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I had a go at making a rough idea of how scowish you can get within the limits.

Bear in mind its been a long time since I tried to make a boatish shape, simple elliptical cross-section & bow profile (not properly tangented -_-)

M4jkQDj.png

IIQCKxe.png

Blunt but proportionally kept relatively narrow by the bow max beams.

I don't think you can really call that a scow bow, probably conventional bow more the go.

 

Interesting that rather than min/max freeboard there is a 70m^3 min volume, I've got 1150mm canoe body to (dead flat) sheer which gives this 74m^3 volume (flat deck/stern & no cockpit) so in the right ballpark.

Also no min LWL so you can do some interesting stuff with bow profiles.

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Aren't there 3 points (screws) located at the waterplane ? : two at the transom located 2 metres either side of centreline and one forward, similarly on the waterplane at 20.7 m. ~ these points have to be 25 mm + / - of waterplane when boat is afloat.

The forward point (screw) somewhat forces a vertical stem bow in the forward waterplane region, don't think a reverse bow is possible given the rule with respect perimeter and geometry control (of perimeter) the way I read the rule. 

Dont quite get the rule about the boat being between 20.6 and 20.7 metres given the screw locations ~ by my quick reading of rule.

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23 hours ago, nav said:
On 2018-04-11 at 8:48 AM, Lakrass said:

 It's not that fun to see 1km+ lead and it can quickly happen with this kind of boats.

Yeah I've watched all the races these boats have done as well - and you are so right

Maybe I didn't express myself correctly but what I mean is that gaps will grow very very quickly if you have one boat sailing upwind at ~35 knts and the other going for a reach at ~10 knts because they stop flying. Did any designer speak about the expected acceleration of those boats compared to AC50? This would be a very interesting parameter as the lower the acceleration, the bigger the gap in case a boat stop flying and the other not.

 

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3 hours ago, Ginko said:

Aren't there 3 points (screws) located at the waterplane ? : two at the transom located 2 metres either side of centreline and one forward, similarly on the waterplane at 20.7 m. ~ these points have to be 25 mm + / - of waterplane when boat is afloat.

Yes I'd forgotten that.

But also

Quote

3.8 Three screws shall be installed on the hull surface for the purpose of locating the reference points. If a
reference point does not lie on the hull surface, the screw shall be installed at declared offsets from the
reference point
, as close as reasonably possible to the reference point.

So you could put the screw in at wherever the actual waterline is and declare its x distance short of the 20.7m reference point.

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3 hours ago, Ginko said:

Aren't there 3 points (screws) located at the waterplane ? : two at the transom located 2 metres either side of centreline and one forward, similarly on the waterplane at 20.7 m. ~ these points have to be 25 mm + / - of waterplane when boat is afloat.

The forward point (screw) somewhat forces a vertical stem bow in the forward waterplane region, don't think a reverse bow is possible given the rule with respect perimeter and geometry control (of perimeter) the way I read the rule. 

Dont quite get the rule about the boat being between 20.6 and 20.7 metres given the screw locations ~ by my quick reading of rule.

 

Offsets are allowed, no?

Edit. @ hoom  :b

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44 minutes ago, hoom said:

Yes I'd forgotten that.

But also

So you could put the screw in at wherever the actual waterline is and say its x distance short of the 20.7m reference point.

Rule 3.7 at (a) and(b) defines the location points of the 3 screws 

Rule 3.8 mentions location or the reference points being at a declared offset and going onto to say reasonably close to the reference points .. .

****. how close is reasonable needs to be defined or perhaps requires further clarification ~ again I have only sped-read the rule to date.

49 minutes ago, hoom said:

Yes I'd forgotten that.

But also

So you could put the screw in at wherever the actual waterline is and say its x distance short of the 20.7m reference point.

Rule 10.6  "The maximum length of the hull shall be no less than 20.6 m and no greater than 20.7 m"

 

 

if the hull is 20.6 m then rule 3.7 at (a) needs adjustment or further defining I would think. Seems to me that waterline length is to be 20.7 m at waterplane (MWP) ~ rule 10.6 has me somewhat scratching my head at the moment given the accuracy (2mm ...) stipulated in other parts of the rule.

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The screws are to define reference points for measurement of the rest of the hull, they aren't the actual measurement.

 

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28 minutes ago, hoom said:

The screws are to define reference points for measurement of the rest of the hull, they aren't the actual measurement.

 

Don't agree with you there, there are stipulated measurements given  pursuant to Rule 3.7 ~ they define a minimum width at the transom and a rather ambiguous Station measurement at the bow (as I read) + / -    

 My take on the + / - of 25 mm is deal with water surface stability (at marina) - possibly ?

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9 hours ago, dogwatch said:

Hey, are you some kind of proton supremacist? That has me so highly charged I might just jump my orbit. Remember, without us electrons, atoms can just turn to plasma and that's so Bohring.

An Electron

I try to stay in the neutron camp :-)

Cheers,

Earl

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15 hours ago, Earl Boebert said:

Yes, again, I have read the rule. And as somebody with a bit of experience in flight control systems (I was on the verification team for the JA37B autopilot) I think they have opened a loophole that you could fly a squadron of B-17s through. Obviously, you can't make a full authority autopilot, but you can make a highly accurate pitch axis crew indicator that never sees an electron. You can also make a mechanical analog computer, equally free of electrons, that indicates what pitch axis control input is required to bring the beast back to level flight. So now you're back to carbon-based robot mode, where a crew member has the job of manually moving a control to line up with an indicator driven by a mechanical computer. If you doubt the feasibility, I suggest you read up on the C1 autopilot (used on B-17s), the Norden bombsight, and any of the multitude of mechanical fire control computers used in WWII.

I don't know if anybody will try it, but since the control system and crew indicator sections of the rule are examples of the whack-a-mole school of rule writing, it seems on first reading that this mole escaped :-) And remember, if you're building a flying machine the likes of which the world has never seen, control is your central problem (see: Wright Brothers). If you don't solve that all the lift and thrust in the world will do you no good.

Cheers,
Earl

 

Fascinating - but what/who spins the gyros?

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2 hours ago, Ginko said:

Don't agree with you there, there are stipulated measurements given  pursuant to Rule 3.7 ~ they define a minimum width at the transom and a rather ambiguous Station measurement at the bow (as I read) + / -    

 My take on the + / - of 25 mm is deal with water surface stability (at marina) - possibly ?

Pretty sure they are to be used as stated ^^ for 'measuring from' - think of them as surveyors' pegs.

Their location is known and other points can then be determined relative to them.

The fact offsets are allowed makes it pretty clear they are not there for the reasons you suggest.

(The entire structure, including these points, must be pre-supplied as a digital file, so class compliance is already determined before the measurers get to see the finished boat. Then a few quick measurements from these points will ensure the boat truly matches the supplied file - voila)

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On 11/4/2018 at 7:55 AM, barfy said:

that was painful, bandwidth from new cal better than at ETNZ base...

Is Fischer back there?

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1 hour ago, Xlot said:

 

Fascinating - but what/who spins the gyros?

I may have missed it, but I don't see any limit on stored energy for crew indicators, so clockwork or pressurized gas would work. The latter would use a simple turbine to spin the gyro. 

Cheers,

Earl

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4 hours ago, Earl Boebert said:

I may have missed it, but I don't see any limit on stored energy for crew indicators, so clockwork or pressurized gas would work. The latter would use a simple turbine to spin the gyro. 

Cheers,

Earl

Even if the gyro was battery powered that would make it electric, not electronic as specified in the rules ;-).

https://www.brightknowledge.org/engineering/electrical-and-electronic-engineering-what-s-the-difference

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41 minutes ago, rh2600 said:

Even if the gyro was battery powered that would make it electric, not electronic as specified in the rules ;-).

https://www.brightknowledge.org/engineering/electrical-and-electronic-engineering-what-s-the-difference

I posited an electron-free design because I didn't want to trigger a protest whose resolution depended on deciding the difference between electric and electronic. If you're willing to accept the risk of such a protest, then a simple indicator is a done deal: just copy the C1 autopilot roll/pitch axes design and drive  voltmeters instead of  servomotors.

It would be interesting to see if such a simple "pitch and bank" indicator (combination of an artificial horizon and  the "needle" half of a turn indicator on an aircraft) would give the pitch/roll pilot enough of an edge over somebody flying by the seat of their pants (which mode is the clear intent of the rule) that the "move the control to here" analog computer would be unnecessary. Easy to find out -- just make one and play with it on some foiling cat or other.  With 3D printing this would be a medium grade Maker Faire project.

Cheers,

Earl

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  ^ Hmm ... "Most modern appliances use a combination of electronic and electrical circuitry". If you were to rummage through military surplus stockists, most likely you'd find gyros powered by 400 Hz asynchronous motors - and electronics are bound to be in the loop

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^ His point is that you could make a 100% mechanical flight control system - or at least a 'computer' that would indicate what the guy controlling the foils needed to to, similar to the system on ETNZ. Just think vintage speedometer with a  slider next to it as opposed to a tablet with a touch screen.

It would be exponentially better than a wand, because it would not be affected by water surface texture.

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On 10/4/2018 at 9:35 PM, sclarke said:

 

 

Some interesting stuff, but this cries out to heaven: Clean - alayhi s-salām - for all his faults would never have produced such a pathetic video

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On 4/12/2018 at 10:11 AM, Earl Boebert said:

Yes, again, I have read the rule. And as somebody with a bit of experience in flight control systems (I was on the verification team for the JA37B autopilot) I think they have opened a loophole that you could fly a squadron of B-17s through. Obviously, you can't make a full authority autopilot, but you can make a highly accurate pitch axis crew indicator that never sees an electron. You can also make a mechanical analog computer, equally free of electrons, that indicates what pitch axis control input is required to bring the beast back to level flight. So now you're back to carbon-based robot mode, where a crew member has the job of manually moving a control to line up with an indicator driven by a mechanical computer. If you doubt the feasibility, I suggest you read up on the C1 autopilot (used on B-17s), the Norden bombsight, and any of the multitude of mechanical fire control computers used in WWII.

I don't know if anybody will try it, but since the control system and crew indicator sections of the rule are examples of the whack-a-mole school of rule writing, it seems on first reading that this mole escaped :-) And remember, if you're building a flying machine the likes of which the world has never seen, control is your central problem (see: Wright Brothers). If you don't solve that all the lift and thrust in the world will do you no good.

Cheers,
Earl

i guess that was my point when i pointed out this loophole with a picture of the babbage computer...an interesting direction. With all teams probably thinking "throw the ball as far as we can" who knows would happen? Thanks for your comment based on obvious expertise.

Problem is for me is that this rule will not promote "trickle on" as the team suggests they are after. Although of course no-one will share their code base, seeing what is possible would drive dev of autonomous systems to really drive these boats, rather than:

 

babage.jpg

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i haven't read the rule about daggerboards closely, but would it be an idea to have a wand on the front, leading to a mechanical device similar to the one that tuke used, suggesting optimum rake?

or is this the kind of system that you are getting at with the mechanical computer?

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it seems a bit tricky. 

Force input device described in 34.36 might allow a wand.

But control systems 20.2.c seems a bit ambiguous...and 20.1 says "control surfaces only controlled by crew", which may be the intent.

hopefully some interesting clarifications in the future.

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One wonders if we could see an arms race in analog computers. Mechanical, hydraulic, pneumatic or hybrid. People do forget quickly - it was only a bit more than a generation ago that most control systems were analog and many were all mechanical.  It would be a pretty cool thing to see. Sort of a steampunk AC.

A basic system of no more complexity than a gun director would probably be all that is needed to fly the boat. An all mechanical computer powered by compressed air could probably be made to fit inside a breadbox with a bit of effort. It only needs to stay aligned and stable for the length of each race, so error accumulation might well be kept under control without heroic effort.

Sadly they will probably just shut the loophole down.

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^ Alternatively, they might be intentionally building a little ‘space’ into the rule in case flying a 71’ boat with a soft sail on two asymmetrically arranged foils turns out to be so intractable that the sailors need a little help. But as EB noted, if he’s reading that correctly, that’s a hell of a loophole.

Having said that, noone judges the moths for using magic wands, so there is precedence for position-coupled mechanical feedback loops. Maybe somebody will come up with something really clever that would apply to other foiling classes. 

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I think they have painted themselves into an interesting corner here. If they mandate that the only legal pitch axis sensors are a crew member's eyeball and inner ear, it may not be humanly possible to control the boat in flight. If they try to limit the technology using the whack-a-mole approach a different mole may escape. The only way out that I see is to mandate the use of a standardized instrument set.

Cheers,

Earl

 

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33 minutes ago, Earl Boebert said:

If they mandate that the only legal pitch axis sensors are a crew member's eyeball and inner ear, it may not be humanly possible to control the boat in flight

 

... as a certain team is rumored to have found out on its first non-surrogate ...

 

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If a sailor can't 'sense it' it does it need to be reacted to?

Someone sailed a non-surrogate* (within weeks of the rule release?!) with an overly sensitive control set-up first time out.....big deal. It took OTUSA months to gain control of their AC72s.

"Get me a Babbage computer NOW!" Farcical.......

 

*and of course that is another insider tip that can't be shared eh - so many insiders, so many super sensitive secrets.:lol: Pics or it didn't happen

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We still haven't figured out why that exception ("unless it contains no electronic parts") was put in the rule. If a loophole results from an omission, one can consider that it was a mistake. Since it was an explicit addition, somebody must have had some reason for putting it there. You guys are the experts on the politics of the rule. What could the reason be?

Oh, and for the record, the Babbage machine is digital, not analog. 

Cheers,

Earl

 

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4 hours ago, nav said:

Someone sailed a non-surrogate* (within weeks of the rule release?! *) with an overly sensitive control set-up first time out.....big deal. It took OTUSA months to gain control of their AC72s.

The Rule's just out, but the essentials were known a long time ago - e.g. remember how/when the French came out with the "unbelievable" 15 m beam, and the 68' LOA

Pics or it didn't happen

Should be someone else's responsibility

 

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On 4/11/2018 at 9:14 AM, Earl Boebert said:

OK, I give up. 22.3.b says:

must be incapable of measuring any part of the yacht state, unless it contains no electronic parts; [emphasis mine]

Why is that exception there?

Cheers,

Earl

 

You could use mechanical sensors, like a bobweight, in the control system.  The Monitor used mechanical feedback of shroud tension to foil incidence, and feedback like that (although to the flap rather than incidence) would be allowed.

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13 hours ago, inebriated said:

i haven't read the rule about daggerboards closely, but would it be an idea to have a wand on the front, leading to a mechanical device similar to the one that tuke used, suggesting optimum rake?

or is this the kind of system that you are getting at with the mechanical computer?

Wands have been considered an appendage under previous AC rules, and thus would not be allowed because the three appendages are specified.

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5 minutes ago, Basiliscus said:

You could use mechanical sensors, like a bobweight, in the control system.  The Monitor used mechanical feedback of shroud tension to foil incidence, and feedback like that (although to the flap rather than incidence) would be allowed.

Well, if that was the intent, the door appears to be open to gyroscopes and mechanical analog computers. And if they whack that mole they'll have to decide if a pendulum-and-hydrostat indicator is legal. That was doing pitch axis control on torpedoes starting in 1868. This could go on for a while.

Cheers,

Earl

 

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11 hours ago, Earl Boebert said:

We still haven't figured out why that exception ("unless it contains no electronic parts") was put in the rule. If a loophole results from an omission, one can consider that it was a mistake. Since it was an explicit addition, somebody must have had some reason for putting it there. You guys are the experts on the politics of the rule. What could the reason be?

It could simply be a nod to the International Moth rule, which is a well-established side-step around RRS 52.

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Possibly, except that the Moth rule (I presume you're referring to 12.2) deals with actuators and not instrumentation.

Upon re-reading the rule, it appears to me that somebody realized that the first clause of 22.b.3, which includes 34.100 ("yacht state") by reference, would outlaw simple compasses. So they tacked on this exception without thinking through what it implied for the other two axes of motion. Presumably this will be fixed, and then we'll see what the fix implies :-)

Cheers,

Earl

 

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2 hours ago, Earl Boebert said:

Possibly, except that the Moth rule (I presume you're referring to 12.2) deals with actuators and not instrumentation.

 

A wand system is kind of both.

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11 minutes ago, sclarke said:

Better video quality

 

Thank goodness, been waiting and looking forward to watching it. The FB link went wrong somehow. 

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Much better vid quality, how the hell did they have such terrible quality that first time...

Interesting that they seem to have had relatively few questions from the public so that they wound up with a bunch of team member/journo hack questions.

 

Edit: they didn't look too much like they believed some of those answers >_>

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33 minutes ago, hoom said:

Much better vid quality, how the hell did they have such terrible quality that first time...

Interesting that they seem to have had relatively few questions from the public so that they wound up with a bunch of team member/journo hack questions.

 

Edit: they didn't look too much like they believed some of those answers >_>

the first video was livestreamed to the public, the second one was recorded and then posted

you can't expect to get similar quality from a live stream than a video unless you live in sweden or some shit hahahaha

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Bullshit.

We have gigabit down, 400mbit/s up residential fibre at very reasonable rates now but you don't need anywhere near that much bandwidth to stream 1080p.

VDSL is more than adequate.

The bitrate they were using for that live stream was probably not even maxing a 1Mbit/s upload on ADSL1/2.

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-0:59 "We're not allowing autopilots of any kind whether it's mechanical or electronic."

So they think.....

As to the journo hack question thing - this was hardly publicised was it?

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7 hours ago, nav said:

-0:59 "We're not allowing autopilots of any kind whether it's mechanical or electronic."

So they think.....

As to the journo hack question thing - this was hardly publicised was it?

They'll amend the rule if needs be...

But to be honest manual flight for this thing is going to be quite a challenge.

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19 hours ago, sclarke said:

Better video quality

Thanks for posting that! They're being pretty coy about the wind limits - which are a huge determinant of the approach to the hull design - and they didn't sound very convincing when they were talking about the 'post AC' life of the new boats - but it looks like they've done their homework given the extremely tight schedule.

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1 hour ago, rh2600 said:

They'll amend the rule if needs be...

But to be honest manual flight for this thing is going to be quite a challenge.

Agree on both counts. Has anybody figured out how you tack when flying upwind? Or is touchdown between tacks inevitable?

Cheers,

Earl

 

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18 minutes ago, Earl Boebert said:

Agree on both counts. Has anybody figured out how you tack when flying upwind? Or is touchdown between tacks inevitable?

Martin Fischer confirmed the hypothesis that ballast should provide inertia and facilitate flying tacks. Besides, the boat will be going upwind at 22 kts min. if on one foil; lowering the other foil, the margin to splash down is slowing to 16-18 kts

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3 minutes ago, Xlot said:

Martin Fischer confirmed the hypothesis that ballast should provide inertia and facilitate flying tacks. Besides, the boat will be going upwind at 22 kts min. if on one foil; lowering the other foil, the margin to splash down is slowing to 16-18 kts

OK, thanks. Looks like roll axis control is going to be "interesting" as well.

Cheers,

Earl

 

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Virtual perimeter of the boat to keep them from hooking foils or bouncing off of each other? Don't these guys know that rubbin' is racin'? 

"He virtually 'rubbed' you, he didn't virtually hit you."

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The big issue with the virtual box is how the heck are the crew supposed to see it?

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14 minutes ago, hoom said:

The big issue with the virtual box is how the heck are the crew supposed to see it?

I assume they will just have a giant "meters to target" readout on the back of the mast (or perhaps next to the steering wheel).

They could always get a fancy HUD.

Or they could just know it is 1m to windward of the ruddy great foil sticking up in the air!

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1 hour ago, Kiwing said:

^ I hope it is a bit more than a metre ??

Yeah. Plenty to sort ou going  forward.  

To me the driving  question is how do they dodge decapitation.

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^ Dan said they will all be in the middle of the boat! Not doing a Slingsby/Spithill hang ten.

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14 hours ago, Kiwing said:

^ I hope it is a bit more than a metre ??

True, but you get my meaning, there is almost always going to be a fucking huge point of reference sticking up for the helmsman to use to judge his distance on even without electronic aids.  Even with both foils in the water they are still going to be a pretty obvious point of reference and there is not that much underwater material sticking out beyond them.

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Maybe the helm will be wearing virtual head gear and the rest of the sailors will be watching the real stuff ?!?

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a big display like some of the AIS I have seen, Time to Closest Approach, Distance at Closest Approach, alarms when distance at closest approach is less than ??.

It's a user interface challenge, i know a few companies that could cook up a sweet solution, i'm sure this is an easy dev problem.

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5895577718_227fbc9f0a_b.jpg

 

GLD-109128.jpg

I wouldn't be surprised if the afterguard wear systems similar to the JMCS and HMSS helmet mounted display systems.

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4 minutes ago, Raptorsailor said:

5895577718_227fbc9f0a_b.jpg

 

GLD-109128.jpg

I wouldn't be surprised if the afterguard wear systems similar to the JMCS and HMSS helmet mounted display systems.

Would be an option, but it makes even less relatable to the every day sailor. Not that it matters that much. 

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Front Page (is it really a thing?) article on the rule http://sailinganarchy.com/2018/06/22/the-new-ac-a-bad-joke/

While I'm not a huge fan of this concept, I take umbrage with a bunch of stuff in this article.

Quote

The levels of detail driving this control mania are astonishing. The nominated restrictions include:

* only eight permitted brands of surface paint

* an allowable variation in hull length of just 10 cm

* 13 separate rules governing hydraulic control circuits

* nine rules (plus detailed diagrams) to regulate electrical and electronic systems

* 10 rules to govern the foil cant system

* a formula with eight components to limit mainsail girth

Not surprisingly, the rules document concludes with no less than 100 separate definitions of the terms it includes.

The end result is that the fleet of AC75s who will race from Auckland in 2021 are likely to be virtually identical. It was much the same with the foiling catamarans in Bermuda last year. The only notable physical difference was the quartet of cyclists on the New Zealand boat. (The new rule even puts an end to that wrinkle: all crew power “must primarily be transmitted through the crew’s hands”.)

8 brands of paint because of the necessity to prevent someone slipping in a boundary layer improving chemical.

This sort of rule has been common in class rules for decades & frankly I'm pretty surprised the allowed brands are as high as 8.

From recollection the rule specifically allows teams to nominate additional brands they want to use & will be added if shown to not provide advantage.

(edit: original release of the rule I have saved had 7 so 1 has been added if its 8 now)

 

Lots of limits to control to prevent fully-auto stability/height control, once decided not to allow full-auto its absolutely necessary to put in comprehensive rules to prevent it whether you believe in the existence of herbie or not.

 

Honestly don't recall mainsail girth rule but presumably a bunch of the components are batten lengths? Also with allowing double-sided sails you do need to do more than normal.

 

Lots of definitions because the AC is notorious for people trying to drive a flying tractor through a loophole...

 

Overall the comparison with the AC50 is completely bullshit.

AC50 explicitly one-designed the entire exterior shape except a small amount of fairings and the foils.

This rule does have tight limits & includes a bunch of OD components but within them there is still a large amount of opportunity for boats to be different in key performance affecting & visually key areas -> I do expect to see a lot of variety.

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"The end result is that the fleet of AC75s who will race from Auckland in 2021 are likely to be virtually identical."

I seriously doubt that. One or more teams will find a winning edge.

 

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2 posts on this thread in 8 weeks! 

I hate to say it but I have a feeling that the front page article has some merit. 

I still struggle to believe these things will work, and I have been playing with foils for over 20  years.

overcomplex rules are never a good starting point.

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49 minutes ago, Chimp too said:

I still struggle to believe these things will work, and I have been playing with foils for over 20  years.

overcomplex rules are never a good starting point.

We should know when the brits test their new boat.

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Whether the maths scales up or not in reality will be interesting. No surrogates will not answer that.

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^ Sim software is very good these days.  They will fly but it will be like chariot racing?

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Rule 26 has been discussed in other parts of the thread (#260#366) but I haven't seen any detailed discussion in relation to down force.

Rule 26.4 says:

26.4 The foil shall not intentionally be used to generate net downforce (combining gravitational and hydrodynamic loads) unless:

(a) the foil is at its fully raised position (maximum cant angle);

(b) the foil is at its fully lowered position (minimum cant angle); or

(c) the FCS is being commanded to drive the foil to a prescribed cant angle.

If the foil is not in one of these conditions and generates a net downward moment, the FCS shall not support the foil at a fixed cant angle and shall move the foil downwards.

Does "combining gravitational and hydrodynamic loads" mean that the foil must always produce enough lift to support not only its own weight, but whatever "gravitational loads" it's subject to (except at full up/down)? And if the foil doesn't do that, that the arm must lower the foil? The rate of lowering isn't specified, it might be really slowly through a bleed valve or similar, but it might be a one–way valve that stops the arm going up with positive lift but doesn't stop it going down when net lift is less than zero.

It seems to me that there will be times when it will be helpful for the foil to reduce its lift below the gravitational weight on it, particularly in the two–foils–down "safe" mode where it's likely necessary to control roll in a gust and also during manoeuvres, where weight and other forces are transferred from one foil to the other. It will make life difficult if during a manoeuvre a foil decides it hasn't got enough load so starts lowering… that might produce some serious WTF moments. 

And what about in non–foiling mode, there will be many circumstances where the foils are producing a "net downward force", though at least in that case presumably the weight of the boat isn't counted as it's supported by its own buoyancy.

I can understand if the foil isn't allowed to produce a hydrodynamic downforce, but including gravitational loads seems unnecessarily restrictive.

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On 6/23/2018 at 5:44 PM, hoom said:

Lots of definitions because the AC is notorious for people trying to drive a flying tractor through a loophole... 

 

Trying? We did more than try my friend!

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21 hours ago, RobG said:

Rule 26 has been discussed in other parts of the thread (#260#366) but I haven't seen any detailed discussion in relation to down force.

Rule 26.4 says:

26.4 The foil shall not intentionally be used to generate net downforce (combining gravitational and hydrodynamic loads) unless:

(a) the foil is at its fully raised position (maximum cant angle);

(b) the foil is at its fully lowered position (minimum cant angle); or

(c) the FCS is being commanded to drive the foil to a prescribed cant angle.

If the foil is not in one of these conditions and generates a net downward moment, the FCS shall not support the foil at a fixed cant angle and shall move the foil downwards.

Does "combining gravitational and hydrodynamic loads" mean that the foil must always produce enough lift to support not only its own weight, but whatever "gravitational loads" it's subject to (except at full up/down)? And if the foil doesn't do that, that the arm must lower the foil? The rate of lowering isn't specified, it might be really slowly through a bleed valve or similar, but it might be a one–way valve that stops the arm going up with positive lift but doesn't stop it going down when net lift is less than zero.

It seems to me that there will be times when it will be helpful for the foil to reduce its lift below the gravitational weight on it, particularly in the two–foils–down "safe" mode where it's likely necessary to control roll in a gust and also during manoeuvres, where weight and other forces are transferred from one foil to the other. It will make life difficult if during a manoeuvre a foil decides it hasn't got enough load so starts lowering… that might produce some serious WTF moments. 

And what about in non–foiling mode, there will be many circumstances where the foils are producing a "net downward force", though at least in that case presumably the weight of the boat isn't counted as it's supported by its own buoyancy.

I can understand if the foil isn't allowed to produce a hydrodynamic downforce, but including gravitational loads seems unnecessarily restrictive.

isn't the gravitational load equal to the weight?

I would expect the hydraulics to be a 2-way ram. and if a bit of downforce was used at the same time it may not generate a net downforce if the foil was moving?

and the FCC which is supplied should automatically negate any downforce flap control inputs i would think. Yes, trying to drive something that has it's own mind and is negating your commands could create some WTF moments for sure. Hopefully there would some feedback to let you know when you exceed your command limits.

 

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3 hours ago, Boybland said:

Trying? We did more than try my friend!

Point is if your definitions are insufficient AC teams will take advantage.

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2 hours ago, hoom said:

Point is if your definitions are insufficient AC teams will take advantage.

Oh absolutely :) it's possible one of the best and yet sometimes most annoying feature all in one!

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On 6/26/2018 at 9:43 AM, RobG said:

Rule 26 has been discussed in other parts of the thread (#260#366) but I haven't seen any detailed discussion in relation to down force.

Rule 26.4 says:

26.4 The foil shall not intentionally be used to generate net downforce (combining gravitational and hydrodynamic loads) unless:

(a) the foil is at its fully raised position (maximum cant angle);

(b) the foil is at its fully lowered position (minimum cant angle); or

(c) the FCS is being commanded to drive the foil to a prescribed cant angle.

If the foil is not in one of these conditions and generates a net downward moment, the FCS shall not support the foil at a fixed cant angle and shall move the foil downwards.

Does "combining gravitational and hydrodynamic loads" mean that the foil must always produce enough lift to support not only its own weight, but whatever "gravitational loads" it's subject to (except at full up/down)? And if the foil doesn't do that, that the arm must lower the foil? The rate of lowering isn't specified, it might be really slowly through a bleed valve or similar, but it might be a one–way valve that stops the arm going up with positive lift but doesn't stop it going down when net lift is less than zero.

It seems to me that there will be times when it will be helpful for the foil to reduce its lift below the gravitational weight on it, particularly in the two–foils–down "safe" mode where it's likely necessary to control roll in a gust and also during manoeuvres, where weight and other forces are transferred from one foil to the other. It will make life difficult if during a manoeuvre a foil decides it hasn't got enough load so starts lowering… that might produce some serious WTF moments. 

And what about in non–foiling mode, there will be many circumstances where the foils are producing a "net downward force", though at least in that case presumably the weight of the boat isn't counted as it's supported by its own buoyancy.

I can understand if the foil isn't allowed to produce a hydrodynamic downforce, but including gravitational loads seems unnecessarily restrictive.

Also, your post in the Foiling Monohull thread:

   On 6/26/2018 at 1:06 AM,  Left Shift said: 

The proposed design has one apparently un-resolvable flaw that makes it a terrible choice for match-racing.  Or really any kind of racing.   

From what I hear, there is a point of serious lateral instability during the relatively slow (compared to the cats) transition from displacement to foiling.  And unless they rapidly find a way to keep the boats on foil through tacks and jibes, manoeuvres will be painfully slow and potentially dangerous.   Just what I hear.

Given that rule 26 regarding downforce says the foils are not allowed to generate "net downforce", it means that when getting up to speed with both foils in the water, the windward foil can only get to net zero lift (and hence RM), then suddenly as it clears the water there's 1.5 tonnes of foil siting several metres off the windward gunwale. That's gotta mess with the lateral stability.

It can generate downforce while it's being raised, but that will call for some very calculated manoeuvres to preempt transitions, the speed of which will be governed by the speed of the rising foil to ensure the boat is setup to deal with the RM of the foil as it leaves the water.

It might be better if it was allowed to generate downforce equivalent to its weight (i.e. zero dynamic lift). That way it can be left in the water until things are sufficiently stable to lift it out. The situation goes in reverse when putting it into the water—suddenly the RM disappears.

 
=====================
 
Great food fot thought. Makes me wonder if the intended sequence of foil deployment isn't the following:
 
- at very low speeds ( < ~ 8 kts) both foils are in the fully lowered position, since the leeward foil cannot even support its own weight and would provide negative stability if deployed, the windward foil acts as conventional ballast 
- as speed increases from ~ 8 kts to takeoff, the leeward foil is canted to its working position and progressively takes up the boat's weight. The windward foil stays in the fully lowered position and is allowed to generate negative (nearly horizontal) lift, which translates into righting moment with the added advantage of not increasing the load on the leeward foil
- at takeoff speed, the winward foil moves to its working position, maintaining negative lift while it moves. At the end of its travel, lift is set to zero/positive, the boat's weight is equalized between the foils and it jumps out of the water 
- finally, the windward foil is brought to its fully raised/dry position
- this all happens on a beam reach, so leeway shouldn't be a factor
 
 
 

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That’s one scenario, some others:

  1. transition from one foil to both (start of a tack or gybe)
  2. transition from two foils to one (completing a tack or gybe)
  3. Recovering from a drop off foils in various states (how many of those are there?)

 

I guess the designers have run a zillion scenarios and think they know how to complete them successfully, but they won’t know until the boats are on the water and some crews try them for real. I think the whole thing would be a lot easier if some downforce was allowed, but for now the rules say “no”. :-(

 

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On 3/30/2018 at 11:29 PM, Xlot said:

 

"19.20  The mainsail shall be lowered to the deck without assistance from crew aloft. This should not prevent crew going aloft to resolve occasional issues "

 

Define "occasional" :D This will make the infamous Alinghi halyard lock / headboard episode seem innocuous by comparison. Imagine all the control wires going up to the various batten levels and the potential for snagging is huge.

Do you think the top control arm will have to be lowered too?

 

If you have to send someone up to lower the sail two days in the row, you should probably expect a visit from the measurement commitee. :)

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Down force will be allowed if the foil is in the altered "fully raised position" and the boat is healed to windward like a moth.

Will anyone be out-here enough to use it.. who knows?

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any guesses which 'final rule' is being released? The only significance I can see for the end of June is that (cheap) entries close.

Most of the story^ is actually about ETNZ's in-house development - towards the AC75 and their fist test boat

33 Dates

33.1 The following items shall be specified no later than the dates specified:
Date Rule Who Item
TBA 5.4 Rules Committee Template spreadsheet to track components.
TBA 6.13 Rules Committee Material certificates and declaration requirements.
TBA 10.24, 16.6 Rules Committee Measurement procedures for loads tests.
TBA 13.1 COR/D Further details of the foil arms.
TBA 11.14, 16.5 COR/D Reserved area for the supplied Media System.
TBA 19.1 COR/D The mast drawing package.
TBA 21.10 Rules Committee Standard types and positions for pressure relief valves.
TBA 25.6 COR/D Media System details and protocols.
TBA 26.1 COR/D Details of the FCS.
TBA 26.10 COR/D FCS system updates frozen.
*TBA 27.3 (f) COR/D Media equipment worn by crew.
*TBA 27.6 Rules Committee Crew weighing schedule.
*TBA 29 COR/D Event branding.
*TBA 30.1 Rules Committee Measurement procedures and documentation.
*These specifications may be amended provided they are published at least 180 days prior to the
first day of racing of the Event in which these specifications apply.

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On 6/28/2018 at 10:56 AM, Kiwing said:

Down force will be allowed if the foil is in the altered "fully raised position" and the boat is healed to windward like a moth.

Will anyone be out-here enough to use it.. who knows?

What "altered fully raised position" is that? There has been speculation in the forums, but nothing in the rules.

As soon as the foils stop providing lift equal to their weight, they're providing downforce (according to the rules), so they must be allowed to create downforce when fully up (i.e. at the maximum raised position as indicated in rule 12) or they're defying the laws of physics.

The current rules specify where fully down must be in rule 12 fairly precisely (or at least the region in which the foil must fit when fully down, with the flaps in all positions). It also indicates where "fully raised" is expected to be in terms of the extent of foil cant system (FCS) movement. There's nothing to say something can't be done to limit that, but modifying the FCS other than as allowed (where "allowed" hasn't be specified yet) is forbidden by rule 26.2.

Rule 26.1 says:

Details of a FCS to control the cant rotation of the foils will be specified in accordance with Rule 33. This system will allow cant to be changed during manoeuvres and to make low-frequency cant setting changes, but the system will not be designed to provide high-frequency cant adjustment.

Full details are yet to be revealed. The very next rule (my emphasis) is:

26.2 The supplied FCS cannot be modified except as expressly permitted in the supplied specification.

So unless the "supplied specification" allows the raised position to be limited so as to keep at least some of the foil in the water, it's extremely unlikely that dynamic downforce can be generated when the foil is fully raised.

Relevant details yet to be finalised:

TBA 26.1 COR/D Details of the FCS.
TBA 26.10 COR/D FCS system updates frozen.

Rule 26.10 is about updates to the FCS that must be installed by all Competitors.

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From https://www.sail-world.com/news/207123/A-new-version-of-the-AC75-class-rule-is-out

The development of the Class Rule has been a four-month process led by Emirates Team New Zealand, working together with Luna Rossa Challenge. From now on any changes can only be made with the consent of all entered competitors. Regular entries close on June 30, 2018 with late entries being accepted until November 30, 2018.

"We are pleased to publish the Class Rule on time as per the Protocol. It has been a detailed collaboration with the Challenger of Record on all aspects of the rule, including the one design and supplied parts. We feel we have done a great job containing costs on certain aspects, while leaving the rule open enough for the America's Cup to continue as the driving force of innovation and technology in sailing," said Dan Bernasconi, Design Coordinator for Emirates Team New Zealand.

Highlights of the AC75 Class Rule include:

  • Strict limitations on the number of components that can be built including hulls, masts, rudders, foils, and sails, thus encouraging teams to do more R&D in simulation and subsequently less physical construction and testing
  • Supplied foil arms and cant system to save design time and construction costs
  • Supplied rigging
  • One design mast tube

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I see the loophole in the clause on crew indication devices (allowing mechanical versions) has been removed. Damn. And here I had already blocked out a nifty pitch-and-bank indicator with a Tesla turbine running on compressed air and driving a mechanical gyroscope, for sale to the highest bidder. :D

Cheers,

Earl

 

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2 hours ago, Earl Boebert said:

I see the loophole in the clause on crew indication devices (allowing mechanical versions) has been removed. Damn. And here I had already blocked out a nifty pitch-and-bank indicator with a Tesla turbine running on compressed air and driving a mechanical gyroscope, for sale to the highest bidder. :D

Cheers,

Earl

 

I remember :D

Are they now permitted to use unilateral phase detractors?

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If the loophole closing was the result of somebody reading this thread, I think I deserve at least a gimme cap from ETNZ :lol:

Not holding my breath.

Cheers,

Earl

 

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18 hours ago, RobG said:

What "altered fully raised position" is that? There has been speculation in the forums, but nothing in the rules.

As soon as the foils stop providing lift equal to their weight, they're providing downforce (according to the rules), so they must be allowed to create downforce when fully up (i.e. at the maximum raised position as indicated in rule 12) or they're defying the laws of physics.

The current rules specify where fully down must be in rule 12 fairly precisely (or at least the region in which the foil must fit when fully down, with the flaps in all positions). It also indicates where "fully raised" is expected to be in terms of the extent of foil cant system (FCS) movement. There's nothing to say something can't be done to limit that, but modifying the FCS other than as allowed (where "allowed" hasn't be specified yet) is forbidden by rule 26.2.

Rule 26.1 says:

Details of a FCS to control the cant rotation of the foils will be specified in accordance with Rule 33. This system will allow cant to be changed during manoeuvres and to make low-frequency cant setting changes, but the system will not be designed to provide high-frequency cant adjustment.

Full details are yet to be revealed. The very next rule (my emphasis) is:

26.2 The supplied FCS cannot be modified except as expressly permitted in the supplied specification.

So unless the "supplied specification" allows the raised position to be limited so as to keep at least some of the foil in the water, it's extremely unlikely that dynamic downforce can be generated when the foil is fully raised.

Relevant details yet to be finalised:

TBA 26.1 COR/D Details of the FCS.
TBA 26.10 COR/D FCS system updates frozen.

Rule 26.10 is about updates to the FCS that must be installed by all Competitors.

Although the FCS itself cannot be modified, Rules 20.2 and 20.3 allow mechanical stops to be placed by the crew for the purpose of limiting the range of motion of hydraulic control systems.  I see nothing in the Rule that says 20.2 and 20.3 do not apply the FCS.  So the fully raised position can be anything the crew wants it to be, provided it is set using mechanical stops.  Downforce can therefore be applied at any cant angle, provided that cant angle is the current fully raised position.  This pretty much guts any restriction on downforce.

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6 hours ago, Stingray~ said:

Are they now permitted to use unilateral phase detractors?

Now now, you know power from modial interaction of magneto-reluctance is banned :rolleyes:

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Ah, I see V1.1 of the Rule is published.  V1.1 specifies a value for the fully raised position that was not included in V1.0:

"27.3 Subject to physical limitations, the FCS will be capable of controlling the cant of a foil to:
(a) a fully raised position, being 119° ±1°; and
(b) any angle between:
(i) the fully lowered position, being 0°, as shown in Figure 13.1; and
(ii) the highest permitted sailing position, which will be confirmed in the FCS specification, but is likely to be between 80° and 90°.
The FCS will not permit the holding of cant angles between the highest permitted sailing position and the fully raised position, this range only being available through transitions."

The "highest permitted sailing position" is a new term introduced in V1.1.  If the highest permitted sailing position is 80° to 90°, then when can the foil ever be raised to the fully raised position of 119°?  I don't see any advantage in raising it higher than the position for maximum righting moment of the dry foil.

Rule 27.4 attempts to limit hydrodynamic downforce:

"27.4 The AC75 Class Yacht is not designed to resist righting-moment created by hydrodynamic downforce on the windward foil. Following sailing trials and experience gained by Competitors, the Rules Committee, with the agreement of COR/D and the Regatta Director, and in consultation with Competitors, may amend this Rule to place restrictions on the use of the FCS including, but not limited to:
(a) a restriction of:
(i) the amount of negative cant moment (moment in the sense of reducing cant angle) that may
be sustained by the FCS; and
(ii) the cant angle that may be set for the windward foil;
(b) which may be applied at all times, or only in certain conditions, such as:
(i) when in a normal sailing mode, and not through a manoeuvre;
(ii) when within certain yacht speed or wind speed ranges; and
(iii) during certain stages of a race.
Such restrictions may be developed through sailing periods, but shall be frozen according to Rule 34."

This sounds good, but again Rule 21.3 renders 27.4(a)(i) moot. 

"21.3 A control system may restrict a control function as follows:
(a) fixed stops, or stops engaged and disengaged mechanically, may limit the travel of a control func-
tion;
(b) locks that engage mechanically at (or very nearly at) either end of the extent of motion of a con- trol function may be disengaged by an ECC and/or HCC, providing those extents of motion are not adjustable; and
(c) locks that limit the direction of motion of a control function at discrete points, e.g. ratchets, may engage mechanically.
However, stops and locks permitted herein shall not be combined to provide greater control of a control function, and shall not be used in mechanisms such as, but not limited to, escapements, to achieve the effect of indexed control or position control."

A mechanical stop can limit the downward movement of the foil as well as the upward movement of the foil.  So all that is required is for the crew to raise the foil a little above the desired position, insert a mechanical stop (as allowed by Rule 21.3), and lower the foil onto the stop.  The crew can then load up the foil with as much hydrodynamic downforce as desired.  The FCS will not be required to sustain the downforce because of the load taken by the stop, and even if it does try to move the foil downward in an uncommanded manner it will be prevented from doing so.  Indeed, given the adverse implications associated with uncommanded downward movement by the FCS, a stop may be a prudent design feature and justified on safety reasons alone.

It may be that Rule 27.4 was designed to overcome this difficulty:

"27.5 The cant rotation of a foil can only be controlled using the FCS."

Rule 22 applies to all hydraulic control systems except the FCS, but no such restriction is applied to Rule 21.  Therefore, one can conclude that Rule 21 is intended to apply to the FCS as well.  The stops restrict the cant control function, but do no work on the foil.  So I think a good case can be made that the foil is still being controlled only by the FCS even in the presence of stops that limit the range of cant control function.

The statement that, "The AC75 Class Yacht is not designed to resist righting-moment created by hydrodynamic downforce on the windward foil," may be an interesting historical fact, but this statement does not say the competitors are prohibited from using hydrodynamic downforce.  Unlike V1.0, V1.1 of the Rule does not have any explicit restrictions on downforce.  You can bet that just as in AC35, the team that can sail closest to the verge of breaking the boat will emerge the winner.

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5 hours ago, Stingray~ said:

Maybe a comparison of V1.0 to V1.1 would help clarify?

One thing GGYC/ACAlphabet managed to do well was put out amendments with a 'highlighted changes' version, I'm missing that here.

 

Edit: copied text to Notepad++ for successful compare, there are definitely a lot of little clean-ups & some bigger changes.

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