Aluminium sailing catamaran build

Discussion in 'Multihulls' started by Donnavan Wright, Sep 9, 2019.

  1. Donnavan Wright
    Joined: Sep 2019
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    Location: Tom Price Western Australia

    Donnavan Wright New Member

    5A1F12F4-544D-4E8E-AE59-4958D5B494C2.jpeg Good day all you salty legends ! I’ve been searching the internet and came across your page . Being a metal fabricator I have put in a lot of thought about building my own aluminium sailing catamaran , 40 to 45 foot would be ideal . I have access to a cnc plasma and aluminium mig welders . Space not a problem either . Time not a problem either as I’m working an ever 6/6 day roster with a 5 year plan . I’ll be starting from scratch building the gigs and developing templates and so on , my question is do I approach a boat designer or is there a site I can download the study plans , drawings and procedures from ?
     
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  2. oldmulti
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    oldmulti Senior Member

    Hi Multihull Structure Thoughts thread on design net. The flowing pages have some aluminum boat details. Page 5 Banana Split 42 aluminium cat with thick skin. Page 14 Osram 7 48 foot cat, another tri. Page 20 Kat'alu 42 aluminum cat. Also Bruce Roberts does some aluminum cat plans in the size range.
     
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  3. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Here is a link to the thread mentioned by Old Multi.

    Multihull Structure Thoughts https://www.boatdesign.net/threads/multihull-structure-thoughts.62361/

    Kat'alu is post #298. Old Multi had posted their catalogue which I will also add here, as she is a pretty neat design.
    It does help to illustrate though that there is a LOT of work involved in building a cat of this size.

    I think that Richard Woods recommends staying under 40' (or maybe even 35') unless you are building a commercial boat, as the time frame for an amateur builder will literally stretch into years.
     

    Attached Files:

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  4. Alik
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    Alik Senior Member

  5. fallguy
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    fallguy Senior Member

    It is taking me 3 years nearly full time work to build a 32' powercat. The design is complex and my hip failed. Finishing a 40 footer in two years full time work plus overtime is possible, but harder for amateurs, and harder for me as my legs don't operate much past 6:30pm. Richard has a beautiful 36' plywood powercat, but that is like a 4 year build.

    The aluminum could go fast, but not for an amateur. Even making mouseholes is in the learning curve. There is still lots of fitment of non-aluminum that will eat the clock.
     
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  6. jamez
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    jamez Senior Member

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  7. Slava
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    Slava Junior Member

  8. Alik
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    Alik Senior Member

  9. Slava
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    Slava Junior Member

  10. Alik
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    Alik Senior Member

    Use 'Contact' page on website.
     
  11. guzzis3
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    guzzis3 Senior Member

    If you are a really good Al welder and have access to the gear it might make sense. Just remember building the hull is at best 1/3 of the build.

    Also remember the time and cost to build te hulls is proportional to the weight. Personally I have never understood big bridgedeck cats. If you build an open deck cat the same weight you get longer hulls, equivalent accommodation, faster speeds and nicer motion. I guess you do get stuck with bigger rig and more expensive registration and storage fees. A 45' open deck cat would still have massive accommodations...
     
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  12. Slava
    Joined: May 2021
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    Slava Junior Member

    Thank you for advices! Do you know example of those 45f open deck cats? Could you please recommend such designs? What do you think about centerboard?
    I'm considering sail+diesel, or sail+ Electric+ PV engine hybrid Cats.
     
  13. oldmulti
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    oldmulti Senior Member

    Attached Files:

  14. Slava
    Joined: May 2021
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    Slava Junior Member

    Nice design, thank you
    Anything similar around 50f ?
    In their web all above this 39f are monohull...
    I've read some articles about bridge deck clearance of cats, that is also affecting speed. How to evaluate this clearance in the plan of the boat(when choosing design of the future boat )? When buy Cat , easy to measure.
    Recommended clearance is 0.7*LOA in inches. If beam is more than half from the LOA, then clearance must be more than 70% of LOA.
    And yes , this article saying that the shorter bridge deck , the better for the speed.
     
    Last edited: May 23, 2021

  15. oldmulti
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    oldmulti Senior Member

    Slava. At 50 foot you need a good designer as the cost of materials alone will be high. ALIK of AMD designs is a good designer but there are many other designers who can do a good design. The real question you need to ask is what is your real requirements. You can have a simple chine V bottom open 50 foot bridgedeck cat built of 10 mm thick aluminum with minimal framing and tube cross beams. Or you can have a round bilge open 50 foot bridgedeck cat built of 5 mm thick aluminum with a lot of framing and tube cross beams. The more complex the design, the more expensive. There are many stock aluminum cabin bridgedeck designs in the 40 to 50 foot range from many designers. Please understand at 50 foot the design criteria to suit you is often more important than the cost of the design, as the total cost of the boat is going to be hundreds of thousands of dollars.
     
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