Cross beam material - 11mtr racing cat

Discussion in 'Multihulls' started by Eliseviv, Jan 15, 2011.

  1. Eliseviv
    Joined: Jan 2011
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    Location: Darwin

    Eliseviv Junior Member

    Hello Peeps,

    Recently moved into the world of Cats, and bought a lightweight 11mtr * 6mtr cat for harbour tripping. The basic design is a pair of fibreglass/foam core/plywood light displacement hulls and 3 aluminium "lightpoles" as cross beams. (There is a minimilistic superstructure which I plan on largely removing). She copped a bit of a hiding a couple of years back (beating into a storm) and broke the front cross beam, with some hull damage on the middle beam due to the extra flexing. The hull damage is pretty basic to repair, but I am a little more uncertain in regards to the cross beam repair.

    I have some experience cold moulding CeleryTop Pine mono hulls, and my first thought was to make up 2 suitable crossbeam from laminated timbers and then bond them permanently to the hulls (instead of the bolted and sikaflexed alu poles) Id leave the rear pole as aluminium simply as a matter of economy, annd it seems sound.

    What is the normal convention, should I just buy Mast section to repair it? Has anyone built modern cats cross beams with laminated timbers? If so are they hollow or solid?

    Thanks in advance for any advice.

    Cheers

    Brett
     
  2. Bruce Woods
    Joined: Sep 2007
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    Bruce Woods Senior Member

    Is that the old shockwave 37, ex miranda hi fi, with added chicken coup, that got into trouble returning from the ambon race?. If so I suspect some one on these boards has the construction details for these old gals, or failing that try Gary Mappas at nautical supplies.
     
  3. Eliseviv
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    Eliseviv Junior Member

    Got it in 1 :)

    Its pretty clear how it was first made, just wondering if an alernative to aluminium cross beams is common?
     
  4. jamez
    Joined: Feb 2007
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    jamez Senior Member

    Yep, wooden box beams are common. Usually of ply sometimes timber top/bottom with ply sides - glassed over. Thing to watch though is weight - timber beams are likely to be heavier than alloy. Foam/glass beams with carbon reinforcing would be lighter but more expensive. There is quite a bit of discussion of alternative beams in one of the B24 threads.
     
  5. Billy_Ingram
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    Billy_Ingram New Member

    beams

    use 6 x 12 aluminum rectangular tubing.
     
  6. Eliseviv
    Joined: Jan 2011
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    Eliseviv Junior Member

    Thanks for the comments fellas,

    I took the lazy way out, and having a complete cross beam made up in mast section, complete with all the fittings attached before its sent to me.

    So its effectively the same sized section which is apaprently lighter and stronger than what was used previously.

    But time will tell :)
     
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  7. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Dunno about lazy, sounds like you did the smart thing:)
    Regards from Jeff.
     

  8. Eliseviv
    Joined: Jan 2011
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    Location: Darwin

    Eliseviv Junior Member

    :)

    Time will tell. I also want to be back in the water before April, and If I fluff around too much the wet & dry season will be over and she will still be in the boatyard. Ill get her back in the water with a fresh splash of paint, and then make an assessment on repairs required after a season splashing about Darwin harbour, and have another play over the next wet season in the yard, freshly inspired by a few new anecdotes (and fresh cracks in the paint!)!
     
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