Turn 2 monohulls into 1 catamaran. Is that viable solution?

Discussion in 'Projects & Proposals' started by TruckoftheSea, Feb 29, 2020.

  1. gonzo
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    gonzo Senior Member

    It would be cheaper, simpler and faster to buy a bigger boat. A 50% increase in hull length will provide more interior volume than two hulls. Also, marina costs for catamaran are very high for their length. For example, a 32' cat will not fit into a 32' slip, it is too wide. You will have to pay for at least a 45-50' slip.
     
  2. bajansailor
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    bajansailor Marine Surveyor

    Truck, I think that you probably want something like a trawler catamaran?
    Here is a 36' 'trawler cat' for sale for $132,000.
    Would this have enough cargo carrying ability (re fuel, water, A/C, generator, fridge etc) for what you have in mind
    2000 Endeavour Catamaran Trawlercat 36 Power Catamaran for sale - YachtWorld https://www.yachtworld.com/boats/2000/endeavour-catamaran-trawlercat-36-3612605/

    I am thinking that the final cost of building a cat trawler from two monohull hulls will be much greater than the cost of buying something 'off the shelf'?
    Here is a bigger version, still with a 16' beam, so she has the same beam (approx) as a typical 45' - 50' monohull.
    2005 Endeavour Catamaran Trawler cat 40 Power Catamaran for sale - YachtWorld https://www.yachtworld.com/boats/2005/endeavour-catamaran-trawler-cat-40-3648844/
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    That was the first thing I thought of, it may be a cheapo way of getting a bigger boat, but the parking will be top dollar.
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    You mean these are not "general" statements?

    Yup - that's the kind of thing. As a guide/principle way fwd.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    I think you'll find he is only intent on building the "crazy cat" because he thinks he can pick up a couple of identical clapped-out sailboats for cheap. The trawler catamaran will be way out of the range of the budget. An Ad Hoc, this "boat" is not what is "generally" adopted, so the "general" calculations applied to catamarans will be less applicable, I reiterate, give us your approximation for the extra drag of this contraption attributable to interference drag. 20-30% do you think ? Bearing in mind it will be forever travelling maybe 6-7 knots tops.
     
  6. TruckoftheSea
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    TruckoftheSea Junior Member

    1- Currently I have a power boat. I don't want to buy 1 more but to build something very my own.
    2- Could I modified the stern to increase the efficiency?
     
  7. gonzo
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    gonzo Senior Member

    To get a relevant answer, you need to define efficiency.
     
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  8. kapnD
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    kapnD Senior Member

    Maybe you should split your powerboat and build a catamaran from the two halves, that’d be unique!
    You could gain lots of deck space, but you’ll add considerable weight with the adjoining structure, so hulls will be more deeply immersed, further diminishing efficiency.
    (2) Again, it can be done, at a price, but it’s a very vague question.
    Specs/pics of powerboat?..
     
  9. TruckoftheSea
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    TruckoftheSea Junior Member

    12345.png
    The side pressurize by the 2 amas actually not a big deal. The big deal is the longitudinal pressure. I hope remove the engine from main hulls and do the stern modified would increase the after stern pressure so I could reduce the longitudinal pressure affect. With the good designed airfoil shape for the fins the water flow would run exactly to the area we want it to. So we just redesign the stern to get the benefit.
     
    Last edited: Mar 2, 2020
  10. TruckoftheSea
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    TruckoftheSea Junior Member

    cross section of lightweight beam for cross-structure
     

    Attached Files:

  11. gonzo
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    gonzo Senior Member

    I don't understand what you are saying at all. What pressures are you referring to?
     
  12. TruckoftheSea
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    TruckoftheSea Junior Member

    When your boat sits on the water it gets the pressure from all directions. When it move forward it has high pressure at bow and low pressure at stern. That longitudinal pressure is the big problem for your boat speeding forward. The longitudinal pressure is the problem so we care about the length to beam ratio. The big ship has large under water surface will get friction problem but the small one that isn't a big issue. So if we want to combat the monohull problem we have to reduce the longitudinal pressure between the bow and the stern. That's just the basic of boat science.
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    Trucker, that is pretty much mumbo-jumbo, with your project here it becomes a case of satisfactorily linking the two boats, powering the thing effectively (not easy to use outboards, even behind the two hulls, and more difficult if hung off the connecting span) and accepting what drag penalty will arise from having two fat boats so close together. Which was why I suggested scale modelling. That the waterways are not exactly awash with such "boats", might suggest it is not worth the trouble.
     
  14. bajansailor
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    bajansailor Marine Surveyor

    I am confused. Have you given up on the idea of using two sailboat hulls?
    What is your current power boat? Are you now looking to build another power boat similar to the one that you have, and attach the two together to form a catamaran?
     

  15. gonzo
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    gonzo Senior Member

    Pretty much it is all wrong.
     
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