34th America's Cup: multihulls!

So its going to be 17-Black and 17-Red? Surely not!! Peter

 

Here is where I think Oracle has yet another aerodynamic advantage, all of the teams have to put this guest racer/liveline box thing on the back, it is thicker than the ETNZ/LR beams, where I think Oracle built it in to the back of the pod and incorporated in the faring to that, could be interesting to see how the others do it.

 

On SA there is talk of the front beam being farther forward, I think it is because if you look at pictures of wing on B2, it is behind the front beam, but the wing looks the like it has the same distance from the back of the boat than on boat 1, plus the cockpit looked a bit more spread out

 

It foils.

 

34th AC

May it fly in beautiful winged circles around that little bird from down under.
Go 17ers!

 

Simeon Tienpont said it started foiling 20 minutes after they started sailing. I arrive in San Francisco on Thursday at 11 am and leave Sunday at noon, hopefully I can catch day 2.

 

You mean 180 degrees (eventually, along with splintering carbon) not circles, don't you, Doug?

 

Artemis sailed their 72 yesterday, I watched on and off for about 3 hours, they would sail upwind in about 10 knots of breeze from near Alcatraz to the GG bridge, then would turn it around, take all camber out of the wing, take the jib down, then get towed back to Alcatraz, work on something for about 15 minutes, then head upwind again. Windward hull barely lifted out and very slow maneuvers.

Spithill is in New York today so I doubt Oracle will be out today.

 

We now know, for sure, that the main foil pivots about the lower bearing to change the angle of incidence of the main foil, that the main foil can be pivoted under maximum load, that the main foil can be moved very quickly, that there is a take off setting for foil angle of incidence and that there is at least one cruise setting for the foil-all because of this one video-check it out about 54 sec. in and you will see the holy grail of the 2013 Americas Cup-the very quickly moving main foil as it pivots from "takeoff" to "cruise #1" !
http://www.youtube.com/watch?feature=player_embedded&v=ItiZuU64pnc

 

As something of a foil nut, it just kinda makes me want to smile every time I see that big boat rise up, adjust the board and level off.

Smooooooth!

If any other team is doing the same, they must be awful good at hiding it.

How about a big mental toast to the Oracle engineering team!

And as a second thought, I guess we owe Uncle Larry a nod for paying the bill to let the engineering team have so much fun with such a cool challenge.

 

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I agree! Take a look at this rough sketch -some seem to have a problem understanding how the foil could work so quickly. This sketch is roughly based on the vast difference between lift and drag which allows the resultant of lift + drag to pass thru the pivot point imparting no force to the control system:

click for larger-

 

Yep,

You posted the above over at SA while I was typing up the below. Maybe our tag team approach will make at least a couple reconsider their "can't be done" attitude.

The primary forces on the board are an Up force and a Side force. These both translate into a very large moment pushing the board at the top of the trunk away from the boat center line. This is simple physics and really does not affect Angle Of Attack (AOA) adjustments as much as some would think.

AOA pivot forces on the foil are a mix of friction and any designed in moment by having the "up vector" offset in front or behind the lower bearing pivot point. If they went neutral for "designed in moment", then it is mostly friction dragging the foil to the rear down in the water. This pushes the foil forward at the top of the trunk. If they want "easy adjust" either way, they would design the "up force" vector to be just forward of the pivot point to try to "balance out" the friction forces.

To rotate the foil as shown could actually take very little force. Pivot friction at the lower bearing does not need to be big. A low friction arrangement for sliding forward/aft at the top is harder to get but not impossible (can you say roller bearings?). A not bad "moderately low" friction choice can just be polished metal sliding on a teflon plate of sufficient area to keep surface stress reasonable.

It is all just about choices. If they need fast and easy AOA changes, they do have deep pockets and a sizable engineering team that should be up to it. If they do not need fast and easy AOA changes, they have plenty of other projects for their engineering team to work on.​

 

If they are cleaver which they are, they organise the geometry so instead of being neutral its biased to push the foil fwd such as we have seen in the video. In this way they have a stop where they want to change the AOA to and just let the sheet or ram go and the foil is pushed fwd to the required place. Just as we have seen. Then the foil is pulled backward at a suitable low load time and the stop is reset (or not) ready for the next time. Trimming is still done via the mechanical systems but for the major movement it could be easy to organise as above. Cheers Peter S

 

Grant Dalton can't complain about Oracle's budget when they are building whatever the heck this is supposed to be at their base in SF. Noah's Arc?

 

I must agree that watching it lift out of the water is the beautiful result of people successfully utilizing natural phenomena.