Free standing masts

Discussion in 'Sailboats' started by Gvidon, Dec 2, 2020.

  1. Gvidon
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    Gvidon Junior Member

    Free standing (usually carbon fiber) masts make a lot of sense. However, for some reason there aren't many sailboats with free standing masts. I can think of Mark Ellis's Nonsuch series, Mr. Tanton with his beautiful Tanton 43 cat ketch, Gary Hoyt of Freedom Yachts and Mr. Herreshoff with Herreshoff 38. Recently, I've come across Ticon 34 designed by Bruce Kirby. It's a cat ketch and it's beautiful and by all accounts a well designed sailboat. Several of Ticon 34's were built and there were plans for a Ticon 44 although I don't believe any of Ticon 44 were actually built. What do you think of this type of sailboats and what do you know of Ticon 34/44 boats?
     
  2. skaraborgcraft
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    skaraborgcraft Junior Member

    I am only familiar with the Freedom range in person. Free standing rigs definately have some advantages, it depends what you want performance wise; the argument against i have heard was the flexiblity of some masts depowering the sail.....some see that as a bonus, but perhaps not when trying to beat off a lee shore. Im not a racer, so feel at home with a free standing mast in a tabernacle, best suited to a low centre of effort rig.
     
  3. Gvidon
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    Gvidon Junior Member

    Well, racers are altogether a different breed. But for a cruising sailboat, I see only advantages in such a rig.
     
  4. bajansailor
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    bajansailor Marine Surveyor

  5. Gvidon
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    Gvidon Junior Member

    Darn, she's beautiful...
     
  6. Ike
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    Ike Senior Member

    Free standing rigs have several advantages but probably the no. 1 is elimination of all that rigging to hold the mast up. By eliminating the stays and shrouds, you reduce wind resistance.

    Many years ago my family had a sail racing dinghy with a free standing mast. By eliminating the rigging, it reduced weight and the mast was able to rotate improving the flow of air around the mast and improving the aerodynamics of the sails. It was really a blast to sail.

    Disadvantages: No forestay sails. No spinnaker. The mast has to be stronger (translation, heavier) . Mast usually bends a lot, but that spills wind in a gust.
     
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  7. alan craig
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    alan craig Senior Member

    The Maltese Falcon has free standing (rotating) masts...
     
  8. tlouth7
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    tlouth7 Senior Member

    A freestanding mast will necessarily be heavier than the equivalent stayed mast and rigging (same height, material, righting moment, margin of safety etc). Of course if the comparison is to a massively over-engineered (edit: over-built) stayed mast then a freestanding mast might work out no heavier.

    The stiffness of a freestanding mast comes to a great extent from its diameter, which must be larger than that of an equivalent stayed mast. For a long time it was believed that this interfered drastically with the airflow onto the luff of the mainsail. Modern CFD is calling that assumption into question somewhat.

    Having two sails, one in front of the other, is an efficient sailplan across a range of conditions (angle of attack and windspeed). A single sail might have greater lift to drag potential, but that will be in a limited range of conditions. Think of how 'planes have single wings, but use slotted flaps and slots when they want to operate at high angle of attack. A forestay is an excellent place to put one of these sails, but then you need a backstay (or raked shrouds) to achieve tension in the forestay, and now you have a stayed mast.

    As well as these logical reasons, there is also the important matter of heritage and tradition: people have been building stayed rigs for ages and are good at it, and customers like them.
     
    Last edited: Dec 3, 2020
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  9. gonzo
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    gonzo Senior Member

    They are not equivalent since the stayed mast is not bending like the self-standing mast. It a mast, or anything else, is excessively heavy and over-built it was under-engineered. Over-engineering would be using aerospace technology on a dinghy.
     
  10. tlouth7
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    tlouth7 Senior Member

    The mast and rigging as a system is carrying the same loads as the unstayed mast, so I think most people would have a good sense of what I mean by equivalent. Over-engineering can refer to making something excessively strong or complex, though perhaps over-built would be a clearer term.
     
  11. gonzo
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    gonzo Senior Member

    The load that a stayed mast carries is usually higher because of its higher stiffness. They are not equivalent.
    As an engineer I make a point of the difference between over-engineering, which means spending time to design for minimal material when it makes an insignificant effect and over-building which means no engineering was used and too much material was added in the hope the structure won't fail. In fact, over-built structures are often weaker.
     
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  12. Gvidon
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    Gvidon Junior Member

    I know that Mr. Kirby is of an advanced age right now. Does anybody know his contact info?
     
  13. Will Gilmore
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    Will Gilmore Senior Member

    My father owned a Freedom 44 named Windwalker. She was a beatiful boat and a pleasure to sail. I like the idea of wire-free deck space, but also thought the larger diameter masts looked a little clunky. Perhaps new materials and Geometry will evolve to allow a free-standing mast to bend and flex or remain rigid at will. Maybe some sort of internal spine and tension cables to adjust the shape as needed.

    Weight can be an issue, of course, but there are models in nature that might help. The way bird's bones, for example, are structured, they achieve strength and light weight from their structural Geometry.
     
  14. Will Gilmore
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    Will Gilmore Senior Member

    Absolutely. Consider the structural loads on the hull added by stay tensions. The compression forces are completely different. Then there are the tension forces on gunnels, transom, bow. All gone with a free standing mast.

    With a free standing mast, it is either deck stepped or keel stepped. Either way, cabin tops and/or deck structures need to resist twisting and bending, not just compression.
     

  15. tlouth7
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    tlouth7 Senior Member

    Stayed masts can be and often are designed to flex appreciably. How about this:

    For a given design righting moment, mast height and material a well-designed freestanding mast will necessarily be heavier than a well-designed stayed mast (including weight of the stays).

    Do you refute that? I'm not saying that there are no advantages to freestanding masts, of course they make sense in many small dinghies for example. For certain combinations of design goals they make sense for any size of yacht. OP however asked why they are not more widely adopted, and I pointed out a valid disadvantage.
     
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