Old vs New Construction Techniques

Discussion in 'Boat Design' started by wholtzclaw, Aug 31, 2012.

  1. wholtzclaw
    Joined: Aug 2012
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    Location: Florida

    wholtzclaw New Member

    Good evening!

    I have a quick question;
    First, I'm building "Jon Boat" as was laid out in Boat Builder magazine in the 70's.

    While building the stem, it states "fasten the framing to the poorest side of the plywood with glue and 1 inch ringed asbestos siding nails..."

    As the magazine is 40 years old, and adhesives have grown by leaps and bounds, when using Epoxy, would you think it's necessary to use fasteners?

    It's a 10hp outboard powered Jon Boat, and I can't see the stem falling apart unless I hit a log or something, but was hoping to get some experienced opinions.

    Also looking to solicit some input as to general changes in construction since the old "Science and Mechanics" days lol.

    Thanks
    Wayne
     
  2. Petros
    Joined: Oct 2007
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    Location: Arlington, WA-USA

    Petros Senior Member

    the screws or nails hold everything tight while the glue cures. Most adhesives break down over time, and I would hate to find out I exceeded the life limit of the glue while out on a lake when there are no fasteners at all.

    I can tell you from personal experience, many years ago one rather large local aircraft building company had some young engineers arguing exactly the same thing about their new assembly methods of aircraft fuselage skins with high tech adhesivs (many now used on boats in fact). Fasteners are often the source of corrosion from trapped moisture as the fuselage ages. The senior engineers who have been around a long time said no way they will build without fasteners, no matter what the youngsters think about their new adhesives. About 10 to 15 years later, after the "old guys" retired, everyone was very glad they had fasteners installed because the glue bonds started breaking down.

    I would use screws instead of nails, and use epoxy or polyurethane adhesive.
     
  3. wholtzclaw
    Joined: Aug 2012
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    wholtzclaw New Member

    Thanks Petros, that's kind of what I thought; I had already planed to skip the nails and move to stainless steel screws.

    I do think I will space them a little further apart though,...

    Went ahead and sealed up, and framed out the stem tonight; I'll do the transom tomorrow...

    Wayne
     
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    In spite of the issues mentioned, epoxy has proven it's value in the last 40 years. Some old farts like to have some metal fasteners, but the jury has come in and epoxy does indeed hold up in the long term. I'm an old fart and there's surely a part of me, that likes a fastener (nails are nearly worthless) in a joint "just in case", but the engineer in me, who's constantly checking the aging reports of numerous tests, says don't bother, except as temporary hold downs as the goo cures.

    The "1 inch ringed asbestos siding nails" are about as good a nail as you can get, though the PC term for these is now "ring shank" as asbestos siding is long gone. The only time I use these is on light stuff, but nothing that will be tweaked, tensioned, twisted, vibrated, etc. Like all nails, they pull out eventually and leaks start. Screws are far superior and through bolts are used when you just have to be sure it'll stay together.

    If your design isn't intended for encapsulation (coating with epoxy) then you can save quite a bit of effort and money just using epoxy as a glue.
     

  5. Petros
    Joined: Oct 2007
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    Location: Arlington, WA-USA

    Petros Senior Member

    PAR,

    Can you post links to those adhesive aging tests? I would like to see some more current ones, preferably for all common types of adhesives if you know where to get them.

    Thanks
     
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