A Question About Planking

Discussion in 'Wooden Boat Building and Restoration' started by Windship277, Jul 7, 2017.

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  1. Angélique
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    Angélique aka Angel (only by name)

    Maybe some of this info also can be found in the below linked Lloyd's Rules 1919 - 1948 . . .


    ‘‘ Lloyd's Rules
    Here are the scantlings for building International Rule yachts, 6, 8 and 12 metres, covering the years 1919 - 1948. These rules also cover the building of these yachts beyond these years in the methods described. These files comprise all of the sections and tables.


    -- PDF links --

    1) - Title, Preface, Index - 4 mb

    2) - Surveys for Wooden and Composite Yachts, Rules for the Building and Classification of Yachts - 7 mb

    3) - Composite yachts having steel frames and wooden planks, Tables 1 - 8 for Wood Yachts - 6 mb

    4) - Composite Yachts - Tables 9 - 15, Anchors - Table 16 - 1 mb

    5) - Wood Yachts - Metric System - Tables 17 - 24, Composite Yachts - Metric System - Tables 25 - 32, Proving Establishments - 2 mb ’’

    Note: I've added a P.S. to my previous post with a guide to YouTube video subtitles in many languages.
     
    Last edited: Jul 14, 2017
  2. TANSL
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    TANSL Senior Member

    @Angélique, I have nothing to do with Enavales. Those videos have been published without my authorization and therefore I am not responsible for anything in them shown. In addition, they are very old. The program has evolved a lot since then.
     
  3. Angélique
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    Angélique aka Angel (only by name)

    Jeez.. I'm glad you cleared that up, I'd always thought Enavales was your second company, thanks !
     
    Last edited: Jul 15, 2017
  4. latestarter
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    latestarter Senior Member

    @TANSL interesting website and gallery.
    For your reading list I recommend "The Elements of Boat Strength for Builders, Designers and Owners" by Dave Gerr, it covers most materials and techniques.
    Also by the same author "The Nature of Boats" interesting and well written.
     
  5. TANSL
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    TANSL Senior Member

    Thanks, latestarter, I'll try to get those books. I have heard them mention a lot, I know they are very good. At the time they were written they were an indispensable reference. I suppose that modern methods have surpassed them a little but represented the state of the art at that time. Perhaps the author have updated them over the years. I'm going to look for them with interest.
     
  6. TANSL
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    TANSL Senior Member

    Accepting the model proposed by laterstarter:
    - Lapstrake = plate with 2 fixed edges and 2 simply supported edges
    - Carvel, glued seam = plate with 4 fixed edges
    And using the equations provided by the plate theory to determine the maximum sigma in a panel, I performed the exercise shown in the attached file.
    I do not think anything about it, I leave it to your free interpretation and, if anyone wishes to comment on it, it will be welcome.
    (If I have been wrong again, do not hesitate to say so. Thank you.)
     

    Attached Files:

  7. DCockey
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    DCockey Senior Member

    Latestarter suggested glued lapstrake, not glued carvel, could be thought of as a plate with fixed edges.

    Glued carvel planking is rarely used.
     
  8. gonzo
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    gonzo Senior Member

    TANSL is demanding formulas for rules of thumb, which shows lack of understanding. These rules are based on ratios and don't offer any engineering first principles background; they are what they are. Further, they work well, which is all that matters for shipwrights, sailors and owners alike.
     
  9. DCockey
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    DCockey Senior Member

    My understanding is the scantling rules in "The Elements of Boat Strength for Builders, Designers and Owners" by Dave Gerr were developed by Gerr, and the basis for the rules is not readily available. I'm not aware of any independent assessment or review of the rules.
     
  10. DCockey
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    DCockey Senior Member

    What would be the cause of that limit?
     
  11. TANSL
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    TANSL Senior Member

    @David Cockey, The paragraph that I transfer below does not have an easy interpretation for me:
    According to him I have interpreted the model that I developed in the example. Perhaps, I do not doubt, another interpretation is more correct. I would like to know, if you are so kind, the model you would pose for an exercise like the one I have proposed, or similar to it. Thank you.

    With all due respect, Gonzo, behind every formula there is always an engineering process that the author has developed. IMO it is impossible to arrive at a formula if an analysis of a problem has not been made, if a model of the problem has not been created, and if have not been used a mathematical formulas that describe and simulate it. That is my conviction.
     
  12. PAR
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    PAR Yacht Designer/Builder

    TANSL, is correct, for the most part, in that rules of thumb are based on theory and engineering, though often, particularly the older versions used observation. A good example was the "best yacht tender" contest that ran about 100 years ago, between several well noted builders and their in house designers. The typical tender at the time was carvel or lapstrake over bent frames and ranged in length from 7' to 10'. These needed to carry a load, tow at displacement speed, they needed to be especially light, yet a robust build, plus several other design considerations. It's generally accepted the Lawley was one of the best and it was built in both carvel and lapstrake to the same lines. The carvel always had slightly less capacity, but still was surprisingly light. Comparatively the carvel version had bent frames on 7" centers, while the lapstrake

    [​IMG]
    the carvel Lawley (12')
    [​IMG]
    the 8' lapstrake with its obviously much wider frame spacing (about 14")
    [​IMG]
    of course the glued lapstrake with the absence of frames.

    Formulas and engineering were performed in the development of these little boats, but mostly they whittled down the scantlings until it was too light or frail and they beefed them back up to suit. This would be typical of the old rules of thumb, though many did use calculations, likely an equal amount just used what they discovered would work.

    The reason I mention the Lawley is it's very difficult to design a small craft to meet the attributes these puppies had to meet. Small, light and strong structures need some serious thought, to get right and the race to develop these little dinks was intense, well thought out and the best of the best, managed to come up with the lightest, most durable and most capable, using both wildass guessing and some engineer too.
     
  13. latestarter
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    latestarter Senior Member

    @TANSL you will be pleased to know Garbine Mugurutha won the Wimbledon tennis championship.

    I am of a similar view to DCockey and Gonzo, pursuing formulas in something this complicated from scratch is a waste of time.
    In Dave Gerr's book he has the concept of a Scantling Number which is defined as LOA x Beam x Depth of Hull divided by 1000 if the sizes are in feet or 28.32 if metres.
    After that he has a whole series of graphs relating the scantling number to different aspects of the design. Why using such a vague number works is beyond me.
    My analogy of considering the plank as a slab with different types of support was to try and visualize how different methods of construction might behave.
    I had no expectation of designing a boat based on that.
    The analogy soon breaks down, if for example the adjacent planks are equally loaded and there is no angle between the planks they all move together and in practice there is no side support at all.
     
  14. Windship277

    Windship277 Previous Member

    Because Im not sure that the clinker is as strong. I dont think it is and the added wetted surface.
    Yes, true enough but do we know how the boat was used? Was it on open ocean in bad weather a lot of the time? Compared to you guys, I know almost nothing about wood boat construction but factors like the mentioned can be unknown but still apply. I have only read that a lapstrake is weaker. I dont know from experience. What WOULD apply as well is the added wetted surface that will deff slow you down and in a small boat on open ocean getting there as fast as possible is very important especially on a coast such as California. The Caledonia Yawl makes prob about 5 knt in force 4. She doesnt plane right?... so her hull speed is her limit. Lots of anchorages are further than 50 miles apart. Thats a day sail. You dont want to get stuck in an open boat in bad weather with nothing to lee but breakers and rather jagged rocks, lol. I have decided that the CY is what Im going to build.
     

  15. Windship277

    Windship277 Previous Member

    The added wetted surface can be the diff between entering a strange harbor or anchorage in the daytime or at night. I dont know what the experience all off you have yet but I have entered strange places at night before I had radar and it was always scarey. Coming in from the sea is a lot of the time confusing even in daylight. How is the clinker build on groundings and encounters with large items that weigh a lot that do not want to move, lol?
     
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