Flat panel edges

Discussion in 'Fiberglass and Composite Boat Building' started by fallguy, Aug 2, 2017.

  1. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Building a hard chine catamaran using flat panel methods. Boat has about ...9 chines per hull. Builder has spec'd using tapes on the seams (variety of call outs, not important here).

    When I put glass onto the panels, if I glass right to the panel edges, I won't be able to form the chines very easily, so can I run the glass a bit short to allow for sureforming a smooth radius for tapes?

    The only other alternative is to use a flap grinder for some 300 feet of chine per hull; sending fiberglass shavings into the jobsite.

    Is this a no brainer? How short can I go? Obviously the tapes need to cover the panel fiberglass, but is 1/2" right or less, like 1/4" better? Tapes are 4" or 2" per panel per chine.

    Thoughts?
     
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    What does the designer specify?
     
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Typically you'd round over your edges, before applying fabrics to eliminate this issue. If the 'glass is already on, just round it over, 'glass and all. A belt sander, a roundover bit in a router, whatever you fancy, just get a clean, uniform radius, so the fabric will lay down. As a rule you'd fair the hull (and it's chines) before any fabrics are applied. In a taped seam build, you'd temporarily hold the panels into position, round the edges (corners) then apply tape. Afterwhich, you can apply more fabrics, followed by more fairing to smooth out the transitions.
     
  4. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    When you are flat panel laminating, it'd be hard to get the glass to form around that radius and that radius will be really hard to define that well before joined and all the radiuses are different! I am building rebates into the panels using plastic that is supposed to raise the fiberglass up into the panel rebate (to allow for the tape joint to be faired easily), but I can't imagine trying to form the fiberglass up onto a panel edge radius. All the panels will be finished and bulkheads and bases installed before any exterior work is to be done (full female mould). I could easily grind all the surfaces later, but it'll be a glass filled mess and the glass and epoxy will grind away slower than the corecell. If I finish the panels a tad short, say 1/4", it seams (ha!) like I could pickup a little bit of surface to fair/grind radius easy, and the expense would be the 2" tape would only pickup 1 3/4" of fiberglass. But here is the real bit, if you think about it, I will be grinding away the fiberglass anyway, so what is the difference if I start 1/4" short? Of course, this is only for the outside pieces. The inside glass will be finished to the edge.

    Holy water?
     
  5. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    RW said I could finish the panels a bit short and so did a reputable vendor. This would only be on the outside-inside pieces will be full size perhaps even a bit large. Below the WL, the boat is getting a full layer of glass over the bottom like a canoe. It'll be a little tricky to line things up. I plan to do a 2 1/4" rebate. The rebate strips will be 2 1/8" thick, and we'll finish the fabric 1/4" short. Hopefully the 1/8" difference in the strip and the rebate won't result in air bubbles. I was planning to use masking tape to hold down the strips in the right locations, but perhaps metal foil tape might be a little more forgiving. Thanks to all.
     

  6. UNCIVILIZED
    Joined: Jun 2014
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    Location: Land O' the Great Lakes

    UNCIVILIZED DIY Junkyard MadScientist

    Rebate the core on each panel by half of the width of the tape that'll be used to connect them. Then glass the core as spec'd by the design, followed by taping all of the panels together.
    One thought on this is to make the rebate deep enough so that when the panels have been taped together, there's still a small "low spot" to the chines. Which you then fill & fair with bog/fairing compound. Which makes for much easier work than sanding/grinding glass. And you wind up with a chine at the same level as the panels. Plus using fairing this way, you can use it in conjunction with battens in order to get the faired chines straight (or smoothly curved). Which can be tough at the best of times, especially when on the stiff part of the learning curve.

    I don't know what you're building, but Grainger, & also Schionning, multihull designs in Australia, for example, sell a lot of catamaran kits which are designed from day 1 to be built using flat panel construction. And thus they have lots of chines. So it'd be worth inquiring with folks like that in order to get some pro tips, & or POC referrals.
    You might also inquire with professional, custom yards about this. To possibly even include hiring on, or a few guys, for a bit to help you get up to speed on such techniques. And in some circles there are even pro boatbuilders who travel, in order to work on projects, for, or with customers. Which, some designers have info on said folks.
     
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