34th America's Cup: multihulls!

When I first built Flash Harry many years ago I set the rudder asymmetric T foil with an angle of attack of a couple of degrees (the main foils were 4) but I soon found that I had to shift my weight well aft to keep the main hull stern down, stop it from lifting too high. It is very easy to lift the stern - so changed the slight positive rudder AoA to zero - and then boat balanced correctly, Then I could sit well forward and the boat stayed level, bit like a Moth, I guess.
Also to remember that when a T section foil is speeding through water, although providing lift even set at zero AoA, the fact that water is passing over said horizontal or near horizontal foil at 20-30 or 40 knots, the latter in the case of AC72's, it is locked in, doesn't want to let go and only when that foil is sliding, turning through aerated water, like passing through the wake of a forward main foil, will it lose its grip, lose its so called down force. Just imo of course, learned the hard way.
I agree with Doug about Oracle 1's arse drag when the rudder snapped: the T section and blade would have initially bent back creating very large negative attack and down force, (and drag) when it broke off, boat came back to level.

 

34th AC

I thought this was a most impressive letter to the editor in Scuttlebutt tonight:

From John Longley --the America's Cup is a winner(dl):

I have been following the countless stories on AC34 in Scuttlebutt for the past few years and been so engulfed in the waves of negativity that I almost bought into it. The whole thing was a shambles; Larry has wrecked the event, blah blah.

Well this week I went down to Pier 27/29 having just arrived in San Francisco. The America's Cup Park was just outstanding. It has been put together with no expense spared and has everything from great bars and AC history displays, to bean bags to lie on to watch the big screens.

It was midweek but there was a big crowd there to watch the crews, like a Space Shuttle crew at NASA, stride down the red carpet (literally) on to the stage to be interviewed by Andy Green. As the interviews progressed a huge wing sail glided in from stage right that literally took your breath away.

Both boats then carefully hoisted their jibs, the last pit crews jumped off onto their RIBS and the two giant cats pulled away and blasted past the crowd.

After they were gone we retired to the astro turf and bean bags to watch the race on the big screens in the sun.

As soon as the Kiwi boat rounded the top mark for the last time some miles away and headed for the last leeward mark, the screens were abandoned as everyone headed for the waters edge to watch the finish.

We did not have to wait long before the huge red and black sail plan came roaring into view literally streaking across the Bay. She pulled off an immaculate foiling gybe at the last mark and came hurtling straight at us at nearly 40 knots.

As she went across the line only a hundred or so metres from us, the crowd whooped it up but gave an even bigger cheer to the Luna Rossa guys who did a sort of foiling "wheely" as they crossed the line, albeit a long way behind.

Sure I missed the spinnaker sets and leeward mark roundings but the whole scene had a huge buzz...and it was all for free.

If the public doesn't show up in their thousands, then they are the losers, because this is one hell of a show.

 

Very good, thanks Doug.

 

Sail Tracks

Does anyone know of where I could go to see downwind "tracks" of the AC72 boats. I'm very curious about the tacks & their VMG vs AWA, polar plots, etc, etc. I've been on a few cats but cannot believe the downwind speed of these boats, without a big headsail. Thanks in advance... gggss

 

...

Loick Peyron said 'Goodbye San Francisco' on his Facebook page today - leaving town to go on vacation with his family; unless there are other French sailors on the remaining teams that I don't know about, it brings the curtains down on what French presence was slightly visible in this America's Cup.

I'm sorry to see Peyron exit so early, but he's not been a heavyweight in this event. His light-hearted appearances on camera are similar to when he was co-skippering Alinghi 5, or guest-helming in the D35 series. France should have produced someone who looked more threatening in these events, but they didn't.

Behind the scenes are French experts with long-acquired multihull and wing and foil expertise, but they are invisible hired hands and there never was a hope in hell that anyone in France would put up money for an AC72.

A few years ago I'd have thought that an AC34 where the French didn't participate, would be as likely as an orgy at a bankers' conference where Dominique Strauss-Kahn declined the invitation.

 

All over at the first mark. Only equipment failure can stave off the inevitable shellacking.

 

After race 6: Ok, all you experts, why the big difference? Sure , it is a combination of factors but, as always there will be one overriding feature. I am beginning to think it is in the wings/sails. How much variation can there be within the rules? All that remains is drag and lift in the foils/keels (plus crew). I cannot see these accounting for such a speed difference. Hull drag is a minor, surely.

 

ETNZ is just simply much faster - cannot beat speed, no matter how good the crew/helm is/are - and the crew on the Kiwi boat is outstanding.
It will be closer when Oracle arrives; that is if some of their original crew is not behind bars.

 

34th AC

------------------
And whats really incredible is this video from a week ago showing Team USA going past TNZ like that.....an America's Cup Preview for Gary:

Go 17ers!

http://www.youtube.com/watch?v=mk-k67O9fjg#at=92

 

It's difficult to see if they were on the same heading. USA looked faster. What is certain, the Oracle boat was rock solid on plane & course. TNZ kept bobbing & sort of footing.

 

I bet those sneaky Kiwis were holding back a bit, give those "17ers" a false sense of security before wiping them out in the Cup finals

 

34th AC

New Zealand putting the hammer on Luna Rosa-JNavas video:
http://www.youtube.com/watch?v=egVFbJDvjaI

 

Foil section for laminar foils, foil loading, whether you hit the drag 'bucket' will have a huge bearing. Much more so than differences in drive and the aerodynamics is a pretty well refined these days for the L/D of those wings.

 

Antics prior to the final will be interesting. Supposing they qualify You will see the NZ team talk up the capability of Oracle as is the case in a lead up to a All Black match, regardless of how weak the opposition. Over confidence is considered a dangerous flaw.

 

Thanks John Navas and Doug, that was better than the official TV stuff - and what a beautiful sight, foiling uphill.
Yes, Oracle can do this too.
Doug, there's a story that Luna Rossa lined up with Oracle and beat her downwind. Course O would have been sand bagging!!
And we've seen how ETNZ just annihilate LR downhill!!