34th America's Cup: multihulls!

34th AC

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Neither did the guys sailing the Oracle 72!

PS seems like TNZ has had several penalties during racing-don't think Oracle has had one racing have they?

 

34th AC

Team NZ stb tack penalty and ALMOST CAPSIZES:
http://www.youtube.com/watch?v=yoOjcDf_dJA

 

Leo, I also dislike the hydraulics. I dislike the power management and servo control aspects. I would much prefer to see a discrete, independent mechanism for each control. No pulling power from a reservoir. No power distribution scheme. Just real-time human-powered direct control. I think the essence of sailing design is in the control system and working out the gain of the control system versus the responsiveness and versatility of the rig and foils. I believe TSpeer mentioned they have about three seconds' worth of storage. That's three seconds too much in my opinion. So it's not hydraulics that are the problem per se - I just think there should be a one motor - one actuator correspondence, and no pushbutton control, no servo. The guy grinding is the guy in control of it.

Does anyone know the working pressure of these hydraulic systems? I'd be interested in seeing a diagram of the hydraulics. Are they using multiple motors driving shafts and cams, or direct acting cylinders?

 

Who's Glowing Now

Who's not Glowing Now and at all times..

OC

 

34th AC

Todays after race press conference: http://www.youtube.com/watch?v=n0GZw4tcsEQ&feature=c4-overview&list=UU0gzXt1Ms4WVQ7tyGgjTmqA

 

I agree. The model is that the widget on the other end of the thingie that the human is wiggling only wiggles when the human is working. This is the essence and intent of Rule 52. If you can flip a switch to get your widget to start wiggling before you are working and or the widget continues to wiggle after you have stopped working there is stored power involved. Such systems are not legal.

I have no problem with hydraulics or electronic methods to transfer crew work to trim function as long as the trimmer is active during the control surface movement.

I have a handheld torch that uses a dynamo to power the lamp. The light only works while you keep the dynamo spinning. Other versions of the torch use the dynamo to charge a battery and the battery to power the lamp. This is a fundamental difference. With my torch you have to dedicate one hand to providing light so the other hand can work. With even 3 seconds of stored energy to power the lamp tasks would be much easier. You have both hands available for those 3 seconds.

I can't wait for the Rule 52 exclusion in the name of safety ... feh ...

 

I'm not sure just an impression from watching the beat the Oracle Team just seemed a little faster than they had been previously in boatspeed and through their maneuveurs

 

"The Flip" - Wow was that close? Well I decided to find out so found a couple of the good photos and analysed them. The boat got to 45degs so is this the point of no return? Looked up the wing weight specs and CG then figured out the following. Statically an AC72 can go to 65degs before it falls over! If the crew are on the high side its a little more, but they maybe/probably falling out by then so I assume as was todays case that they are in the low hull. So ETNZ had a long way to go before they would actually fall over but then if a gust pushed on the underside of the tramp its probably all over red rover. I think luckily the wing was slightly cambered up so as the airflowed over it it was pulling up not down and the 3 crew on the high side were worth every kg they had on them from the analysis. The boat behaved really nicely and rounded up and landed softly. Hopefully no damage and they come out fighting tomorrow. So at 65degs we have the wing pulling down with about 16000kg.m and the platform pulling down with about 16000kg.m At 45degs we have the boat pulling down with about 30,000kg.m and the wing pulling down with 9000kg.m so the boat is winning once the initial momentum of the roll has been absorbed . Cheers Peter S

 

Mechanically there is no difference between a rope and the hydrualics used on an AC72. The 3 secs Tom mentions is something to do with the slight elasticity in the systems. The advantage of hydrualics is that they can push and pull and they can be servo driven. ie someone can be the engine someone can be the controller. With a rope the engine and controller has to be the same unless you say the grinder is under servo control by the helm via voice which is a fair thing in my view. So there maybe a couple of philosophical points to cover but practically they are the same. Taking this further hydrualics allow us to acheive higher leverage ratios with less losses so this is why we do it. If we need more then 30:1 leverage ropes become a bit of a problem with space/friction logistics. So once we know the load required we can work back and see if ropes are the answer or not. In the case of ETNZ they have a push/pull hydrualic system that controls their camber which is nearly impossible to acheive with a rope or ropes. They mucked up their timing today in terms of flicking the switch or timing the "pump/grinder" eg physical fatigue of the grinder may have been a factor. So in summary Phil I believe your sentiment is being realised with the AC72 its just the details are a bit hidden at present. Cheers Peter S

 

Thanks for that Peter. It did seem as though the sailors did the right thing by grinding to get the hydraulics back on and both Deano and Ashby steering up into the breeze. If they didn't steer up then the aerodynamic package may have been enough to push them further.

cheers

Phil

 

Except Kyle.

AFAIK, Oracle have had an unblemished record since they were penalised for
premeditated cheating and bringing the AC into disrepute. It shows that even
vile scum are capable of being rehabilitated.

 

They were definitely a little faster, but I'm not sure if it will be enough to make
up for the previous large margins. They certainly seemed better co-ordinated.
They did enough to go into the next races with more confidence and with the
knowledge that NZ aren't invincible.

 

James Spithill said later at the presser they were considering going astern of ETNZ to throw a hook - when the Kiwis too quickly tacked - but looking at their course, Oracle didn't appear to pay off at all ... and when they saw the dark shadow of the tractor's undersides in front, threw their own quick tack .... and maybe saved the Kiwis arse (aside from not ramming them) ... because, I'm guessing, they were upwind at the crucial moment when Gashby swung helm enough for ETNZ to go head to wind ... and Oracle may have been blanketting the tractor; that plus wind getting under wing, saved considerable Kiwi horror and embarrassment. So thanks, James - and goodonyer mate.

 

Hmmm... Nice. Would that be Jimmy being unaware of himself exercising "good seamanship"....? Ha.

 

@Petereng:
Good points about hydraulics. I have missed TSpeer's post in which he talks about hydraulic lines giving power for 3 seconds, can someone give a link to it? In the meanwhile, we could reason with few numbers. An untrained healthy male can produce around 200 W of mechanical power for a very short time. A well-trained individual (like these sailors are) can probably give double that value. So, let's say it is 400 W per person, which probably becomes 350 W when mechanical losses are accounted for (85% overall - pump, actuators, various gears and rotating bearings and joints). Multiply that by the number of grinders and that is the power available for moving foils, wing etc.
It would be interesting to see what is the power required by these moving aero/hydrodynamic devices, and compare it to the available one. It would show if the 6 bar accumulator and the elastic oil lines are actually used to just transmit the human power (as required by the rules), or if they add a little power boost during maneuvers. If the latter is real, than the hydraulics has that additional advantage over the ropes and sheaves system.
I am unable to do it right now, as I'm writing this from the smartphone, but it would be a nice engineering exercise...
Cheers