50'+ fiberglass catamaran design plans

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

  1. fallguy
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    fallguy Senior Member

    A 60' boat is going to need a lot of materials, whether core or other, you are close to a full semi load of freight. At some point, logistics of shipping beats logistics of building around shipping logistics.

    You could even build with Plascore. They have a plant in Michigan I believe and that could all be done by hand. Be cautious though; it is resin thirsty stuff and easy to build too dry.
     
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  2. mariobrothers88
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    mariobrothers88 Senior Member

    Yes good point Dan.

    Tansl are you saying that monolithic (pure fiberglass with no core material) is lighter than plywood? My understanding was that it would be heavier to do monolithic compared to ply please correct me if I'm wrong.

     
  3. TANSL
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    TANSL Senior Member

    To have something concrete to talk about, I have made a calculation of a panel on the bottom of a boat. With monolithic GRP it would be necessary to lay a 7.8 mm thick laminate, weighing 4.5 kg/m2, to which it would be necessary to add, in the worst case, as much resin; total, 9 kg/m2. Plywood board capable of withstanding the same design pressure should be 20 mm thick, weighing 12 kg/m2. To that should be added the weight of one or two layers of exterior/interior laminate, which are normally added.
    We are talking about a saving, in weight, of 30%. Another thing is the labor necessary in both cases and the price of the materials.
    It would also be interesting to study the weight of the reinforcements, hollow omega profile in one case and solid wood profile in the other.
     
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  4. fallguy
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    fallguy Senior Member

    Glad you mention reinforcements. If he is building flat panel frp; he needs to add two layers or more of tabbing to the exterior. To fair this out requires even more materials and weight unless workboat finish. Wood probably same.

    with foam core; it can be relieved, saving lotsa weight and work fairing
     
  5. TANSL
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    TANSL Senior Member

    Foam core not always saves weight.
    When working with composites, surprises can be found because it is not as "intuitive" a material as any homogeneous material can be. In FRP you always have to do some numbers until you get the most suitable composition for each case.
     
  6. Rumars
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    Rumars Senior Member

    Your calculations are a little confusing for me. Plywood comes in different densities (kg/m3), okoume 480-530, khaya 600-650, sapeli 680-730. A 20mm panel could just as well weigh 9.6kg.
    Your monolithic laminate is equally confusing. At 9kg and 7.8mm I calculate a density of 1160kg/m3, but that does not fit a 50% fiber ratio.
     
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  7. TANSL
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    TANSL Senior Member

    Regarding plywood, it is conceivable that there may be boards of very different densities. I would not use okumen for a bottom panel, I would use something more resistant. But every designer has his tics.
    Regarding the laminate, these are my calculations which, if I have not been mistaken, are in accordance with the method proposed by ISO 12215-5. As for the matrix, there can be no doubt, I have applied a fiber/resin weight ratio=1.

    Edited : I forgot to clarify that in my laminate, the thickness refers to the dry fiber, without taking into account the thickness provided by the resin (perhaps it would not have been necessary to clarify it because it is well known). Maybe that's why you don't get the same numbers as me.
     
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  8. mariobrothers88
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    mariobrothers88 Senior Member

    I am also very interested in kss. Does anyone know where to buy pvc foam core panels in San Diego?
     
  9. fallguy
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    fallguy Senior Member

    Simple side by side comparisons of panels suitable for torturing would almost always result in foam being lighter. Why argue such a basic concept on the potential for making a 'heavy' foam panel? I think this type of response my friend is why others often tangle with you on the forum. The OP came on here asking about panels of frp, and 'pretended' weight was not a factor. It is.

    I suggested plywood for build speed because he has no mould. He responded by suggesting frp panels. I said it was not done, most likely for weight and the resultant costs. You mentioned reinforcements to which I replied foam can be made to do reinforcements easier and lighter and didn't mention plywood reinforcements might be less, but they may.

    Now you respond with something completely not on topic that foam can be heavier after I support your comment regarding reinforcements (for OPs benefit).

    It is no wonder people get upset with you. Despite having a c.v. and people supporting your very statements; you never cease to be argumentative, and at times with nonsense. Of course a person can make foam heavier! But that is not even generally true. If you build a comparable foam laminate to the ones you specified in the compare; is that heavier? Of course not.

    So frustrating.
     
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  10. TANSL
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    TANSL Senior Member

    @fallguy, frankly, I am unable to understand why you are upset with me. I have not intended at any time to attack or despise you. It only seemed to me that, perhaps, it was necessary to clarify some issue. Perhaps it was all so obvious that my comments were off the mark. Sorry. Nor do I have the impression that the entire forum rejects me. There are people who, in various ways, try to appear what they are not and, yes, they will not be comfortable with my comments. For the rest, I am in favor of discussions and it seems very good to me that someone refutes my opinions and, honestly, I think they always do it very politely.
    Don't be frustrated because of me, please.
     
  11. fallguy
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    fallguy Senior Member

    to clarify, how often is a solid frp versus plywood versus foam for the same vessel, a 50-60' cat, result in foam being heavier?
     
  12. TANSL
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    TANSL Senior Member

    To clarify, at no time have I compared the monolithic with a foam core. Nor have I compared, to my knowledge, foam core with plywood. It
    is very clear that, if it is applied where it should be, the sandwich is lighter than the monolithic one.
    Regarding the other part of your question, I have to say that I don't know. One would have to study both solutions in each case, in each part, of a structure and, furthermore, it will depend on the type of ship and each zone within that ship. My idea is that, in general, a FRP hull is lighter than a plywood hull. I admit discrepancies with this opinion and, if you feel like it, raise a specific case and, with great pleasure, I will study it
     
  13. fallguy
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    fallguy Senior Member

     
  14. Rumars
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    Rumars Senior Member

    Ok, now it makes more sense. I never consider dry fiber thickness only the finished panel, since that is important for stiffness.
    As for the ply density, yes it varies with wood species. What is even more important is that the mechanical properties also change with the species and one can make thickness changes.
    For actual examples of real boat structures we have an excellent thread.
     

  15. TANSL
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    TANSL Senior Member

    Dear and respected @fallguy, what do you mean in post #28?. I can't understand its meaning or its purpose.
    I don't want to frustrate you either, I know I have to be very careful with what I say or how I say it. So please do not see in my words more than an intention to clarify things. Having said this, I think I should remember (not to clarify, because probably everyone already knows) that when working with composites, the thickness may not be very indicative. A large thickness, achieved with a large amount of resin, may be totally insufficient because the resin provides very little resistance to tension/compression. That is why we speak of dry fiber thickness. In fact, the factor to consider is the "t/w" (thickness/weight) ratio. In addition, on many occasions the thickness may seem sufficient, it may comply with the standards, but when analyzing the laminate layer by layer it is observed that in some of them the design load is exceeded.
    What thread are you referring to?
     
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