34th America's Cup: multihulls!

What if the reaction times necessary for it to work right are outside what humans can consistently achieve using manual controls?

 

34th AC

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We know thats not possible-see post 800- which is a description of sailing a Rave using two joysticks. As a boat gets bigger it gets easier to fly manually.
In other words if you can fly a Rave(with twice the work load) you can fly a 72 assuming a fast and responsive system.

 

In my view fast & dynamically stable beats fast & on the edge of control.

 

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So you've decided that manual control="the edge of control"? I disagree -I sailed my 16 foot foiler manually and it was flat easy to sail. Lots of other problems but not with altitude control. If you read the Rave article it might help-they thought it was fun too and better than wands.

 

My view is that TNZ was wise to give their catamaran more buoyancy in the hulls than Oracle gave theirs.

 

I think if something broke causing the crash we would have heard the excuse by now so they wouldn't look so silly.....How far aft has anyone set a wing sail?

 

Doug - What I and others are trying to say is that the foils (and hulls whether in water or out) only provide a transverse righting moment when the sail loads are athwartships. ie the boat is sailing upwind. Once the sail loads point forward (sailing downwind) the foils have absolutely no way to provide the required fwd righting moment to support the boat. So the boat pitches, then it becomes the job of bouyancy to right the boat. If sailed correctly it is sailed "upwind" all the time. ie the major loads are transverse and are Ok. If the sail is not trimmed correctly as it bears off the very high sail loads point fwd and its hopeless. So it comes down to operator error. This is exactly the same physics whether its an 18ft cat or a 72ft cat on or off foils. I drive the support boats for our local multihull races and the bear off is the main culprit for all of our capsizes & the boat can't be blamed. Its sometimes a hard task to right a Tornado if the winds up! They should have cut the wing loose a long time before it broke up then they would have been able to right the hull at that instant and prevent a lot of damage. But its the first time its happened and as Murray says they are learning a lot. Peter

 

Oracle2, if they are determined to retain the non-buoyant bows, need to shift the foils further forward (check out all the successful trimaran like Hydroptere's positions)- but then they'll need larger, deeper rudders to counter the weather helm problem.
Her major problem was the tip forward (pivoting nose down on the lee foil) and sweet FA bow volume - that set the disaster occurring. The horrible platform twist ... this has been well covered ... say no more.
Alternatively they could copy ETNZ's brilliant and larger/safer foil design, in fact buy the the whole damned boat design from the (soon to be) conquering Kiwis. Just joking.

 

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Peter, as I mentioned earlier the foils are a fair ways ahead of the CG and should have kept the boat from pitchpoling. Thats based on my experience foiling a Rave, designing the F3, Aeroskiff and on what the Oracle top guys have said. One of them came right out and said the boat was designed to have the foils prevent a pitchpole. If thats true then the altitude control system malfunctioned. Many people underestimate the power of the main foil-it could have prevented the pitchpole.

From Dirk Cramers of Team Oracle:
from Scuttlebutt tonight Oct. 19
But herein, quite possibly, lied the onboard conflict. Observers have noted
that the defender's AC 72 opted for a narrow bow shape design, which is
good for reducing weight and windage but does not prevent a pitch-pole like
a fuller shape. So how did the designers expect their AC 72 to avoid
pitch-poling in strong winds?

As team engineer Dirk Kramers explains, their AC 72 is supposed to be
foiling when they bear away. "Our hull is quite small, much smaller than
Team New Zealand's, so we are reliant on the foils to keep it from
pitchpoling in a bearaway," explained Kramers.

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Note: The boat was on foils when the incident began.

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Pix-F3-never pitchpoled while I had two boats over two years:

 

Doug - suppose for just a moment that there was no mechanical malfunction. What do you think is the next most likely scenario? Is it possible the failure to get the windward hull fully out of the water was a problem (in light of ...their AC 72 is supposed to be foiling when they bear away)?

 

I do think that's an accomplishment. Mazel tov.
About foiling moths: My understanding is the wand controls the flap on the main foil, while a tiller extension twist-grip controls the flap on the rudder.
Curious: What would be the consequence of reversing that and reversing the direction so pressure on the wand would dump lift from the rudder while the twist grip controls the main foil?

 

34th AC

Extraordinary snippets of TNZ foiling-some of the best shots I've seen yet!
And more: http://tvnz.co.nz/close-up/ultra-fast-catamaran-hits-water-video-5181761

 

34th AC

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Failure to have a backup plan that allowed near instantaneous deployment of the windward foil on a separate control system.....

 

34th AC

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In the early days of the Moth foiler the rudder flap was not used a whole lot. The Rave and Osprey also have separate control for the rudder foil flap. But the most stable form of altitude control is by controlling the main foil flap and rarely adjusting the rudder foil flap.(80% of the load on the main foil, 20% on the rudder foil) The guys that used manual controls on the Rave controlled only the two main foil flaps with small adjustments to the rudder foil for conditions-but the rudder foil did not need constant or even frequent adjustment.
As to the Moth I can't speak to the techniques they're using now but earlier they rarely adjusted the rudder foil flap. Moths have had crashes(far fewer now) related to the boat flying too high and the wand coming "unglued" from the water and springing forward. When it did that it moved the mainfoil flap up a lot causing an immediate crash. That would never happen if the main foil was manually controlled. To my knowledge no one has tried twist grip control of the main foil flap on the Moth even though it would reduce drag. Somebody will someday.
My 16 footer had twist grip control of the main foil flap and it was relatively easy to control. There was a separate dial for adjusting the rudder foil.
The guys on the 26' Mirabaud did set up a manual control system but wound up thinking it was too much hassle for the third crewman. It worked fine, however.
Putting the wand on the rudder foil probably wouldn't work very well-it would likely result in serious "pitch excursions" .

 

The red letters reminded me Christmas is coming and I for one am opting out of the drawing to tell Doug about Santa Claus....But really Oracle doesn't need foils, they need Rudolf! Of course the Kiwi's have a boat with 2 red noses......