Coefficient of Scantling

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

  1. Annode

    Annode Previous Member

    Well you are making my point. Each one of these boats was designed by a VERY competent NA. They are probably very well built. In the case of teddibear, if you look at the fit an finish, and whats crammed into that boat, its amazing. Jay Benford did a fantastic job. But then you look at the picture and it looks like what it is: 2lbs of cr** in a 1lb bag. Its absurd. The proportion is horrendous. length to width to height.
    Steve Dashaw is a very good NA, yet he designs a very very capable boat that looks like the greenhouse at Kew Gardens crossed with lookout towers from a turkish prison, built by DeLorean. Mind boggling.
    NA school obviously needs a full semester course in art history and sculpture appreciation.
    Would I ask any of these excellent NAs to design my boat... probably not, but I would ask them to take my design and engineer it "properly".
     
    Last edited: Apr 14, 2020
  2. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    If you use the software shown in post 67 you can get something similar to this. It is a valid starting point, in my opinion.
     

    Attached Files:

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  3. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    Yes that's exactly what I mean. Example: small walk in engine room, 2m long, 2m wide, 2m high. This room has a volume of 8 cubic meters and to immerse it completely in saltwater you need it to weigh 8200kg. If you put 4000kg of engine, gearbox, workbench and spares in the room you still need 4200kg to submerge the room. So a simple design choice of wanting to service your engine without beeing a contorsionist either upped payload or ballast.

    Then the resulting boat would look similar to the Jonghert, right down to the decksaloon.

    Aesthetics is a part of the SOR, and a big one. You can rest assured that those boats you don't like had their aesthetics approved beforehand by their owners.

    You are right and wrong at the same time. Yes the above water weight infuences the submerged volume that is underwater, since the boat needs to float. The shape is fixed by SOR. The boat does not decide by itself if it's going to be a full keel with slack bilges. You may be forced into a specific shape by your SOR, that is true.
    The above water shape is a function of your aesthetic and accommodation desires. A "classic" lined boat will have a (proportionally) much lower freeboard than one with modern boxy lines. That means that a good part of the living areas are partially under the waterline (if you want to preserve headroom) wich now forces more volume underwater. More volume underwater means more needed weight to maintain the abovewater optics, either in ballast or structure (see the engine room example). Similarly, if you want long overhangs you either make the accommodations smaller or you lengthen the boat.
    I repeat, yachts are designed by volume, if your SOR says 3 master bedrooms with king size walk around beds and enclosed heads with showers you have to put them somewhere. Now if your SOR also says low freeboard, flush deck with skylights what are you going to do?
    You can of course say "I want the boat to look this way and whatever interior comes out is fine". That is also SOR. But there is no magic coefficient or shortcut trough the initial design process of estblishing a coherent SOR. The only shortcut that exists is copying an existing design and making minor adaptations to it. In wich case you don't need any magic tricks, you need some basic statistics for that specific design and some photos. Then you change the shape of the portlights and move some furniture around and call it done.
     
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  4. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    You keep on complaining because what you expect is not justified by the laws of physics and engineering principles. Your posts deride members of this forum because everyone keeps on telling you your expectations are unrealistic. The magic number does not exists. Your position is that of New Age people that say wishing is all you need and the Universe will provide. This forum is not the best place for that. Scantlings are calculated to satisfy the SOR. You have no SOR. Do the necessary work, and this forum will have answers for you. Whine and complain, and nothing will come from it.
     
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  5. Annode

    Annode Previous Member

    Zzzzzzzzzzzzzzzzzzzzzz
    projection
    noun
    unconsciously taking unwanted emotions or traits you don’t like about yourself and attributing them to someone else.

    a defence mechanism in which the human ego defends itself against unconscious impulses or qualities by denying their existence in themselves while attributing them to others
     
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  6. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Annode, if you want people to help you, it is not very wise to continuously and sarcastically lambaste everyone who offers advice that you do not like.
    Rumars has told you the procedure that you have to follow. Please do listen to his wisdom, and co-operate, and then folk on here will be more inclined to help you in return.
    You are not going to get anywhere by attacking people.
     
  7. Annode

    Annode Previous Member

    and here we go again....
    You are being manipulated by a troll. Ask youself if ANYTHING he posted is relevant to this thread?
    1. You keep on complaining... blah blah blah
    2. you expect... blah blah blah
    3. your posts deride members... blah blah blah
    4. your position is... blah blah blah
    5. You have no SOR... blah blah blah
    6. Whine and complain ... blah blah blah
    Look at that list of pointed accusations that are completely off topic and ask yourself:
    • How much did that contribute to this discussion in general?
    • How much was it realted to WEIGHT ESTIMATION
    • how friendly , civil and polite was that?
    • how many of those statements have I ACTUALLY MADE?
    • how much do think my "position" is really understood?
    • Is this the SECOND time he has tried to assert that the final stage of the design spiral is the only valid process at the start of the design spiral
    • How much does this sound like an angry rant to start a fight until the forum mod shows up and closes the thread.... just like the last two?

    So before you jump in to defend this nonsense, please take a moment and think about how you and everyone else is being manipulated by this blobiating nonsense

    And now I just wasted another 10 minutes of my lfe dealing with trolling on a thread about WEIGHT ESTIMATION
     
    Last edited: Apr 14, 2020
  8. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Annode, YOU are the one who is trolling - everybody else is trying to help you.
    If you want us to help, please co-operate. Supply the info that Rumars has requested - like the elusive SOR and the drawings that you have produced so far.
     
  9. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    I find it interesting that Annode claims the SOR is the final step of the design spiral.
     
  10. Annode

    Annode Previous Member

    I think we have very different ideas of help...
    7 pages to derive a simple weight estimate. please
    You insistence upon dragging this thread into a discussion about the relevance of SOR is an attempt to take it off topic.


    THIS IS A WEIGHT ESTIMATION THREAD

    Not a design spiral discussion thread, or a SOR development thread or anythig else. Nonethelessm I have given a very detailed response to the assertion that an SOR that specifies fine details is the starting point for a design. I have argued for aesthetics. I understand that many engineers here dont do it that way and we are just going to have to agree to disagree on that point.

    So Do you have anything to add to the comments about estimating wieght? YES OR NO?
     
  11. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    No.
    Because there is simply no point. Nobody is going to help you unless you supply the info that they have requested.
     
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  12. Annode

    Annode Previous Member

    [​IMG]
    Aw Jeexe, not this again...


    THIS IS A WEIGHT ESTIMATION THREAD

    Thank you for your opinion. Now could you please go "contibute" to some other thread. thx
     
  13. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    Thank you for the reminder, I will do exactly like you so kindly suggested. I wish you good luck in your quest.
     
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  14. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell "Whatever..."

    troll1
    /trōl/
    Learn to pronounce

    noun
    1. a mythical, cave-dwelling being depicted in folklore as either a giant or a dwarf, typically having a very ugly appearance.
    2. Annode
     
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  15. Annode

    Annode Previous Member

    Sheesh, what are you guys the borg? I comment on 3of9 and his baseless attackes, 5of9 jumps in to respond. I invite 5of9 to either post something on topic or be gone and 8of9 takes offence. Now here is 2of9 with a pointed jab.

    Ys know, you guys are bullies but ya dont intimidat me. You may have been at this longer than I have, but that doesnt make you right on all points, or da vincis of design. You can beat on me all day long if you wnat. It says more about you than me.

    So anyone in the borg hive have a comment about the factor of 3 to scale Jogert with? Perhaps you 3 of 9 ... (that was pun)
     
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