New build question

Discussion in 'Boat Design' started by Pietr Belosguardo, Oct 27, 2019.

  1. bajansailor
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    bajansailor Marine Surveyor

    Pietr, please take heed of what everybody is telling you in the posts above - they are giving you good advice based on hard won experience.
    Ignore it at your peril - you will only give yourself twice as much work, and four times as much aggravation, in the pursuit of your 'perfect' hull design - which will invariably not meet your expectations in the end.
     
  2. gonzo
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    gonzo Senior Member

    Do an internet search of how many hours it takes to fair the master mold for a car body
     
  3. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    How much difference is between a professional and beautiful mirror like what OP posted originally, and maybe a somewhat shoddy looking "good enough" job? Basically only fairing below the water line and leaving the rest somewhat ugly but functional.
    OP should probably clarify how "similar to" in style and finish it has to be.
     
  4. gonzo
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    gonzo Senior Member

    Why finish the bottom to look pretty, when only the fish can see it? Usually it is the opposite; a nice deck and rougher bottom. However, the bottom is the easier part to fair since it has less curves, hollows, etc. I could do it in maybe 30 hours, but a lot longer for a beginner. Fairing is the job the most experienced boatbuilders/shipwrights get in the shop.
     
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  5. Doug Halsey
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    Doug Halsey Senior Member

    I built the main hull of my 15' trimaran (Broomstick) this way.

    The shape had compound curvature over less than half the surface, but the fairing still took a lot of time. It would have taken even more, except I was unwilling to add more weight in filler.

    My original plan was to build all three hulls this way, but after finishing the main hull, I opted for a simpler ama shape allowing stitch & glue plywood construction.
     
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  6. Doug Halsey
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    Doug Halsey Senior Member

    This technique has been used for a long time. My Dad (Norman Halsey) built my first Moth this way in 1961.

    Because of the curvature, both hull and deck were planked entirely from 1" strips of Styrofoam. He had built something like 50 boats previously, so he was able to do the fairing fairly quickly, but it still seemed like a lot of work to me (of course I was an impatient 13-year-old at the time).
     
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  7. Pietr Belosguardo
    Joined: Oct 2019
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    Pietr Belosguardo Junior Member

    Here is something that could speed things up:

     
  8. fallguy
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    fallguy Senior Member

    I own the flexicat tools. They are good; not perfect.

    For my hulls, the 3' filler is useless. The hulls are not round and thus it is a waste of time to fill with it.

    However, the 3' long board is a great torture tool. It uses abranet and even has vac. There is a platen or stiffening bar on it that I hold in with butyl as it tends to fall out.

    The guy in the video is well trained and makes this work look much easier than reality.

    For a mould; you need to polish it nearly. This filling part is not that. Once filled, you need to sand and sand and then keep taking grits up to something very high so the mould will readily release and shine coming off if you want to look like those Drake rigs. If you build with epoxy; you need a tie coat if you want to gel I think as well.

    So, in addition to the build being fair; you also need to plan the type of finish.

    Most amateurs paint nowadays.

    Then spray or rolling or brushing?

    We rolled on our primer. Looked horrid. So now we are refairing. No lie. We just had too much orange peel from the rollers. A very innocent, but troublesome deal. Used a 3/16" roller, but not foam...not good enough.
     
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  9. fallguy
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    fallguy Senior Member

    We have about 40-60 hours into these small cat steps. The bottom you see is the motorwell. This pic is awhile ago. This was a hand creation once off the female jig for the hulls. The mould for such a thing would be more work than this..and these steps are mainly aesthetics as the boat is outboard and narrow hulls, so walking here is unlikely..

    Anyhow, everytime we look at these steps, they seem to want more fairing compound, but star hull close to done. Custom tools are required. For fairing complex rounds, templating is done. Fortunately, our templates are all flat screeds. For round hulls or features; you need to build templates with curves.

    My point is building a mould is a bad idea for one boat..or here, two even.

    I did build a few moulds. We made a mould for the beaching keel, so moulds can be done, but a whole hull mould would be wasted efforts for the entire hull.
    B2F4B9CF-B0FA-43F1-A2C0-A811FA655820.jpeg
     
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  10. fallguy
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    fallguy Senior Member

    Here is the beaching keel mould. Not a high polish, just brushed on Duratec for the keel bottom of boat.

    CFF8A008-949A-4B4F-B547-75DF7D10533C.jpeg
     
    Last edited: Oct 30, 2019
  11. fallguy
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    fallguy Senior Member

    Here is a female jig with developable panels. The designer created the stations and I had them cnc cut. You would want to do something similar for a foam build. You can do round shapes, but more battens would be needed in the radiuses.

    This is a Richard Wood's design Skoota powercat.

    For your smaller boat; you could build on male or female, but female allows the installation of bulkheads easily, prior to flip. And this was a walk in jig.

    00100AEA-60C3-4A6C-8D4A-66555D2DE8B0.jpeg 450122C4-6D1C-47E4-83E3-09284D03B236.jpeg
     
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  12. Pietr Belosguardo
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    Pietr Belosguardo Junior Member

    Thanks for the info and the nice pictures. Your son looks proud of your work! If a find a design, i will use your advice and start with a female mold instead of a male mold.
     

  13. fallguy
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    fallguy Senior Member

    The designer will specify for you.
     
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