Using aluminiun masts sections as tranverse structure instead of bulkheads

Discussion in 'Multihulls' started by Roni, Jul 20, 2020.

  1. fallguy
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    fallguy Senior Member

    There is bolting. However, there are other methods such as those used by Wharrams like lashing which also can work. You can also use strapping like the strapping I showed, but from the bottom, etc.

    We are using a combination of the above.

    I used rivnuts in the tubes. The nuts are stainless, so we do expect some galvanics. How much is the big question.
     
    Last edited: Jul 23, 2020
  2. redreuben
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    redreuben redreuben

    Someone mentioned tubes, yes lots do it, ovals are easier to clamp however as they don't rotate, also with mast sections you can utilise the luff groove for trampoline attachment if applicable.
    For clamps I would use composites and epoxy rather tham metal to avoid any possibility of electrolysis or galvanic corrosion.
     
  3. fallguy
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    fallguy Senior Member

    we have a rubber spacer so the strapping is isolated, but close to the section

    do you think rubber spacing will be enough?
     
  4. redreuben
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    redreuben redreuben

    I'm not an expert but I'd say yes.
     
  5. brendan gardam
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    brendan gardam Senior Member

    My inter 23 is 45 years old and lived on a mooring for years. The 2 sliding beams are fitted with stainless steel saddles and fixed beams are bolted. There is very little corrosion.
     
  6. brendan gardam
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    brendan gardam Senior Member

  7. fallguy
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    fallguy Senior Member

  8. Roni
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    Roni Junior Member

    Rivnuts seem easy to install, i like that.

    Regarding the strping I was wondering wich would be better the bridgedeck on top or under the beams. I'd feel more confortable with the bridgedeck sitting on top of the beams, but then they would be stiking out underneath and that doesn't fell sound. With the beams on top I'd get a flush bridgedeck underneath, but the load through bolts in tension
     

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  9. brendan gardam
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    brendan gardam Senior Member

    Yes. It was moored in salt water for decades.
     
  10. brendan gardam
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    brendan gardam Senior Member

    With the outboard raised there is no metal anywhere touching the water. That's probably why it hasn't corroded.
     
  11. fallguy
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    fallguy Senior Member

    I am thinking about a lightening system. I think that uses grounding plates. Hmmmmm
     
  12. fallguy
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    fallguy Senior Member

    Our cabin is probably 2 tons. The only option is to set it on with a crane. I'd avoid the load in tension idea. There are saddles that cradle onto the beam to even out loading. A point load or kinking from the strapping would be a critical failure.

    To deal with the issue of the bdeck not being flat, we use plates or for the middle beam; it is raised up a step and exposed to the sea above the bdeck or in a stepped bdeck if you prefer.

    I am probably getting way out too far here on disclosures.

    You can see details of my build here in a public forum. That way I am avoiding getting into troubles with Richard.

    Woods Skoota 32DM - Bateau2 - Builder Forums https://forums.bateau2.com/viewtopic.php?f=12&t=62495
     
  13. brendan gardam
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    brendan gardam Senior Member

    I have not seen lightning conductors fitted to powerboats.
     
  14. fallguy
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    fallguy Senior Member

    The reason is the operator position is a high helm and the cabin is beneath it, so it is for occupant safety.
     
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  15. Roni
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    Roni Junior Member

    Yes I agree the load in tension is not a goad idea, it never felt quite rigth.

    Thanks a lot Fallguy. I hope I didn't get you into any trouyble. I'll have a look at the you posts on the construction. Send my regards to Richard
     
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