Planing Trimarans II-the real thing?

Discussion in 'Multihulls' started by Doug Lord, Jun 2, 2010.

  1. Doug Lord
    Joined: May 2009
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    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Roh--jomo>

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    The significance of the model in the pictures above is the geometry. It was created with a lot of calculation and a preliminary lines plan and then was carved from balsa based on the previous info. What is shown by the model is that, in fact, a hull like this is possible-which I had my doubts about when I first conceived it. The fact that a stepped planing hull and a high L/B displacement hull as top and bottom of the same hull could be achieved for the proper numbers is flat remarkable. It still blows me away. It could "easily" have been patented but I chose not to. It offers a lot of potential with the remaining problems nothing compared to the geometrical solution the concept is based on. For those with no clue the inception of "planing" on the stepped hull is at a very slow speed so the imagined tacking problem is a non-starter as proved, incidently, by Parlier's work on an RC model, a small prototype and L'hydraplaneur.
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    Click on image and then again on resulting image to increase or decrease size:
     

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  2. Chris Ostlind

    Chris Ostlind Previous Member

    Doug,

    Aside from the rubber arm back slapping of oneself so evident in your own write-up, you have managed to create a non-event duck looking for a place to land.

    You have broken the continuity of the external skin of the ama at a place where it needs to have maximum strength as a cantilevered form. This will necessitate a seriously robust internal beam that can carry the loading and will drive the complexity and cost of the build into the stratosphere... not to mention the added weight for a boat that thrives on light, responsive hulls.

    A component of the submerged hull will be further hampered with poorly designed flow optimization by placing the needed groove for the rotating mechanism precisely where best flow is supposed to happen. This flow breakdown will happen for either surface of the ama that is presented. Installing a flap on the leading edge of the slot will not solve the problem anymore than the same type of application solves the issues surrounding the use of a typical centerboard, You can "maybe" reduce the damage to the smooth flow a tiny bit, but you'll never make it go away completely. This fact, alone, is a killer for this design's effectiveness.

    I would think that you would want to look for better performing shapes for existing hulls, simpler, less fussy control sets on deck, better aerodynamics for the overall boat and a design that could either be built easily by the average dude, or manufactured easily and affordably as a production example. None of those hit list items are in evidence here.

    "For those with no clue the inception of "planing" on the stepped hull is at a very slow speed so the imagined tacking problem is a non-starter as proved, incidently (sic), by Parlier's work..."

    If the above statement is true, then how come Parlier, himself, said that his cat would not plane until it was hitting 20+ knots and all sailing done below that speed was sluggish when compared to standard hull forms not dedicated to a planing function? Those comments are all over the place at both this site and at Sailing Anarchy's forums and are easy to obtain, should it be necessary to squash a bug.

    We get the feeling, Doug, that you are afraid of dealing with the potential drawbacks of a design such as you propose and only wish to hear comments that don't ruffle your feathers.

    You have been told many times on these pages that there's no free lunch in design. That to get something you desire, you have to give something up to get there. That the further you press your desire to drop everything in the name of what you see as Holy; that being your search for speed as the most important thing for sailors... the further you travel from having an all-around tractability within the same design.
     
  3. Doug Lord
    Joined: May 2009
    Posts: 16,672
    Likes: 339, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

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    You should read more about stuff before you ostlindize it! The refined version,
    not shown in the model, uses a one piece hull with the forward attachment point a flush(where it has to be) collar that allows rotation and robust strength. The model simply illustrates the geometry and the concept-not the details of construction but some of those details are covered in a previous post.

    post #8:

     
  4. Doug Lord
    Joined: May 2009
    Posts: 16,672
    Likes: 339, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    ============================
    Parlier's boat would begin to plane at 12-14 knots but its drag would not drop below that of a high L/B displacement hull until around 20 knots where it had about half the drag of a skinny hull. At 40 knots L'hydraplanuer had only 25% of the drag of a skinny hull!
    Parliers cat was very wide for its length(50'=.83LOA, L/B overall 1.2) and some would conclude that meant it tacked slowly-I wouldn't, necessarily, and have written Yves to ask him.
     
  5. Chris Ostlind

    Chris Ostlind Previous Member


    Well, to be bluntly honest about it all, Doug.... in my Ostlind-ized fashion. If you show images with a current discussion, then it is you who should hold off on the bombast until you get your act together enough to show your, "refined version".

    You can do this with well executed 2D drawings that are clear and show the setup in three views to scale along with a well drawn perspective view... Or, you can provide a set of multiple view 3d rendered objects that correctly illustrate the so-called, refinements.... Or, you can make one of your hand-axe fashioned balsa models with crummy photography and buffalo your way through the presentation.

    However you do it, the representations are totally in your area of responsibility and the old images should not be shown again unless they are germane to the discussion, which you so loudly admit in your own rant when you speak of the refined version.

    Ya, wanna blab about your magical thingy, then get it together and build a model, or any of the above versions of your magical thingy, or quit talking about it as if it were presented in the here and now.
     

  6. Doug Lord
    Joined: May 2009
    Posts: 16,672
    Likes: 339, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

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    The answers to the above questions may be able to be interpolated based on Parliers boat. The ama represented by the model is 13' LOA and is designed to work with an 18' LOA tri.
    What is known based on the ama geometry is:
    1) the displacement ama has a L/B ratio of 20/1,
    2) the displacement ama will support the whole weight of the boat(though it shouldn't have to) at low wetted surface,
    3) the planing ama should begin to plane at about 5-6 knots of boat speed,
    4) the LCB of the displacement ama is designed to be slightly ahead of the static LCB of the main hull.
    5) the center of lift of the planing surface is a bit further ahead of the static LCB of the main hull when the main hull is flying.
    6) the rotational system is so simple that an 18 footer could easily(and advantageously) be sailed single handed particularly in light of the foils on the main hull(see below).
    Note: the hull would be built as one piece-with a flush collar behind the step supporting the hull forward. The displacement ama and the planing ama can be set up with an angle relative to the main hull as viewd from forward. Both angles can be preset and would be different. Approximately 6 degrees for the displacement ama,bottom toed out. Approx. 13 degrees for the planing ama, bottom toed out.
     

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