34th America's Cup: multihulls!

34th AC on Foils!

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Steve , I posted no picture of Oracle foiling on the day of the incident. I think you either didn't read what I said or misunderstood: the picture I posted of Oracle up in the air(from a while ago) was to illustrate the power of the mainfoil.

 

34th AC on Foils!

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Nobody on that boat has a LOT of experience in handling a foil system with manual altitude control! There are comments by some people here and on SA that are guaranteed to have more experience with manual altitude control of a foiler(Dave Carlson for one). A Class cat or Moth experience DOES NOT prepare one for handling a foiler with manual altitude control-totally different animal! The foil system and its manual altitude control is not like any system on any other boat-the only thing remotely close is the manual altitude control system used on Raves 10 years ago and the manual altitude control system used on Mirabaud about two years ago.
What is amusing are the comments from people who think that sailing any other boat* -in any way- prepares one for handling a 72' foiler with manual altitude control.
*What has prepared the team is the work they did using the manual altitude control system on an AC 45.

 

Is that an argument for allowing sensor wands or more extensive electronic sensors and fly-by-wire?

 

34th AC on Foils!

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No, not really. Look at how much we are going to learn about manual altitude control of foilers. The manual,fully submerged system of Oracle and the combination manual, surface piercing system of TNZ are extraordinary solutions to foiling that will benefit multihulls for years to come.
In Oracles case finding out exactly what happened will give a lot of insight into their system IF they make it public.

 

34th AC -no rudder t-foils on Artemis?

Artemis is designed by the very innovative Juan K and he has chosen not to use rudder T-foils. And his main foils seem very different:

 

Here is one for you Doug.....it would seem the NZ foil would have a more gentle rate of change and the advantage of reducing area at higher lift and speeds avoiding some of the over control issues. Are those L foils too twitchy at higher speeds for easy control? Those flippers look outsized for fine control....a race car that is too hard to drive won't win even if the numbers say it is fast.

 

Well I'll take Steve Clark's reasoning on the easing / sheeting in of the wing as the final comment on the subject, as he has probably more experience in that field than anyone else.
My point was that, when the bows are down and the rudders are about to leave the water, sheeting out is a 'too late' option, as it powers up a LOT before you get to the point where it is depowering the rig. Sheeting out during the bearaway, allowing the boat to accelerate and then sheeting back in as it does so is the safest way to do a bearaway in breeze.
Stephen asks "Is that an argument for allowing sensor wands or more extensive electronic sensors and fly-by-wire?"
I would think no, the rules were probably written to prevent foiling, and if the teams want to work around the rules by being clever (which they have) then they need to either make sure their concept works properly, or follow a different path. Grant Dalton said in an interview that just because they've proven foiling is possible, does not mean it will be effective on the racecourse given the venue calls for short legs and the conditions they are expecting.
I do believe that in gusty conditions with large counter-chop, stability while foiling is going to be difficult under the rules,manually controlled foils sound wonderful until the windstrength changes rapidly every few seconds and the boat is leaping out of the water, and then re-entering the water with a bow-down attitude. A man holding a joystick is going to be kept very busy here.
If the designers are going to make these boats foil reliably in these conditions, they probably need to have designed some self-correcting ride height adjustment into the boat that still complies to the rules, whether they are using foil twist, platform twist, or whatever they can dream up. A man holding a joystick is not going to work unless he is also holding the tiller and the mainsheet, or his brain is directly wired to the skipper's thought processes.

 

CT, there is absolutely no comparison to the talent aboard Oracle compared to the posting punters here ... but it was there in front of our eyes; they bore off, boat design faults took over or the expert crew lost control and they crashed nastily, well, pretty softly - and we're glad it was so because it halted human damage - but when the twisting bows went down, it seemed there was little that professional crew could do. So we can criticize the design; in fact, have been accurately pointing out the faults from the very beginning, just looking, observing from our own experiences and relating to what we saw.
Actually my point about A and C Class cat sailors was referring to carrying headsails, actually not carrying headsails and that the una rig A and C experts learn how to tack these designs ... and that, given the sea and wind conditions Oracle was in, way overpowered, maybe no headsail would have reduced total sail area and reduced the toppling moment of the very high CoG wing. Certainly it wasn't released until just before the death and even so, had it been dropped earlier, a flapping, dragging headsail wouldn't help the big cat's equilibrium. Just an observation.

 

Of course there's the possibility they have foils in the works other than the ones we see in the early photos...

 

34th Ac on Foils!

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You can't argue(too much) with success:TNZ foils and foils very well. As best I've been able to tell it is a surface piercing foil with automatic altitude control with manual adjustment for a given range of conditions. They're sailing at twice windspeed which is excellent for any foiler.

 

34th AC on Foils!

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I think Oracles system is a good one-for some reason it didn't work the way it was supposed to. One of their guys said the reason their hulls are so small compared to TNZ is that they were depending on their foils to prevent a pitchpole. Oops.... something did not work well.

 

My opinion is that they should have written more open rules that allow sensor wands and more ailerons/flaps on the hydrofoils (by not prohibiting them). Better the engineers evolve solutions to actual problems without artificial constraints. Not sure about electronic systems with servos (fly-by-wire).

There; I've said it succinctly. In order that I not be guilty of taking discussion in the wrong direction please post any reply concerning the possibility of future rule changes to http://www.boatdesign.net/forums/sailboats/next-2016-so-americas-cup-ac-35-a-44996.html.

 

Doug, would you not say this is a design error, and a big one - I think foils work well in a certain range of conditions, and not well in others, like lumpy seas and gusty conditions. Video I've seen of moths leads me to believe this, they come flying out of the water and then park nose down shortly afterwards in rough conditions.
If the boat was a good design, would it not allow for sailing in conditions that are not optimal for foiling, ie if the regatta rules state that racing will happen up to 30knots, you design a boat that can be used in 30knots, and then add a percentage for safety. OR17 looks optimised for 10-18knots, and gets exponentially interesting after that. It may well be an awesome design when used in the conditions suited to it, but I don't think it is 'fit for purpose'.

"You can't argue(too much) with success:TNZ foils and foils very well. As best I've been able to tell it is a surface piercing foil with automatic altitude control with manual adjustment for a given range of conditions. They're sailing at twice windspeed which is excellent for any foiler."
Do we actually know ANYTHING about how either team is controlling their foils, or is everything just speculation on this subject ?
TNZ looks to be able to adjust how high it flies and how much lift the boards produce by changing the depth it inserts the boards into the cases and therefore the foils angle, but I don't see them issuing a press conference on how they maintain stable flight. All teams will be trying to keep their breakthroughs as secret as possible, I'm sure.
I personally can't imagine some method of adjusting daggerboard AoA or any other aspect under full load that isn't driven by serious hydraulics, the forces on these foils must be incredible. One guy pedalling as hard as he can in a pod while another wiggles a joystick are the last things I'd think would work at all..
And if that IS how it's being done then I'm not surprised at all at the end result.

 

I couldn't disagree more, the rules are there and the smart teams will bend them as far as they will go, then produce a boat that works in all conditions required of them to race in. Designing a boat that can't be driven hard if it's not foiling is an error of a design team, not of the rulemakers. The rulemakers never stipulated that the bows should not have adequate bouyancy to cope with a bearaway in 30knots.

 

34th AC on Foils!

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At this point I don't think it was a design error-I think it was a malfunction in the foiling control system. The foils are extremely powerful and if they had worked properly there would have been no pitchpole. Of course, that malfunction could have been caused by a design error in the control system.
Just an aside on the Moth: the Moth uses a wand based altitude control system and sometimes in waves the wand comes loose from the water and springs forward causing an immediate crash.
Concerning the control system: most everything is speculation except that a source who should know( and someone I trust) told me that Oracle uses a joystick connected to the main foil. Prior to that little tidbit I had been eduguessing that that is how it was done. The whole foil is pivoted about the lower bearing(which supports most of the load).
On TNZ, it's basically eduguessing -that is-an educated guess based on the type of foil they are using-a surface piercing foil vs Oracles fully submerged foil. TNZ probably also has a facility to adjust the angle of incidence of the foil for conditions and to change the lift profile of the whole foil by deploying or retracting it based on conditions.
The "edu" part of eduguessing, in my case, is based on having worked with and studied hydrofoils for a long time. For instance, you can tell by looking at Oracles foils that little to no vertical lift is derived from the daggerboard and TNZ's foil shape is consistent with a surface piercing foil. But both systems are one of a kind and have never been done in just this way before.