Dinghy Design: Open 60 influence?

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

  1. SteveMellet
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    SteveMellet Senior Member

    Doug, seems like we are misunderstanding eachother - my reference to stuck daggerboards was not directed at the Nacra F20, but at the concept of a dinghy in which the foils would have to be raised and lowered each time it tacked, all while under load, with your projected 50% extra sail area. I`m sure you`ll understand it more clearly when re-reading my post. My jibe at testing it in 37knots in Cape Town was in jest - except that we have had that most of summer in the afternoons, so a boat with 50% more sail area might not be too marketable here.
    Likewise I misunderstood you - By the original title of the thread I thought that your design idea was directed at a dinghy, ie a small lightweight craft normally launched from a beach of sorts, whether on a lake or open sea. If the design is limited to ramp launching then your target audience just got smaller. If the craft can be beach-launched, even if only on a launching trailer, there will always be a time when it gets pulled up the beach (typically in breaking surf) while one crew runs for the launching trailer. It`s then that daggerboard cases are prone to collecting sand, not good for internal rollers, if they are used. Other than that they might not be a bad solution.

    Good luck with the design, it looks interesting in concept.
     
  2. CutOnce

    CutOnce Previous Member

    +1

    I'm all for posting design ideas here - although I get frustrated when people post quantified exclamation! marked! conclusions about design concepts before actually testing. How can anyone post percentages in increased sail area, lower crew requirements and higher speed potential percentages without testing, data collection and peer review? As someone who has had to submit a thesis for academic peer review before my research was accepted, I have come to doubt the value of conclusions reached without acceptable research process and independent review.

    In addition to making claims of serious performance/power/RM increases, actual experience doing the activities proposed is a critical element in evaluating the potential of ideas. Lifting even perfectly straight loaded daggerboards in small high performance skiffs is difficult to impossible when under way. When this type of real world truth is ignored, it points to the obvious conclusion the person claiming it possible has no experience doing so. Considering the problem of lifting curved, highly loaded boards with a tight 1.5-2' radius, while also dropping the other side during a 8-12 second tack or gybe doesn't seem easy or even possible - especially with complex curves and variable profiles necessary to accomplish all proposed functions.

    I think there may be merit investigating concepts like this, although decades of experience have taught me test first, conclude later is the best strategy to gaining credibility. I'd be much more positive if the original poster posted his idea, and asked for feedback without making performance claims, quoting percentages or getting defensive.

    --
    CutOnce
     
  3. Doug Lord
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    Doug Lord Flight Ready

    ===========
    Steve, my apologies for any misinterpretation on my part. When I started this thread I hadn't conceived of the reverse curve foils and was interested in peoples thoughts on the trickle down from Open 60 development*. These foils seem to me to have a wide potential for use on dinghies on up but there are many problems left to research. The analysis of how the lift works in both directions and what the negative repercussions, if any, of the foil configuration might be. I will update as I know more.
    * I'm very much interested in peoples thoughts on the potential trickle down from the proven Open 60 foil technology.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    =====================
    I don't think you have done any boat design/foil development. When you come up with a concept and look at it in analytical way it is possible to draw some conclusions about the concept. That is not hype- I have repeatedly stated that there is a lot of work to do-research, model testing etc to validate the concept but if you didn't have the potential benefits as I have described them, how would you know that it is worth the effort to investigate further?
    If you didn't theorize that there were potential gains why waste time playing around?
    Thats part of the danger of making a process like this public: conclusions are reached by some who have no idea about the concept in the first place!
    That's a risk worth taking for me in order to share a new concept from the very begining through to conclusive results-one way or the other.
     
    Last edited: Jan 29, 2011
  5. CutOnce

    CutOnce Previous Member

    Wrong. You may be able to estimate and set targets to be accomplished through building and testing, but drawing conclusions is impossible.

    It is worth investigating further on the potential of the technology. It seems like the cart is being placed ahead of the horse here.

    There is no inherent danger in making research topics public. That is nonsense spouted by the patent industry. Ideas can not be patented - only specific documentable implementations of ideas can be.

    You asked in a public forum for feedback on the applicability of Open 60 technology to small, fast dinghies. I thought long and hard, applied both experience and theoretical analysis and provided polite, well reasoned feedback. I think there is great potential in foil research when applied to dinghies. As stated, I think this specific dual foil concept would be difficult to impossible to reliably and easily function in a skiff type boat. I think this boat type is already approaching it's maximum speed potential as a planing hull, and adding more power and more righting moment to support that power will not result in notable speed gains.

    I've reached no conclusions, and only tried to politely respond to your request with thoughts on the topic at hand. If you do not want feedback, do not post this on a public forum. If you have a problem with my feedback, put me on forum ignore and problem solved.

    Cheers,

    --
    CutOnce
     
  6. Doug Lord
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    Doug Lord Flight Ready

    --------------------------

    You miss so much: if you read the NACRA 20 thread on SA you can see that the nacra 20 guys adjust the boards all the time. They've tried leaving them both down, as Steve said, and found that it is not fast but they say that the whole boat is lifted(and its a wild ride) . What you don't get is that the Nacra 20 is 10.5' wide but the foils curve into the centerline reducing the distance between the center of lift of each foil with both down to somewhere around seven feet while the difference on the dinghy sketch with both down is about 9'! And when the dinghy heels the the RM goes up whereas the Nacra RM goes down.
    With a single foil down the NACRA LOSES RM but the dinghy gains RM. With one foil down and moving the dinghy is much more stable than an equivalent dinghy without the foil. With both foils down the dinghy is nearly as stable as a cat when moving.
    Since this is a new concept that hasn't yet been tested this is well researched speculation about the performance that should be able to be achieved with reverse curved foils assuming they are designed properly and correctly matched to the boat.
    The "labor intensiveness" comments ,are in my opinion, nonsense-at least they will NOT be more labor intensive than correctly using the foils on a Nacra, DNA A class cat or any boat with asymetrical leeboards. I don't see that as a valid criticism at all but time will tell.
    There is a major hydrodynamic issue to solve before anything else is done. If that works out than I will test model versions of the foils compared to a t-foil on the new test model I am building.

    Nacra20
    Boat length 6.20
    Boat width 3.20 10.5'
    Mast Lenght 10.45
    Area mainsail 21.00
    Area Jib 5.20
    Area Spi 28.00
     
  7. CutOnce

    CutOnce Previous Member

    I actually know Steve Clark in person, not from the Internet. A Catamaran is a completely different thing from a skiff. Adjusting boards on a Cat is completely different as well. Windward boards are moved when the hull is flying, therefore there is NO load. Leeward boards are moved when both hulls are in the water at low speed. It's easy because the boat is stable due to two hulls in the water. My skiff will not stand up for two seconds on it's own. It falls over instantly if you are not actively balancing it, and is not in the least stable until it is moving well under sail - and once it is, you can't move the daggerboard. That is ON THE WATER experience speaking, not information from someone else's posts on the Internet.

    How is it that you can reach conclusions like this without one shred of real-world evidence? You have no proof this concept is any more stable than Jared Loughner. Proof means demonstrate-able, repeatable results, not conjecture. Please separate facts from conjecture in your discussions and there will be far less issues with your claims. I'd certainly buy it if you claimed "I think it would be more stable" instead of certainty as your write.

    Come on Doug. Face reality. If history is any indication of the future, you are never going to build this ever-more-complex test platform, and it will never sail. That's okay - I'm not interested in calling you out on using boatdesign.net as a fun place for you to spend your time daydreaming and congratulating other people who build things. This new boat already is supposed to include foiling and non-foiling configurations. Twistable for trailering Trapwing and no trapwing options. Planing stepped buoyancy pods and no pods in the high performance version. Centerline bucket seat and plug in bench seats. Retractable amas. Retractable rudder gantry. Twist grip rudder t-foil. Anyone here building lists from your prior posts can go on and on adding things. Foil jumping when in optional manual control mode. Mobility challenged mode. There are more features and technology on this proposed boat than on a cold war budget nuclear submarine.

    Now you are adding curved daggerboard slots with bottom side inserted curved foils. By my guess, these foils will cost more than a used car to build, and will require a designer of Mr. Speer's caliber to put pen to paper. That brings the total foil slots to three or four, depending on if you have different centerline slots for the foiling versus non-foiling versions. Every one of these foil trunks requires suitable structure and reinforcement - the loads will be tremendous - especially if you stick to your guns regarding the ability to carry 50% more sail area than conventional designs of the same type.

    It all seems so .... over the top. I'd be more convinced you were going to build something if you bought an old 29er and got out the Sawzall to add your foil trunks. Simple. Cheap testing of concept removing all the other distractions from the table. Each one of your "innovations" is so major that trying to fit them all in one test platform is a harder job than Obama has cleaning up the State of the Union.

    Again, if history is a reliable indicator of the future, this thread will die down once I let you have the last word. Once it subsides, you will post to it randomly for a while trying to revive it, and continue to do so on a less and less frequent basis. Then the next great idea will emerge, and you will be all over it. New "design discussions" reaching new stupendous performance increases of xyz% will be touted, and those features will be added to the 19' testbed platform. And the cycle will repeat again and again. And you will never put down the keyboard and go out to the shop.

    I'd love for any of your schemes to work. I'd really love faster boats that require less effort. I'd probably even love a People's Foiler if one ever got built. For any of these things to happen however, it would require time, money, effort, focus and persistence. You are persistent and seem to have lots of indoor web surfing time, I'll give you that. I'm not so sure about focus, money, shop time and effort however. Best of luck proving me wrong, I'll be cheering you on.

    --
    CutOnce
     
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  8. Cheesy
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    Cheesy Senior Member

    Are you actually sure that this idea hasnt been tried before and discarded? As you know form the Moth class there are a lot of experiments that are failures which are dropped without any sort of widespread publication
     
  9. Doug Lord
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    Doug Lord Flight Ready

    Open 60 influence

    --------------
    No, I'm not. But a few friends and I are doing a lot of research.
     
  10. Doug Lord
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    Doug Lord Flight Ready

    -----------
    I was referring to Steve Mellets comment.....
     
  11. Doug Lord
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    Doug Lord Flight Ready

    ============
    This is an uniformed comment that illustrates what YOU don't know. But the use of that murderer's name in the context of a boat design discussion is one of the most insensitive, over the top comments made on this forum. Saying something like that is waaay out of line.....

    1) You are fond of making remarks about "real world experience" which you describe yourself as "the voice of". Actually, your experience with foils is nil-you have NO real world experience whatsoever. My experience with foils on dinghies goes back to 1975-77 when I put foils on my experimental "Tantra", a 15' dinghy. They extended outboard from the molded in leeboards doing similar work to the "reverse curve foils". You can see the port side foil if you look close in the picture below. The increased stability of the boat with those foils was amazing-and it didn't have to move very fast for a large increase in stability. I designed the boat, the rig(one of the first square top rigs anywhere), the foils and did the test sailing. Thats real world experience with a high performance dinghy and foils going back 36 years!
    ---
    I designed built and foiled the aeroSKIFF 16 but you didn't have to foil to see the(feel) the increase in stability of the boat as compared to no foils. The main foils had dihedral tips which made a difference under sail. I designed, built, sailed and foiled the boat. I designed the foils as well and the rig(one of the first square top jibs anywhere). That's real world experience with a high performance dinghy and foils going back 10 years!
    ---
    I have worked with hydrofoils on dinghys and done hydrofoil research for 40 years with numerous full size and model experiments along the way. I know, for instance, that the Moth is more stable on foils,at least in roll, on foils than off. I've had many, many hours of sailing a Rave foiler that gets all its stability from foils. Thats real world experience that covers the gamut from design, building to sailing to testing and I'm pretty sure is far, far more extensive than any experience you have with foils applied to dinghies.
    ---
    This experience gives me the ability to make a well informed, accurate judgement as to the viability of the foils in question with the caveats I've already discussed. But its not just me-if you were well read on the subject matter you would know that my comments on the RM of the Nacra 20 or any other cat or mono hull with "normal" curved foils is right on the money, from the designers of those foils to the sailors themselves.
    -
    Sorry, Bistros, but you have very clearly illustrated what YOU don't know, and that you are more than willing to comment from the standpoint of a major lack of knowledge. And you've done it in your inimitable style with false insinuations and a remarkable distaste for knowing what the facts are.

    click on image and then again on resulting image for greatest detail: left= Tantra 1975 design 1st sail 1977, end 2004; right-aeroSKIFF 16 1999-2000 design, 2000-2003 build, still alive in a bit of a different form.
     

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  12. Doug Lord
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    Doug Lord Flight Ready

    Reverse Curve Foils compared to "Normal" curved foils

    Illustration of "normal" curved foils on a NACRA(or A Cat or etc) and the reverse curve foils in a rough illustration.
    With one foil retracted it is obvious that the "normal" curved foils reduce RM a bit and equally obvious that the reverse curve foils increase RM. Also,if the reverse curve foils prove out, they could work on multihulls as well as monohulls. In either case they might be prohibited by beam restricitions in class rules:
     

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  13. MalSmith
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    MalSmith Boat designing looney

    Doug,

    It should be simple enough to do an analysis of your reverse curve foil, to see if there was any real benefit to it (I'm not volunteering to do it though).

    Just from looking at the diagram, I can see that in order to prevent leeway with the top of the foil and provide lift at the bottom of the foil, there will be a large transition zone in the middle which is doing nothing useful. What you have is effectively two seperate and opposing lifting surfaces joined by a strut. Each "lifting surface" will be higly loaded, whilst being, effectively, of a low aspect ratio and therfore not very efficient. My eyeball analysis is that this system is of dubious benefit.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    reverse curve foils

    ==========
    Thanks, Mal- you may be right. There are possible solutions like a fence but that causes a problem with the trunk. You've identified the major potential problem and its being looked at carefully.
    It's interesting to look at the "J" foils on the Hobie Tri foiler: one foil always has high and low pressure on the same side(surface). With the foils facing outboard *the lee foil has high pressure on the outboard vertical face while having low pressure on the same surface on the lifting portion in exactly the same way as it happens with the reverse curve foils. The question is: does the tighter curve reduce the problem to acceptable levels-or is there not a problem?
    *UPDATE: 1/29/10 they face inboard, see page 4 for more info.
     

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  15. MalSmith
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    MalSmith Boat designing looney

    Doug,

    The windward Hobie Trifoiler foil is not the highly loaded one, and may be, as often as not, producing some downforce. Note also that the radiused part is relatively small, and the vertical and horizontal sections are straight. The lift/leeway functions have been separated to some degree.
     
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