50'+ fiberglass catamaran design plans

Discussion in 'Boat Design' started by mariobrothers88, Mar 6, 2022.

  1. rxcomposite
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    rxcomposite Senior Member

    I do not tab plywood. I glue, screw or nail them.
     
  2. rxcomposite
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    rxcomposite Senior Member

    Where did you get that? That is not in my example posted. That was the purpose of the study. For the same performance parameter, how much will it weigh? I think you missed the point.
     
  3. fallguy
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    fallguy Senior Member

    I just cited the wrong dimension.

    So, RX. The flat panel, hard chined boat made with ply or frp. The frp would require tabbing is all. Tabbing would mean lotsa fairing.

    I haven't missed any point. Ron needs to consider all factors.
     
  4. rxcomposite
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    rxcomposite Senior Member

    The study was to give an idea of what to expect, not design. I gave it a safety factor of 4, not 3 or 2 as other rules would require. The FS vary depending on the location of the part. To give me a level of confidence, I used a software (image inset) to validate my long hand calculations. I analyzed only the center of the panel as analyzing the edge is design detail (or tabbing as you call it) of end fixity and would complicate the study. There is primary, secondary, and tertiary structure.

    As far as the 40% ratio of the supporting structure is concerned, I am within the range as far as experience and my data analysis shows me. I do cost analysis and material consumption report in my daily grind on boat design. It is also the guiding ballpark used by DG Watson in his Practical Ship Design book which shows value for aluminum, mild steel, and high strength steel. So I am correct and guided by general procedure on shipbuilding.

    So please be patient, I am not designing yet for "Ron" and my design will be highly confidential to the client.
     
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  5. fallguy
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    fallguy Senior Member

    Does anyone know of any vessels built in this way? Hard chine, solid frp panels?
     
  6. Rumars
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    Rumars Senior Member

    I'm sure someone has done it, but it doesn't make much sense, especially on a big catamaran. Direct female molding is the thing for big one offs. Even more return on a cat, sand once for two hulls.
    Here an Imoca 60 as an example, the bottom is single skin:
     
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  7. fallguy
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    fallguy Senior Member

    28,400 man hours...

    can you expound on single skin?

    when I hear single skin; I have visions of flimsy, but these boats are incredible
     
  8. garydierking
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    garydierking Senior Member

  9. Rumars
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    Rumars Senior Member

    Imoca's have a problem with pounding. There are foams that can take it but they are considered to heavy for a raceboat. Newer boats have at least part of the underwater hull (the forward areas) in single skin carbon with closely spaced ribs as stiffeners, some are completely monolithic underwater. The skin thickness is on average around 3mm, depending on hull area even less. The ribs and stringers are either preformed and glued on, wet laminated, or infused with the skin.
     
  10. fallguy
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    fallguy Senior Member

    3mm carbon...how many layers is that Rumars?
     

  11. Rumars
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    Rumars Senior Member

    Depends on what they used exactly and how, the stacks are normally all unidirectional with one woven layer each on the perimeter (abrasion ripstop measure), but it's similar to glass, approx 900g/m2 per mm, or in imperial ~29oz/yd2 per 3/64".
     
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