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Thread: A cold molded overlay over carvel?

  1. #36
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    Default Re: A cold molded overlay over carvel?

    Many old boats in Sweden glassed. From some i have seen, you could literally remove all the wood and just fit out the glass hull, though not all have such a heavy lay-up. Its actually a cheap fix, to put 1/2in of glass over a wood hull than to pay to have a proper repair job done. Plenty of old coastal trawlers have had an extended working life with this procedure.

  2. #37
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    Default Re: A cold molded overlay over carvel?

    Which is, essentially, the Vaitses method. Built a fibreglass hull around the old wooden hull.

    But if the hull is dry and sound, a layer of biax or two provides waterproofing and additional strength.

    I think both methods are excellent. Adding layers of timber is also a great method, of course, but I think I'd always want to sheathe that.

    Maybe it's worth noting here that dry wood is stronger than wet wood, all glue adheres better to dry wood than wet wood and that all fastenings eventually corrode in wet wood, even copper. Monel might be an exception to that and bronze corroded VERY slowly!

    Rick

  3. #38
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    Default Re: A cold molded overlay over carvel?

    I do recall hearing or reading that the Carrs regretted not putting a layer of something over the cold moulded timber on Curlew. My impression at the time was for abrasion and sealing rather than any added strength.

  4. #39
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    Default Re: A cold molded overlay over carvel?

    Quote Originally Posted by John B View Post
    Because glass tends to not like salt water bleeding out of old saturated wood, and more often than not there aren't enough glass layers to fix underlying structural problems . The boats I'm aware of have delamination issues. The exception is one particular boat that had so much glass added that her wood hull was famously described as 'being a passenger'. In other words , the glass was to such thickness that could have made a hull by itself.
    what is going to hold the layers of veneer on?

  5. #40
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    Default Re: A cold molded overlay over carvel?

    Quote Originally Posted by John B View Post
    I do recall hearing or reading that the Carrs regretted not putting a layer of something over the cold moulded timber on Curlew. My impression at the time was for abrasion and sealing rather than any added strength.
    Yes sheathing is essential for keeping the wood underneath dry and keeping the worms out ! Australian teredos are vicious !

    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  6. #41
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    Default Re: A cold molded overlay over carvel?

    you probaably know abouty this Peter but check out this one if you dont

    http://www.woodworkforums.com/f32/sh...-veneers-48484

  7. #42
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    Default Re: A cold molded overlay over carvel?

    I hadn't seen it, thanks Andrew. An interesting thread.
    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

  8. #43
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    Default Re: A cold molded overlay over carvel?

    I removed the single layer of 100 gsm glass from an area in front of the keel of Haumuri to repair some cracked glue joints in January this year.
    After repairing the cracks I put 2 layers of 400 biaxial and a layer of 200 gsm over the top over this area.
    The resulting performance gain is probably greater than a new set of sails and is permanent.
    I'm now thinking about doing the rest of the hull (in stages) to stiffen up the rest of the hull. It is a massive job (14 metre yacht), but will be well worth it I think.
    A naval architect who surveyed her advised it as well.

  9. #44
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    Default Re: A cold molded overlay over carvel?

    http://www.parker-marine.com/Constru...geImagine.html
    About the most detailed sequence I've seen on the subject, a restoration by Reuel Parker.

  10. #45
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    Default Re: A cold molded overlay over carvel?

    John B is right. I've mentioned elsewhere that Allan H. Vaitses (who also wrote "Lofting") developed a method that uses a mastic to hang plastic planking and then glass that. All detailed in his "Covering Wooden Boats With Fiberglass". It amounts to treating the old hull as a left in male mold.

    It works.

    Quick and dirty methods, to extend an old fishing boat's life for example, include treating the hull as a mold for ferrocement sheathing. This has generally not been cost-effective as the life extension is typically less than a decade.

    What does not work, whether you wood or glass sheath, is thinking the job will be cheap or easy. If you skip steps, you'l encapsulate rot and the job won't last a decade.

  11. #46
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    Default Re: A cold molded overlay over carvel?

    Quote Originally Posted by Ian McColgin View Post
    John B is right. I've mentioned elsewhere that Allan H. Vaitses (who also wrote "Lofting") developed a method that uses a mastic to hang plastic planking and then glass that. All detailed in his "Covering Wooden Boats With Fiberglass". It amounts to treating the old hull as a left in male mold.

    It works.

    Quick and dirty methods, to extend an old fishing boat's life for example, include treating the hull as a mold for ferrocement sheathing. This has generally not been cost-effective as the life extension is typically less than a decade.

    What does not work, whether you wood or glass sheath, is thinking the job will be cheap or easy. If you skip steps, you'l encapsulate rot and the job won't last a decade.
    IIRC, the Vaitses method was applying a heavy layup of glass woven roving and securing it to the victim with a zillion screws. I had the sense that it was effective and used mostly to extend the life of workboats.

    Seeman C-Flex was strips, maybe 12" wide of solid glass composite rods embedded in a glass mat&roving scrim. It was used mostly for the first layers of building some ugly one-off workboats.
    Seeman later managed to patent methods of composite infusion, called it SCRIMP, for Seeman Composite... THey've done well with it and infusion is now normal practice inn volume manufacturing.

  12. #47
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    Default Re: A cold molded overlay over carvel?

    Quote Originally Posted by Jim Oppy View Post
    I think I read somewhere that the increase in volume offsets the increase in displacement so boats having this kind of treatment float close to original waterline.
    <SNIP>
    It depends. If the weight of the total overlay (Area * thickness * laminate density) equals the displacement of the immersed overlay (wetted surface * thickness * water density), the boat will float at the same height.

  13. #48
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    Default Re: A cold molded overlay over carvel?

    Quote Originally Posted by JimConlin View Post
    IIRC, the Vaitses method was applying a heavy layup of glass woven roving and securing it to the victim with a zillion screws. I had the sense that it was effective and used mostly to extend the life of workboats.

    Seeman C-Flex was strips, maybe 12" wide of solid glass composite rods embedded in a glass mat&roving scrim. It was used mostly for the first layers of building some ugly one-off workboats.
    Seeman later managed to patent methods of composite infusion, called it SCRIMP, for Seeman Composite... THey've done well with it and infusion is now normal practice inn volume manufacturing.
    Vaitses' method was intended for yachts or cruisers - I don't recall much mention of workboats. Unwoven glass, stapled to the hull and saturated with 3 or so layers of polyester and vinylester (p then v then p), I think. Woodenboat had an article a couple of years ago with a guy who rescued an old yacht in this way.

    Rick

  14. #49
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    Default Re: A cold molded overlay over carvel?

    I don't know why people don't just replace the pieces of wood. Wooden boats are almost perfectly built to have structure replaced bit by bit. There are lots of ways to do it wrong, but you have a template of the piece you are replacing. I worry about burying a problem and hoping that the miracle of epoxy will save the day. That doesn't mean that I haven't glued a split plank back together......
    Halsey Herreshoff stiffened Ragosa by putting a +/- 45 cold molded ceiling inside. He fastened the completed ceiling to the inside of the ribs with srews. This was adequate to replace the diagonal strapping which had wasted away, and didn't require the total disassembling that would have been necessary to replace the strapping. It also maintains the carvel planking and keeps all the structural bits accessible for later replacement/repair. I always thought that was particularly un dumb.
    SHC

  15. #50
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    Default Re: A cold molded overlay over carvel?

    It is right to worry about burying a problem. Every successful sheathing or splining job started with eliminating rot. But replacing rot is not the only issue.

    Every time a boat is refastened - at least every forty or fifty years and sometimes more - you need to go up a size in fastenings. By the second or third time, you're pushing the limit of how big a screw you can put through that frame. Of course, you could replace the perfectly good, not rotten, frame at that point.

    No matter how good your replacement of rot is going, at some point an otherwise sound boat is simply not able to withstand the stresses of hard sailing. At that point, you might choose to go gently, sailing sheltered waters. It's your call.

    But if you have a boat like Wanderer or Cerlew, that might just not be your option. And that's where the effective and honest approaches to sheathing come in.

    Sneer at anything other than original method if you want to stay near shore. Sheath if you want to take your aging darling off soundings.

  16. #51
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    Default Re: A cold molded overlay over carvel?

    Exactly.

    Rick

  17. #52
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    Default Re: A cold molded overlay over carvel?

    What you have been debating is killing a wooden boat. It is much easier and cheaper to replace a carvel boat than to carefully preserve and nurture rot under veneers and frozen snot. If she is that far gone then build a copy and transfer the hardware and name.

  18. #53
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    Default Re: A cold molded overlay over carvel?

    Quote Originally Posted by Dannybb55 View Post
    What you have been debating is killing a wooden boat. It is much easier and cheaper to replace a carvel boat than to carefully preserve and nurture rot under veneers and frozen snot. If she is that far gone then build a copy and transfer the hardware and name.
    Just wondering whether you have ever done that, or just spouting a well worn traditionalist line. It does seem that NZ in particular has some pretty good examples of very old boats which have had substantially extended lives by sheathing.

  19. #54
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    Default Re: A cold molded overlay over carvel?

    Quote Originally Posted by Dannybb55 View Post
    What you have been debating is killing a wooden boat. It is much easier and cheaper to replace a carvel boat than to carefully preserve and nurture rot under veneers and frozen snot. If she is that far gone then build a copy and transfer the hardware and name.
    How many old clapped out carvel boats have you easily replaced?

  20. #55
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    Default Re: A cold molded overlay over carvel?

    If a boat has a nice interior, it probably took more time, money and skill to build than the hull. Yes, a hull alone is "easy" to build. Sheathing, wood or cloth, saves this as well.

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