Open source 12-15m high performance/semi-cruising catamaran design

Discussion in 'Multihulls' started by groper, May 10, 2017.

  1. UpOnStands
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    UpOnStands Senior Member

    Downloaded the xls and am still working through it. Looks like a lot of hard work to code it right.
    Is there a parameter for distance between edge supports?
     
  2. groper
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    groper Senior Member

    distance between supports - thats the length of beam l.
    Ive updated the XLS to include an approximation method for calculating foils section modulus, deflection and stress for quick preliminary design reference. This is close enough to compare sections and sizes and roughly work out laminates etc as the laminate stress should be roughly proportional to the inverse square of the cantilever length of the foil. This last part still hasnt been added - it would be great if all of the above information was collated into 1 great big spreadsheet that could easily calculate many of the composite design problems that need to be worked out- again feel free to make a start - i did find a really great example of such an XLS document which was for the design of a boeing wing section - extremely comprehensive XLS document!

    Also find attached reference material to help you code the XLS document - the excel document its not user friendly yet - feel free to make it so :)
     

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    Last edited: Jun 25, 2017
  3. groper
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    groper Senior Member

    Here is an example of a really well done XLS document as an aircraft wing design tool - The BDnet community should work on a similar document for composite boat design / hydrofoil design, structural design etc - imagine the possibilities :)
     

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  4. UpOnStands
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    UpOnStands Senior Member

    That XLS file is a great guideline but the big problem would be reaching agreement on how to set the factors determining loads. Designs that are so conservative that they are bulletproof (and thus too expensive for most) are useful?
     
  5. groper
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    groper Senior Member

    Well if you were a professional boat designer with the legal responsibilities of a design that may become involved in a huge court case when something goes wrong- whether its your fault, the builders fault, the owners fault, or any other 3rd partys fault - everyone gets dragged through the court regardless. So as a professional, wouldnt you be a little conservative too? I know i most definitely would- as a professional. Im not going to risk my livlihood for a client- would you?
    Designing and building for yourself- now you can do whatever you want to whatever level of risk your comfortable with... blame litigation man- hindering progress since the lawyers invented it...
     
  6. UpOnStands
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    UpOnStands Senior Member

    Exactly, so there must be some way in the user can input how conservative the design should be (also to allow for confidence in building skills?) and I suppose also intended purpose. Lake, coastal, offshore, racing?
    There are so many variables it's a valuable but daunting task.
     
  7. groper
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    groper Senior Member

    No not really. The design factors are based around several main design varibles. Boat displacement, boat speed, and operating seastate. All of the above affect the pressure the hull experiences. The methods the professionals use and required by class societies is sound- its the safety factor multiplier which goes on top which causes the weight increase beyond whats nessesary.
    If you would like to know more about how they arrive at the design loads and pressures, google "veristar BV NR500" and you will find online source of yacht design class rules. Its a good read if your interested.
     
  8. jorgepease
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    jorgepease Senior Member

    Have you seen this one?
     
  9. Doug Lord
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    Doug Lord Flight Ready

  10. UpOnStands
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    UpOnStands Senior Member

    C-boards facing outwards, whatever are they thinking? :p
    Seriously though, this does make a serious effort to directly improve pitch and heave motion, needed given the displacement of 13,400kg and the racing-oriented canting rig(??). Or is this a marketing teaser?
     
    Last edited: Sep 14, 2017
  11. Doug Lord
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    Doug Lord Flight Ready

    I wouldn't call them "C" boards-they're much more like DSS foils on monos, in my opinion.... DSS- frm hugh.jpg DSS Infinity 36 launched just before 5-29-12.jpg
     
  12. jorgepease
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    jorgepease Senior Member

    Funny! I mentioned the horizontal sliding foils earlier on and these appear to be at same depth. I don't see this as being very light either.
     
  13. UpOnStands
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    UpOnStands Senior Member

    Given the lack of a big A cassette arrangement on the deck to handle board kink they do appear to be C-boards. But "official" confirmation is needed.
    The difference from my arrangement is that this 58' McCollough uses dedicated daggers for lateral resistance.
    My main concern is that the foils are too close to the surface, even 1 m swell might be enough for the foil to occasionally fall out of the water.
     
  14. groper
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    groper Senior Member

    This is okd news - its the gunboat G4 - renamed DNA F4 when they bought the design off gunboat... plenty info out there, but its proven no good in rhe open ocean - its a small regatta racer not a performance cruiser
     

  15. Doug Lord
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    Doug Lord Flight Ready

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