Glass between Keel Laminations?

Discussion in 'Boat Design' started by abosely, Aug 29, 2015.

  1. abosely
    Joined: Mar 2015
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    abosely Senior Member

    The Narai keel is laminated from 5 - 1" planks glued & screwed.

    Somewhere I read about epoxying a layer of glass cloth between each lamination to provide a barrier to prevent rot from spreading from one layer to the next if rot starts in one layer.

    So was wondering if that would be a good idea or not. The labor to do it would be minimal, so that wouldn't be an issue, but didn't know if would be unwise to do for some reason.

    If I put layer of glass cloth between each layer of keel I will drill over size holes and fill with epoxy then drill holes for screws so if water ever got into area it wouldn't be able to penetrate into wood from screw holes. Which I am going to do for all screws and bolts anywhere on boat.

    It takes a little more work but I'm building for long term durability and want to make sure that moisture can't migrate into wood from screw holes.

    Cheers, Allen
     
  2. Ilan Voyager
    Joined: May 2004
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    Ilan Voyager Senior Member

    Is it the Narai by old (87 years) Wharram? As the keel must be well sealed outside with glass and epoxy, and using well dried wood there won't be any rot if maintained correctly.
    The purpose of the glass fibre (sometimes plywood) in complicated laminations is to prevent splitting in some highly stressed places like a centerboard box through a keel; it's better to use a +-45 degrees for this purpose. Keep the glass for the outside, besides glass in a lamination is the best way to ruin in minutes the blades of a planer...
    Oversizing and filling the holes with epoxy putty is for the screws with high stresses and in direct contact with the outside as the deck hardware for example. This method has no strength until the epoxy hardens.
    There is no need for screws left inside a keel lamination and after covered by glass and epoxy to go to this amount of work.
    And it's also counterproductive as you are using the screws to tighten the lamination, so you have to go fast with screws immediately functional and able to keep the planks tight. Or you will need hundred of big presses making the screws useless. Or the purpose of the method is the saving on the cost of expensive big presses you'll use only once.
    It's far better to make pilot holes of the good size with the countersunk, fill the holes with bare epoxy resin, let it soak a bit and put the screw which will go smoothly as the fresh epoxy will serve of lubricant. The epoxy will seal and harden the wood around the fillets.

    General information for those planning to use the epoxy just as glue; Epoxy glues do not withstand cycles of swelling retracting in outdoor exposed painted wood for example. The USDA Forest Service Forest Products Laboratory (FPL) has plenty of documentation about this phenomenon. When you are using epoxy glues you have to seal completely the pieces (and the boat) with epoxy to keep them dry, it's a complete method of boatbuilding...

    If I remember well the Narai is a wood plywood epoxy construction, so no problem.
     
  3. abosely
    Joined: Mar 2015
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    abosely Senior Member

    Yes it's the Wharram Narai Mk IV, and everything is epoxy encapsulated, interior will have minimum of 4 coats epoxy and varnished for UV protection and everything exterior will be sheathed with 4oz glass that is going to be bright finished and the decks, hulls & cabin tops will be sheathed with Xynole cloth, the decks & cabin tops will have Xynole fabric weave showing and then painted to look similar to painted canvas.

    Main reason I was thinking about this is for long term durability, as in the future sometime if water were to get in thru a crack or damaged spot and not be known, it would contain the water ingress & rot to limited areas.

    Cheers, Allen
     
  4. Ilan Voyager
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    Location: Cancun Mexico

    Ilan Voyager Senior Member

    That takes time before a serious rot, do not worry. Rot is a sign of very poor maintenance or engineering on a epoxy boat. Better to check the underwater part of the hull and to inspect the inside taking out the floors regularly. Renting a diving tank and making an inspection of the hull 2 o 3 times a year or after an "accident" is a good expense...I met Wharram and his girls friends (Ruth and Hanneke) too many years ago. Seeking in Internet I've learnt that James is now 87 years old, that Ruth, a first class sailor, passed away on 2013 at 92 after 2 strokes. I suddenly feel very old...
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Assuming the laminations within the wooden elements are continuous, the rot (or moisture for that matter) can't cross this line, unless it's breached somehow.
     

  6. abosely
    Joined: Mar 2015
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    Location: Big Island Hawaii

    abosely Senior Member

    Thanks PAR, I guess I should have thought of that. Anything that could breach the epoxy glue joint would probably not go unnoticed.

    Cheers, Allen
     
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