Coefficient of Scantling

Discussion in 'Boat Design' started by Annode, Apr 3, 2020.

  1. Annode

    Annode Previous Member

    arrogant - adjective
    unpleasantly proud and behaving as if you are more important than, or know more than, other people:
    Hmmm not congruent with your accusation.. conclusion: insult bait to tank this thread. Not biting. Sorry.

    "design a boat PROPERLY" now there is a statement you could debate for 80 pages in your own thread, but not here thx.

    "buy a set of plans" or its implied unstated equivelent "just give up and hire a Naval Architect"
    That seems to be the point of singulatiry in the general responses here from Naval Architects. I may at some point to check MY design. But I am here because I want to do this myself, not because I am a better designer, but because I WANT TO DO IT MYSELF. Again:

    THIS IS WEIGHT ESTIMATION THREAD... not a debate as to why my process is inferior to "proper" design.

    So, Do you have any numbers to post?
  2. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I agree with Bluebell, the number, in decimals, as you like, is: ~ 1.2803029 :D
  3. Annode

    Annode Previous Member

    So I guess its not a serious thing when done by someone that isnt an NA? Then its just a joke? A waste of time? Do you know my backgraound? do you know my qualifications? do you know what I have built? Do you even know what software I use. no. so now whos displaying arrogance?
    Your comments and your attitude indicate that for you, boat design is some mystical art that cant be taught and takes decades to understand to the point where someone can actually whip out a welder and create a boat. Well I respectfully disagree.
    I dont mean to pick on you per se. You represent the attitude I have encountered in many threads I have read on this forum. The vilification Brent Swaine for one, who obviously has not studied engineering yet got built a number of boats. Then there are the Chinese. Ever seen one of their hulls? Theier welds are even porous.

    This thread is just the light entertainment of the day for you right? How much useful information have you posted in your numerous responses?

    Lets see if you can actually contribute something to this black art of designing a floating object in steel, for example, what software do you use that outputs scantling weights?
    Last edited: Apr 9, 2020
  4. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I suppose that you, even having great knowledge of many things, have decided to intervene in this forum or to ask for help on something specific or to exchange opinions, theories, procedures, etc. So in the most conciliatory tone you are using in your closing lines, I want to say that I would be delighted to work with you. I don't want to train you, I don't want to teach you anything, I just want to try to answer the questions that you politely and humbly want to ask here. I will answer you politely and humbly too.
    Answering your initial question again, I will repeat that, in my opinion, that number you are looking for does not exist or that, if it did exist, it would probably not be suitable for current designs. I, of course, have never used similar numbers, nor do I think I will for the time I have left.
    Answering your question about what software I use:
    • MS Office
    • AutoCAD
    • Rhino
    • Maxsurf
    • ARQN
    • DwgTools
    • SCT (scantlings) and MyR (mast&rig)
    each for very specific functions. I also have Solidworks and Inventor but only to be compatible and to be able to exchange information with a client who uses these softwares.
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  5. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Annode, may I offer an observation?
    Everybody on here has been remarkably restrained and polite really when you respond to them with sarcastic remarks when they try to help you.
    Equally, everybody has a limit. Quite honestly I am amazed that anybody is even bothering to try to help you any more.
    Because it is the same predictable outcome with every thread that you have started on here. You remind me of somebody in the news who goes on the offensive big time whenever anybody says something that he disagrees with.
    Please, bear in mind that nobody on here is going to intentionally try to wind you up or offer you false information - if they are going to allocate the time and effort to compose a reply to you you can be guaranteed that they are offering the best possible advice possible, subject to the information that you have initially provided.
    And yes, you do not need a degree in naval architecture to be an amazing boat designer - I have a degree, and I also have former work colleagues who did boatbuilding and drawing office apprenticeships who know far more about 'small' craft design and construction than I could ever hope to learn.
    Equally, you cannot pick up this experience overnight.

    How about now giving us a re-cap as to what your statement of requirements is for your dream boat? And what you expect to do with it? What will your budget be for building it? Will you get an established yard to build it, or will you set up your own yard and manage your own workforce?
    DogCavalry, TANSL, BlueBell and 4 others like this.
  6. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    I completely agree with bajansailor. You want to use this forums wealth of information and experience you don't make up some metric wich you don't even express properly and then get upset when people tell you it's nonsense.

    Publish the line drawing you have and give us at least a minimal SOR. Then people can tell you "my estimate is x tonnes lightweight displacement", "6mm plate is enough", "you need more ballast for that sail area", etc.

    Just to be clear, nobody is offering you shortcuts because they don't know what shortcuts to give you. You keep saying "this is a weight finding thread" but you never once clearly stated what that weight is for. Is it the lightweight or loaded displacement, ballast, all structural elements, hull plate only, etc. You are all over the place and nobody understands what your way of thinking is.
    I can tell you for example that in the days before true CAD designing it was normal practice to specify "trimming ballast" of up to 10% of the total ballast. Or that a conservative way of estimating cruising boat payload is 1 metric ton per head. I have no ideea if that helps you or not because "sailboat between 20 and 40 meters" is about as specific as "car with six windows".
    bajansailor likes this.
  7. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    Okay, I was having you on, but it was two-fold.
    There is no such number in boat design!
    Well, not an established, published, peer reviewed, official, Engineer endorsed, publicly accepted number or ratio.
    It's not a conspiracy against you or the general public.
    Relax, have a beverage.

    Now, if you'd like to proceed in a polite and respectful manner please reread and follow some of the better points in previous posts.
    I look forward to making progress with your ideas.
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  8. messabout
    Joined: Jan 2006
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    messabout Senior Member

    Quote from Annode post.

    arrogant - adjective
    unpleasantly proud and behaving as if you are more important than, or know more than, other people:

    Here's news Annode. Gonzo does in fact know more than many other people. Gonzo works in the trade and has been around the block quite a few times. Several other of the respondents also have some relevant credentials that qualify them to offer sound advice. We will collectively appreciate a bit more civility.

    Ad Hoc, rxcomposite and bajansailor like this.
  9. Annode

    Annode Previous Member

    I think you mean respect...
    1. formal politeness and courtesy in behaviour or speech.
      "I hope we can treat each other with civility and respect"
    1. admire (someone or something) deeply, as a result of their abilities, qualities, or achievements.
    There's a small problem with demanding respect:

    These responses are civil.

  10. Annode

    Annode Previous Member

    OK. I chose the title of this thread because there is no such number defined in marine engineering for obvious reasons. We all know that. so what?
    I know the plating weight, now I need to estimate the framing weight FROM the plating weight.
    I can guestimate the other weights, but I have not deigned metal boat framing before, so I dont have a sense of it.
    To make this a dimensionless number, any competent engineer would simply represent this as a fraction.. thats the definition of a coefficient.

    Why do you want argue about the name of this ratio/coefficient? who cares? I am just looking for an approximate number. Instead we have four pages of intense pushback to the very notion.

    Your number of 1.2 sounded a little low to me. But you stated that is was based on years of experience so I took you at face value. Then you blew all credibility by making my question into a joke for everyones amusement. I have no problem with humor, but not at the expense of credibility. I am left wondering if I can take anything you say seriously, which is a great shame, because if you really do have years of experience, that number would have been very valuable to me and those that follow 10, 20 years from now.
  11. Annode

    Annode Previous Member

    Wow that is some list. I only have Rhino. I need to estimate weight to find the waterline.
    I appreciate your offer of help, but please try to understand I am doing hull design at this point on the design sprial. I dont have SCT, I havnt done scantling design before, and I am not going to park hull design while my head is filled with ideas, to learn all about framing and do a complete "proper" design to estimate the weight (as a proportion of the hull plating), only to change the hull shape and size entirely, and start all over again.

    So, if you really want to help, pretend I offer a $10,000 reward for an approximation of framing weight expressed as a fraction of hull plating weight (not including ballast). I have the utmost confidence that you can do it )
  12. TANSL
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    TANSL Senior Member

    No reward is needed. I am sure that, if you ask for it properly, everyone in this forum will be willing to offer you what each one can do. I can give you the following information :
    • Runabout 10 m length, in wood: shell and deck plates, 65% of the total
    • Recreational trimaran of 7 m length, in aluminum: shell and deck plates, 62% of the total
    They are real figures. There may be opinions against it, but these are the real figures that I can offer. I hope that helps you get an idea, although it should be noted that these figures depend a lot on the type of structure you want to give to your design and the type of boat. A figure between 60 and 65%, for starters, may be correct.
  13. Annode

    Annode Previous Member

    I am not sure what asking "properly" means. If my quesion was unclear, clarification could have been requested :/
    Thank you for those numbers, but they refer to significantly smaller boats and not steel. I dont have the experience to be able to translate those to a steel hull 35-45m long. Is 0.6 - 0.65 reasonable for steel at that length?
  14. TANSL
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    TANSL Senior Member

    The type of material should not influence these proportions and I do not think that the size of the boat will vary much in these figures. It can greatly influence the type of boat and, above all, the structure that you design.

  15. gonzo
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    gonzo Senior Member

    0.6-0.65 what? You need to specify units. Otherwise, to make it unitless, the equation has to cancel all units.
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