Who's better Skene, Gutelle or Larsson & Elliasson?

Discussion in 'Boat Design' started by Gashmore, Dec 13, 2009.

  1. Gashmore
    Joined: Feb 2008
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    Gashmore Junior Member

    I have been working on a spreadsheet to calculate shroud loads on my 2 spreader continuous rig. I have Skene's long method and the NBS from Larsson & Eliason set up and just added Gutelle.

    Comparing Skene to NBS Skene is about 8% over on the lowers, right on with the intermediate and about 5% over on the cap. That is a fairly comfortable range that I can live with given the different approaches. Comparing Gutelle to NBS however Gutelle is 5% low on the lowers and intermediates and almost 15% low on the cap. I dug out Gedes' spreadsheet from back in '01 and get almost the same numbers as Gutelle.

    My quandary is that I am rigging in Dynex Dux so my choices are 9mm and 11mm for the cap shroud. If I go with the Gutelle numbers I can use 9mm. Skene and NBS say 11mm.
     
  2. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    Sorry, I have only read Skene, but given that his weights are slightly higher leads one to believe you have a higher margin for safety against failure of the rigging.
     
  3. Greybarn
    Joined: Apr 2006
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    Greybarn Junior Member

    You may want to check the stretch of your "synthetic" shrouds against rod or wire. I thought that the "synthetics" usually get sized for the stretch while rod or wire are sized for breaking strength.
     
  4. Gashmore
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    Gashmore Junior Member

    Actually the creep rate is critical rather than stretch and therein lies the problem. If I design for creep using Gutelle 9mm will be just under the creep limit and the stretch rate will give the mast a nice even bend to leeward. Using Skene 11mm is required to control creep but the stretch is so low that, should Gutelle actually be correct, the mast makes an S curve with the top section bending to windward.
     
  5. dskira

    dskira Previous Member

    I had the chance to know Gutelle. A great man. He was living in Paris, and it is on the same trip I went to see Uffa Fox, also living the winter in Paris.
    Pierre Gutelle was a very shy man, with a great talent, and an eye to understand the plywood constrution.
    The three books are very different, depending the kind of boat you want to design.
    But the best is to have your own desision and take the book just as a guidance.
    Lloyd's will still the reference anyway.
    As for the rigging the Euler method, is used by all. And from that you can choose the different opinions.
    In matter of boat rigging, we still in a grey area, since we can't rely on static calculation. One day the boat sail by force 1, and other time in a tropical storm.
    Uffa Fox method: The shroud should be on one side enough to lift the boat. Period. It worked very fine, and took one minute of research for the right cable. Double the diameter of the shroud for the turnebukle and you are in business.
    Cheers
    Daniel
     
  6. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Interesting, I use a similar, simple formula for cruisers, which is a multiplier of the boat's full up displacement.
     
  7. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    PAR...Question:

    I recently came into possession of a 200+ ft roll of 7x19 316L stainless 3/16" wire rope...Off the top of your head, what general size boat Length or displacement or both would use this sized wire as standing rigging? Or perhaps more appropriately...mast height and SF. I am sure it is larger than anything I would contemplate but just to give me an Idea.
     
  8. Greybarn
    Joined: Apr 2006
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    Greybarn Junior Member

    On the 29 foot sailboat we build (about 4,400 lbs lightship with 1,958 pounds of ballast) we use 1/4" 1x19 SS wire for the side shrouds and headstay. This is on a 1 spreader, fractionally rigged mast. We could maybe use 3/16" for lower but it is borderline on being too stretchy. Something like a Dragon, Etchells or Atlantic use 3/16" wire.
     
  9. dskira

    dskira Previous Member

    4000 lbs
     
  10. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Close enough Daniel.

    Steve, you will not see this on more then a boat in the Catalina 22 class (a fat ton). Even though it's breaking strength is around 4,000 lbs. you could exceed this pretty easily on a 3,000 lb. boat in a pitching sea. Of course it would be nice if this was the weak leak, but it's usually not and typically a much smaller part, like a screw head, tang hole or clevis.

    Nice find, you wouldn't happen to need to mail it to central Florida for winter storage would you?
     
  11. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    Sure...the wire gets a tan and I freeze my gronicles off. Nope...it'll have to endure the cold j u s t like Me. Thanks for the info tho folks...I just might end up having a use for it...eventually.
     
  12. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    Lewisboats, time for a summer holiday.
    Yes, you can now take a nice healthy tan take back home.
    SA is just the place for you to visit.
    First class accomodation in true african style.

    Our well-trained staff is always available to ensure that your stay is as comfortable as possible.
    Your hosts has been in the business for years and their hospitality is without comparison.
    Personal attention to detail will ensure a memorable stay.

    Bring that figgin wire rope with.
    It's going to get stolen if you leave it there... :D
     
  13. lewisboats
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    lewisboats Obsessed Member

    Too bad I'd have to sell the rope...clunker cars...house...kids and precious boat building tools just to afford the trip. I would certainly love to visit someday tho.
    Suppose we should get back on topic or the original poster is going to get a little hot me thinks.
     
  14. Gashmore
    Joined: Feb 2008
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    Gashmore Junior Member

    s'OK. I'm sitting here in Georgia freezing and wondering if anyone in SA needs a boat delivered to the Caribbean. :D
     

  15. terhohalme
    Joined: Jun 2003
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    terhohalme BEng Boat Technology

    I would only trust a method based on maximum righting moment of the boat in fully loaded condition.
     
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