America's Cup-37 Class Rule

Discussion in 'Sailboats' started by AlexanderSahlin, Mar 17, 2021.

  1. AlexanderSahlin
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    AlexanderSahlin Junior Member

    ETNZ won the America's Cup today. Both the defender and challenger demonstrated exceptional skill when sailing these not-so-easy-to-sail AC-75 boats.
    But we have seen races, like race 8 in the final, where one boat was stuck in the water, unable to take-off, while the competitor led by some nautical mile. We have also seen at least one capsize resulting in a flyoff and crash from 10 m height, depending on the pitch-roll coupling of the hydrofoil-configuration. When the boats have been righted after capsizes, they have got help from tender-boats pulling them up with a long rope (the reason for requiring ballasted foils was that the boats should be self-righting). We also saw American Magic losing the last race in the challenger's semifinal because a problem with their electro-hydraulic Foil-Control-System.
    So, shall the next America's Cup be sailed in similar boats? I was going to challenge ETNZ with the 75 x 75 x 100 ft simple box-rule I suggested in post-285 in the thread "AC-36 Foiling Monohulls" AC 36 Foiling Monohulls https://www.boatdesign.net/threads/ac-36-foiling-monohulls.59160/page-19
    But the British team was quicker and challenged before me. So now I sit at my computer writing posts on this forum instead of discussing my new class-rule with ETNZ in Auckland.
    But what kind class-rule do you think they shall use for the next AC?
     
  2. sharpii2
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    sharpii2 Senior Member

    First, I think your box is too big.

    Few are going to be able to afford something that big.

    Personally, I prefer a sum rule.

    This forces the designers to make real trade-offs rather than just maxing something out.

    Just maxing something out seems to bring in edgy engineering solutions that rest on the edge of failure. So just one little thing goes wrong, and the other boat makes an easy gallop to triumph.

    I would also like to see competing technologies instead of competition in the same technologies.

    For example:

    Suppose the rules allowed multi hulls and chanting keels, but only monohulls would be able to have the canting keels.

    Under a sum rule, the mono could be much longer than the multi and the multi much lighter.

    This is just a crude example of what may be possible. The J boats and the 12 meters, which reigned over much of the AC history, were based on some kind of sum rule. More of one desirable trait meant less of another.

    It may be time to abandon the hydrofoiling. These boats really don't go anywhere, and now they do it a warp speed. I think there is a relevance problem here. Few if any sailors are going to go to hydrofoiling any more than powerboat people are going to go for hydroplanes. And even then the hydroplane has much more in common with the typical planing runabout than the hydrofoiling sailboat has with the typical racing dinghy, never mind daysailor.

    I also think the hydrofoiling monohull is a bit of a stinker. It is clearly no more self righting than a hydrofoiling multi is, and the hydrofoiling multi is a whole lot more practical (and probably less expensive).

    If we ever see cruising size hydrofoiling sailboats, they are most likely to be multis.

    Well, that's my $0.02.
     
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  3. wet feet
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    wet feet Senior Member

    I can't imagine anything other than a very minor tidying of the current class.The speed differential between foiling and non-foiling is crucial to keeping the interest alive until the finish is reached.They aren't boats that have much other application and there won't be too many crews capable of extracting maximum performance.

    If anybody has a novel design for a performance class they are free to post it here and elsewhere in the hope of finding somebody to take the concept further.
     
  4. AlexanderSahlin
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    AlexanderSahlin Junior Member

    I can rather imagine a major tidying of the current class. There are elements in the AC-75 class, that are improvements over previous AC-classes, but there are also some quite crazy features:
    The outboard canting T-foils are e.g. an improvement. Apply them on a multihull and you can get a very good package. Have a look at the 20 ft. Vampire in England. A multihull will have much easier to take-off in marginal foiling conditions, so we may see less races where one boat is drifting around at 10 knots, while the other is foiling at 30 knots some nautical mile ahead. The configuration, used on the Vampire, also had less lateral separation between foil and rudder, resulting in better behaviour during rapid changes in heeling angle.
    If they can stop pretending that the boats are self-righting, the ballast can also be removed from the foils.
    However, a foiler at this size will still require a very powerful system for rising and lowering the foils (if necessary). But it is hard for me to accept a battery-powered system, where the battery is allowed to have a lower level of charge after the finish than before the start. (If this is allowed, I made a design some 27 years ago where onboard power was used for lowering the foil, that I called Trampofoil®TRAMPOFOIL® https://www.trampofoil.com. A battery-powered version of the Trampofoil® would be a very strong challenger in a low wind race.)
     
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  5. AlexanderSahlin
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    AlexanderSahlin Junior Member

    Maybe the box I suggested is too big. I just took the size from the AC-75 class we were discussing then.
    There may also be more clever ways to limit the size than having a fixed box, the boats have to fit in.
    Also I would prefer a competition open for different technologies. I think a development of the simple box or just a sail-area limit can allow that.
    I think the America's cup shall be sailed in the fastest and most extreme course-racing boats that exist. As it was 170 years ago, when it started. That is the beauty with this competition. The boats don't have to be affordable for anyone.
    Although most sailboats are still sailing without foils, there are some foiling dinghies and multihulls available for the general public. When we can improve them, I am sure that market will grow.
    I fully agree, that a multihull is the most practical platform for a sailing hydrofoil substantially above the dinghy size.
     
  6. revintage
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    revintage Senior Member

    Don´t you think the Kiwis got, at least to some extent, inspired by the Vampire Project;)? Anyway a foiler with the T-foil far to leeward is not to far-fetched.

    Hope it is OK to publish your thoughtful and well written article(no hydraulics) from the IHS-Newsletter 17-18, page 7-9, that I have saved as PDF?
     

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  7. AlexanderSahlin
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    AlexanderSahlin Junior Member

    Sure, the Vampire was sailing a few years before the the AC-75. And the advantages of this configuration are quite obvious. You are welcome to publish my article where you want, as long as the year I published it first is attached.
     
  8. wet feet
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    wet feet Senior Member

    It is precisely because one boat can be in displacement mode and one foiling that I think the concept is already quite good.Similarly,endeavouring to have some element of self righting is a good thing.Im know from unfortunate experience that a very light hull will blow to leeward of the rig after a capsize and when righting is attempted,an immediate repeat of the capsize almost always happens.Once we accept foiling,doesn't the extra hull of a multihull become unnecessary?After all the boat is supported by the foils and the hull or hulls provides an anchoring point for the foils and rig and somewhere for the crew to operate.It also keeps the water out until foiling is achieved.With the AC75's the foils are as far from the rig as they would be with a slim catamaran and without the complication of an extra hull.
     
  9. AlexanderSahlin
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    AlexanderSahlin Junior Member

    If you want a safe victory for the boat, that can stay on the foils, I recommend a zero-hull boat, that can not go anywhere after a touch-down. If both boats touch down, you award the victory to the boat that came the longest way around the course until it's touch-down. Such a boat can be launched at 25 knots by some catapult before the start.
    I think we discussed the issue about take-off for foiling boats in the AC-36 thread, but the advantage of e.g. a catamaran is that you combine a large righting moment with a very low drag below the speed where you get enough righting moment from the leeward foil.
    I can give you a short advice from my experience of capsizing with my International Canoe: when you have righted the canoe after having the mast pointing to windward, stay at the centre-board and follow it below the hull when it capsizes again, and when you are on the windward side after that second capsize, you can right your canoe so quickly that it doesn't turn around and you can easily enter it on the windward side.
    However, in the America's Cup this is not an issue, since they have tender-boats taking care of that.
     
    Last edited: Mar 18, 2021
  10. gggGuest
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    gggGuest ...

    The trouble with such a rule is that unless the rule writers are almost impossibly lucky then the tradeoffs won't be even, and there'll be corners of the rule where everyone ends up after some very expensive flops demonstrate where the wrong corners were. A straight box rule is liable to deliver some kind of consensus more quickly. 100 years ago formula rules were useful in giving experience about what tradeoffs were useful in general design, but these days I submit the basics are sufficiently understood that there's not too much to be learned that's generally applicable.
     
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  11. revintage
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    revintage Senior Member

    This is Alexander Sahlins article already written in IHS newsletter 2017/2018 with is thoughts about a later coming AC37.
     

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  12. Gary Baigent
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    Gary Baigent Senior Member

     

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  13. revintage
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    revintage Senior Member

    Hi Gary, I guess you want to show the idea of how the windward foil lifts above water at speed by sailing with some heel, do you have any images of Frog flying on the leeward foil only?
     
    Last edited: Mar 21, 2021
  14. Gary Baigent
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    Gary Baigent Senior Member

    Only have this image of leeward float and foil - but the windward one always flies clear because of beam dihedral.
     

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  15. revintage
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    revintage Senior Member

    Thanks Gary!
     
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