reduce catamaran beam

Discussion in 'Multihulls' started by brendan gardam, Feb 11, 2020.

  1. brendan gardam
    Joined: Feb 2020
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    Location: east gippsland australia

    brendan gardam Senior Member

    hi everyone. i have purchased an old crowther international 23 which is in great condition.
    i am toying with the idea of reducing the beam to 10 ft to make it trailerable without having to
    spend hours setting it up at the ramp. i know the sail rig will need new calculations and cutting down to suit. would it still be a reasonable performer with a 10 ft beam . if i was leaving the boat on a mooring i wouldn't consider doing this but i prefer to keep boat at home if possible. in australia we can get oversize permits for daylight travel up to 3.5 mts. just wondering what you think of this idea and if anyone else has done something similar. another option maybe a side tilting trailer like some racing cats use. don't know if thats practical though.
     
    Last edited: Feb 11, 2020
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Welcome to the Forum Brendan.
    When I googled your cat some photos came up which suggest that she is already very beamy for her length - I couldn't find any dimensions, but maybe 14'?
    If so, reducing the beam to 10' will be quite drastic.
     
  3. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    Brendan. You said the oversize permit allows you to trail a 3.5 meters wide or 11.5 foot wide boat. The International 23 in original format was 11.5 foot wide when expanded. No need to cut the beam down at all. Or if you want 10 foot (3.05 meter)beam just push the hulls together do a small screw or bolt to hold hulls at 10 foot. Yes the side shrouds will need to be altered at 10 foot but nothing else needs to change. Just be a little more careful when sailing the 10 foot wide boat. Hope you have fun.
     
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  4. Alik
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    Alik Senior Member

    can You carry the boat heeled, on trailer?
     
  5. rxcomposite
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    rxcomposite Senior Member

    Yup. Saves a lot of trouble.
     
  6. brendan gardam
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    Location: east gippsland australia

    brendan gardam Senior Member

    thanks for the replys. if its only 11ft5 then i don't need to do anything. thanks oldmulti. i thought they were 16 ft wide. i haven't opened it up yet. converting trailer to heel was another option but sounds like i don't need to now.
     
  7. brendan gardam
    Joined: Feb 2020
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    Location: east gippsland australia

    brendan gardam Senior Member

    thank you, i have been a member of boat design forums but not for a few years. i read a post of oldmultis where he stated the 14 ft beam was a misprint.
     
  8. brendan gardam
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    Location: east gippsland australia

    brendan gardam Senior Member

    after looking at the boat expanded out there is no way i would want to tow it like that. the new plan is to narrrow the beam to 2.7mt or 9 ft. i know i will lose performance but i am not a racer and it is still going to outsail most mono trailersailers while sitting flat . i know if i put it on a mooring i won't get enough use out of it . as a proper trailersailer it will get used and i can do all the maintenance at home.
     
  9. brendan gardam
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    Location: east gippsland australia

    brendan gardam Senior Member

    hi old multi, just wondering why you thought the inter 23 was 11'5 beam, i haven't measured it yet but the rudder tie bar is over 12 ft long, would they have altered the beam over the years they were built.
     
  10. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    The original design was a trailable 23 foot cat. Locke designed the boat on that principle. The maximum length of the cross beam therefore could not be any longer than 8.2 foot. The amount of beam left in the fiberglass tubes was at an absolute minimum of 1.6 foot. The very first brochures said 11.5 foot and the two 23's I have seen have that beam. Now it depends on what International 23 you purchased. There was a modified one in Werribbee ? which did not have fixed keels and other mods done by a guy who wanted more performance. No fixed keels equals not standard. Later versions may have been wider or people may have tried to push the hulls out further on the beams leaving only EG 1 foot in the fiberglass tubes. When I spoke to Locke at the time of production he said wider beams may be able to be done but he did not predict a long life and there was minimal safety margins in the fiberglass tubes, that the beams were inserted into, if you still maintained the 8.2 foot beam. The E8150 crossbeam was OK, it was the tubes that they inserted into was the problem. If the aluminum beams are 8.2 foot and the fiberglass cross beam support tubes are 4 foot you have a "standard" boat otherwise you have a later or modified version.
     
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  11. brendan gardam
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    Location: east gippsland australia

    brendan gardam Senior Member

    thanks for the quick reply . it amazes me how much knowledge you have about cats and willing to share it as well. my boat is the one from werribee, named matuka. the previous owner told me he bought it off a guy that did a lot of mods for speed, and it held the race record for the geelong to st kilda race for a while. it has daggerboards and no keels. there are no fibreglass tubes so i guess he must have swapped them for aluminium. the po told me it is 16 ft beam which would be the same as a seawind 24.
     
  12. brendan gardam
    Joined: Feb 2020
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    Location: east gippsland australia

    brendan gardam Senior Member

    1 more question. do you what the hull beams are. i am working on the trailer at home and forgot to measure them when i put it on the mooring.
     
  13. oldmulti
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    oldmulti Senior Member

    Sorry I dont have full details of the Internal 23 at hand the attached diagram may help.
     

    Attached Files:

  14. brendan gardam
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    Location: east gippsland australia

    brendan gardam Senior Member

    excellent. thanks.
     

  15. brendan gardam
    Joined: Feb 2020
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    Location: east gippsland australia

    brendan gardam Senior Member

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