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Tabernacle/Mast Pivot Structure

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  • 23 Mar 2017 09:17
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    Reply # 4684717 on 4684665
    Anonymous member
    Chairman JRA wrote:Beautiful workmanship - the man is obviously an artist with steel, but it's the sort of boat that makes me run away screaming!  It's so BIG.  However, what really frighetn me are those hatches.  Very clever and elegant, but can you imagine what would happen if your had your hand over the rim and knocked the piece of wood out?  They would scare the wits out of me.  But what a ship - I wish him only the very best with his venture.
    Already a nine year project, and easily another nine years to go. I have to wonder why people do it. The only conceivable reason is that they want to spend their life building a boat, with the idea of actually sailing it as secondary. The design for those hatches shows a gas strut as part of the hinge, so that they will act like a car boot and close gently - the wood strut is temporary.
  • 23 Mar 2017 08:03
    Quote
    Reply # 4684665 on 4147617
    Anonymous
    Beautiful workmanship - the man is obviously an artist with steel, but it's the sort of boat that makes me run away screaming!  It's so BIG.  However, what really frighetn me are those hatches.  Very clever and elegant, but can you imagine what would happen if your had your hand over the rim and knocked the piece of wood out?  They would scare the wits out of me.  But what a ship - I wish him only the very best with his venture.
  • 22 Mar 2017 08:08
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    Reply # 4682020 on 4147617
    Anonymous member

    An interesting design for a tabernacle on a big steel boat
  • 25 Jan 2017 16:03
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    Reply # 4568053 on 4147617
    Deleted user

    My tabernacles are of steel and made for GRP lamp poles, which are tapered top to bottom. Not the ideal thing, the stress will be concentrated at the top of the tabernacles. I've posted some pictures of the tabernacles. They haven't been in use long enough to declare them a success, but I'm planning an Atlantic crossing later this year and if all three are still standing on the other side, I'll be informing everyone here on the JRA about it. I'm pretty sure they will be, but it would be tempting fate to celebrate just yet.
  • 22 Jan 2017 17:16
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    Reply # 4562151 on 4147617
    Deleted user

    I'm sure others will come in here,  but a tabernacle can certainly be made for a tapered mast.  The question is should you have a mast that tapers all the way from the bottom.  All of the lampposts and flagpoles I've had quoted are straight for the bottom few feet: the rolling technique they use in manufacture on 6063-T6 can accommodate this fairly easily.  

    If you cannot source one,  then I'd make sure that the mast diameter at the top of the tabernacle is at least as large as the spec for max diameter worked out.  Maybe a bit larger since masts actually tend to fail a little above the partners/tabernacle top.  This will mean that the actual base of the mast will be significantly wider than spec. 

    Last modified: 23 Jan 2017 14:34 | Deleted user
  • 22 Jan 2017 15:00
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    Reply # 4561882 on 4147617
    Anonymous member

    The tapered aluminium lamp posts and flagpoles always have a cylindrical lower end.
  • 22 Jan 2017 12:40
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    Reply # 4561766 on 4147617
    Anonymous member

    So if the mast is made from a tapered lamp post, it cannot be installed with a tabernacle?
  • 22 Jan 2017 09:54
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    Reply # 4561644 on 4147617
    Anonymous member

    The mast should be at its largest diameter at the top of the tabernacle, the point of maximum bending load. It can be either parallel or decreasing in diameter below that, but there's no reason for it to increase in diameter.
  • 22 Jan 2017 09:24
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    Reply # 4561623 on 4147617
    Anonymous member

    How about a tabernacle for a tapered mast (tapered all the way from the base to the top)?

    Is this even doable?
  • 17 Jan 2017 17:27
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    Reply # 4552854 on 4547089
    Deleted user
    Phil Brown wrote:


     

    When planning to convert I considered a tabernacle with a midpoint pivot for clearing the cabin and transporting the mast in the tabernacle while staying away from the area of greatest stress at the tabernacle top. This would also provided greater side to side support sooner as the mast was raised and brought into the tabernacle both above and below the pivot. It would require a 2 1/2 sided tabernacle.

     


    With the pivot half way up the tabernacle, , you could put a face on the lower third of the aft side and the upper third of the forward side. That would provide quite of bit of positive stop when it hits vertical, plus some stabilization of the otherwise open U shape.
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