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Thread: Design Log of a Lug Yawl

  1. #1
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    Default Design Log of a Lug Yawl

    I have always been moved by the pilot cutter hull form but I don't live on deep water or have deep pockets. But I am hoping to build something small with traces of the lines of boats like Mischief.
    20200612_104739.jpgI have been working off and on now for about a year on the design of a half decked 18' lug yawl. I started out with Delftship and moved fairly quickly to paper and pencil and some books. I made some lead ducks and battens and have made 1 paper model, 3 half models, and three flotation models. Making the half models is probably the most enjoying work with your hands and towing the flotation models is like being a kid again. Greg Rossel has a fantastic book on making half models AND explaining how to take the lines OFF from a model with the "Booth Machine".
    I am planning on glued lapstrake hull with 9mm ply. I don't want an engine but I live on a creek on a river in Charleston, SC and our tides are 6-7 feet and I'm still working. If I was on a bay or a harbor or retired, I would probably not put an engine on it.

    In the beginning I put down what I thought were the basic boat requirements for me and my area:
    easy to launch and recover, single axel trailer with guides, quick rig ie lug, swing centerboard and rudder for muddy shallow water, sharp entry for chop (the weather produces some chop but that's nothing compared to the motorboat traffic and wakes which are real boat momentum stoppers, reasonably weatherly - cause tacking back and forth in a narrow creek or river against the current and not making much progress is bad for morale of crew and captain, ability to plane when reaching, easy to reef, comfortable seating but able to stand while steering (some lower back issues), row-ability for short distances not miles, sun/rain protection option - tarp, dodger, solo to 4 people, self recovery possible. likely water ballast tanks vs lead bags.

    The first models I made were aimed at a hull form similar to Ian Proctor's National 18 with the modified lug yawl rig.
    luke-gaff-18-lugsail-yawl-1997-for-sale-fowey-cornwall-united-kingdom-001b.jpg(Plans are not available for that design and I was obsessed and focused (maybe too much) on recreating the boat, "Surprise". But then something caught my eye: Gil Smith's Lucile and it made me think back to the page I bookmarked in Howard Chappelle's American Small Sailing Craft - you may know the one - page 161 Fig 59. Ransom style Kingston Lobster Boat. So I have made a humble attempt to draw a hull with lines similar to those of the Kingston boat (I grew up in Duxbury).

  2. #2
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    Default Re: Design Log of a Lug Yawl


  3. #3
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  4. #4
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    Default Re: Design Log of a Lug Yawl

    Looking good. I've always liked the combination of plumb stem and long overhang at the stern.

    I'm curious, though: What is the functional effect of such a long overhanging stern?

    The plumb stem maximizes waterline length, but the overhanging stern does just the opposite. What benefits does it offer in compensation?

    Edit to add: thanks for posting! I'm looking forward to following along with your design and modeling process.

    Tom
    You don't have to be prepared as long as you're willing to suffer the consequences.

    www.tompamperin.com

  5. #5
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    Default Re: Design Log of a Lug Yawl

    Then see what lines look like on paper
    20200630_192158.jpg
    20200630_192253.jpg

  6. #6
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    Default Re: Design Log of a Lug Yawl

    20200712_145527.jpg
    triangle contraption is "Booth Machine"
    20200724_203905.jpgtrimmed lines down some more and started on flotation model
    20200726_110702.jpg
    0.8 mm plywood

  7. #7
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    Default Re: Design Log of a Lug Yawl

    1/12th scale if I didn't say above
    20200729_214723.jpgset of three
    20200729_214835.jpg
    20200802_193250.jpg
    in a very safe harbor

  8. #8
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    Default Re: Design Log of a Lug Yawl

    Attachment 66640

    Attachment 66641
    sorry for upside down - where's Jack Sparrow?
    Attachment 66642

  9. #9
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    Default Re: Design Log of a Lug Yawl

    Trying to now determine sail area, CoE, CLR, etc and mount on cherry back board
    Attachment 66643

  10. #10
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  11. #11
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    Default Re: Design Log of a Lug Yawl


  12. #12
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    Default Re: Design Log of a Lug Yawl

    currently lofting 1/4 scale. Wrestling with keeping counter with rudder tube vs. shortening counter and more simple hung rudder. leaning towards latter.
    20200808_114616.jpg

  13. #13
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    Default Re: Design Log of a Lug Yawl

    Tom - Thanks. I'm not an expert but I think that the long overhanging stern lengthens the waterline when heeled and also when the boat speeds up and the stern is sucked downwards. The working old sailing and oar oysterboats and fishing boats had angled transoms because they knew when their craft was loaded with their catch they did not want the slow speed that would happen if the stern was digging into the water. Picture rowing an overloaded dinghy with a flat transom - the immersed edge of the bottom of the transom and the hull acts like a water brake.
    20200727_114928.jpg
    20200708_093707.jpg
    20200816_111542.jpg

  14. #14
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    Default Re: Design Log of a Lug Yawl

    Hello Gray Duck,

    Whow! Respect! I love what you are doing. Designing boats with a Half Model, Pencil and Paper must be fun and a very rewarding occupation. When I look at your thread and see your photos I think you found your "Zen" in that what you are doing. I hope you will build "the big one" and find enjoyment in the whole prozess from the first thought to go sailing in her.

    I also started boat design with paper and pencil, so I learned and enjoed it "the real way" too. Switched to CAD just a few years ago. And I always build a model, but on major projects I prefere rc-models sailing.
    My preferences are chined boats and sharpies with modern design under the waterline, perhaps as you know from my raidboat thread here on wooden boats forum.

    What I learned from "paperwork" is that, if you are familiar with a fairing batten and a pencil producing a harmonic hull, you get a feeling for good shapes, what is working and what is not. Well, a half model is not useful for chined boat design so I did'nt used it and never learned it, but seeing you now, Iam a little jealous (smile).

    One little thought to make you think: I know that the waterflow does'nt want to be pushed around too much, so I think your hollow lines at the bow and the exit of waterline are a little too radical. Looking good but are they functional? In todays boats you have no hollows anymore with good reason.


    So have fun and enjoy yourself, Michel

  15. #15
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    Default Re: Design Log of a Lug Yawl

    Quote Originally Posted by gray duck View Post
    currently lofting 1/4 scale. Wrestling with keeping counter with rudder tube vs. shortening counter and more simple hung rudder. leaning towards latter.
    If you go for a transom hung rudder you have to alter the rake of your stern. As this is a heart project it lives from your sence of beauty. Can you cut your stern for practical reasons?

    Michel

  16. #16
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    Default Re: Design Log of a Lug Yawl

    It's obviously a balance. If not for combination of creeks AND ripping tides where I live I would go for overhang and no engine.
    Lofting completed at 1/4 scale. 3"=1'
    20200904_193258.jpg
    20200907_102309.jpg
    and transom swung out from plan
    20200907_103459.jpg
    Build is put on hold for father-son project build of Lillistone's "Fleet"

  17. #17
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    Default Re: Design Log of a Lug Yawl

    This is a fascinating thread, must have missed it last month.

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