Lowerable Mast on 40-45 foot yacht

Discussion in 'Sailboats' started by colinb, May 2, 2009.

  1. ancient kayaker
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    ancient kayaker aka Terry Haines

    I have a small sailboat being finished, and the local lake has several bridges, so I am also interested. Since it is a small boat I think I can just brail up the sail and pick the mast out of the step, but I will check to see if there is enough stability to do that first. I can still put in a tabernacle if I need to.
     
  2. stefan.b
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    Location: Hamburg

    stefan.b Junior Member

    We have a 12.2m (40ft.) mast on a Contest 33 that I lower and raise again while underway. The main feature to make that safe is that the shrouds are hinged in a (more or less) common axle with the mast's tabernacle. Swell from upcoming ships and subsequent motion of our boat is no problem with this system. I see no reason why the setup shoud not be scaled up for a yacht of 45 feet - apart, maybe, from that it is a lot of work to raise the mast by winching it up with a sheet winch. I should install an electric winch, and i would not recommend it for a bigger boat without one.

    Regards,
    Stefan
     

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  3. yipster
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    yipster designer

    thanks for sharing your experience and view stevan.b
    you confirm my thoughts on a A rigged 45ft cat, welcome to the forum :)
     
  4. Erik de Jong
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    Location: Halifax

    Erik de Jong sail freak

    In Holland they had the same problem, in Holland is a lot of water and a lot of cargo is transported by ship. In the late 1890s and the early 1900s they used a lot of "Skutsjes" it is a type of sailing ship without a keel, with daggerboard at the side, very long crago hold (85% of ship length) and they all had a lowerable mast. The could even lower it with the sails hoisted. When they approached a bridge, they lowered the mast a few meters before the bridge with the speed the vessel had, they were able to pass the bridge and after that hoist the mast up immediately. The system used is with a contra weight. A wooden mast (with 1 forestay and two shrouds) I have two pictures of the mast foot. the first one is with the mast in upright position, you can see a peace of wood on the deck, that is a hatch for the contra weight to pass trough. The second picture is with the mast horizontal, you look trough the hole in deck and see the winch.
    http://www.skutsjejongerein.nl/nieuws_2.htm
    The first picture is at "02 august" left below, the second picture is at "2 juni" at the right side.

    You must make some sacrifices to the interior of your boat, but it works :D
    Just google the word Skutsje, you will find a lot of pictures...

    Oh... a skutsje is between 40 and 55 ft long.
     
  5. yipster
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    yipster designer

  6. stefan.b
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    stefan.b Junior Member

    The mast in your example is stepped on the front end of the nacelle. A boat like that could easily be designed in a way, that the mast is just in front of the nacelle. It could then reach down, probably past the beam and below the trampolin and carry ballast there - should not be too hard to work out a solution. The question is, if 'adding ballast' is the proper answer on a catamaran. A system that utilises a spring, or even a hydraulic arangement might be a better alternative.
    The system on your pic just resembles the widespread solution (as on my boat), where an A-frame (here by combining the spinnacker poles) and a pulley are used.
     
  7. rwatson
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    Location: Tasmania,Australia

    rwatson Senior Member

    I came across a 40ft yacht that uses a galvanised steel wishbone, that hinges from the sidestays. I cannot remember for the life of me what the name of the designer is.

    I have done a very crude illustration.

    The wishbone (blue) hinges (green) are mounted at the base of the sidestays (orange) in line with the hinged mast (brown).

    The wishbone (blue) acts as a solid pulpit when the mast is raised, but acts as a cantilever when lowering the mast with a high gain pulley on a stubby bowsprit (black).

    The forestay (light green) is always attached to the point of the wishbone.

    The owner reckoned he could do the 45 foot mast by himself.
     

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  8. ancient kayaker
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    ancient kayaker aka Terry Haines

    Lots of sailboats are still active on the Norfolk Broads in UK:-

    \http://www.norfolkbroadssailing.com/2006-sailing-log-tuesday.htm
    http://www.keeping-up.co.uk/Canals/1960s/Broads7402r.JPG

    Low aspect ratio Bemuda or gaff rig, sometimes loose footed cat rig, mast counter-weighted in a tabernacle, sail stays rigged when mast is lowered. Quanting or poling is sometimes necessary but most boat handlers routinely get under a bridge without poling: when I was there few if any of these boats used engines even if they had them.

    There is probably lots of information on the web and several rental companies that might send you a photo showing the details. I haven’t been there for about 50 years so I don’t remember much more.
     
  9. wardd
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    wardd Senior Member

    couldn't the keel act as a counter weight to the mast or at least an asist?
     
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  10. yipster
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    yipster designer

    bringing the weight down was allway's there but send you some points wardd, thats even better and smart thinking
     
  11. ancient kayaker
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    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    Interesting idea! If you had a centerboard or daggerboard and provided it was at least part-way down at the time, it should be possible to link it to the mast. Has it been done before? One would still need to adjust the board height independently but it sounds do-able and desirable for a boat that encounters bridges often enough to make it worth while.
     
  12. wardd
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    wardd Senior Member

    it could be done in such a way the the cable could be unhooked and either done independently, it's all in the details
    it's just an idea for when just being launched and both are extended
     
  13. colinb
    Joined: May 2009
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    colinb Junior Member

    Hi all,

    Wow, some awesome ideas coming out, and I'm glad to see there is interest from other boaties encountering the same problems. I really like the wishbone idea, hadn't thought of anything like that. At first glance appears to be easily engineered into the cabin roof suitable for retrofit. More sensible and less likely to cause problems than using the boom as a cantileaver. Solid wire rope around a pivot pulley running back to an electric or hydraulic winch should work very well?

    I like it. Could the rigging be incorporated into this system so the entire system remains rigid while being lowered, avoiding the need to retension stays?

    This has huge potential, once again thanks for all the ideas, I believe between us we will solve this engineering challenge!!!

    Col
     
  14. rwatson
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    rwatson Senior Member

    Yes. It isnt clear on my simplistic sketch, but the stays fasten right on the top end of each wishbone arm, so they can rotate while still tensioned.

    The Macgregor 26 uses a similar method of winching the mast down, but you have to attach temporary 'baby-stays' that are in line with the mast hinge.
    The main stays go slack as the mast gets lowered,

    It impressed me to see it on quite a large boat.
     
    Last edited: Oct 8, 2009

  15. stefan.b
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    Location: Hamburg

    stefan.b Junior Member

    I have made some photos at my marina that is located in Hamburg 'behind the bridges', so everyone needs to be able to tackle the mast in one way or another. The wishbone is the way to go if you want to retrofit a system.

    On this kingscruiser 33, the pulley configured as a wire system with an electric winch located in the anchor locker. The system is configured entirely to operate with minimum possible preparation, they just lower and raise the mast in a couple of minutes while underway. The boom is shifted to starbord and usually supported by a small wooden strut connected to the rail, so that the rail wires are not stressed in excess by carrying the booms weight. The mast is supported by a strut permanently mounted to the aft pulpit.
    [​IMG]

    This pic also shows the extended shroud supports, that bring the shrouds pivot-axle in line with that of the mast.


    [​IMG]

    [​IMG]


    This wishbone on another kingscruiser is designed with a low profile to nicely fit on the deck. There is virtually no reduction of forestay lentgh:

    [​IMG]


    Another solution utilizing a rope (six sheeve) for the pulley. When in use, the rope is feeded through the genoa sheet wagon and into the self tailing winch (originally, they guy who owns this boat just retrofitted a small electric pulley winch to his cockpit sill just for this).

    [​IMG]
    [​IMG]


    More rope, a bit better visible:

    [​IMG]

    Here's another one on a motor-sailer with a very high pivot axis and a bowsprit:

    [​IMG]


    We have another boat in the club that has an extra trailer winch mounted to the wishbone that connects the rigid forestay to the wishbone. So the owner is able to remotely disconnect the wishbone from the forestay, once the mast is down and supported by the strut at the cockpit. This way, he is able to reduce the passage height of his boat for another 2 meters, by lowering the wishbone.
     
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