Pontoon/Trimaran concept?

Discussion in 'Boat Design' started by terra, Mar 29, 2011.

  1. terra
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    terra Junior Member

    Hey all,

    My first post here. I've grown up around boats from a recreational standpoint but never known much about them. Picked up some books recently and started doing some reading. I go from a mechanical background and feel like trying to build my own concept. The goal is a super efficient 25-30' boat capable of relatively long distance trips while maintaining maximum efficiency. Family has a 33' Regal and $7000 for a weekend trip doesn't sound fun to me! Here's what I'm thinking:

    4 carbon fiber pontoons connected to a main structure via independent suspension. The main cabin would be supported about 1-2' off of the surface but the suspension will allow it to raise and lower with the effects of the waves.

    I'm forcing myself to learn this new 3D modeling program and this is only day 2 so don't be too hard on it haha.

    [​IMG]

    I've got a few rolls of carbon laying around, a full machine shop, and access to any other raw materials I could ever want.

    If the answer to why this isn't feasible is simple, please let me know why. I'm trying to expand my knowledge and put the concept through all necessary revisions.

    Thanks all,

    Alex
     
  2. BATAAN
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    BATAAN Senior Member

    Generally speaking, all practical concepts have been tried. Are you saying the 'suspension' is active and keeps the main hull relatively motion-free? This really reminds me of a car and not a boat. Remember, the flotation has to support the hull and there is no substitute for displacement. Just eyeballing your masses here it looks very wrong as the floats are too small, plus now you have 4 small, short waterline hulls, with all the wave making and turbulence times 4. Easy motion and efficient powering in a displacement craft lead to a long, lean shapes with easy lines as water-line length wave making has such a huge effect on performance.
    I knew a fellow in the early '70s built a raised center-hull thing on aircraft drop tanks full of foam for flotation with much the same idea. It didn't work either. He set out for the 'south seas' to give away bibles but only made 500 miles in 3 weeks before an expensive, difficult, dangerous rescue was needed, as his 'boat' was built without a knowledge of the real ocean, and went to pieces under the actual strains of seagoing.
     
  3. terra
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    terra Junior Member

    Thanks, all I needed to know!

    Yes, the suspension would have been active. The center cab would be more monohull shaped and not flat bottomed but I ran out of time on my flight home.

    Back to my sketchpad then.
     
  4. BATAAN
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    BATAAN Senior Member

    Decide what your projected vessel needs to do for you, what its job is, and that designs the boat, or guides in selecting an existing design
     
  5. terra
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    terra Junior Member

    Thanks!
     
  6. BATAAN
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    BATAAN Senior Member

    Find the book "Capt Nat Herreshoff" by LF Herreshoff and there is a lovely wealth of material on super-efficient power vessels. These tend to be over 50 feet in length and 11 feet or less in beam. "Little Sovereign" built 1904, 112' x 11'6", consistently ran at 26 mph on very little fuel. Long hull needed for efficient wave-making, otherwise you're trying to go uphill on your bow wave all the time.
    Alternative is very light planing hull with little carrying capacity. In Okinawa I got a ride in a local dive charter boat about 35 feet long and it easily did 30 knots over a good chop. Hull was very different from US types with low freeboard, a centerline 'planing plank keel' and a light turbocharged diesel of about 100 hp. Construction was fiberglass, but very well done with nothing that didn't have to be there.
     
  7. PAR
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    PAR Yacht Designer/Builder

    Terra, pick one, two or three hulls and forget about articulation.

    As Bataan suggests, establish a set of goals or a Statement of Requirements (SOR) then develop the hull form to address the specifics within the SOR. For example, you'll have a several choices or avenues of pursuit for each design decision you'll need to make. The selection process is much easier if you have the SOR to guide the process.

    In the end, since you want super efficient and maximum range, your ultimate design will probably be a cat, built as lightly as practical.
     
  8. terra
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    terra Junior Member

    Well the whole thing will be carbon fiber, probably built to hold 2-4 people on day trips. I'm actually looking at a couple other threads with trimarans to get some ideas.
     
  9. aranda1984
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    aranda1984 aranda1984

    Playing with ideas...

    Hello Friend.

    You got the little gray cells working. That is always a good thing!

    Now all you need is a little basic inforrmation that will put your ideas straight.

    What you have there is called a pentamaran with a race car suspension..
    Google this and you will see research done on the subject. Even videos on actual testing.

    May I suggest some reading material for you that might make a watercraft out of your idea.

    1. Multihulls for Cruising and Racing, by Derek Harvey.
    (A good book to start with.)

    2. The Cruising Multihull, by Chris White.
    (More ideas on multihulls.)

    3. Elements of Yacht Design by Norman L Skeene.
    (A simple basic, all manual boat design guide.)

    4. The Elements of Boat Strength for Builders, Designers and Owners, by Dave Gerr. Maybe even the Propeller Handbook by Dave Gerr.
    (Now we are getting somewhere with some nitty-gritty nuts and bolts.)

    5. Boat Building with Aluminum, by Stephen F. Pollard.
    (Just in case...)

    You can get all these from Amazon.com for about $ 20 each.

    By the time you finished reading them, you will have a good basic understanding of what you will be able to do by yourself and what should be left to professionals.

    Keep on dreaming and keep the graycells busy.

    Regards,

    Stephen
     
  10. daiquiri
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    daiquiri Engineering and Design

  11. terra
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    terra Junior Member

    Many thanks. I'm headed to Amazon to start reading!

    Ya, saw that about a month ago.
     
  12. BATAAN
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    BATAAN Senior Member

    Nothing wrong with a raised center hull, 2 hulls in the water power boat catamaran. It must be very light and rigid to work. Saw one in Port Townsend a while back, made in a local shop. Seemed to work well but Russell Brown, the designer/builder has been at the game a long time. One centerline 4 stroke outboard, 2-4 passenger, light wood/epoxy/other laminates as appropriate build.
    Can't find a picture but here's another that's been built and tried out. http://smalltrimarans.com/blog/?p=4366
     
  13. BATAAN
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    BATAAN Senior Member

  14. BATAAN
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    BATAAN Senior Member

    Here's the work of a genius, but then his dad is Jim Brown, one of the guys who invented modern trimarans.
     

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  15. BATAAN
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    BATAAN Senior Member

    15 hp, 15 knots, 1 gal per hour.
     
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