causes warping. This can be driven by temperature differences.

    My '84 Catalina just has an oiled finish on the interior (solid mahogany and ply mahogany) Maintenance consists of wiping it with Murphy's Oil Soap and then tung oil twice a year. Takes about an hour each time. The galley gets a bit more attention. The interior is as good as new. The bilges are wet, and the boat has lived in Florida for much of its life. While I have nothing against sealing interiors, I suspect an oiled finish is actually better in the tropics. I did have to replace the raw wooden mast step that had been sitting in bilge water for 20 years when I bought the boat. I replaced that with an epoxy sealed stack of hardwood ply. The companionway ladder is varnished and the drop in floor ply panels (they drop onto a solid fiberglass liner) are varnished on top. They are only 4 mm thick and they can equalize fast enough from one side.

    For comparison, the boat is in need of a third set of stainless steel sinks.:rolleyes:
  7. snowbirder

    snowbirder Previous Member

    Oh boy...

    From your other posts, I know you're both pretty smart guys.

    And you disagree. Very interesting.

    I've had mold problems using Tung oil. Mold grew on the oil. Any thoughts? Just more air flow, which I've already designed in?
  8. alan white
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    alan white Senior Member

    I agree with PhilSweet. He isn't saying that wood should be installed unsealed. Oil can be a good option for many. Oil can mean natural or synthetic. Natural (tung) oil may be more susceptible to mold than synthetic. I have had good luck with Sikkens oil. I did an outdoor railing (Africn Mahogany) with three coats and it still looks good after two brutal winters. It looks like varnish but takes a fraction of the time to get great results.
  9. snowbirder

    snowbirder Previous Member

    Ah, I see.

    Thank you. I'm very challenged when it comes to wood.

    I'll try the synthetic tung oil.
  10. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    I've had mink oil on boots go rancid to where I had to leave the boots in the back of the truck they stunk so bad. I imagine moldy tung oil would be a nuisance forever.

    I kind of liked Deks Olje the little bit I used so long ago on a toolbox. I just used the first part and it was fine.

    The way I use polyurethane on woodwork now, and I assume it might work for varnish, etc., is to slop on a saturating coat or two, sand it smooth, wipe it down with a little paint thinner to pick up the dust and then use a pad of fabric, or sponge or t-shirt or something to wipe on a very thin finish coat. It leaves no brush marks or paint sags and is so thin that dust doesn't settle into it and leave it felling rough. It also dries a lot faster, so in addition to being too thin for most dust to settle into, the window of vulnerability to dust is shortened from hours to 15 minutes or so.

    The guy that showed me that made wooden vases. He would rub in a coat of regular polyurethane on bare wood, then rub off all the excess until the wood wasn't sticky at all and you could hold it in your bare hands. It took about two minutes, and then in 30 60 minutes he'd do another coat etc.
  11. snowbirder

    snowbirder Previous Member

    Very interesting and worth a try as well.

  12. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Polyurethane and various oil-based coatings will stink for a considerable time in an enclosed environment, low odour water thinned coatings less so.
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