Dinghy Design: Open 60 influence?

Discussion in 'Sailboats' started by Doug Lord, Jan 22, 2011.

  1. Magnus44

    Magnus44 Previous Member


    Doug, I am reluctant to reenter the discussion at this point, but you have just entered my area of expertise when it comes to the analyzing process of one part against another and by extension, how efficiently it might be built in a production scenario.

    Does not two boat testing with identical hulls make sense to you in order to sort out the differences that may be provided by the design separation of which you speak? Go ahead and use your Tantra? to run a test, but there are several other properly configured dinghies out there that are obtainable for next to nothing that could be more than suitable and will rapidly allow a grouping of analytical data points to determine the potential.

    Right now, it would seem that you are shifting analysis possibilities in order to support the argument. Serious analysis proponents would tell you that once you shift the discussion and the elements, you have made necessary a whole new set of data points. If you do not have a pair of T's from which a proper and credible analysis can be drawn, then you look for the next best set of data point producing subjects to get something that might indicate the possible success of the hypothetical suggestion you make. From that you may, or may not proceed, but without the correctly produced data, you are simply guessing as to the possibilities



    Are you saying that it is better to have two non-identical boats for this process? I am afraid that you have left the realm of science in the process and entered the realm of something else if you think that two nonidentical boats equipped with different setups will yield supportable data.


    Are there any T1's on the planet that are capable of being modified and from which to draw conclusions, or is this a supposition based on something that existed years ago and is not available now? The answer, of course, is to build two T1's with the same configuration and equip one of them with the curved foils and then test them side by side in order to gather proper, equivalent data for comparison. Nothing like the present to build the paired craft and run the tests with full understanding that they may not yield the data you seek. I know this from years of building test modules of this sort and finding that the original assumptions were faulty and that the product had no future as a manufactured item.


    Right now, it has no potential and I am sorry to say that here on Boat Design. You have made assumptions. These assumptions have not been proven through standard means and at present, they are not able to be reproduced. What you have here is a collection of assumptions based on things that are not of the type that manufacturers seek before they tool-up in a prototype process, much less a full build.

    You have said that this boat is not for home builders and that is what originally made it a non-issue for me and my interests. Now, it looks like the boat is also a non-manufacturable entity. It shall remain that way based on my experience in the field until a satisfactory prototype has been built and successfully tested against an identical design without the proposed changes.

    At this point, I am out of the discussion based on both points of interest. No reasonably interested average person can build this boat outside of a factory and there is no proof that such a boat could work, even if it were built by a qualified factory.

    Thank you for your time, Doug, but this is a dead end for me as I suspect it is for others who have been reading along with interest.
     
  2. Doug Lord
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    Doug Lord Flight Ready

    Thanks for your comments, Magnus. I have been involved in design ,building and testing of boats for over 50 years and believe that I am qualified to design a development program for a new boat which I have done several times in the past. Based on your comments I think you may have missed the highlighted sections of the post below:


     
  3. Doug Lord
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    Doug Lord Flight Ready

    T2 Curved foils compared to Nacra Catamaran Curved Foils

    Here is an illustration showing the Nacra 20 foils and their curvature and the rough sketch of the proposed dinghy foils for the T2. The biggest difference is that the dinghy foils have more curvature and, hence, more vertical lifting area as a percentage of total foil lift. From a design standpoint curved foils offer a wide range of options that allow them to be tailored to a specific design:

    (click on image)
     

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  4. Munter
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    Munter Amateur

    It seems a bit harsh to say the idea has no potential but perhaps Doug has underestimated some of the challenges of actually going from a design idea to a working example.

    Back in the design space for a minute, what part of the concept represents the "exceptional level of innovation" claimed above? How are these curved boards meaningfully different from bruce foils used to stabilise experimental vessels as shown in the AYRS for decades? I know the curved boards theoretically go up and down in a trunk differently to a straight board but why is the curve significant? Is it just that it allows an inboard retraction pull? Is it that curved boards avoid a greater total beam when retracted? Is it that it allows the reduction in lifting area before a reduction in lateral area? Doug - do you believe there are benefits to curved boards compared to bruce foils beyond those listed above?

    If not, do these are these factors add up to a good enough reason to go through the added complexity of creating a curved boards and cases instead of straight inclined boards?
     
    Last edited: Feb 16, 2011
  5. Doug Lord
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    Doug Lord Flight Ready

    Tantra II / curved lifting foils

    See page 8 for a summary of the princible design concepts of the T2 and more on the curved lifting foils.
     
    Last edited: Feb 18, 2011
  6. Gary Baigent
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    Gary Baigent Senior Member

    Doug, you're all over the shop. What about those numerous other designs and models you were getting revved up about? Jeez man, pick one and begin bloody work on it. We're interested with what you produce ... but everyone has gone to sleep on the screeds of figures and high flying proclamations. Not insulting you ... just want some real activity.
     
  7. Doug Lord
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    Doug Lord Flight Ready

    Dinghy Design: Open 60 influence? / Tantra II

    =============
    I'm building the SRT model now-and have a thread about my progress in multihulls. Will have the first results in a month or so I hope. That hull will test numerous ideas as is described in detail in the thread. I wish I could go faster but.......
    How's your 24 coming along?
    --
    I'm not going to build the Tantra II for a long time but someone else may. I am going to continue developing the basic concept and may do a final design. You reminded me about numbers-I have done very little preliminary numbers crunching with this thing- just enough to know the basic potential-- I'll have to take care of that. Thanks.

    PS- did you see the stuff I posted from Greg Ketterman on the "reverse curve foils"?
     
  8. sean9c
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    sean9c Senior Member

    Sort of been following this thread. Haven't understood it from the beginning. Can't really believe that the mechanics of handling 2 boards on a high performance dinghy would be feasible.
    Saw this on SA yesterday. A quote from Bob Hodges from the A cats.

    It appears that light air performance is not negatively impacted and upwind and downwind performance as the breeze builds is certainly improved. The curved boards reduce the righting moment of the platform forcing a more physical and dynamic sailing technique and what has evolved from this is sailors starting to use their trapezes downwind in over 10 knots of breeze.

    Now I also cannot understand why it would be a positive to reduce RM on a performance dinghy by adding curved boards.
     
  9. Doug Lord
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    Doug Lord Flight Ready

    Dinghy Design: Open 60 influence? / Tantra II

    Rough illustration of the approximate variation of vertical lift with incremental board retraction :

    (click on image)
     

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  10. Doug Lord
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    Doug Lord Flight Ready

    ==============
    Sean, thanks for the comment. The curved lifting foil reduces RM on a multihull because the center of lift of the foil is inboard of the center of buoyancy of the lee hull which results in reduced righting moment-and a small amount of vertical lift.
    On the T2 concept the center of lift of the foil is outboard of the center of buoyancy of the hull resulting in increased righting moment along with vertical lift. Further, the curve of the T2 foil is tighter with more foil area used for vertical lift.
    The T2 concept is a "performance daysailer" not a high performance skiff type dinghy although the foils will allow very good performance throughout the wind range. Because of the fact that the curved foils increase RM substantially on this design it will be able to carry more sail than would a comparable boat without the curved foils.
    --
    Handling twin foils won't be a problem-its done on scows all the time and singlehanded on Open 60's, mini's and high performance cats and tri's.
     

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  11. Munter
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    Munter Amateur

    Doug, that is a long response but I don't think it really answers the questions that I put to you:

    So the innovation is in combining molded in storage with a daysailer with foils? Seriously?


    I also don't see how the use of the curved foils is meaningfully different from Bruce foils. You say the curve is "very important" but don't explain why straight foils couldn't do the same job.

    The variable lift angle that you get with a curved board only applies if you adjust the immersion of the board. Given that it will be all but impossible to do under load this is only something you could do on the windward side and the effect would not be felt until the boat tacked. By integrating some form of adjustment you could probably do the same with a straight board anyway.

    Shallow draft is nice but not revolutionary nor unachievable with a straight board or an L board. I doubt many sailors would be willing to risk an inevitably expensive vessel by sailing in waters that are only just deep enough. Collision with a sand bar is sure to cause major damage, particularly as the tips of curved boards could impart huge torsion on the case and top of board.

    Automatic ride height control is a by-product of having angled surface piercing angled foils. As I see it the curved shape would actually reduce the effectiveness of the ride height control as the first area to rise above the surface is the most vertical and therefore has the least impact on reducing lift. A standard straight board would be more effective I think.

    I don't deny that curved boards are proving effective in other classes by the way, but I don't see why they contribute anything particularly special to this latest concept.

    Is there any more to it than this or will this concept join the long list of ideas/bandwagons which you have become excited about and then moved on from before verifying that the claims you make for it are actually real?
     
  12. CutOnce

    CutOnce Previous Member

    The groundbreaking innovation is that the concept include a foil component that theoretically contributes vertical lift. Some fractional potential contribution of vertical lift by a foil is the principal criteria by which our hero assigns innovation brownie points. Every one of our favorite foiling friend's enthusiasms from models to Hydroptere meet this criteria.

    All your rational commentary will be ignored, disputed or go without reasoned response. There will be a numbered list posted containing no substance, references to previous posts by the same responder containing no substance and your motives will be questioned and your knowledge and experience doubted.

    Yes.

    Yawn. Thursday.

    --
    CutOnce
     
  13. Cheesy
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    Cheesy Senior Member

    I think a good alternative would be an esky on a hobie 16......
     
  14. Doug Lord
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    Doug Lord Flight Ready

    What's an esky?

    found the answer- cooler or in NZ a "chilly bin"--thanks
     

  15. Cheesy
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    Cheesy Senior Member

    Just be careful when you go shopping for a thong......
     
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