Spar formulas from Iain Oughtred's "Clinker Plywood Boatbuilding Manual"

Discussion in 'Boat Design' started by laukejas, Mar 12, 2017.

  1. laukejas
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    laukejas Senior Member

    Hi guys,

    Long story short, I need to calculate how stiff I should build a wooden yard for my lug sail (current yard is too heavy, and obviously too stiff). However, I would not like to guess here. Spar dimensions for traditional rigs are kind of hard to come by nowadays. I was told that Clinker Plywood Boatbuilding Manual by Ian Oughtred has formulas for lug rig yards, as well as for other traditional rigs that I might build in the future.

    I have quite a lot of boatbuilding books, but this specific information is unique to this particular book. I live in Lithuania, Eastern Europe, we don't have this book in libraries, and buying it second-hand from Amazon, with all the overseas shipping, would set me back at least $25, and take months. That's a lot of money for a few formulas, given that the rest of information on Iain's book may be nearly identical to what I already have on my other books.

    I would like to ask, hoping it's not a copyright issue, if someone owning that book could please quote these formulas for me? Maybe even take a picture or two of the relevant pages? I believe that these formulas can be found around page 147. I'm sure they are present in 2004 and 2000 year editions of the book, maybe the 1998 edition too.

    Thank you in advance... Hopefully I'm not overstepping my boundaries here.
     
  2. Richard Woods
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    Richard Woods Woods Designs

    can you not get it from a library? At least talk to your local librarian about what you want.

    RW
     
  3. laukejas
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    laukejas Senior Member

    As I said, this book is not in our libraries. There is not a single copy in the whole country, I checked the catalogs. Think of it as a third world country, and you'll be in the ballpark.
     
  4. laukejas
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    laukejas Senior Member

    So, um... Anybody?
     
  5. PAR
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    PAR Yacht Designer/Builder

    Really, $30 bucks is too much? Go to the "book store" section of this site or any online bookseller and order a copy. You can have it in your hands over night if you're willing to pay for the shipping, if not regular mail can have it there in a few weeks at most. In short, it's unlikely anyone is going to scan the appropriate pages and post them for you, particularly given copyright infringement issues, so the obvious choice is to bite the bullet and purchase a book and have it shipped to your door.
     
  6. laukejas
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    laukejas Senior Member

    Look, I don't really want to sound cheap, but $30 is A LOT of money around here. Especially just for a few formulas that I need. For that kind of money, I could sew a new sail for my boat... Or even set up an entire rig. I hoped that someone would be willing to help out, because all I'm asking for is information, knowledge. Okay, scanning infringes copyright, but maybe someone will be willing to just quote that bit of information... I don't think that would be against the rules... Or so I hope.
     
  7. Nnnnnnnn
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    Nnnnnnnn Junior Member

    I generally suggest to my customers that for solid spars on small boats they use Iain Oughtred's formulas for diameters. We don't seem to be having a rash of broken spars, so they must work pretty well. For a spritsail, the mast would have a maximum diameter measurement between 1/50 to 1/52 of the mast's length above the partners. 99% at half height and tapering to 80% at the masthead. Below the partners, the mast can taper at the heel to 2/3-3/4 of maximum diameter.

    Sprit: Diameter 1:80. Taper: heel 75%, peak 60%
    Boom: Diameter 1:56. Taper: heel 80%-85%, peak 70% (might be able to go a fair bit lighter on a sprit-boom).

    I'm not sure how much you might need to adjust these for a Bird's Mouth construction.


    from here:
    http://forum.woodenboat.com/showthread.php?84994-Spar-Design-Details-Spritsail-Rig&p=1943104#post1943104
     
  8. laukejas
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    laukejas Senior Member

    Thanks, Nnnnnnnnn, but I have already scouted out that bit of info on Wooden Boat Forum, and written it down, just in case. :) But I'm wondering more about the lug rig spar dimensions, since that's the rig of my boat... And I couldn't find proportions for these spars anywhere on the internet, which is why I resorted to asking about the book. I could, of course, copy similar design, and hope for the best, but guesswork isn't exactly my cup of tea.
     
  9. Nnnnnnnn
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    Nnnnnnnn Junior Member

    If you are not building something very original, it's possible to find prototype to your rig, IMHO.
     
  10. laukejas
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    laukejas Senior Member

    Well, yes, and that's what I've been doing up to now, but I'd like to educate myself a little more so that I know the recommended minimums of spar proportions, instead of just copying the prototypes :) For example, Skene's "Elements of Yacht Design" provides a complex formula for a wooden mast, and then simple proportions for other spars: booms, gaffs, spinnaker poles, etc, as well as recommended tapers. That is a very useful starting point. However, Skene doesn't provide any numbers for traditional rigs, like lug. But Iain does, which is why I'm hunting for that piece of information!
     

  11. messabout
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    messabout Senior Member

    Even if a book was free, the potential import duty in Lithuania is beyond belief. True, the book can be had for a fair price from Amazon or elsewhere, but in the end the shipping costs and the import duty would cause the cost to be prohibitive. A book shipped from the US would have a US postal cost of about 27 dollars. No telling what the import duty would be. That is a matter of capricious assessment by the corrupt postal service of Lithuania. Capricious and corrupt being the operative words.

    My experience as to shipping small items to that country have not been a walk in the park. .....Just sayin'
     
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