Coastal house catamaran (EC cat. C or D) "kit"

Discussion in 'Powerboats' started by Sinclair D-R, Apr 1, 2014.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

  2. Sinclair D-R
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    Sinclair D-R Junior Member

    Thks.Mr. E...

    Same as the one i gave you.
    Google earth: 21 Conifer St., Hillcrest, Queensland, Australia.

    Called each and all of the numbers they publish.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    Try during the week, Sunday is the Lord's day of rest ! :)
     
  4. Sinclair D-R
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    Sinclair D-R Junior Member

    Lateral stability:


    Given LOA: 15 x BOA: 4.50 m* cat

    *: This BOA is a maximum as this cat is to travel canals where sometimes the max width is 5.00 m. leaving less than a foot on each side.

    With slim narrow hulls 12/1 how could i increase lateral stability along the longitudinal axis?

    Hull form with some kind of "knuckle" all along ?
    Ideas?
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    Lateral stability won't be the problem, not scraping the side could be, if you have such small clearance. I don't understand why you want to increase lateral stability, it is irrelevant to the side clearance, surely ? Anyway, it should be rock-solid.
     
  6. Richard Woods
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    Richard Woods Woods Designs

    A catamaran is a form stable vessel. So the only useful ways to increase stability is by increasing the overall beam (or hull spacing) which you cannot do, or by lowering the CofG. However the latter is only relevant at high angles of heel - over 60deg say. So probably not relevant on a canal. The third option is to make the boat heavier, which you also don't want to do.

    Ultimate stability is not often relevant on any powercat as a boat is stable in waves providing the wave height (unbreaking) is less than the beam of the boat. Not many 4.5m waves in the canals either!

    As an analogy, imagine a solid rod (monohull) and a hollow tube (catamaran) of the same diameter. Both are almost equally strong in bending (heeling), yet the hollow tube is much lighter.

    Having said that, several UK narrowboats capsize each year on canals, but then they are 70ft x 7ft. They capsize when going round a corner and the bow meets the rushing water from a weir, thus rolling it over. But as the canals are only a few feet deep usually no lives are lost.

    Richard Woods
     
  7. Sinclair D-R
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    Sinclair D-R Junior Member

    Thanks to you both gents.

    Please let us all keep in mind that this vessel will be registered EC Cat. C

    http://www.britishmarine.co.uk/what_we_do/technical/recreational_craft.aspx
    In 2013, the book was 369 pages, sure there are tens more by now. (Richard, you know them all by heart? :D)
    Recreational Craft Directive
    EC Category C implies: Inshore,
    Designed for voyages in coastal waters, large bays, estuaries, lakes and rivers where conditions up to, and including, wind force 6 and significant wave heights up to, and including, 2 m may be experienced.
    Category Significant Wave Height Beaufort
    A- Ocean Exceeding 4m Exceeding 8
    B - Offshore Up to & including 4m Up to & including 8
    C - Inshore Up to & including 2 Up to & including 6
    D - Sheltered Up to & including 0.5m Up to & including 4

    This -coastal house cat- will cruise canals, rivers and lakes! she must also be able to sail from Constanta, Romania -- W to Marseille, France -- N to Rouen then -- NE to Tromsø, Norway for a midnight breakfast above the Arctic Circle a fortnight or so after the summer solstice.

    Yes, lateral stability is of interest to me. True, i will be extra cautious before leaving a safe haven and crossing fjord where downdrafts are perilous.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    I would be cautious of getting involved with boats with a knuckle a little above the waterline, some make more noise at rest than a good night's sleep will allow.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    It would be close to the least of your potential problems. Some cats have greater stability laterally, than lengthways. It is hard to imagine how a cat that fits your height restriction could ever be found wanting more lateral stability.
     
  10. Sinclair D-R
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    Sinclair D-R Junior Member

    Bruce Harris design attached pics

    Knuckle: Roger that Mr. E!
    Thanks, Zzzzz! Zzzzz! Zzzzz!

    Pics of a Bruce Harris design 2011, for sale in Phuket, Aussie flag, 600 k $
     

    Attached Files:

  11. Sinclair D-R
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    Sinclair D-R Junior Member

    Mr. E.

    Could not roll easily, sure not:
    15 x 4.50 x Air draft: 3.00 m.


    Point well taken,thanks for reminding me! i nearly forgot! :eek:
     

  12. Sinclair D-R
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    Sinclair D-R Junior Member

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