Carolina flare build and materials

Discussion in 'Boatbuilding' started by lenm, Dec 11, 2014.

  1. lenm
    Joined: Dec 2014
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    Location: australia

    lenm Junior Member

    Hi all,
    Was hoping for some advise from some of the more experienced here. I'm planning to personally build a cold moulded (Male mould) 20ft Carolina flare sport fish boat.
    The design plans specify plywood construction, however if you were to build with no cost constraints, what material would you use any why?
    Should I stick to ply for the classic/traditional approach?
    Or go to advanced composite/sandwich?
    I'm hoping the finish will be immaculate rather than a workboat.
    I guess the boat will be used mostly for coastal/offshore sportfishing. I would also like low maintenance, strong and for it to appeal to majority if I were to sell it.
    Thanks
    LM
     
  2. gonzo
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    gonzo Senior Member

    If I had no cost constraints, I would buy Bryunzeel plywood. If you want to build with a different method, the plans you have won't work. The boat will have to be re-engineered for different materials. As far as the finish goes, it depends on your skill and the amount of work you are willing to put into it. Hiring a crew to fair the hull may be a good investment and only a small percentage of the total cost.
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    If cost was no constraint, then I would use carbon, maybe with a Kevlar or Spectra inner skin for penetration resistance.

    The real point is, you can't simply change build methods and/or materials without re-engineering the scantlings to best take advantage of these materials. For example, a plywood to steel conversion would likely mean the hull lines would require some alteration to accommodate the weight. The same would be true of an alloy or composite build, again to rearrange scantlings and structural reinforcements, indicative of these different material properties.

    Simply put, you can't use the same scantlings from one build type to another and expect a reasonable outcome.

    As for immaculate, flawless finishes, well these take serious skill and lots of labor. In fact, it's nearly all very skilled labor, starting with the mold. Even a pro crew to fair and smooth (yep, they're different) the hull will need more time and materials, for a flawless finish and at that, you still may find, what they think is acceptable, is not a necessarily immaculate finish, just what they think they've been paid to get done.
     
  4. lenm
    Joined: Dec 2014
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    lenm Junior Member

    Thanks Gonzo,
    I have found supplier of the ply you mention which is located not too far from me which is great.

    PAR, if I were to stick with plywood, what is your opinion re skin composition
    I would like to keep the standard glass sheathing/layup schedule as advised on design plan, but incorporate an extra layer of the Dynel fabric you mention in your boatbuilding guide.
    Is this best positioned underneath the glass, on top or in between glass layers?
    I am not concerned about extra weight.
    I can obtain a carbon/kevlar fabric for a good price - is this worth applying purely as a good protection barrier for the timber (below water line).
    The thought of having anything other than a solid laminate (below the water line) concerns me a little (waterproofing and timber rot).
    Thanks for your thoughts.
    LM
     
  5. WindRaf
    Joined: Oct 2014
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    WindRaf Senior Member

    marine mahogany plywood super layered,
    outer skin kevlar glued with epoxy,
    two coats of paint polyurethane coating.
     
  6. WindRaf
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    WindRaf Senior Member

    ah...why:

    - is better never change the matierial of the original;
    - super layered mahogany plywood is the best material that exist;
    - this modern composite wood, like all woods, has only one flaw: the fragility scratch surface. For this the outer Kevlar;
    - the two final hands of polyurethane because the epoxy has no resistance to ultraviolet
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Dynel or better yet Xynole are applied to the outside of a laminate and it's sole use is abrasion protection. Kevlar would be used on the inside of a laminate to offer penetration protection and carbon to add stiffness, neither of these would be a a good choice on your build. Dynel and Xynole dramatically improve waterproofing qualities, over substrates.

    You can make material and/or wood species substitutions, but they need to be evaluated for suitability, such as similar weight, density, modulus, etc., which is why the general recommendation is to follow the plans. With some research and study, reasonable substitutions can be made, but it can get more involved then it might initially seem.

    I'm not sure what this comment is all about.

    It's certainly not based on any facts or industry standards. Again, Kevlar is best on the inside of a laminate, not the outside, though it has good abrasion protection, it's very difficult to fair and frankly, just doesn't offer all the physical properties it can in a plywood molded build. Carbon and Kevlar are best employed in light weight highly loaded structures, other wise are just a costly waste of properties and materials in a build like this.

    It's difficult to go into specifics, without knowing what you're building. For example, what species of plywood would you like to change, what's its application? What design is this?
     
    Last edited: Dec 15, 2014
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  8. WindRaf
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    WindRaf Senior Member

    PAR,

    Maybe you did not read my posts well.
    What does the use of carbon with plywood?
    And what does the kevlar inside?
    A single outer layer of Kevlar has the aim to protect the marine plywood from surface scratches.
     
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    You might need a better translator, as I don't understand you plywood/carbon question.

    Kevlar at the retail level is about $12 per sq. ft. and though effective, not particularly beneficial, except for abrasion resistance on the outside of a sheathed plywood build. This simply isn't putting the physical properties of Kevlar to good use. On the other hand, if the Kevlar is on the inside, it offers considerable penetration resistance, though still not taking full advantage of this materials physical properties.

    On the other hand, if Xynole is employed on the outside, which offers about 6 times the abrasion resistance of regular 'glass cloth, at $2.50 per sq. ft., a much more appropriate and economical approach is employed and this is in keeping with the rest of the structure.

    Simply put, if you have more money than common sense, you can employ fancy fabrics, that cost dozens of times what the rest of the structure requires. Conversely, you can use material choices, more in tune with the nature of the build. In a nut shell, would you put a laminated Kevlar mainsail on a 19th century replica or would a Dacron cloth mainsail be more appropriate.

    You build to the work . . .
     
  10. WindRaf
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    WindRaf Senior Member

    PAR,

    is not traslate problem, is that you are not able tu undertand:
    first - the problem in the title of this thread, and second what i suggested.
    - i suggested dont change the original material, so plywood, - i suggested to use mahogany plywood superlaminated ( but you maybe dont know what it is )...and then protect against surface scratches with a skin of Kevlar.
    A boat built with marine plywood mahogany super laminate, is enormously strong, and lasts one hundred years.
     
  11. PAR
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    PAR Yacht Designer/Builder

    So, enlighten us - what is a "superlaminated" sheet of plywood and why must it be mahogany?

    Why would someone build a plywood boat with a Kevlar sheathing? Have you ever faired a Kevlar sheathing? Why do you think a plywood hull needs to have the expense of a Kevlar sheathing? You can't think of anything more in keeping with this build type?

    Simply put, Kevlar and carbon really don't have a place on the vast majority of plywood builds (98%). No one using plywood, needs Kevlar or carbon, particularly when other materials will serve well and preserve the cost effectiveness of the application. An example of this might be, covering a 48"x96" sheet of $60 plywood with $400 of Kevlar as you suggest, instead of $80 of Xynole as I'm suggesting.

    In the end, this (my assumption) is likely a simple translation difficulty. Then again, you may be right, in that I don't understand my own language syntax, as well as you, nor the materials and properties the industry employs regularly.
     
  12. WindRaf
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    WindRaf Senior Member

  13. WindRaf
    Joined: Oct 2014
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    Location: Italy

    WindRaf Senior Member

  14. WindRaf
    Joined: Oct 2014
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    Location: Italy

    WindRaf Senior Member


  15. WindRaf
    Joined: Oct 2014
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    Location: Italy

    WindRaf Senior Member

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