Best way to seal wooden hull

Discussion in 'Wooden Boat Building and Restoration' started by bubblehead620, Jul 1, 2014.

  1. bubblehead620
    Joined: Jul 2014
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    bubblehead620 New Member

    Hi! I'm a new member and I'm not sure whether I'm in the correct forum. I'm a member of the US Submarine Veterans Group, Inc. Our base is in Millington, TN. We were fortunate to receive a wooden submarine hull model from the Navy Test Basin in Memphis, TN. We bought and reconditioned a trailer and mounted the hull on it. We built everything from the deck up. Our model is the hull of the USS Halibut. Myself and a retired Master Chief maintain the float including the trailer and the boat. The original hull is supposed to be mahogany. All our built items are regular pine wood from a home store.

    Our biggest problem now is maintaining the hull and deck structures due to weather. Our hull appears to have been built from layers like a laminate and when water gets into the wood it bulges and splits a bit. We try to maintain a good coat of oil based black paint on the boat but it does chip off. We'd like to seal the hull using polyurethane or fiberglass. Neither of us are boat builders so we're not sure what to use or how to seal a hull. We didn't design or build the original hull but we're trying to keep it in good shape.

    If anyone can make recommendations, we're all ears. Or feel free to direct us to any source of info that we need. Thanks, bubblehead620:confused:
     
  2. Petros
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    Petros Senior Member

    welcome to the forum,

    fiberglass also breaks down in the sun, it requires a number of laywers of UV resistant paint to keep it in good shape. It might work, but as it ages it could break down and allow moisture under the surface. this would trap moisture against the wood and allow it to rot from the inside out.

    traditional wood boats require stripping and repainting once a year, with continual touch up year round. Wood expands and contracts with moisture and temperature, allowing tiny cracks in the finish that allows moisture to get to the wood, hence starting the paint to peel off.

    Something that might be worth considering is covering it with nylon fabric and tightbond III glue, and than coat it with 5 to 7 layers of paint. Similar to what you would do with fiberglass but less costly, it would support the paint so it does not crack and allow moisture into the wood. Also, this would be easier to strip off later if you wanted to restore the original wood finish.
     
  3. gonzo
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    gonzo Senior Member

    The first thing to do is figure out what kinds of paint have been used. Shellac is a really good sealer and not too expensive.
     
  4. Petros
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    Petros Senior Member

    true traditional shellac is not water proof, the modern synthetic ones might be, but the key issue is UV protection. If the final finish does not have UV inhibitors it will not hold up very long outdoors.
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The shellacs are only moderately able to resist moisture vapor. It's better than most paints and varnish, but has poor UV resistance.

    Fabric set in TiteBond III will not hold for long on a static display, if it receives much wet/dry cycling. It would also be more costly than epoxy and cloth.

    What is the scale of this model? SSN-587 was 350' long. What are the goals for this model and how will it be displayed?
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    Acrylic house paint would be my choice, the only thing that will last on wooden step treads and timber decking, out in the weather all the time.
     
  7. thudpucker
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    thudpucker Senior Member

    How about Log Oil? Just plain ol' Porch and Deck Oil.
     
  8. PAR
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    PAR Yacht Designer/Builder

    The problem seems to be swelling, contraction and UV related, so sealing and stabilizing the wood, is preferable to just paint. No oil or paint is going to do this, so the seams and joints will just open and close to changes in the environment.

    Paint will solve the UV issue, but not the wood movement, which is why I recommend epoxy.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    A good quality exterior acrylic has exceptional resistance to cracking on exterior timber, put on three liberal coats and it should last 10 years. The same product on vertical surfaces can easily last 20 years, and it is simply due to it remaining quite flexible with aging. That's how often ( 10 years) I paint the front steps, and they get walked on every day ! And the timber is not 100% sound either. Considering it can cost in the region of $10,000 to get a timber home painted here, it is just as well that the era of alkyd enamels is over for such work, or that bill would be coming in every five years.
     
  10. hoytedow
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    hoytedow Wood Butcher

    Black is the enemy of wood boats. It soaks up the heat and accelerates degradation of wood. It would be best to keep this replica out of the sunlight as much as possible, no matter what the coating may be. Climate control its environment.
     
  11. gonzo
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    gonzo Senior Member

    I meant shellac as a primer. It has been used for many decades with success. Also, it is very forgiving of rosin, oil and previous paints.
     
  12. jehardiman
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    jehardiman Senior Member

    You might have trouble getting anything to stick. Actual tunnel models made of laminated mahogany where generally sealed with warm linseed oil, varnished, and waxed. If the urea glue that it was made out of starting to fail, it might be better to splash a fibreglass copy because the shape is really not that complex (I assume it is the 587 since that hull would be easy to identify, though how that model got to Memphis is beyond me....Maybe a picture and I can tell you which model it is.)
     
  13. bubblehead620
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    bubblehead620 New Member

    sealing hull -ssn 587

    I'm not sure how the hull got to Memphis, but our base Commander, an active duty FTCM(SS) at the time, contacted someone at the test center on President's Island in Memphis. They gave us photos of a number of hulls they were going to scrap and let us choose two. One was the hull of the Halibut, SSGN/SSN-587 and the other was a fiberglass hull of a Mackeral class submarine. We decided to use the Halibut's hull for our float as it had an interesting history after becoming an SSN and a "Special Ops" boat. We repaired the damage to the planes, shaft struts and other tidbits, and built the sail and the Bat cave on the foredeck. If I can figure out how to add photos to the thread, I'll send some pictures of the boat now, which is painted presently for show. Prior to next year, we want to take her down to wood and seal the hull and then repaint her. The old trailer we are using to carry the model is so old, the wheels and tires were museum pieces. We couldn't find a spare wheel, so we finally decided to R&R the axles and put five lug wheels on it so we could carry a spare tire. I'm not sure if we have the wherewithal to make a fiberglass copy. We have considered laying fiberglass mat over it if there are no roll on or paint on urethane products that would work. The boat is painted with Rustoleum, oil-based, black paint presently to maintain its "underway" appearance. Bubblehead620
     
  14. bubblehead620
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    bubblehead620 New Member

    I'll try to reply to all of the questions that were asked. The model is about 20-feet long. We use it as a parade float and display for various events around the greater Memphis area. We have not traveled very far with it due to lack of a spare tire. I've almost completed replacing both trailer axles with modern 3500# axles that use 5-lug tires and wheels. We don't have indoor storage for the float. During down time, the float stays at the "shipyard" which is my buddies farm. We keep it under a portable carport and keep it covered with a tarp, but it is subject to moisture and some sun, wind, etc. Right now its in my driveway for trailer overhaul, but will return to the farm. As a display and parade float, it is painted black with white lettered hull numbers on the sail and name on the rear quarters. We've tried to use good oil-based paint, usually outdoor housepaint and mostly use Rustoleum brand if available. We don't wish to keep the hull stained or shellacked unless we can paint over it. We recently scrapped off the chipped paint and sanded the rough spots on the hull for a local veteran's event. It looks good from about 15 feet, but if you get closer, you can see the cracks in the lamination. Also, the hull was built like jigsaw puzzle due to the center being hollowed out for various instrumentation being carried during cavitation testing. Our desire is to seal the hull smooth since its testing days are over and so we can pass this model on for future generations to see where submarines came from. Please keep the suggestions coming and THANKS! Bubblehead620
     

  15. PAR
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    PAR Yacht Designer/Builder

    If looking for long term durability, you really have to stabilize the wood, which will require epoxy and likely a sheathing, followed by a fairing and smoothing process, before painting again. Another option is truck bed liner, which will keep out much of the moisture, but the substrate below this will need to be repaired and smoothed first.
     
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