Aluminium sailing catamaran build

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

  1. Slava
    Joined: May 2021
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    Slava Junior Member

    Thanks a lot Oldmulti and Guzzis3, you really give me some nice ideas in what direction to continue my researching Hope soon will form my wishes and requirements :)
     
  2. guzzis3
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    guzzis3 Senior Member

    Just one more suggestion. Cost the aluminium then cost foam/glass/resin. Check Utek in china as they are the cheapest for PVC foam. You might be surprised at how the numbers fall. It's easy enough to teach yourself fiberglass techniques and plastic boats are pretty indestructable. If the aluminium costs more than glass/foam I'd still go with the latter. 2c...
     
  3. Slava
    Joined: May 2021
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    Slava Junior Member

    I choosed aluminum material due to lower maintenance in future, solid structure and less problems with osmosis.
    I have local welders with experience who can do this job for me.
    Plasma cutting will be on outsourcing.
    Now I'm searching stock plan for around 50f Al open deck bridge with round bilge.
    Unfortunately Bruce Roberts designs are with long bridge deck. If I will not find something proper , maybe I will go to Euro Cat 1500 of Bruce Roberts...
    I like Outremer 51 design , but I guess they will not sell plan only :)
    One more thing, I read about solar cloth using in sails. Do you think it's working idea to charge LiFePO4 battery by solar sails?
     
    Last edited: May 23, 2021
  4. Alik
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    Alik Senior Member

    This is very true. Also composite structure will be much lighter for a sailing catamaran.
     
  5. guzzis3
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    guzzis3 Senior Member

    Fiberglass is lower maintenance. If you use epoxy you have to paint it to keep UV away. Vinylester is unkillable. Polyester can get osmosis but again you can manage that with coatings. Aluminium is susceptible to electrolysis, corrosion. Yes some alloys are less prone but they can all fizz in the right conditions.

    I am not sure an aluminium hull is necessarily heavier in this size range. If it's engineered properly it should be similar to glass.

    I wouldn't touch anything by Bruce Roberts. Search his history.
     
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  6. Alik
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    Alik Senior Member

    It will be for sure heavier if engineered to the same standard. We did cats in alu and in composite, sometimes the same model but in different material. The difference is significant.
    To add, on sandwich cat there is no need for insulation and interior finishing is very easy. In alu, one needs insulation and interior panels to cover all those stiffeners.
     
  7. waterbear
    Joined: Mar 2016
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    waterbear Junior Member

    You might consider consulting Richard Woods for advice on selecting a design. Richard doesn't offer any designs in the size you are interested in, but he does have an enormous amount of experience sailing different multihull designs. He also has 40+ years of experience as a multihull designer and he sits on the ISO buoyancy and stability committee as the multihull expert. His consulting fee is very reasonable and he can help you select a well designed boat (and avoid a poorly designed one).

    Sailing Catamarans - Consultancy Service https://www.sailingcatamarans.com/index.php/consultancy-service
     
    Last edited: May 27, 2021
  8. redreuben
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    redreuben redreuben

    I’d take osmosis over electrolysis any day. as mentioned vinyl-ester resin problem solved.
     
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  9. Iridian
    Joined: Jan 2020
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    Location: MD

    Iridian Junior Member

    You should look into the Mumby 50. The guy who builds the Mumby 48s and Mumby 50s in Thailand also sells the plans for both.



    The video below has a Q&A with how to get in touch with Mumby about his designs.



    Its a high performance cruising alucat with semi-modern lines and a lot shorter bridge deck than the Bruce Roberts design.
     
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  10. Slava
    Joined: May 2021
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    Slava Junior Member

    Nice video mate. And this Cat 48f have light displacement 6100kg. Weather fiberglass cat will be 30% lighter ? I think everything depends on design and Alu Cat can easily be lighter than of fiberglass made. Isn't it?
     
  11. Alik
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    Alik Senior Member

    Not sure if we can trust this number. We did similar 53' cat which was built, alu structure (all in 4mm plates) only was 5400kg, and lightship weight was 8800kg. (In fact, it came out a bit heavier, if fully fitted with genset, some teak, etc.).
     

  12. waterbear
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    waterbear Junior Member

    My impression is there is no weight savings when building a cruising aluminum cat in this size because you need to insulate the boat and then build a full wood and/or fiberglass interior, which adds a lot of weight. In the Mumby Q&A the guy says he knows of three aluminum catamarans, including two Mumbys, sailing with unfinished interiors. I'm guessing the owners ran out of funds during the construction process? Large boats are an enormous amount of work. I personally know three people who self built large catamarans (42ft+) and only one of them finished his boat, the other two passed away after spending far more time building than anticipated.

    If you build in wood or fiberglass you don't need insulation, so you can use the interior of the hull as the interior of the boat, which saves a lot of work. Note the exposed stringers and chainplates in the pics below.

    [​IMG]
    [​IMG]
     
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