Glass over good plywood hull?

Discussion in 'Wooden Boat Building and Restoration' started by Ed Hoban, Feb 8, 2005.

  1. Ed Hoban
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    Ed Hoban New Member

    I've recently bought a George Buehler designed boat home built in the eighties. There is no rot anywhere on the boat, and the previous owner ground off all of the bottom paint. The now exposed plywood hull has been epoxied, with glass cloth at the garboard seam and waterline chine. He sanded through the epoxy in a couple of spots What's the best step at this point? Should I just roll another coat of epoxy on and paint it? Put glass cloth on the whole hull (below the waterline) then epoxy? Or is it best to continue sanding right down to the wood, then tack glass cloth and epoxy. Also, is it possible to put glass cloth and epoxy over painted plywood, provided the paint is sound? Any advice would be appreciated.
     
  2. boatbuilder.org
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    Location: Olympia Washington

    boatbuilder.org Junior Member

    ---

    It would not hurt to glass just to protect it from scratches that may go to wood and if it is fir plywood there is better chance the plywood will check so glass would help with that as well. If it is not a boat that stays in the water then glassing may be a lot of uneeded work and just resealing the bottom with epoxy may be fine. It is a good idea to always grind through paint and primer and get to epoxy, glass or wood before re-sealing with epoxy. Always remove bottom paint completely befor aplying anything other than more bottom paint.
    ---Joel---
     
  3. PAR
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    PAR Yacht Designer/Builder

    I can tell you what George would say. "Take that stick-um and cloth off the boat" and he'd be right. George designs boats as hefty as they get, capable of "bashing through tings" as he'd put it.

    Hagar is one of his smaller sail designs at 28' on deck. She's 8000 pounds, has 3/4" planking 3" thick floors, the keel is laminated stack of 8 pieces of 2 x 6. That's a well built boat.

    If you have no rot and just 'glass work on the chines and garboard seam, then pull the stuff off, fair it out and repaint. If you run into anything with the momentum his boats carry, then a thin 'glass skin will not save much. Any breach in this sheathing will just trap water in the wood and promote rot.

    I'm very familiar with his work, which design do you have? He doesn't much like plywood, preferring solid lumber planking, but has designed for ply many times.
     
  4. boatbuilder.org
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    boatbuilder.org Junior Member

    If you get into any glassing or epoxy sealing, you need to go all the way and encapsulate. If this is a "large boat" and you sheathe the hull use Dynel not glass which has better abrasion resistance and will leave you with a thicker epoxy barrier. You are not sealing and glassing to avoid damage from collision, but rather the every day scraping and wear. Breaches in the epoxy coating can be addressed at yearly haul-out. I have an all or nothing attitude toward epoxy construction and and don't advocate one way or the other, but I don't thing it is a good idea to mix the the two construction methods. I think PAR will agree with the last statement. The first part of this message applies only to plywood hulls. You get into covering dimentional lumber with composits and I would have to back track, I do not have any first hand experience, but it does not seem like a sound building practice to me.
    ----Joel----
     
  5. Par, you make a very good point, which I think everyone wishes away. I have just brushed my boat over something. It could not be that much damage. Check it at the end of the season, or, never. I forgot about it.
     
  6. Ed Hoban
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    Ed Hoban New Member

    George the Iconoclast

    thanks for the replies. my boat is a hagar, but only 26 feet along the deck. The first hagar he built was 26, but he must have re-thought the length when he drew up plans, because they are all 28' in his drawings. He does seem do advocate glassing and epoxying his plywood hulls, I guess what I was really wondering is whether I have to sand off all of the old epoxy before starting over. By the way, above the water line is 3/4 fir planking, which I have no intention of messing with. It's in perfect shape. What is Dynel? Is it a type of glass cloth or an epoxy system? One answer leads to ten more questions. . .!
     
  7. boatbuilder.org
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    boatbuilder.org Junior Member

    No need to sand old epoxy off, if it is in good shape. Dynel is a product I use for sheathing hulls and decks instead of using glass. It has better abrasion resistance than glass. It is more difficult to work with but the end product is better protection and it does not itch when you grind it :) . It is applied with epoxy like glass is.
    ---Joel---
     
  8. Ed Hoban
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    Ed Hoban New Member

    Joel, is Dynel generally available? More expensive than fiberglass? Glass is tough enough on an upright hull, but I'll look into this stuff. Thanks for the reply, if you're ever in Bellingham stop in, maybe this boat will be fit for the water by then. -Ed
     
  9. boatbuilder.org
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    boatbuilder.org Junior Member

    It is becoming fairly common and you should have no problem finding it. Email me your phone number and I will give you a call to talk it over if you like.
    ---Joel---
     
  10. PAR
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Ed, your correct George drew up Hagar, built it, then sailed it around for a while. He then redrew it with all the changes he would have liked in the original version, apparently with additional length. It's pretty cool you have one of the originals. Does he know? Call him and ask about it, he may have some information about it's history. He was out on Whidbey Island, WA though I have a PO box for him in Freeland, WA, try the phone book.

    For epoxy encapsulation to work it has to be true encapsulation, which is every sq. inch of surface, inside, outside in the joints and fastener holes, everything. This can't be retro fitted, but only possible in new construction or a complete restoration of the pieces involved. Without this encapsulation, water will get in and have limited ability to get out, particularly between the sheathing and outer layer of ply.

    Epoxy sticks to itself very well if it's clean and abated (sanded/roughed up to provide some tooth) Dynel is a reinforcement fabric and has about 3 times the abrasion resistance of regular cloth. There are other fabrics that are even better. A fiber glass supply store will know what it is.

    I don't think it's a good idea to sheath a hull that will spend it's season on a mooring or dock. There's to much time for beasties and rot to get a foot hold in the event of a coating breach (which will happen). Sheathed boats also don't dry out well when ashore for the off season, making repairs difficult using epoxy, which needs very dry wood to stick. Sheathing wood works well if two things are done; encapsulation and quick repair of breaches in the coating. Moored/docked craft don't get the inspection necessary to implement quick repairs. Trailer boats can be looked over quite well and easily so I do recommend sheathing them.
     

  11. Ed Hoban
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    Ed Hoban New Member

    Joel, 360 312 1827. PAR, I wouldn't have imagined epoxy would be risky, but never thought of it that way. I e-mailed George B. He's on vacation, but hope to get some type of dialogue going with him. Thanks for your replies. ED
     
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