June 18, 2017

Did Anyone Else See This?

By Doug
In race 4 of the America's Cup final, Oracle trailed Emirates again by 400 meters. The coverage has been fantastic as we get to see much of the live action on each of the boats. Take a look at this short clip to see what Oracle was doing to gain a little speed.

If you listen closely, the sound of the winch gives it away - the wing trimmer is pumping the main! With the help of hydraulics, this can be done with just one hand.

I'm not sure if this is legal, but the idea of pumping a sail this big is pretty amazing!


  1. Well spotted. But the video is now unavailable (at least to me.) But I take your word for it.

    1. Someone took the video down, so another version is up again.

  2. Interesting. Is it pumping or just frequent adjustment to keep the boat foiling? I haven't ever sailed a fouling boat, but all the videos I see indicate a lot of adjustment needed to keep it fouling. Much more adjustment than a non-foiling boat.

  3. Pumping was an issue in the last Americas Cup. It was the main reason USA was able to stay on the foils for longer and indeed, start foiling before ETNZ. They were not secretive about it at all, but their systems allowed them to do it whereas ETNZ wasn't able to. The AC rules then were silent on pumping, leading to speculation that USA cheated by breaking Rule42. I had presumed it was OK.

    Not sure about this contest though.

  4. An interesting discussion! The trimmer is certainly not staring at the sail but he could also be looking at the angle of the boat for adjusting the foil. In a Laser, this rhythmic trimming is illegal but there's a lot more going on in these boats. Two things are clear:
    1. Now we know why the grinders have to generate so much energy, and
    2. Oracle has to find another way to gain speed!

  5. I'm an Australian on holidays in NZ where I can see replays of the AC races four times a day- and loving it!
    All I know about foiling AC cats I've learnt from Sailing Anarchy, which agrees with Bruce above.
    NZ tv also showed highlights from the ISAF World Cup and I couldn't believe the 470 antics with the crew continually jerking the trapeze to flick the mainsail leech in the light winds. Athletic, but not sailing as I know it.

  6. Mmm, seeing that vid today, I'm not sure that trimming movement comes close to what could be considered pumping. It just looks like sheeting to me.

  7. I thought I read somewhere that pumping was specifically allowed in the AC rules and that was one of the ways TNZ was faster than the other boats in lighter air earlier on in the competition as they had mastered the pump before everyone else.

  8. A cat on one hull is unstable so it must always be trimmed and/or steered.
    Unstable, because horizontal distance from CentreOfGravity -to- (centre of bouyancy or foil) reduces with extra heel.

    Think broomstick balanced on end:
    - frequent small movements or fewer large movements are required to keep it upright
    - no movement is not an option
    - maybe TNZ are "many, small" vs OR "fewer, large"?

    Monohulls increase RM with heel, which tends to hide trim and steering sins.


Related Posts Plugin for WordPress, Blogger...