Little America's Cup 2010-C CLass-the real one..

Discussion in 'Multihulls' started by Doug Lord, Apr 12, 2010.

  1. TTS
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    TTS Senior Member

    I wonder what the cost is on the wing. On C-class cats, they are extremely expensive. Ben Hall's wing was about the same as the cost of mast and sail for the A-class. As far as who will whin, Steve's boat Aethon is great looking as is fred's new platform Caanan. Two very different thought processes in the design department. I think that I like Steve's platform over fred's from what I can see of both. Since neither boat have sailed against each other yet, it is too early to tell. Fred's new wing is fantastic looking. Higher aspect ratio and looked stunning in light winds. We have yet to see Steve's new wing, but hopefully we will soon see it as well. I have to believe that Steve will finish it soon since racing is now 17 day and counting. both teams will have a lot to do to shake down both the new boats and new wings. Neither team will be able to come up with new wings after they have seen each other's. So nothing gained by waiting any longer. As to fred's teams, I wish them all the bast with the rebuild of the damaged wing. I am heading down to Newport tomorrow to see if I can see the boat at Sail Newport. My money is on Steve and his team. though Lars and andrew sailing on Cogito is a formadible team. Lars is one of the top cat sailors in the world. You also have the team of Glenn Ashby/ James Spithill for Fred. Glenn is 8 times A-cat world champion, Olympic medalist and Tornado World champion. So he will be one of the contenders. You cannot count out Inviticus with its new wing and Larso at the helm. All in all, this should become one of the best C-Class regattas ever.
     
  2. Paul B

    Paul B Previous Member

    Are you talking material cost? Surely Hall would not build you a wing for the cost of a Hall mast and Glaser sail?
     
  3. TTS
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    TTS Senior Member

    No, Ben would not build you a wing for the cost of a glaser Main, RBS Battens and a fully rigged Hall mast. He was the one who quoted the cost of the wing. I posted that here when the wing was first rolled out and on SA and catsailor.com at the time.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    Little Americas Cup

    ============
    One of the things most interesting about the Moth wing is the degree to which it will be better than the extraordinary "normal" Moth sail/rig. And it is interesting to note that when Larso and Team sailed against a Moth they were very close in speed. Does all this add up to a 24' monofoiler with a wing being faster than the best C Class?? Hopefully we'll find out some day...
    --
    As to the race, I want to see Steve's wing before I commit-but I'm leaning the same way you are. That Canadian wing is awfully impressive, though....

    ---------------
    Ben Halls reflections on his Wing:
    I sailed with the wing at the Worlds in November 2007 finishing 30th out of 100. I sailed the wing in a few Midwinter events with good results. Due to the extra time of rigging the mast and the inconsistent performance through the wind and wave conditions, I have gone back to a conventional rig/sail combination. I did not use the wing at the 2009 North Americans.

    The project was successful in that it met the weight goals set out in the beginning, it survived a capsize with no damage, it was reasonably competitive on a World level, it was a very cool build project and was a great experience to work with “wing nuts” Dave Hubbard (designer of the wing) and Steve Clark (moral and build advice support). It was one thing to build a complex lightweight structure and another thing on how to make it go fast on the racecourse. It also survived numerous heavy air days with no breakage.

    As an afterthought this project has shown that the standard rig development in the A-Cat is highly developed with a combination of carbon airfoil mast sections and modern sail fabric/design. Many have asked if you had it to do all over again, what would you do differently. I have a long list but I have yet to decide if I will have another go at it.


    http://www.sailingscuttlebutt.com/news/09/0810/
    --------------------------------------------------------------------------------


    Ben Hall's A Class rig:
    (click on image and click on resulting image for best detail)
     

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  5. Doug Lord
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    Doug Lord Flight Ready

    Comments on SA Thread regarding curved foils. Steve Clark is the only C Class using them in the upcoming LAC, but the A Class has been using them for awhile.

    comment one:
    We spent three days on Lake Pontchartrain training on A-Cats this weekend. We had three boats sailing; my ASG3 with Fiberfoam/Ashby mast/sail, a Marstrom Mk V with Fiberfoam/Glaser-Landy, and an updated Flyer MkI (update is higher aspect straight daggerboards) with Hall/Ashby. We had a high pressure system in place so we never had more than 10 knots of breeze doing most of our sailing in 6-8 knots (in and out on the wire upwind, more tiring than heavy air sailing!). From my perspective, we confirmed that curved daggerboards did not seem to have any significant overall performance advantage/disadvantage in the light air and this was consistent to what we saw at the 2010 A-Class WC. The only thing in regards to the foils was on several upwind runs, we had the Marstrom sailing with the windward board pulled up. It certainly did not seem to hurt its performance (not sure if it was helping). On the ASG3, I tried it twice and had two impressions, the helm lost some "feel" and it seemed like I was losing some height. Draw your own conclusions, the ASG3 has symmetric curved blades, the Marstrom curved blades have some asymmetry. At the beginning of the weekend session, one boat was consistently faster than the other two upwind and downwind. By the end of the weekend, the other two sailors had made some changes to rig/sail trim settings and all three boats were sailing pretty equal upwind and downwind.-----

    comment two
    I have quite a few years worth of VPP modelling on multihulls, their foils and rigs - much of it aimed at both C and A class. There are several key issues but, to keep it very simple, a cat hull of this type is working within the bounds of slender body theory. You aren't really worrying about wave drag from the hull but you are worrying about surface drag. If you partially lift the hull out so that its length reduces then the length to beam ratio can go down and you start worrying about other drags. Far more significant a drag component is the induced drag from the foils. Induced drag is directly related to the lift generated by the foil - the more lift it generates, the more induced drag it creates. If you try to lift the hull with a curved foil you have to increase the lift produced by the foil and thus increase the induced drag considerably. To make it worse, with curved foils the effective aspect ratio of the foil (which determines the ratio of lift to induced drag) decreases and so you end up making more drag relative to the lift. All this results, with a light weight cat, in the increase in drag from curved foils being significantly greater than the reduction in drag caused by lifting the boat. Tuning the foil section for the conditions is really key but difficult in practice. You tend to have to simply design for what you expect and run with that. The easiest variable that you have is to decrease the amount of foil you have in the water. Thus, as soon as you are fully powered up in an offwind course, don't just dump power in the rig, reduce the amount of foil in the water and increase the lift to drag ratio of the wing; you'll slip further sideways and heel less but you'll also possibly go faster (assuming you've got your polars right!). Never leave the windward foil down.

    So, you ask, why do people who sail A's with curved foils think they are going faster? Well, it's not because the foils are reducing drag but because the lift generated makes the platform more stable and thus easier to power up and sail. this is especially true in big wind where control and maintaining power is more important than reducing drag. For minimum drag, the right asymmetric section with negative dihedral will be fastest (ie so that the leeward foil is vertical when the windward hull is just off the water). Of course there is a caveat - you could go faster if you could get the whole boat out of the water and on foils but so far only Moths have gone around a normal course faster when on foils. You also have to bear in mind that very few people can sail anywhere near 100% of the theoretical maximum speed.

    So why do the big multihulls have curved foils? Because they are a lot heavier and different issues come into play.

    Finally you might ask why I am stuck in an office in the middle of London when all this is happening, 21 years after I last appeared at a C class event. The answer is simple: I'm a mug.

    --

    And a response:

    I certainly see the validity of everything you state about curved foils on light catamarans like the A and C. I believe the biggest surprise for us has been how competitive the boats with curved foils still are in light air.
     
  6. Doug Lord
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    Doug Lord Flight Ready

    Little America's Cup-----Oh, Canada

    From Magnus on SA regarding the Canadian boat:

    To set the record straight, no pun intended, Canaan does actually have a wee bit of curve to the foils. As to how much, why, reasoning etc. I'll leave that till later. Also, before someone asks or worse yet, forgets, again, they are assymetric foils, and yes we do pull the windward one up, every time.

    I cut it twice and it's still too short
     
  7. Doug Lord
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    Doug Lord Flight Ready

    Little America's Cup-----Oh, Canada: Little Wings

    Upon further review: check out this video and notice the little "wings" on the rudders. I don't think they are fences... Also, in some of the shots you can see the slight curve of the daggerboards mentioned by Magnus above:

    http://www.youtube.com/watch?v=2u3nnP9W34Q
     
  8. Doug Lord
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    Doug Lord Flight Ready

  9. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    Little Americas Cup

    The race schedule thanks to Tom Siders: ( some select editing by DL)

    Little America's Cup
    International C Class Catamaran Championship

    August 22-28, 2010

    New York Yacht Club

    Harbour Court, Newport, RI



    GENERAL FORMAT The International C Class Catamaran Championships (IC^4) will be hosted at New York Yacht Club in Newport, RI from August 22-28, 2010. The IC^4 is the Little America's Cup for the for C class catamarans.



    Racing begins with an up-to-12 race series of fleet racing to determine the seeding for the match racing. The top two seeds will have a first to five point match race series to determine the winner of the Little America's Cup. The course is a 6 mile windward-leeward, with one mile legs and up to four races each day. The course area will be weather dependent, but either north of the Newport Bridge or off Beavertail. Boats will launch off the beach at Harbour Court and store their wing sails in a duo-purpose hospitality tent.





    SCHEDULE SCHEDULE Aug. 15-22Facilities at Sail Newport available for trainingSaturday Aug. 21 Measurement at Sail Newport by appointment Sunday Aug. 22

    1600-1800

    1800

    1830

    Measurement at NYYC by appointment

    Registration at NYYC Sailing Center

    Competitors meeting at NYYC Sailing Center

    Opening Reception

    Monday Aug. 23 1100

    Warning signal for the first fleet raceTuesday Aug. 24 1100

    Warning signal for the first fleet raceWednesday Aug. 25 1100

    1800

    Warning signal for the first fleet race

    Cocktails & BBQ Dinner

    Thursday Aug. 26 0900

    1200

    Meeting with the Umpires (for top two teams)

    Attention signal for the first match race

    Friday Aug. 27 1100Attention signal for the first match race

    Saturday Aug. 28 1100

    TBD

    Attention signal for the first match race

    Final Awards ceremony after racing

    Sunday Aug. 29 Break down and departure
     
  10. Doug Lord
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    Doug Lord Flight Ready

    C Class -Aethon---------new wing

    Here is Steve Clarks new wing:

    (click on image and then resulting image)
     

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  11. TTS
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    TTS Senior Member

    Wow, that really is different than what I thought it would be. Still three element and you can see how it works. Doug, can you place photos of the two wings, Fred's and Steve's side by side?

    Thanks
     
  12. Doug Lord
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    Doug Lord Flight Ready

    Here you go----
    Canada has more span:Tom Speer always says the best way to reduce drag is increase span... Canada's wing seems "prettier".
    But I'm with Steve-theres some techno wizardry under those skins.... Hope he wins big time...
     

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  13. TTS
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    TTS Senior Member

    Thanks Doug,

    I do not know what to think here. Both projects have definately gone in their own direction. You from a shear looks standpoint have to love what fred has done with Canaan and it's wing. But performance wise, I do not know what to think. Just finished re-reading the Cogito project from 10-2000 which details the team involved their and I doubt they would put any less thought and effort into this one. We will see soon.

    Tom
     
  14. TTS
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    TTS Senior Member

    Posted by Tom Speer on SA.
    The C-class has a maximum sail area. You want each section of the wing to have about the same lift coefficient, because otherwise when the heaviest loaded section gets to maximum lift and stalls, the rest of the area won't be getting to its maximum lift and you wouldn't be getting as much out of the rig as you could. So the planform shape of the rig should look similar to the spanwise loading of the rig.

    The spanload is a compromise between heeling moment and induced drag. The induced drag is minimized by imparting a sideways velocity to the wake that changes linearly from the foot to the head. A uniform sideways velocity to the wake has minimum drag for a given rig height, but the center of effort is too high. A good compromise is to have the sideways velocity go to zero at the head, which lowers the height of the center of effort, allowing the rig to be taller for the same heeling moment and have less drag.

    Here is what the spanloads look like for the case with the sideways velocity in the wake going to zero at the head, taking into account the interference between the wing and the water surface. (The different lines correspond to different sizes of the gap between the wing and water.)

    There is a graff that I couldn't post.

    The maximum chord will be about a third of the way up the rig. Steve's new planform is a straight-line approximation of this shape, and should come close to producing the same lift distribution.

    Compared to a single-taper planform, the foot will be loaded more, making that area more effective. The induced drag will be less than a single taper planform of the same height producing the same lift. The center of effort will be a little higher than the single taper planform of the same height.

    The proportion of flap chord to total chord is less at the bottom than the middle and top. That changes the aerodynamic twist as the flap is deflected. As the wing is cambered up, the center of effort will shift upwards even more than the planform shape, and become more like the optimum spanwise lift distribution for a given span. That should reduce induced drag when going downwind where maximum lift matters more and heeling moment is less. I'm not sure what it does to maximum lift, but the foot would normally be operating with less angle of attack than the middle, due to the influence of the wake, so it may not need as big a flap. The foot may still not be producing as much maximum lift as the middle of the wing, but with the double-tapered planform, more of the area would be in the sweet zone downwind

    Upwind, with less flap, the boat will be in the mode of maximum efficiency for the heeling moment. Less flap deflection would have the lift distribution looking more like the planform shape.

    The combination of planform shape and flap shape would have the aerodynamic twist changing with camber as the wing is shifts gears between upwind and downwind, so the physical twist doesn't have to do the whole job. That would leave more twist authority available to adapt to different conditions, like wind shear, or to reduce the amount that twist has to be played in concert with changes in wing trim.

    At least, that's my speculation! Steve may have entirely different reasons.
     

  15. tspeer
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    tspeer Senior Member

    [​IMG]
     
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