The project fast lightweight power catamarans - is possible?

Discussion in 'Boat Design' started by romanewas, Jan 6, 2017.

  1. kilocharlie2
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    kilocharlie2 Junior Member

    I said UNDER the golden ratio - 1.618 to 1 or LESS. Actually, I'm not sure if it isn't the other way around- wider than tall, but my point is to ask a SWATH guy.

    I was only a pinhead (deckhand's assistant) substituting for a deckhand who was covering the office for a day. That vessel had the underpinnings not at right angles. The pylons, well more like sponsons on that boat because it was more of a tunnel hull morphing into a pylon, aimed out and down at about a 30 degree angle, so the deck was very high above the water, the pontoons were outboard of the deck by a good amount.

    The whole vessel seemed to only move up and down gently. It did not rock side-to-side noticeably. We fished some spots that I had not worked before, caught some rock cod - red vermillion and barber pole rockfish if I remember correctly, and headed back because it was an afternoon half-day trip. Back in harbor so fast that the deckies had not finished filleting the fish.

    There is still another boat in the area that may also be a SWATH, I think it is called the Speed Twin, working out of Channel Islands harbor in Oxnard, California. It may be just a tunnel hull, it may indeed be a SWATH. I'll try to find out.

    ********************

    Nope, it's a twin hull power catamaran. www.channelislandssportfishing.com/speed-twin-sportfishing
    Sorry, I had it posted as a SWATH for a few minutes there, due to bad info from someone at CISCO sportfishing, but it is a Catamaran, not a SWATH. I'm trying to remember the name of that other vessel. It was a SWATH. That was close to 40 years ago.
     
  2. Emerson White
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    Emerson White Junior Member

    SWATH designs are not a good fit for inexpensive craft.

    I think you want to look for something similar to this http://www.bahamawatertaxi.com/ but with a bit more heft to it to take to more substantial seas.
     
  3. kilocharlie2
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    kilocharlie2 Junior Member

    That's what every one told him about his performance call out. Large passenger count, high speed = high price, high power.

    SWATH gives the desired ride stability in the conditions he mentioned - 6 foot seas. SWATH or power catamaran are both pretty close to the mark. He'll be able to do it - he may need to get it financed. He seems to have regular a market for the run. If the angel investors agree there's a steady profit in it, he's in business.
     
  4. Emerson White
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    Emerson White Junior Member

    I think a power catamaran will get across the water in 6' seas at about 10% the cost of a swath, not at 20 knots, but at a reasonable pace.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    Show us all the SWATH commuter or tourist boats, I say. They are not there, but there are cats galore.
     
  6. Angélique
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    Angélique aka Angel (only by name)

    -
    Not all I guess, but here some SWATH tourist boats, and some others....

    Aero Hydro ---> Navatek Ships ---> Navatek LTD ---> Pacific Shipyards International (PSI) ---> Past Projects

    P.S. - Navatek I at Honolulu


    The Honolulu Advertiser ---> • Graphic: Navatek goes military​

     
  7. TANSL
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    TANSL Senior Member

    I suppose sailing at 20 knots with 6 foot waves and comfortable for the passage is only possible, albeit difficult, with a SWATH type boat. But I would not even make sure the passage was very comfortable.
     
  8. kilocharlie2
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    kilocharlie2 Junior Member

    It's entirely possible, just expensive. He'll need a hell of a pair of engines.

    Had y'all thought about a Consolidated PBY Catalina? Seems it has the speed and stability if you have a landing harbor.
     
  9. Angélique
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    Angélique aka Angel (only by name)

    -
    See: post #3

     
  10. Emerson White
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    Emerson White Junior Member

    It's pretty common for boat design to have conflict and compromise. When the budget conflicts with the requirements I feel like you need to take a good long hard look at those requirements before you throw the budget out. Designing a SWATH is a very complicated endeavor. Do we want to maybe talk to the OP about looking for a design than can transit at 20 knots in 3 foot seas and at a slower rate in higher seas?
     
  11. TANSL
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    TANSL Senior Member

    The SOR for the boat is very reduced, it is practically limited to a speed of 20 knots with waves of 6 feet and comfort for the passage.
     
  12. Emerson White
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    Emerson White Junior Member

    Sometimes the SOR needs some work. The OP is not a professional organization with a long history operating on the sea whose purpose trained and experienced executives are coming to an NA or ship yard. The OP asked if it was possible to meet those goals, and the answer is "Yes, but at a very high cost..." and when we learned more about his situation it doesn't take a great thinker to realize that helping him form a budget realistic SOR to carry forward and find a design is probably going to do more for him in the end than regaling him with all kinds of stories about how awesome boats too expensive and complex for his goals are at handling the difficult sea conditions he may face.
     
  13. romanewas
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    romanewas Junior Member

    Colleagues and what do you think about this ?: View attachment Catamaran 1080 boat.pdf
    Chinese claim that this can swim up to 8 'waves :) What do you think - is it possible to realistically swim something like this to 5' waves?
     
  14. Emerson White
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    Emerson White Junior Member

    That boat looks very much like I had in mind for a solution for you.

    I'll bet with the right engines that cat can go 20 knots in 3' seas. I'll bet that cat can also safely cross 8' seas. I'll also bet that it can't do both at the same time. If you try to go too fast when the waves are big you end up launching off of one and diving into the trough. It's super unpleasant and it slows you way down. Also everyone will hate the slamming and no one will want to use your company ever again.

    Wave piercing designs can keep from launching off of waves and give you some more speed, but they tend to need to be bigger than what you are looking for to be at their most effective. A SWATH can cut right through the waves too, but expense...
     

  15. romanewas
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    romanewas Junior Member

    So I have to start with something simple. I have to reduce spending on the boat because I'm not sure the success of this business. It is investment risk. Besides, I need a certified passenger ship in accordance with these rule (Directive 2009/45/EC)?:
    https://publications.europa.eu/pl/p...b7a6f-8939-4393-be73-2a6b13084203/language-en
    I mean, that I need so-called passenger ship class B ...
    The question is whether the certificate of CCS* will be recognized by the maritime authority in the European Union? It must here be re-registered under the Spanish flag.

    *CCS is Chine Classification Society http://www.ccs.org.cn/ccswz/ and is a member of IATA...
     
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