Pointers about my 6.7m sailing boat design (total noob)

Discussion in 'Boat Design' started by ArchiSail, Mar 21, 2020.

  1. ArchiSail
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    ArchiSail Junior Member

    Gonzo, okay I'll refer to it as a drawing if that's what you're supposed to do. I'd still consider it a design, albeit not finished.

    I think it's a bit restrictive to claim that one should not draw a hull before you have all the necessary technical knowledge.
    How are you supposed to find the motivation to learn if your not allowed to draw?
     
  2. gonzo
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    gonzo Senior Member

    That depends on what you want to learn, drafting or boat design. Boat design is largely math and engineering concepts. We use drawings to illustrate the concepts. The problem with your drawing is that is has too many fundamental errors and missing information. For example, what material is the hull built of? Materials limit the shapes an object can be built with. That hull shape, going downwind will broach and capsize. Sailboats, unless very lightly built and designed for planing, will have curved buttock lines and narrow toward the stern; particularly with flat bottoms.
     
  3. TANSL
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    TANSL Senior Member

    Gonzo, how can you be so daring as to try to teach how to design boats?. You may have read many things in this forum and others, but that doesn't make you a boat designer. Stop bothering ArchiSail.
    Who are "we"?
     
  4. ArchiSail
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    ArchiSail Junior Member

    Now, I'm not a naval architect, but I am a designer and architect, and id disagree with you ok that quote. Design is much more the just engineering concepts. Engineering concepts limit the design and can shape the design alot. But design is so much more.
    Fiberglass, possibly some carbon fiber as well. But that's all up for debate and change since it's just a idea.
     
  5. clmanges
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    clmanges Senior Member

    Maybe, but if you look at them you'll see that the hull has enough rocker that the transom is above the waterline.
     
  6. gonzo
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    gonzo Senior Member

    I agree design is more than just the engineering part. However, if the design is not properly engineered and it fulfills its purpose, it is a bad design. Even in architecture, the drawing is not the design but a graphic representation of it.
     
  7. messabout
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    messabout Senior Member

    Archi, you asked for comments about the geometric characteristics of your boat. You said that it is to be a SAIL boat.

    You have drawn a powerboat that itself has some fundamental flaws. What you have drawn has the characteristics of a power boat, not a sailboat. It is conventional to have a mostly straight keel line (as viewed in profile) with the forward quarter of the keel curved a bit upward. If you take out the roundness of the chines in the after part of the hull it will make a better powerboat. Make the aft chines hard not rounded. O.K. that is the shortest of comments for a power boat.

    For a sailboat, what you have drawn is a real dog. Yes it could be made to sail but it would not sail well or fast. Further than that it would "hunt" in even a moderates chop. The transom would drag half the ocean behind it if you fail to get it up at least to the waterline or preferably a bit above the WL. The transom as drawn is too wide. If you put some rocker in the bottom, in order to get the transom above the surface that will be a good start. When the transom is as wide as that, it will drag the corners of the transom when the boat is heeled regardless of the excessive chine curvature that you have shown. . Conventional designs often us some bottom camber, or alternatively, some vee as the bottom approaches the transom. Those are design features that are necessary if the boat is to sail decently. You also need to get the forefoot (front end of the keel) raised almost up to the waterline. If you fail to do that the boat will be very stubborn when tacking and it will be difficult to steer when quartering wakes or waves.

    DO not take these comments as a personal affront. That is certainly not my intention. Your boat, as drawn, needs some major revisions if it is to be as successful as one would hope.
     
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  8. gonzo
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    gonzo Senior Member

    You also need to calculate the weights and moments so the boat floats on her lines. It is not like a house where you can put walls, appliances and furniture wherever is convenient. Anything on the port side needs to be counterbalanced by something on the starboard side.
     
  9. TANSL
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    TANSL Senior Member

    And longitudinally? ... or you designers do not worry about that?
     
  10. messabout
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    messabout Senior Member

    Tansl, the Op told us that he is a "noob" Translated, that word means that he is just beginning to try to design boats and his knowledge is at the beginning stage. No need, at this time, to confuse or discourage him with the more esoteric parts of the process. Thus, no mention was made about lateral or longitudinal trim, CB, CLR, CE, RM and so on.
     
  11. TANSL
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    TANSL Senior Member

    Yes, messabout, I am sure you are quite right. The OP, I had not understood, is a total novice in boat design. So when he is told that every weight on the port side needs to be offset with another weight on the starboard side, I, who am not a rookie in ship design, and want the OP to understand the problem in its full magnitude, feel the obligation to advise him that the same must be done longitudinally. I think this way I help him more than telling him only half the problem. I am sure you agree with me.
    I take this opportunity to thank you sincerely for explaining the meaning of the word "noob" to me. I really did not know and Google translator, in that, has not helped me.
     
  12. ArchiSail
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    ArchiSail Junior Member

    Messabout, great comment and I will take that into consideration. I will try to add camber such that the transom is above the WL.

    I have not yet considered keel designs, although I know I'd like a fin type keel.
     
  13. clmanges
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    clmanges Senior Member

    Be careful not to get too attached to any particular feature yet. Designing a boat isn't like choosing options off an a la carte menu; it's an iterative process, and each feature of it may need to be changed at some point in the design process so that in the final product, every part of it serves a set of desired performance characteristics. And this set of performance criteria is something you need to define at the outset. These things get complicated, too; for instance, if you want it to go really fast, you then have to decide if it's to go fast upwind or down. You might get a really fast boat that's uncomfortable or even punishing to ride in. Everything affects everything else.
     
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  14. Mr Efficiency
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    Mr Efficiency Senior Member

    The drawing creates immediate impression of unacceptable "suck" at the stern, and the bow says "wet as all ****" . I suppose there is some appeal to "I designed a boat", but if there are already well evolved designs that are much better, then it is a case of "vanity, vanity, all is vanity".
     
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  15. Ad Hoc
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    Ad Hoc Naval Architect

    Same MO... :oops:
    Thus, you're first question should have been - rather than jumping in at light speed and also to criticise others - is to have asked - what does 'noob' mean.

    It avoids your endless polemics and and attacks on others owing to your lack of comprehension in the first place. You can't point the finger at other posters for supply only "half" of what you consider a full reply, if you're unable to comprehend the question from the OPs perspective to begin with yourself! Kettle calling the pot black ...

    As it says on any production drawing - IF IN DOUBT, ASK.
     
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