Own design project of A-Cat

Discussion in 'Fiberglass and Composite Boat Building' started by Vector77, Apr 8, 2014.

  1. Vector77
    Joined: Apr 2014
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    Vector77 Junior Member

    Hello,
    my name is Viktor. I'm from Czech Republic (Europe). I'm student of industrial design. But after school I spend most of the time on the boats. Specialy multihulls. Also I work as boatbuilder and dealer of composite products in Czech Republic and Slovakia.

    After few years of experiences with sailing and boatbuilding I decided to build my own boat. After long time of thinking I decided to build A-Cat. So I started to design it... Idea is to build it by Herex/Airex sendwitch technology.

    My friend offer me Herex strips 1000x72 mm to use it... So it means that I would have to use "horisontal planking" system. But with that I don't have experiences. Could you please give me some advise? I found some information on website of catamarans LR5 and LR4...

    I attache a few pictures/renders of hulls for some ideas...
     

    Attached Files:

  2. petereng
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    petereng Senior Member

    Hi Viktor - don't be taken in with the steep reversed bows. Straighten them up a bit. You also need more volume forward unless its a foiler that will be out of the water all the time! If its a displacement design you need to get your prismatic ratio up Cp to 0.65 plus if possible.

    Cheers Peter s
     
  3. Vector77
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    Vector77 Junior Member

    What do you think now?
     

    Attached Files:

  4. petereng
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    petereng Senior Member

    A-Class

    Hi - Looking better. Is it a displacemnt boat or a flyer? The hull line shown is not fair so if its a displacement boat you need to smooth this. cheers Peter S
     

    Attached Files:

  5. Vector77
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    Vector77 Junior Member

    Project is mainly displacement boat... typical A-Cat... but I will build modificated C boards and mix of C and J board... so in future it will be flyer....

    So do you think that bow part woudl be higher then this moment?


    Thanks
     
  6. TANSL
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    TANSL Senior Member

    Viktor, makes no sense to start two different threads for the same boat and same things to discuss. It would be more comfortable for all work with a single thread.
    Contact, if that's okay with the moderator to merge the two in one
     
  7. petereng
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    petereng Senior Member

    Hi Victor - if displacement boat you now need to learn about hydrostatic ratios. You need to look at the beam max, prismatic coeffient, Cb, Cf, sinkage etc etc and decide if they work for your design. Lots to learn, plus how to get fair boat on CAD. The extremely pointy bow won't help you downwind as it will dive, need more bouyancy up front. The Cp will help you understand this. What is the design displacement of the hull? and design weight of boat and sailor? do they match? lots to do Cheers Peter s
     
  8. Vector77
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    Vector77 Junior Member

    Could you please tell me where I should find this information and material? In Czech Republic isn't boatbuilding or design program at university..

    Thank you...

    I try to find the best way (middle course) for A-Cat. Total weight of boat I expect 100kg (maximum - I use Airex core and carbon fibre as surface, carbon fibre mast and beam). Weight of salor maximum - 90kg.. so total weight would be 190kg.
     

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  9. rwatson
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    rwatson Senior Member

  10. Vector77
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    Vector77 Junior Member

    Latest design is inspired by DNA A-Cat...

    I think it isn't so bad, right?

    Talking about hull... I think about material... I have experiences with AIREX/HEREX core... so I think, 12mm HEREX C70.75 and carbon fiber woven, weave 2/2, 200 g/m2 from both sizes. Is it OK? Could this work?



    V.
     
  11. Stumble
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    Stumble Senior Member

    Vector,

    Cool project, but given what's going on in the A class right now I would probably recommend looking at designing around the J board and assume a flying boat. My bet is that if you optimize for flying you can make a substantially faster boat than modifying one to do so down the line, and frankly my bet is that in two years a non-flyer is going to be worth a fraction of their cost today.

    I was actually planning on buying a DNA cat this year until worlds, and now am looking to buy a old junker as a trainer until the first generation of purpose designed flyers come out.
     
  12. petereng
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    petereng Senior Member

    victor - yes 12mm 75 and 200g CF each side is fine but fragile. 400g is better for endurance. Stumble is right. There are a spat of flying small cats being built and displacement mode is out in the A class. So stick to it as an exercise but if you want to make a race winner better get up to date on foiling. May as well make the A class hulls from blow up canoes now. Cheers Peter S
     
  13. Vector77
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    Vector77 Junior Member

    Peter: So do you think I could use 2x200g/m2 of that one type of CF woven, weave 2/2 from both sizes? Because I have a really nice price for that woven... :D

    Viktor B.
     
  14. petereng
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    petereng Senior Member

    Yes Vector sx200gsm would be good. Peter
     

  15. Vector77
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    Vector77 Junior Member

    I think about using thinner core... like 9 mm.... do you think it is possible to use it for construction like Farrier trimarans? I mean "vertical strips planking".
    Does the Herex/Airex foam been stabel (doesn't change form/mold) after it is puted in to the wooden moulds ad it is glued together by epoxy?

    Do you know what I mean?
     
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