Fiberglass Scantling for Hurricane in Selway Fisher Micro 8

Discussion in 'Sailboats' started by mtumut, Apr 1, 2016.

  1. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Personally I think 8 feet is too short, even if you want to minimize weight and cost.
    I think you want to minimize weight and cost, not length.

    Shorter boats are slower and require more food, so they end up being bigger than something longer. For single handed ocean sailing, minimizing cost and weight, I think you will find that 14 feet is short enough.

    Before pocket cruising, why not coastal dinghy cruising. You might consider building a Mirror Dinghy first. These can be car topped, and can be used for coastal cruising. You can build them in fibreglass or plywood. You could also buy a used one, and then beef it up a little for whatever you want to do with it. What you learn from that, including how to sail, you could apply to your 8-14 foot pocket cruiser for longer voyages

    Here is a forum dedicated to coastal cruising in Mirror Dinghy's.
    http://mirrorsailingscotland.org/index.php?option=com_weblinks&view=category&id=6&Itemid=9
     
  2. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Strength isn't the issue here. The OP is asking how to achieve a given thickness. I think it would be wrong to build to the same thickness in plywood. 1/4" inch thick is a good start. You can always add more layers wherever it needs it once it is assembled. Thicker than 1/4" complicated how you will feather and stitch and fibreglass tape the panels together. It is more important that it remains afloat even with a hole in it, and to have access to anywhere you need to repair. So you need some positive floatation in addition to storage compartments, but you also need to be able to get into all these spaces. Again, I think if the goal is an ocean passage at minimum cost and weight, it would be better to go to a 14 foot design with less displacement. I think designs shorter than 14 feet are done for the novelty of breaking a record, not for reducing cost or weight.
     
  3. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Sorry though, I did mean to use 10 ounce cloth not 6 ounce.
    So...

    1. Cloth + Resin e.g. 340g + 340g = 0.68 kg
    2. Mat + Resin e.g. 450g + 900g == 1.35 kg
    3. Roving + Resin e.g. 800g+800g = 1.60 kg
    4. Mat _ Resin e.g. 450g + 900g == 1.35 kg
    5. Roving + Resin e.g. 800g+800g = 1.60 kg
    6. Mat + Resin e.g. 450g + 900g == 1.35 kg
    7. Cloth + Resin e.g. 340g + 340g = 0.68 kg
    =============================
    Total = 9.96 kg per square meter, and about 6.64 mm thick = 0.26"


    Question: Is 1.5 ounce (450g) mat thick enough to go between two layers of 24 ounce (800g) roving?
     
  4. Westel
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    Westel Senior Member

    Amen to that Mother Theressa :D
     
  5. upchurchmr
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    upchurchmr Senior Member

    It really is a pity that talking on a forum really doesn't let you know what a person is actually like.

    Easy to say or understand the wrong thing.

    No one would ever compare me to her.:p
     
  6. Westel
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    Westel Senior Member

    Someone just did :D

    Bottom line is, if mtumut wants to risk his life in a flimpsy fiberglass boat, it's his life, his responsablility, his choice, no matter what advize has been given/taken. It's up to him........
     
  7. TANSL
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    TANSL Senior Member

    Westel, I agree, it is his life. But worse thing seems to me advising a laminates schedule without knowing at all what the boat, or what he wants to do with.
    Let me be a bit drastic: he can play with his life but we should not play with it.
     
  8. PAR
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    PAR Yacht Designer/Builder

    We do know what the design is, a Selway Fisher Micro 8. A 'glass conversion is certainly possible, though I don't think the OP has any idea what he may be able to tolerate, in the sea state condisions he seems to think this design is capable of floundering in.
     
  9. Westel
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    Westel Senior Member

    Tansl,

    NOBODY can play with his life, he decides to accept the advize or neglect it, it's up to him to go to sea with whatever he decides to build.
    If we go the US road of liability crap than it's better to close all public forums because anything that's being said can make you partial responsible.

    I reckon mtumut is a grown man and can decide for himself what is "safe" or not, to risk his own life.

    I can understand that in his neck of the Woods marine ply might be very difficult to get or insane expencive but I think it still would be better to use a lesser grade plywood, stick to the plans for the build and in worst case scenario cover the hull/everything with a few layers of epoxy/cloth.

    The Tinkerbelle II might be an option for him as it seems a simpler boat to build, probably sails better and if some coastal cruising in good/bad weather makes him happy....well the Micro 8 may be something for him to do the "big work".
    The Tinkerbelle II stands a better chance of selling if all goes not as expected, the Micro 8 will rot away in a yard somewhere....which weekend sailor wants an ungly duck like that :D
     
  10. TANSL
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    TANSL Senior Member

    Westel, of course, neither he will play with his life or anyone, with an advise, will put his life in danger. They are ways of speaking. What I mean is that you can give general advice but say, to the hundredth of a millimeter, and to the hundredth of a kilogram of accuracy, how should he do his ship, it seems very lax.
     
  11. Jamie Kennedy
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    Jamie Kennedy Senior Member

    It would be interesting to look into using some sort of hemp cloth as a coremat. It would be a real challenge to build a Mirror Dinghy first. I would be a lot more challenging because the panel stiffness would be much more difficult to achieve without using marine plywood or exotic core materials. I think the Mirror Dinghy uses only 5mm marine plywood. I know they build them in fibreglass now but they use core material. Are we wrong to assume that core materials aren't available in Turkey at a reasonable price? Probably.

    Nonetheless, hypothetically speaking, for DIY building a Mirror Dinghy for coastal cruising, what would be the best way to replace 5mm or 6mm marine plywood with some combination of basic polyester resin, fibreglass cloth or mat, and some other materials available in Istanbul Turkey at a reasonable cost, like less than say $10 per board foot?

    1. 340g cloth + 340g resin (~0.45mm)
    2. 300g matt + 600g resin (~0.60 mm)
    3. ??? (~3mm) low density core material, if available
    4. 300g matt + 600g resin (~0.60 mm)
    5. 340g cloth + 340g resin (~0.45mm)
    =========================
    Total = 3.16 kg/m2, more than the plywood and we haven't added the weight of the core material yet.

    Alternatively, if we had a coremat type material the mat layers might not be needed

    1. 340g cloth + 340g resin (~0.45mm)
    3. ??? (~4.5mm) partially saturated coremat type material using hemp fabric, or DIY plywood.
    5. 340g cloth + 340g resin (~0.45mm)
    =========================
    Total = 1.36 kg/m2, plus another 2-3 kg/m2 for whatever is used for the higher

    The DIY plywood would require access to a bandsaw. The hemp coremat would be an interesting option.

    My recommendation
    1. Make some test samples from available materials and do some testing. Test samples could be 300mm x 600mm.
    2. Before building a pocket cruiser for ocean travel, build a Mirror Dinghy for coastal cruising.
     
  12. TANSL
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    TANSL Senior Member

    Frankly, I had never thought that having an academic degree could make you less able to build a small boat. What surprises gives life!:)
     
  13. Jamie Kennedy
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    Jamie Kennedy Senior Member

    I would rather discuss boats and boatbuilding, and sailing, and ideas, not people.
     
  14. TANSL
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    TANSL Senior Member


  15. Jamie Kennedy
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    Jamie Kennedy Senior Member

    No worries. So what do you think of the idea of building a Mirror Dinghy for coastal cruising before something heavier, and shorter, for the ocean?

    Also, what would be cheaper alternatives to marine plywood in Turkey, or where you are in Spain? What is the relative cost of polyester, vinylester, epoxy resin where you are? Are core materials or marine plywood relatively expensive. Would DIY plywood be an option for a home builder? What do you think of the idea of using a hemp fabric as a coremat? What are your thoughts on sustainability?
     
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