Building a “C-Class” Catamaran

Discussion in 'Multihulls' started by Nordschleife, May 23, 2021.

  1. Nordschleife
    Joined: Jan 2020
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    Nordschleife Junior Member

    Recently I came across the Lindahl Composites page documenting the build of their LR6 A-class catamaran.
    LR 6 https://lindahlcompositedesign.weebly.com/lr-6.html
    I’d like to use this same method to build a larger, “C-Class” catamaran. Why the quotations? Well, I can say with almost absolute certainty that I will never race this boat, and so it’s rigid conformation to the C-Class rulebook or even competitiveness compared to those professionally designed boats, is not of concern to me.

    I’d like the boat to be double-handed, be able to fly around a racecourse, and equipped with a wingsail. Foils will ideally be able to deploy and retract based on the tack the boat is on, but this is not a necessity.

    Any suggested reading or suggestions are more than welcome.
     
  2. wet feet
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    wet feet Senior Member

    Interesting idea,but may I ask if you have ever built a carbon boat before?If the answer is in the negative then I suggest you begin with a small and simple rowing boat to gain some familiarity with the techniques involved.If it succeeds,you will be much better prepared to take on the task of a considerably more complicated and expensive project.If it fails,you won't have lost too much.
     
  3. Erwan
    Joined: Oct 2005
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    Erwan Senior Member

    The cost effective solution would be to buy a plateform with consistent track-record:
    And you are a lucky guy as this plateform exist:
    2016 - FOILER - Easy to fly - Guillaume Verdier

    If at first glance it looks more expensive than your DIY boat, even after sailing a few years it will keep some market value compared to your DIY vessel.

    Regarding the wingsail, exept if it is for a research program, it will be a garbage, as the wing sail will be useful below 6 knts TWS, above , a teardrop mast with full batten sail will make it and will be much cheaper, not to mention capzise consequences with a wingsail, and related insurance costs.

    If addict to DIY, you should consider an A-Cat first, then a B-Cat to sail with girl friend, and later a C-Cat if not yet discouraged.

    Cheers
     
  4. Nordschleife
    Joined: Jan 2020
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    Location: NY

    Nordschleife Junior Member

    I have built carbon Marblehead 50/800s before. And I do own a DNA A-class - I just want to build a boat :D.
     
  5. upchurchmr
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    upchurchmr Senior Member

    Good luck to you.
    I no longer know where to find build descriptions for previous c-class boats.
    Perhaps searching on the boat names, like the Patient Lady series.

    The Gougeon Brothers book on wooden boat construction had a section on a "C-class" trimaran, although designs have moved on for a long time.
     
  6. oldmulti
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    oldmulti Senior Member

  7. upchurchmr
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    upchurchmr Senior Member

    perhaps you could point out which pages have actual C-class boats.
    With 120 pages and most of them cruisers it might be hard to find actual C-class boats.

    25' x 14' x 300sq ft sail area with 2 crew. No cabin of course.
     
  8. Steve Clark
    Joined: Jul 2004
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    Location: Narragansett Bay RI

    Steve Clark Charged Particle

    We may have exchanged thoughts on another forum with regard to a 25' version of an AC50. If not I offer the following:
    There is nothing inherently wrong with the Lindahl technique. There is nothing particularly novel about it either. It is a fairly cost effective way to get 85% of what can be achieved by the best available practices.
    If simply building your own boat is the objective, there are some hull molds in the area which will save you some time and reduce some of the risks. I have molds for "Cogito" and "Aethon" here in Rhode Island. both of which have produced good boats.
    The ETS team in Montreal also has an inventory of tools and parts which might be available as they have dissolved their C Class team and are now focused on Eco-Moth building. Their second design seems pretty credible, but was never really worked up. I don't know the weight however.
    If you are intent on designing your own hulls none of this will interest you.
    I also have a fairly complete set of molds for building the composite wing surfaces.
    I also know where most of the bones are buried, many are in my back yard.
    If I can help just ask.
    SHC
     
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  9. upchurchmr
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    upchurchmr Senior Member

    Best offer I've seen in a long time.
    If the OP is serious he will talk to Clark.
     
  10. Erwan
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    Erwan Senior Member

    The ETS team, achieved an awesome result for their main spar: in a composite Professional revue, it was mentionned that their main spar was around 16kg, with only 120mm diameter, while similar spars for Cogito or other North-American C-Cats were more around 200 mm diameter , no idea for the weight???
    According to the EI formula, with such a lower internia, the modulus is probably much higher, they may use a TPT approach to minimize weight, in addition?

    It remains a mystery for me, and I wonder what would be the specs of an A-Cat's spar with the same technology ??
    Would they accept to run their FEA to design an A-Cat tube, I would send them a "Carton of Bordeaux or Burgundy"

    Cheers

    EK
     
  11. upchurchmr
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    upchurchmr Senior Member

    What is TPT?
     
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  12. Erwan
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    Erwan Senior Member

    Thin Ply Technology, based on Pr Tsai research / Standford University (afai)
     
  13. upchurchmr
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    upchurchmr Senior Member

    Can you tell me what it is about, basically?
     
  14. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    Strength. Simple explanation. One layer of a fabric that weighs 400 gsm has big gaps between the fabric components. When you lay it up you end up with resin filling those gaps, adding weight. Now fabric technology has improved and they now know how to align atoms in materials better so that the same strength can be obtained in thinner and lighter fabrics. At its extreme there is a product called carbon nano tubes which is an extremely thin light and strong form of carbon. Building up several layers of these thin fabrics has less resin take up and makes a lighter stronger structure. There are many strengths of carbon fibre. The jpegs give the idea.
     

    Attached Files:


  15. Erwan
    Joined: Oct 2005
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    Erwan Senior Member

    Well, Oldmulti has provided us with some insights, I am not sure I can add much, the only thing I though I understood is the following:

    Putting aside the classic carbon fabric and considering only UD, here are the 2 main ideas I remenber when it comes to TPT:

    1-Intead of using a 200 g/sqm UD you should use 4 x 50g/sqm. (Thin Ply instead of Thick Ply)

    2-In addition, if you don't go beyond 22.5° angle between 2 adjacent layers, then the composite would be more resistant to delamination (everything else equal)

    It seems to work so well, that an US bicyles company use TPT to wrap their bicycles frames with something like 32 or more layers of ultralight UD, and itheir frame's tubes seem to meet isotropics caracteritics.

    AFAIR I think it is in an article about this bicycle company that the "Out Of Autoclave" concept was mentionned .
    It means that with TPT just using vaccum and a little post cooking, your epoxy you could achieve same stifness than with an autoclave, but much cheaper of course.

    Googlezing :TPT/ Out of Autoclave / Pr Tsai + composite should provide you with more reliable and serious infos than those above-mentionned.

    Happy week end

    EK
     
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