Dinghy Design: Open 60 influence?

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

  1. Doug Lord
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    Doug Lord Flight Ready

    Reverse Curve Foils

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    Gary, Hugh Wellbourn(as far as I know) first came up with the idea of a single retractable sliding foil that when deployed to leeward increased RM by creating vertical lift to leeward of the boat. Vlad Murnikov came up with the idea to add vertical surfaces to a DSS-like foil to create lateral resistance.
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    These reverse curve foils can be widely varied in design. The version in the sketch above has the angle of incidence of the vertical lifting portion of the foil adjustable by moving the top of the foil fore and aft about a pivot point* in the trunk. The lateral resistance portion of the foil would have a fixed angle of incidence-say 4 degrees or so- the front of the foil toed- in relative to the boat centerline**. Or possibly, the trunk could be built to allow this to be adjustable** though I'm not sure it would be necessary-a fixed angle of incidence for lateral resistance should probably be ok. Be nice to see if this is adjustable on the 60's.
    See page four for more info on the perormance potential(or lack thereof) of these "reverse curve foils".

    *horizontal axis of pivot
    ** vertical axis of pivot
     
    Last edited: Jan 29, 2011
  2. Gary Baigent
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    Gary Baigent Senior Member

    Okay, moving the foils at a pivoting point allows for varying angle of incidence, that gets round that problem. Does the whole case move too? However, you may be thinking sort of a wide V shaped fore and aft upper case, which will allow AoI movement, plus wedges, yet still have a non drag and mostly sealed case at the foil exit point. Fine, that will work. But getting over the symmetrical to asymmetrical sections will still be tricky. I've built foils with helicopter type blade twist, but never changing foil sections as required here, that is quite radical. Have you?
     
  3. Doug Lord
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    Doug Lord Flight Ready

    Reverse Curve Foils

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    No, but I think it can be done but I'm not sure the sections couldn't stay symmetrical. Nice challenge for some serious design work by a foil designer like Tom Speer. I'm thinking it has a lot of potential -particularly on any size planing monohull.
     
  4. CutOnce

    CutOnce Previous Member

    Ground control to Major Tom

    I love technology. I spend my life creating and maintaining technology products and the intelligence behind the function. I like new ideas, and relish critical thought in how to apply ideas to the needs of people.

    I sail small fast unstable boats. For real - this is not a theoretical armchair Internet exercise for me. Frequently I get into trouble and mess up, ending in a swim. Small fast boats are complicated and sensitive, getting high performance due to overpowered designs with little to no margin for error in maneuvers and balance. I don't know about anyone else, but every time I try to adjust foils under way, they bind and it takes huge effort to move them. 505s have adjusting tackles from 4:1 to 8:1 to move their ONE gybing centerboard up and down. 5-Oh's generally will tweak their boards twice per lap around the cans - raising them partially on rounding the windward mark and dropping them fully at the leeward mark. This process also automatically locks out the gybing capability going downwind - because the gybing isn't manually adjusted, it is handled by a fixed flat surface angle on the board head inside the square trunk. Going upwind, the board automagically flops from one tack to the other, resetting the angle of attack.

    Basically, I think foils that adjust in more than one plane, that require curved trunks and complex adjustments are not practical in twitchy boats expected to tack and gybe in 8 to 12 seconds. I think ONE foil is more than enough challenge to handle in a small boat, let alone two. I think that adding RM by foil lift is unnecessary as there is no righting moment problem that needs to be solved. I think adding structure and weight to support dual foils is unnecessary and counterproductive. I think (actually KNOW) the crew are too busy with other things to stop and fool with changing boards while tacking and gybing in an unstable monohull (Cats & scows are a different story). Sail in a two-man skiff and see for yourself - there just isn't time to stop and frig with anything, because if you aren't clipped on and out on the wire when the boat powers up, you are swimming. Period.

    You've asked for feedback and people's thoughts on applying Open 60 technology to performance dinghies. I don't think it applies. Perhaps if people wanted a complex, work intensive day sailor, it could be made to work, but that is exactly 180 degrees out of phase with daysailors - they want relaxed, non-intense fun.

    It is a fun theoretical exercise to try to apply technology to different situations - but sometimes it doesn't jibe with reality. I'm sure your opinion won't change at all, but other people reading this will probably realize the wisdom, careful thought and experience that have gone into my response.

    Oh, well now I'm ready for the upcoming denial of reality rant and point by point explanation of how more structure can be lighter, complex operations can be made simple, and how making something physically heavier so it can make it hydrodynamically lighter at speed can be faster. Maybe we can add joysticks, batteries, UAV software and gimbaled cupholders.

    Simplicate and lighten.

    --
    CutOnce
     
  5. Doug Lord
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    Doug Lord Flight Ready

    No more power in all of dinghy design....hmmmm

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    Thanks for your comments, Bistros. This one sentence says it all.......
     
  6. CutOnce

    CutOnce Previous Member

    Yes Doug, it did. Perfectly adequate righting moment in a performance dinghy is provided by crew (and often helm) on a trapeze. This is the most efficient, adaptable to variable condition solution possible. Crew can react to wind shift, lulls and gusts better than any mechanical or architectural solution. Crew are intelligent, quickly movable, infinitely adjustable and fast.

    No architectural solution like DSS and your proposal can actively respond to gusts and lulls - you can't turn a foil on and off without complex mechanical linkages and/or crew initiated movement.

    For once, actually go sailing on a current high performance dinghy on water instead of in your imagination. Theory and reality collide more often than you are aware. Five minutes trapeze helming a 49er or I14 around a race course and your opinions of what works in performance dinghies will change a lot. And you will have much opportunity to work on perfecting your swim strokes.

    It is one thing watching a tack on a Youtube video and timing it on the Internet. It is completely another experience putting the helm over, unclipping, running to the other side while grabbing the tiller extensions, picking up the jib sheet tail, clipping on and pushing out while swapping hands on the sheet and tiller. Ah, yes while doing so you are adjusting trap height and keeping an eye on others around you, whether or not you crew is powering up the main and anticipating gusts and lulls, as well as sea state. Gybing is twice as intense as you are going double to triple the speed while doing all the above.

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    CutOnce
     
  7. Doug Lord
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    Doug Lord Flight Ready

    Open 60 influence?

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    Bistros, that is such limited vision! Thats like telling the Mustang guys in 68 that a 4 cylinder engine moves the car just fine so there is no need for a V8!
    You know I've spent over 55 years sailing mostly high performance boats and the limits you place on what is possible with a crew are just nonsense-no offence. My God-at various times you have single crew's sailing Open 60's with twin daggerboards ,twin rudders and canting keels! And single crews sailing 100' trimarans with dual curved daggerboards and two to three rudders with enormous SA. Don't tell me a twin trap dinghy crew couldn't deal with dual curved daggerboards! Especially for a 10- 20% or so increase in speed! And IMPROVED handling!
    And , I'm afraid your attitude toward design improvements not only shows an incredible lack of vision but to actually say that in all of dinghy design there could not be conceived a twin trap dinghy that could use more RM is just not in touch with reality. The reverse curve foils allow a boat to be designed to carry more sail area for the same weight as a "conventional" boat-about 50% more SA! Saying the "perfectly adequate RM" of conventional dinghies is the measure by which any new design should be considered is preposterus from a design and innovation point of view. The gain is too great to so lightly dismiss such a technological advance.

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    The reverse curve foils are not limited to dinghies and could be used on Mini Transats, Open 60's and numerous different types of planing hull sailboats. They can reduce wetted surface and increase power to carry sail. See page four for more info on the performance potential of these foils.
     
    Last edited: Jan 29, 2011
  8. CutOnce

    CutOnce Previous Member

    There never was a NEED for V8 engines in cars carrying two to four people. Four cylinders can more than adequately move a car to far beyond safe speed limits. The world would be in a very different state if people had actually rationally thought about fossil fuel consumption in the 1960s. Detroit might not be the industrial wasteland it is today.

    There is a world of difference between a one or two man crew unballasted high performance dinghy sailed in races and keelboats raced around the world. The limits are real and if one was actually experienced in skiff sailing, they would easily acknowledge this.

    Yes, that is exactly what I am telling you. There will be no real speed improvements if the design is unsailable.

    When I was in grade school in New England as a boy, I used to think in a very linear fashion. If something was good, more of it had to be better. Much more of it had to be stupendously better. That was before I became a more sophisticated thinker and started to realize the world was not a simple place, and that things were far more complex than I had understood. Adding power is a game of diminishing returns, and you quickly reach a point where added power does not affect overall performance in the slightest. Where you can affect overall performance more is in efficiency and reducing the need for power to achieve a particular speed.

    There are many factors in play in any engineering and design discipline, and every time someone alters one variable in a system, others change as well. With transportation, things become exponentially more difficult as speeds increase, and there are practical limits that are reached very quickly.

    Perhaps the world is not as complex as I have come to believe. Perhaps my substandard education and obviously inadequate work experience has blinded me to the simple solutions discussed here.

    Build the world a boat that proves these theories can work, and restore my boyhood faith that simply more is better. I'd like the world to be that simple and fun once again!

    --
    CutOnce
     
  9. Doug Lord
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    Open 60 influence

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    What you miss is that this is not a case of "simply more is better"-it is a case of design innovation that offers the designer significantly broader choices than are possible without the technology:

    1) a boat using this technology can be designed to carry significantly more sail area than would be possible w/o the technology,
    --
    2) a boat using this technology could be designed to be able to be sailed with less crew for the same sail area as a boat w/o this technology,
    --
    3) a boat using reverse curved foils could be designed to be sailed w/o trapezes where traps would be required w/o using the foils,
    --
    4) In summary, any boat designed properly using these foils can expect to be faster, easier to sail and/or require less crew and/or carry more SA for the same weight and be more stable than a boat w/o these foils. That is progress as a result of serious design innovation and is the kind of application of technology that can benefit sailors throughout a wide range of possible designs from dinghies on up. At least thats the way it looks now.......See page four more more on the theory of how these foils would actually operate.
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    Problems/ More Research Required
    1) crew interaction with raised trailing edge of foil or how not to slice crew in half with a sudden stop,
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    2) this foil has some interesting hydrodynamic quirks that I don't fully understand yet: a frontal view of the foil with the "Lateral Resistance" portion at the correct angle of incidence and the "Vertical Lift Portion" at a postive angle of incidence shows a zero degree crossover point at approx. half the length down. On either side the foil has a high pressure AND a low pressure area when set as described. I don't understand how this will behave-yet.
    very rough sketch-click on image:
     

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    Last edited: Jan 29, 2011
  10. Gary Baigent
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    Gary Baigent Senior Member

    I'm guessing your sketch is just showing the leading and trailing edges and not the overall thickness - otherwise it is quickly going to snap like a wafer in the mid section.
    But the tricky thing is that to go from anti leeway, semi-vertical section with the front low/rear high (to the hull CL) to the zero AoI mid section and THEN to front high/rear low lifting section ... means that the leading and trailing edges will only fit in a box-like case ... and then you have a drag problem at the exit point. Or do you see these problems in a different way?
     
  11. Doug Lord
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    Doug Lord Flight Ready

    Open 60 influence: Reverse Curve Foils

    I see it entirely differently.The illustration is just the trailing and leading edge-nothing to do with thickness. The foil is NOT twisted-it is simply toed in and angled back which creates the illusion of twist. It would slide in a trunk just like any other curved foil! It is very interesting and I've learned that in aero dynamics they call this a "non-planar" wing. The ultimate example of a closed non-planar wing may be the concept drawing below for the MD-90 airliner. The questions I had(and still have) were motivated by the fact that the reverse curve foil probably would tend to have high and low pressure on both sides of the zero degree point and on the same surface at the same time as it seems to me the MD-90 concept wing would. Lots more to learn-maybe I can incorporate some foil tests into the 18' self-righting tri model(multihulls thread) just to try to understand more.
     

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  12. SteveMellet
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    SteveMellet Senior Member

    "The reverse curve foils allow a boat to be designed to carry more sail area for the same weight as a "conventional" boat-about 50% more SA!"

    My advice : Build it, then test sail this theory in Cape Town in summer. 50% more sail area in 37-39knots could be mildly entertaining, watching the crew lifting and lowering stuck daggerboards.
    The Nacra F20 works because the boards are left down, the crew flies a hull so that the windward one is seldom in contact with the water. They might pull them halfway up downwind, but not swopping them over through tacks.
    Doug, you`d perhaps get more positive responses if, like Steve Clark, you first built it, sailed it successfully, and THEN wrote about it.
     
  13. Doug Lord
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    Doug Lord Flight Ready

    Open 60 influence: Reverse Curve Foils

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    Steve, since I just came up with this concept a couple of days ago my first inclination was to share it with the community at boat design. I'm not satisfied that the concept is worth building yet though it looks like it has potential. To me, it is important to share DESIGN ideas on this forum where very knowledgeable people can offer suggestions, help, insight and constructive criticism-all of which I value a great deal.
    Thanks, but I've received several positive responses from people I respect immensely. And the learning experience in trying to understand the way the foils will actually work is just plain fascinating raising issues I've never considered before.
    ----
    Interesting take on the Nacra-seems a shame that the boards appear to not work too well in their trunks. I think that it would be very important on any design using reverse curve foils(or any foils for that matter) to have a first class, well designed, easy to use and fully functional board/trunk system.
     
  14. SteveMellet
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    SteveMellet Senior Member

    Doug, I`ve not heard about the Nacra boards not working too well in their trunks, can you direct me to where you`ve read comments from those who have sailed them ?
    My comment on the boards being left down is not as a result that they can`t be lifted while sailing, although this would be an issue for any loaded boards, I sail a catamaran with straight symmetric boards, and they are impossible to lift when any decent speeds are done, certainly not while sailing upwind - have you tried lifting a daggerboard when it`s loaded ?
    My point was that, in contrast to a monohull, they have no need to lift and lower boards as they can sail upwind on one hull & most of the windward board out of the water most of the time.. As others have mentioned your solution creates a boat that starts to become more labour intensive to sail than one without these foils, unless they can both be left down. Perhaps if your trunks had rollers in to assist lifting & lowering boards while under load it might be feasible, but being an off-the-beach type boat, I`d not want to add sand to that suggestion..
     

  15. Doug Lord
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    Doug Lord Flight Ready

    ==============
    1) Perhaps I missread you but you are the source of the story on Nacra boards:
    2) I wouldn't lift the board while it was loaded to the point I knew it couldn't be lifted. These "reverse curve foils" develop vertical lift-they'll probably be locked in position by some means and tend to jump up when the lock is released.

    3) as I have mentioned I believe that the foils can be easily dealt with by the crew as has been shown in scows and mini transats for years and years.

    4) Good suggestion-something to think about in various incarnations of a design using these foils. I never mentioned "off the beach sailing" though I see no reason why one of the versions of a boat using these foils couldn't be beach sailed.
     
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