Trimaran motorboat / stabilized monohull

Discussion in 'Boat Design' started by Eric DEBORDE, Oct 12, 2009.

  1. Eric DEBORDE
    Joined: Oct 2009
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    Eric DEBORDE Junior Member

    Hi all ! new drawing !

    [​IMG]
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    The complete boat will be 14m long by 3.2m wide / 600kg with 70 to 90 hp outboard / the CG is 4.5m from the prop.

    Comments and Critics welcome!!
     
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  2. u4ea32
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    u4ea32 Senior Member

    Very cool!
     
  3. permagne
    Joined: Aug 2009
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    permagne Junior Member

    For comparison...

    Your figures are very much similar to mine.

    I've a 50HP Suzuki four stroke. Boat is Castello Marine 533HT

    http://www.seilas.no/photoalbum/view2/P3NpemU9b3JnJmlkPTI1ODAxOQ

    WOT is 25kt on a good day, and cruises at 20kt usig 0.5L/nautical mile.

    My boat is a conventional 5.33m fibre glass hard top. Boat weight is 450kg+engine (approx 100kg)

    In my mind I expected better figuers from your design, but I certanly believe you have a very good speed range with less of a planing treshold. And a very nice ride over/through the water.

    Per Magne
     
  4. Eric DEBORDE
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    Eric DEBORDE Junior Member

    Planing and Displacement Boats

    Thank's Per Magne, it is interesting to compare planing et displacement boats in the 20 Kt range !
     
  5. erik818
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    erik818 Senior Member

    Eric and Per,
    I'm not particularly surprised that a planing boat and a trimaran displacement boat of the same weight come around about equal regarding fuel economy at 20 kts. My understanding (purely from calculations and simulations) is that the stabilized monohulls excel at speeds that are traditionally semi-displacement speeds. If you want to go 20 kts and faster it's more efficient to travel on top of the water instead of trying to push it aside. Reduce the speed to 12 knots and I expect that the stabilized monohull is a very fuel efficient boat. Eric, do you have any figures for 10 - 15 kts?

    Erik
     
  6. Eric DEBORDE
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    Eric DEBORDE Junior Member

    12kt using 0.35L/nautical mile (half loaded boat-no wind)

    100 hours of navigation, must be around 1500 nautical miles !!
    The boat is OK except minor cracks on the top of the cab.
    The driving is verry easy (particulary under autopilot).
    It make me think to a 50cc bike !
     
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  7. Bob Oram
    Joined: Jun 2009
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    Bob Oram Junior Member

    excellent

    Hello Eric,
    Firstly congratulations on all your work. It is probably some of the best reality based work out there for this configeration of boat.
    I notice some good input from others especially Rick W and Will.
    Other comments from people trying to make the stabilised mono or power trimaran configeration work are also valuable.
    Trying to the solve the economy, sea keeping, genuine oceangoing, cruising boat conundrum is an endless task.
    If all the man hours of thinking, building, testing then alterations then testing again had to be paid for at market prices there would be no development at all.
    I have said for ages that it is the enthusiast's [they may also be marine industry professionals but rarely, and if they are, then a lot of it goes unpaid] that do so much of the ground work for advancement when it comes to boats.
    It is probably why there aren't many wealthy designers or boat builders out there.
    The only real impediment I see to the acceptance and success of the S/M and P/T configeration is the roll in beam and quartering seas without the use of mechanical stabilisers and foils.
    I have always been concerned with foils developing a negative angle of attack with bad results in the open ocean at speed in the middle of the night. Especially on Mum and Dad cruising boats.
    Mechanical stabilisers are just something else to go wrong and more weight.
    My 40' power podcat has been a very successful and fit for purpose excercise although I have been bitten by the 'move on bug'.
    The S/M and P/T config has always fascinated me and it is the next logical step.
    A friend built a 60' P/T nearly 20 years ago.
    It wasn't a light boat [11/12 tons cruising] but it was a very interesting excercise.
    Anyway good luck with your work and boats, there a lot of people out there that get joy from your success's.
    Please keep posting.
    regards
    Bob
     
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  8. Alik
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    Alik Senior Member

    I have simple question: how to access bow mooring cleat and anchor?
     
  9. brian eiland
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    brian eiland Senior Member

    Attached Files:

  10. Willallison
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    Willallison Senior Member

    Ha.... I was just about to post a link to Adastra... and was then going to pose the question... how do the guests get on and off... or the crew tie it alongside a pier...? ... great minds, as they say...

    I helped to move the Ady Gill when she was here in Hobart, just prior to her ill-fated trip south. It took over an hour to untie the boat, turn it 90 degrees, then re-tie it alongside an adjoining pier. I'm afraid that the compromises inherent in the power-tri are just too overwhelming for general use, IMHO...
     
  11. brian eiland
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    brian eiland Senior Member

    i understand what you are saying Will.

    That's why I think the Humphrey's design, or the littorial ship configuration makes much more sense....pulse a much more usable aft deck area.
     
  12. brian eiland
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    brian eiland Senior Member

    Correct Length and Placement of Outer Sponsons-Hulls

    Eric, et al

    Would like to hear your comments on this question I posted on another forum this morning:
    http://www.yachtforums.com/forums/126895-post153.html
     

    Attached Files:

  13. bertho
    Joined: Aug 2006
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    bertho bertho

    Eric,
    I like very much your concept and approach..
    I was working years ago on this concept, call ? stabilized monhull? main problem was to manage the bow wave to interact with sponsons.., at different speed and sea condition, a Naval architect in Brest (France) have a sexy proposal, using laterals floats out of the water ( with big steps, looking like hydroplane floats) with tiny foil to stabilize the boat under speed, almost no drag, no interaction problem with bow wave, foils are very effective,
    problem come when you stop, really unstable platform.. , solution was flooding one empty part of the bilge (automatically, by a large opening on the transom, same as you find on some extreme deep V RIB) to increase the draft and lower the lateral float to have a stable platform.
    when you take some speed, this empty cavity just empty alone, and the laterals floats come out of the water.
    foils can be permanent position, but I was thinking to using a standard autopilot to control the foils, as we look for a horizontal control instead of a direction, I was wondering if a magnet balancing under the standard flux gate compass can be fast enough?.. is like if you create a fictive vertical "north attraction" the magnet have probably to swing on a oil or liquid to avoid balancing to fast. and we still have all existing correction from the pilot, but for horizontal motion.. .
    just for fun !!
    sorry for the frenchglish..!!
    all the best
    bertho
    www.fusionschooner.blogspot.com
     
  14. Eric DEBORDE
    Joined: Oct 2009
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    Eric DEBORDE Junior Member

    New boat

    Hi all !
    The new boat is nearly finished, in the water next week or so !
    You will have numbers soon !

    [​IMG]

    500kg for the hull (sandwich airex and plywood)
    For now power is 115 evinrude.
    180l fuel
    long : 13.85 m, large : 3.2 m.
     
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  15. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Look out for japanese whalers, they like that type of vessel for target practice !
     
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