Canters tacking

Discussion in 'Sailboats' started by usa2, Mar 24, 2005.

  1. usa2
    Joined: Jan 2005
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    usa2 Senior Member

    Has anyone come across any information that would state that a canting keel yacht will tack quickly while going upwind? "relatively quickly" would mean it is faster than another canter, but has anyone either read anything that would suggest they can hold their own in a tacking duel, or actually seen a tacking duel between a fixed keel and a canter? Skandia and Konica Minolta may have had some inshore tacking duels last year, not quite sure....
     
  2. Doug Lord

    Doug Lord Guest

    tacking duels /canters

    The Schock 40 does well in tacking duels with fixed keel boats around the same length because the twin foils allow quick turns and the light weight due to the canting keel allows fast acceleration. Not only that but in light air the Schock 40 guys use the canting keel to roll tack the boat. The small jib on the Schock helps as well....
     
  3. Paul B

    Paul B Previous Member

    Which Schock 40, in what regatta, against what boats?

    Did you notice if they made any significant leeway after the tacks until they got up to speed?

    Did you see any of this at all, or are you again only parroting some website/magazine/sales brochure?
     
  4. usa2
    Joined: Jan 2005
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    usa2 Senior Member

    a testimonial on the Schock 40 website says that the biggest difference the canting keel makes is off the wind, since the keel makes the boat a ULDB type that carries enough sail to plane relativly easy and it is capable of 15 knots off the wind. The testimonial also said that the CBTF foils did not make much of a difference upwind. Have you(Lorsail) sailed on one before to accurately explain what exactly the performance differences are upwind? If any? From the looks of it, conventional sport boats did pretty well against it.
     
  5. Paul B

    Paul B Previous Member

    SoCal PHRF Bouy Ratings:

    Schock 40 = +6

    J125 = 0 (fixed keel with bulb)

    Farr 36 = 0 (4 feet shorter, fixed keel with bulb)

    Farr 40 OD = +12 (with the Schock being faster downhill you might assume the Farr 40 OD will be quicker uphill in most conditions)

    The new T1150 (37+ footer NorCal rating) = -6

    Note: Currently there are no S40s on the PHRF SoCal valid list, although there is one parked about 100 feet from my boat and I know they raced PHRF a few weeks ago.
     
  6. Doug Lord

    Doug Lord Guest

    Schock 40 /CBTF

    2&B: I do a lot of research on this topic and have for 5 years or so; I've designed,built and tested numerous RC models using several different canting keel/lateral resistance solutions with the assistance of some of the most knowledgeable people around.I read everything on the subject I can find and talk to as many experts in the field as I possibly can in an effort to learn about this subject and its various iterations.
    My previous post was an almost direct paraphrase of an answer I received from Tom Schock when I wrote to him asking about his experience with CBTF and tacking duels against fixed keel boats in the same size range.
    His full size experience is reflected in model tests as well....
     
  7. usa2
    Joined: Jan 2005
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    usa2 Senior Member

    Paul B-
    have you raced against any head to head? what do you think of them and their tacking duel characteristics? Are the ratings accurate for their performance capabilities?
     
  8. Paul B

    Paul B Previous Member

    Yes, S40s I have.

    My experience is the S40s struggle a bit upwind in the light against boats that are not really optimized for that condition.

    I've watched a lot of CBTFers racing, and have yet to see the fabled "negative leeway" effect. In fact it seems like some of them like to sail low and fast.

    Downwind the S40s sing in all conditions. That's about what you would expect for a boat 40 to 50% lighter than the other boats in the class, yeah? In fact, the S40 rates -21 for offwind Courses, so if you assume 50% upwind and 50% downwind for the bouy rating of 6, then they would sail to about a +27 uphill. I think they might be just a bit better than that.

    The Farr 36 in LoCal struggles, maybe some crew issues? I think they sailed pretty well at Key West a couple of years ago with a rating of -6? Grins did OK this year out there with a 2nd in the Sportboat class, but rated +9, maybe a bit gifty. No S40 to compare to.

    In fleet racing you rarely see "tacking duels".
     
  9. Paul B

    Paul B Previous Member

    Here's a hint: Reading magazine articles and website content is not "research". Neither is pestering people in the business.


    Tom Schock is a very nice man. I guarantee I know him better than you do.

    I'm not surprised that he might comment about his product in the best light possible. He is in business to sell that product.

    Is there any man who would not say his daughter is beautiful?
     
  10. Doug Lord

    Doug Lord Guest

    Tom Schock

    B, many of your comments tend to be on the far side of reality but you're 100% right about Tom Schock: he's a nice guy and is willing to help people understand the Schock 40 and CBTF.
    However, in my limited contact with him he does not strike me as the kind of person who would embellish the facts ,as you imply he does ,in regard to the performance of the 40 in a tacking duel. I believe he gave me straight info to the best of his ability as he has before. He's a first class individual and one of the most experienced around with CBTF....
    You say you've had experience with the Schock 40 and yet have never seen "collective". You probably don't understand how it works. See the thread on "gybing centerboards"; the hull of a boat using collective will actually point lower than a fixed keel boat and it will go faster;the VMG to weather of a CBTF boat will be better.
    There are ample descriptions of the use of "collective" in racing starting way back with Wild Oats against numerous other boats.
    Sounds like you may have seen collective being used but you just didn't understand it.Quote from a previous post: "..never seen the fabled negative leeway , in fact some of them like to sail low and fast".
     
  11. Paul B

    Paul B Previous Member

    Check my posts. I've not used the term "collective". Please don't throw quotes on something I have not said.

    Whenever someone points out your inaccuracies you claim they "didn't understand" the technology. You simply don't want to listen. I perfectly well understand weather gauge and VMG, but I wonder if you do. If two boats are separated by 2 BL of weather gauge, then 5 minutes later that separation is 4 BL, then the leeward boat has not been sailing as high. Has absolutely nothing to do with the direction the hull appears to be pointed. It is pretty simple, even you should understand it.

    If in that time the leeward boat has move forward more than 2 BL they have been sailing a better VMG. If less than 2BL, they've lost. Simple.

    So if I'm on the hip, 2BL up and 2BL back from a S40, and 5 min later they are 4 BL to leeward, then their "collective" hasn't made them sail with "negative leeway", has it?

    When are you going to tell us about your experience with canting keel boats, or CBTF boats?
     
  12. gggGuest
    Joined: Feb 2005
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    gggGuest ...

    What's leeway got to do with VMG?

    Your VMG in a completely different shape and style of boat compared to a canting keel one says just about exactlly nothing about the pros and cons of dialing in the angle of attack on rotatable foils so that the boat sails straight down its track, with bow pointing to windward of the track (positive leeway) or to leeward of the track (negative leeway). All it proves is that different boats perform differently. Like wow.
     
  13. Paul B

    Paul B Previous Member

    I'm not sure if these comments are directed at me or not.

    Your heading questioning leeway's effect on VMG is strange. Leeway is a component of VMG. If you make one BL of leeway for each one BL forward, what would the VMG be? Less than a boat making (theoretical) zero leeway?

    I don't think you are going to see a boat sailing efficiently with the bow pointing below the track. Do you? I have yet to see this with my own two eyes. Have you?
     
  14. usa2
    Joined: Jan 2005
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    usa2 Senior Member

    if the bow is below the track, your either trying to decieve the opposition(but usually you point higher rather than lower to accomplish this) or you are having problems. Why would the bow be pointing below the track in the first place? Even if you are suffering from leeway, you are still going to have the bow pointed on the same heading. You just happen to be going sideways as well as forward.
     

  15. gggGuest
    Joined: Feb 2005
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    gggGuest ...

    [FX sigh]
    Look there's nothing magic about leeway, and its only the *hull* going sideways by coincidence - well almost. Its all about the underwater foils. They have to create lift in order to provide a sideways force for the rig to work against. They also have to be symmettrical so that you can change tack. The way you get lift out of a symmettrical foil is by having it at a slight angle - angle of attack its often called -to the medium flowing past it. Its the same for sails as for keels/daggerboards.

    Upwind you need a lot of sideforce at low speed so the keel has to be at a greater angle to the water. Downwind you need less sideforce and are going faster so you need the keel at a considerably smaller angle. If your keel or daggerboard is fixed rigidly on the centreline then the only way you can sail is to set up the angle of attack/angle to the water with the whole boat. So it seems as if the boat is going sideways, and you call it leeway. Its just a refelction of what the keel is doing, nothing more.

    Now if you can rotate the keel relative to the hull then with angle of attack of the keel the track stays the same - it has to stay the same to get the required sideforce. The keel is always at the same angle to the track. However the direction the hull is pointing relative to the track varies according the amount of angle you put on the hull.

    Now I have little idea and care less about whether having the hull pointing above the track, right on the track or below the track is better. I can think of pros and cons for all of them and it would take serious research to find out, and the results would probably be individual to particular hull configurations.

    OK this is a slight over simplification because water flow round the hull does contribute to the sideforce, but with a high performance keel and a flat modern type boat it doesn't contribute very much.
     
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