Uneven Fiberglass Stringers for Plywood Boats

Discussion in 'Boat Design' started by DouglasEagleson, Sep 29, 2016.

  1. DouglasEagleson
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    DouglasEagleson Junior Member

    http://douglaseagleson.blogspot.com


    I saw the woodenboat show testing self righting of a P.Bolger boat. It is a design from the old days. Dying of exposure in cool May weather is not allowed. So my strong goal is in-tune with enclosing with decks and footwells filled with foam.
     

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  2. TANSL
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    TANSL Senior Member

    I'm probably not understanding you correctly, but a well-sized chine can avoid putting any reinforcement in it.
    On the other hand, puting nails or rivets or any other fixing system passing through the shell is, in my opinion, very bad idea.
     
  3. DouglasEagleson
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    DouglasEagleson Junior Member

    Yes it is rather experimental in intention. It is basically targeted to no chine seams. I see designs without them.

    You are right the nails are a issue. Do they function on fiberglass? Is wood compression necessary to nail usage? Obviously small pilot holes would be drilled for them.

    Its really nonprofessional, but I might try it. Cutting chines is shipwrights work. ergo the no chine boats.
     
  4. PAR
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    PAR Yacht Designer/Builder

    I disagree and/or have problems in a few things here. First, nails or fasteners aren't a bad thing and structural elements have been fastened for centuries, without difficulty. I don't see what's going on other than substituting a chine log for a taped seam. The idea of a composite "chine stringer" (what is that) isn't anything new either.

    I don't see what built in floatation has to do with chine logs or taped chine seams. The only way to avoid a chine seam is on a round bilge hull form. If it's the chine log you're looking to eliminate, well taped seams are well established, proven and seamless, once completed. On my site, I offer ratios for making fillets and taping schedules, based on plywood thickness. These ratios are safe, though a bit much on particularly small craft (canoes and kayaks) or small racers, where every ounce counts.

    Chines don't have to be a chore or even difficult. There's a number of ways to cut them, but my prefered method is to spring battens around the panel perimeters, so they stand off of the molds, rather than be "let" into them. This permits a flush cutting router bearing to ride on this batten, when the time comes. The next step after the batten "line off" is to use stiff board (not corrugated) to pick up the panel shape. I use this stuff you can get at the local big box store and it's intended as a floor saving product, used during remodeling projects. It's a stiff "chipboard" product, cuts easily and it's cheap and acts just like plywood will, if draped over a set of molds. Cut off a piece (it comes on 3' tall rolls) to cover the panel you want to create, stapling or tacking it down to the battens lightly as you go. Now, trace the panel outline from below onto the chipboard. Remove the template from the boat and a perfect tracing of the panel dimensions is in hand. You can cut it, but I don't bother. I just place it on the planking stock and cut both the template and plywood at the same time, saving the trouble. I don't cut to the line, but about an 1/8" outside of it. In fact, you don't need this template step at all. You can just place the planking stock directly over the molds, with enough hanging over all the edges and simply go right to the router, but this takes a bit of bravery most don't have. The router bit will follow the battens and cut a perfect representation of each panel.

    I use this method on lapstrakes and hard chine hulls. It's fast, precise and if you're confident, you can skip the templating process and cut the planking stock right on the station molds.
     
  5. TANSL
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    TANSL Senior Member

    Even rivets have been used, I know, but in cases that are not exactly as indicated by the OP.
    Not everything has been done for centuries nowadays is considered good idea. I have been careful to say "is bad idea" (I did not say impossible or something similar; I did not say it was difficult, on the contrary, is very easy)
     
  6. rwatson
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    rwatson Senior Member

    Metal fasteners through glass chines are a really bad idea.

    You arent even supposed to leave staples underneath an epoxy chine layup, as the metal xpands and works gaps where moisture get in. Metal fasteners are not needed for strength, unless you are crazy enough to try to use chop-matt f'glass as this diagram seems to indicate.

    The idea of building up 1/2" stringer with glass is way redundant from a strength point of view, and why you would want to create moisture/dirt trap in the way of stringer edges when you can have a no-edge fiberglass join escapes me. The comments "messy finish" on the diagram indicates the author is a real novice with f'glass, and has never heard of peel ply or proper layup techniques.

    It goes without saying that you are at least going to completely line the inside of the plywood hull with epoxy and glass, for proper protection, but even if you didnt, metal fasteners allowing water to sit behind an impervious stringer against a plywood hull is going to cause problems. Just look at what happens to timber stringers that have a failed glue line behind them.
     
  7. Petros
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    Petros Senior Member

    I would not fill under deck areas with foam, eventually it will soak up water over time and it will trap moisture and rot the boat from the inside. It will also add a lot of weight.

    A far stronger, lighter, and safer more durable way is to make enclosed water tight compartments (where you would other wise use foam), with simple low cost plastic screw on access hatches. That way you can regularly inspect the inside of the compartments, use them for storage if you want, and get to the inside of the compartment to patch up the eventual seepage the boat will develop as it ages.
     
  8. DouglasEagleson
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    DouglasEagleson Junior Member

    it is just concept. The copper nails would really add strength. Except nails are for planking not plywood. Bolts are not necessarily an invalid alternative. The goal here is to make structural fiberglass chine seams. Taping for waterproofing does not add a lot of strength, just water tight. A proper wood chine is obviously the only correct method.

    It is a personal compromise method for myself.

    Concerning foam. Thanks I forgot moisture issues. My only concern is the quality of plastic hatch plates.
     
  9. gonzo
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    gonzo Senior Member

    Plywood is planking. A wooden chine is one of many methods that works well. For example, metal framing with wooden planking is a very successful method. Stitch and glue forms the chines with fiberglass over a round fillet and also works well.
     
  10. rwatson
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    rwatson Senior Member

    Chines on a Clinker built ( overlapped planks ) are not required on a well designed boat.

    Copper nails ( Roves) are fine without f'glass, but not with.

    F'glass chine logs are an impractical idea for so many reasons.
     
  11. DouglasEagleson
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    DouglasEagleson Junior Member

    I agree it is not to be professionally recommended. If somebody actually made a proper mold for a pure fiberglass chine it would look good enough to recommend. It would have to be a 3D replica though.
     
  12. gonzo
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    gonzo Senior Member

    I agree. A 2D chine wouldn't work well.
     
  13. TANSL
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    TANSL Senior Member

    Sorry, what is a 2D chine and/or a 3D chine?. Could I see an example of both cases?
     
  14. DouglasEagleson
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    DouglasEagleson Junior Member

    It is kind of hard to explain, but it is like taking a normal mold and forming a plank only mold from its surface. Any direction replicating. So it is equivalent to making molds for steam bent planks.
     

  15. TANSL
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    TANSL Senior Member

    I think I'm closer to understanding what it means. Many thanks.
     
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