carbon braced tabernacle

  • 02 Jul 2011 06:55
    Reply # 641126 on 608802
    Jeff, just a passing thought as I look at your impressive rig parked up in the desert:
    The trailer is an A-frame. When you get to make a tabernacle for the mast, I'd make a mast-hoisting A-frame that takes the trailer as its template for size and shape, so that it can be lashed neatly onto the trailer for transit and after use.
    In fact, could you make an A-frame to the same size as the trailer frame, and would it then be so big that it could be used as a gantry to lift the mast in and out as it is, with needing to make a tabernacle? You  only need to get a couple of feet above the CG of the mast as it is about to enter the partners.
    When Tystie had a 23ft yard, I used it as a derrick to step the 37ft mizzen mast.
    Last modified: 02 Jul 2011 07:05 | Anonymous member
  • 19 Jun 2011 05:34
    Reply # 624938 on 608802
    Should I have said that 'China Moon' was a catamaran?  'Missee Lee' was 20ft and weighed about a ton.  She had twin keels, too, so was really quite different from 'Sea Blossom'.  But as you say - not that much different.
  • 18 Jun 2011 05:19
    Reply # 624391 on 624259
    Deleted user
    Annie Hill wrote:Jeff - Pete Hill is putting his masts in tabernacles on his new catamaran that he's building.  He did the same on 'China Moon' and I assume they must have worked well if he's repeating the 'experiment'.  Certainly the one on 'Missee Lee' worked a treat, but what works for baby boats doesn't always translate to their bigger sisters.



    At 27 feet and 4 tons + Seablossom isn't that much bigger a sister.
  • 18 Jun 2011 02:26
    Reply # 624259 on 608802
    Jeff - Pete Hill is putting his masts in tabernacles on his new catamaran that he's building.  He did the same on 'China Moon' and I assume they must have worked well if he's repeating the 'experiment'.  Certainly the one on 'Missee Lee' worked a treat, but what works for baby boats doesn't always translate to their bigger sisters.


  • 11 Jun 2011 04:07
    Reply # 618631 on 608802
    Deleted user
    Thanks, Jef, that sounds like a practical approach. It has also occurred to me that having a carbon mast made with the hinge and tube included would be a nice approach. I need to look at the money. Looking online it doesn't look as expensive as I would have thought.
  • 10 Jun 2011 18:37
    Reply # 618177 on 608802
    Deleted user
    Jeff McFadden wrote:
    Seablossom has a wooden mast bolted to the step and very secure.  It is also, at this time, glued to the partners with a horrible substance known as SparTite, but that will be gone when I bring her home and replaced with normal wedges.  This is all well and good - except I want to set her so that I can transport her by trailer once or twice a year without it being a major hassle.  Therefore I am considering cutting her mast in two in such a way as to create a tabernacle, preferably leaving sufficient "stump" out of the deck that I can slip the sail bundle down and not have to remove it.

    My vision is that I would cut the mast in such a fashion that I had two longish sides, or "ears", growing up from the stump, and a blade extending from the round portion of the upper mast that pivoted down between them.  If, as I believe, this is a hollow birdsmouth mast, I will also have to fill and brace the ears and the tongue, probably with wood cut to fit and epoxied in place.

    In order to give this structure sufficient strength to support itself underway, I would stand the mast up, wrap it in plastic sheet, and wrap that in carbon fabric, one wrap, one coat of epoxy, another wrap, another coat of epoxy, and so on until I had sufficient wraps to give me the strength I need, quantity tbd.  It is my expectation that I would taper the layers of carbon toward the upper end so as not to create a concentration of force that might tend to break the mast.  At the completion of the carbon - epoxy application one should be able to remove the plastic sheet and have a freely sliding carbon sleeve over the tabernacle.

    I envision this carbon sleeve slipping upwards to fold the mast.  Given that the mast tapers going that direction that function ought to be automatically available. 

    Comments, anyone?

    Jeff

     Several times I have made a sleeve around tubular constructions and was always surprised  how much  force you need to get the sleeve off,even with a layer of plastic under it. The solution I found in the Gougeon book on boat construction.

    At first you grease the place where you want the sleeve with teflon spray. Prepare a layer or two with wetted glass or carbon and wrap this around your mast, finish with a layer of peel ply  as tight as possible. Next day you cut the sleeve lengthwise with a sharp knive.

    Open the seam as wide as you need to have the fit you want by placing a smal piece of wood in the seam, fill the seam with thickened epoxy. Keep a  plastic tape under the seam to prevent it gluing to the mast.Next day you can check if the sleeve is tight enough and continue with layers of carbon after you have removed the peelply

    Jef

  • 02 Jun 2011 13:22
    Reply # 611270 on 609829

    Webbing Hinge:

    Take, say 4" of old seat belt webbing,  clamp each end between two pieces of wood with 45 deg ends and small gap between each side.  In this case it can then allow 90deg of hinging.  Very cheap and robust for where accurate movement is not required.

  • 02 Jun 2011 00:04
    Reply # 610684 on 610413
    Jeff McFadden wrote:
     if we should choose to try something like the US Great Loop then we would have to create the A-frame, as the mast would need to be raised and lowered on the water for different portions of the journey.
    Now that's a great idea! Just drop Seablossom into the Missouri, and away you go!
    Last modified: 02 Jun 2011 00:04 | Anonymous member
  • 01 Jun 2011 20:38
    Reply # 610539 on 608802
    Deleted user
     http://www.duckworksmagazine.com/11/columns/guest/iron/index.htm sure this isn't the correct thread for this but if you fancy a read and a couple of pics of Junks......I'm still trying to work out how you handle an 11mtr tiller!!! 
  • 01 Jun 2011 17:55
    Reply # 610413 on 609959
    Deleted user
    David Tyler wrote:The Needlespar/Sunbird mast hinge is machined from two pieces of solid aluminium alloy bar, with a fork in one piece and a matching tongue on the other, just as you are proposing. The size, from memory, is about a 1" slot and a 1" pin, for a 4" dia mast. The tube that drops over it is not too tight, and you should also make a slack fit, by using a total thickness of plastic wrap of, say, 1/32" - 1/16".
    When the boat is on a trailer, you can have someone walk away forward on the ground with the halyard, whilst you support the mast athwartships; but if you do it afloat, you need an A-frame with pivot points in line with your tabernacle pin athwartships, to keep the mast under control, and to give you enough leverage. Take a line from masthead to frame, frame to bow. There are pictures of this in many old textbooks.
    I'd hesitate to say "just muscle it up", with a heavy wooden mast.
    Thank you, David.  

    My mast is closer to 8" diameter than 4", and although it will take some figurating to make the layout and cuts to get my hinge, it sounds like I'll be as well off with that as with the cast aluminum one.

    I was intending to go several layers of plastic to create some space, probably not less that 1/16.  When one wraps that gap all the way around it's not much at all.

    The initial use will be while on the trailer.  if we should choose to try something like the US Great Loop then we would have to create the A-frame, as the mast would need to be raised and lowered on the water for different portions of the journey.

    It has occurred to me to put a winch on or near the bow to raise the mast, but I suppose that with a block or two on deck I could lead the halyard back to one of the 2 primary winches, which are all it has.
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
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