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pacice

Foiling Monohull - what would it look like?

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27 minutes ago, Sailbydate said:

So now you're bitching because the ACC is too radical? Give us a break, Stinger.

No, despite sharing many of the reservations above and wishing they’d done a ‘real’ multihull, I do love this concept. Compare it to what ‘a return to monohulls and tradition’ could have meant.

Bernasconi et al have my salute, here’s hoping it works out well. 

We should all have a level of concern about how tepid the response has been from outside NZ and the promotional press release; few if any independent design experts have weighed in with support, Basiliscus expressed a pretty serious issue and Cammas was tepid at best. Where are the rest, tongue-tied? Time will tell.

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2 hours ago, ~Stingray~ said:

No, despite sharing many of the reservations above and wishing they’d done a ‘real’ multihull, I do love this concept. Compare it to what ‘a return to monohulls and tradition’ could have meant.

Bernasconi et al have my salute, here’s hoping it works out well. 

We should all have a level of concern about how tepid the response has been from outside NZ and the promotional press release; few if any independent design experts have weighed in with support, Basiliscus expressed a pretty serious issue and Cammas was tepid at best. Where are the rest, tongue-tied? Time will tell.

A little bit stunned, like many of us I suspect.

This JC-Lizzard foiler concept might get knocked back a little closer to 2021 'reality' if no-one else buys into it.

 

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those foils look dangerous.

Thinking about when the Aussi...errrr Japanese Softbank team just about cut their opponents on GBR Rover boat in half in the Bahamas when they flew over their hull.

These foils look like they could kill someone if they come over the the windward boat, or if they drop heel due to lack of air flow and jam their foil into the opponent's deck like a biker stabbing his wooden leg with a knife. That would not end well for either team.

Thought Death Race 2000 was supposed to be run in autos..

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13 minutes ago, Foreverslow said:

those foils look dangerous.

Thinking about when the Aussi...errrr Japanese Softbank team just about cut their opponents on GBR Rover boat in half in the Bahamas when they flew over their hull.

These foils look like they could kill someone if they come over the the windward boat, or if they drop heel due to lack of air flow and jam their foil into the opponent's deck like a biker stabbing his wooden leg with a knife. That would not end well for either team.

Thought Death Race 2000 was supposed to be run in autos..

 jesus dude you are truely livin up ta your name!!! BAR were the ones that tried to slice and dice Softbank, and the event was in Bermuda!!!!!!! Trump for 2020 eh

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4 hours ago, ~Stingray~ said:

No, despite sharing many of the reservations above and wishing they’d done a ‘real’ multihull, I do love this concept. Compare it to what ‘a return to monohulls and tradition’ could have meant.

Bernasconi et al have my salute, here’s hoping it works out well. 

Dunno hwot haz tipt you in the direkshin ov sweet reezin, but long may it larst!

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22 hours ago, jaysper said:

I'm going to make America's (Cup) great again! :D

By building a wall around NZ that the Auckland city council will pay for?

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Just now, Varan said:

By building a wall around NZ that the Auckland city council will pay for?

Nah. Wall just needs to be put around Auckland to stop all the illegal Auckland immigrants getting to the rest of NZ.

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1 hour ago, jaysper said:

Nah. Wall just needs to be put around Auckland to stop all the illegal Auckland immigrants getting to the rest of NZ.

No worries for the Capitol though, Jays. JAFAS all know about Wellington's weather.

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I thought the cats were fucking stupid. This is even more ridiculous. Can't you just sail yachts, for fucksakes? I supported ETNZ for the last 10 years, all in the hope the cup would come back to the southern hemisphere - and now we are faced with some mongrel/hybrid/vapourware video game shitter. 

Sail BOATS you fucktards!

 

 

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The operating of the foils - is that by using electric power from a battery? 

Before in AC history - was it possible to use engine og electric power like that? One thing is instruments - but if you really cant sail it without som type of engine..?

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3 minutes ago, richiec said:

I thought the cats were fucking stupid. This is even more ridiculous. Can't you just sail yachts, for fucksakes? I supported ETNZ for the last 10 years, all in the hope the cup would come back to the southern hemisphere - and now we are faced with some mongrel/hybrid/vapourware video game shitter. 

Sail BOATS you fucktards!

 

 

Eloquently put!

At least etnz have not shown any signs of the same buttfuckery that Orifice did. Long may it continue. 

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22 minutes ago, SeaGul said:

The operating of the foils - is that by using electric power from a battery? 

 

That's the intention... could be one design batteries maybe? (As in formula E motor racing)

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43 minutes ago, SeaGul said:

The operating of the foils - is that by using electric power from a battery? 

Before in AC history - was it possible to use engine og electric power like that? One thing is instruments - but if you really cant sail it without som type of engine..?

It was argued and proven to be legal and used in the Alinghi v Oracle deed of gift match.

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10 minutes ago, Boybland said:

It was argued and proven to be legal and used in the Alinghi v Oracle deed of gift match.

The cat vs the tri?

So the last two ACs with the 72 cays and the 50 cats - they also used battery power - operating what? Was that really necessary? ...  

 

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37 minutes ago, SeaGul said:

The cat vs the tri?

So the last two ACs with the 72 cays and the 50 cats - they also used battery power - operating what? Was that really necessary? ...  

 

valve solenoids , and yes

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Im still trying to get my head around this new boat ,foil package and exclusion diamond .

Does this mean a penalty can obtained by a boat some 20 metres or more to leeward initiating a luff during the pre start ?

Most unfortunate if this is going to be the case !

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6 hours ago, Boybland said:

It was argued and proven to be legal and used in the Alinghi v Oracle deed of gift match.

SNG made a late change to their own rules, allowing engines. Since A5 was going that way, DZ installed one too.

The AC75 will likely have way more power than that, it’s essentially a double-canter.

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10 minutes ago, ~Stingray~ said:

The AC75 will likely have way more power than that, it’s essentially a double-canter.

Yes, but shifting just 1-1.5 t

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In the AC SF and Bermuda Cup cycles not one of the preceding ACWS events were raced in Cup Class boats. This time they will almost certainly be, Challenger boats against the Defender boat, although some deference is given in the Protocol about how those points when racing the Defender will be scored for the Prada Cup seedlings.

The ‘return to tradition’ sounded noble but it was nebulous at best especially given the new Class. 

The mono is there, upwind starts, and and ....

So a return to 'tradition' in some areas, development in others (so sorry, not binary - can you cope?) and in terms of a 'single class right through' and 'Defender vs Challengers before the Match', that you mention above - pretty much the same as the London plot - and you spun that bigly! :lol:

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2 hours ago, Justaquickone said:

Im still trying to get my head around this new boat ,foil package and exclusion diamond .

Does this mean a penalty can obtained by a boat some 20 metres or more to leeward initiating a luff during the pre start ?

Most unfortunate if this is going to be the case !

 

The umpires were too slow in AC35 to set reasonable distance limits at which a boat had to react or be penalised. They initially had to be a second or 2 from catastrophe before the umpires would dish out a penalty - sanity reigned in the end but so did the general confusion over what was going on.

So it's good that this is already being considered and once some of these things are sailing and their capabilities are better understood hopefully a sane take on what is reasonable will be adopted.

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7 hours ago, snaerk said:

valve solenoids , and yes

Yes but there is a mile of difference between control voltages (12v Or less) and the power required to actually move the foils and winches which is what DOGZILLA and Alinghi had.

A return to that situation with these new boats would be a sad sad concept IMO. But given they have 12 crew and have shown actual grinding going on, I think we are safe from that abomination at least.

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9 hours ago, richiec said:

I thought the cats were fucking stupid. This is even more ridiculous. Can't you just sail yachts, for fucksakes? I supported ETNZ for the last 10 years, all in the hope the cup would come back to the southern hemisphere - and now we are faced with some mongrel/hybrid/vapourware video game shitter. 

Sail BOATS you fucktards!

 

 

Let it all out, Richiec. Don't hold back. ;)

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4 minutes ago, Rennmaus said:

Am I blind? Where is the thread "The Next Boat----2020"?

Yeah, What's up with that?

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Some reactions at SButt

AMERICA’S CUP AC75 YACHT REVEALED (#4965)
Not impressed. Basically a monohull bastardised on a cat platform with more complexity, more danger (big leeward foil out of the water could cause carnage). They will be slower, less maneuverable and less interesting. Another start from scratch development dead-end.
- Hamish McNicol

All the downsides of a cat, a canter, a mono and a foiler brought together in one package. And this is supposed to be something that mainstream sailors can relate to?
- Chris Thompson

Flying is flying and sailing is sailing. Apart that it's on one hull instead of two, I don't notice any difference. I hoped so much AC goes back to sailing. That's very sad news.
- Gilbert Jentgen

For purists, it's hard to see the future. To go back is like holding on to race Kialoa again when Commanche is available. Change is assured and it's here. Looking forward to being there to watch whatever is deployed.
- Todd Mehserle

I'll be happy to see where they can take this. It used to be that there was some tech transfer from America's Cup boats to the general sailing community. How many of you sail on wing sailed rigs, in under 15 knots of wind, that require half a marina to moor in?
- Don Cavers

I look forward to them hooking foils during prestart maneuvers.
- Scott Inveen

OMG how cool are these things. Got me excited again for the next Cup. I thought no cats would be boring but far from it!!!
- Rod Andersen

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On 9/11/2017 at 1:52 PM, pacice said:

What would a AC foiling monohull look like?

I mean one that can foil downwind and maybe upwind, not just foil assisted reaching?

How can you match watch with foils poking up to 10 metres out the side of the boat.

How fast will they tack or gybe?

1. Now we know

2. Now we know

3. We dont know

4.We dont know

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10 minutes ago, ~Stingray~ said:

Almost looks like, for absolutely max RM, you’d want to fly the ww foil below the limit. Right? The aero could be better too.

3EDAC5C6-1F6C-4C21-8FA0-5FA73D96FB53.thumb.jpeg.820870e94453dab0e7a1089fbe9374aa.jpeg9EFD9A22-6ED5-435E-B6D3-E04492A41876.thumb.jpeg.69b74039cc1c22dc9d7d7dbad2347657.jpeg

 

I think you will want to be adjusting the angle if cant on the fly as the heel angle changes. 

You will probably also find that on flat water they have the whole boat heeled to windward to get additional righting moment from the rig and this will put the optimum angle for the WW foil back to a higher position.

The optimum angle will be highly dependent on the final shape of the foil arms which I suspect is still under development.

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10 minutes ago, Boybland said:

I think you will want to be adjusting the angle if cant on the fly as the heel angle changes. 

You will probably also find that on flat water they have the whole boat heeled to windward to get additional righting moment from the rig and this will put the optimum angle for the WW foil back to a higher position.

The optimum angle will be highly dependent on the final shape of the foil arms which I suspect is still under development.

I wonder too how much micro-adjustment they will do; the amount of stored energy in the batteries might be a limiting factor.

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^ I wonder if they've chosen electrically actuated hydraulics (over direct acting stepper motors) because of the possibility of some type of energy recovery which would reduce the total demand? Regardless, twin canting foil/keels - one of which will need to support the full 7 tons while cantilevered out 13 m from the centerline when they are foiling - is going to require some serious stored power.

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Bold concept from ETNZ. Really hope it works like in the animation, but those simulations are not proof of concept - far from it. Will be some serious engineering to move those 1.5t foils around as shown in the anim as well.

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Quote

Former America's Cup skipper Chris Dickson says the new foiling monohull yacht design released by Team New Zealand today will help make the event more relevant to ordinary sailors.

 

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20 minutes ago, ~Stingray~ said:

Gtran:

Granted, these renderings of the octopus-like America's Cup Foilers look so futuristic they could be considered an April joke. But there is a lot of genius behind it. Duel of the AC75. Will they look like this? © ETNZ "Spinning", "figment of the imagination", "what did you smoke?". So there are some comments to the release of the new AC75 Foiler for the next America's Cup 2021. As if the forms had sprung from the brain of an art student. In fact, the renderings are based on the reflections of perhaps the brightest minds in sailing. A leading figure is Team New Zealand Design Director Dan Bernasconi. His name has been traded rather in the background, also because he is a newcomer from Formula 1. For six years he worked for McLaren, but in 2006 he joined the Cup team of Kiwis. After the painful defeat in 2013, head of design Nick Holroyd took on the lucrative exchange offer from Japan, and suddenly Dan Bernasconi was responsible. With his back against the wall, he made the construction the most extreme way of all teams, and the result is known. The America's Cup victory was his accolade. Dan Bernasconi, perhaps the most important man in the Kiwi Cup victory. © ETNZ All the more one can assume that the considerations for the next America's Cup class are no spinning. Together with the specialists of Luna Rossa, he has come up with a truly groundbreaking design. Absurd monohull discussion Now it is obvious that the discussion about single or multi-rider, back or progress was completely absurd. The question of the number of hulls is almost irrelevant if the vehicle sails predominantly over the water. That's what the makers at the New York Yacht Club think, where it is suspiciously quiet after the announcement of the extreme Foiler. Ainslie (BAR), Cammas (Team France) and also Tom Slingsby, who is looking for funds for an Australian team, find admiring words. Slingsby even believes that his ex boss Larry Ellison may be weak again given the exciting prospects. The New Yorkers but should be flattened. They had hoped to bring their knowledge from the TP52 (Quantum) and Maxi72 (Bellamente) campaigns. But this Foiler sailing is so far from the known that they can not expect a competitive advantage. Everyone starts with a blank sheet of paper. Without a cost brake The problem with all the euphoria, however, is the cost control. This aspect does not seem to have played the biggest role in the considerations, and so Ainslie already says that you will not get along with the budgets of the past Cup by about 100 million euros.

Dan Bernasconi has explained more details about the new Cupper at Sail-World, which, interestingly enough, will be just as long as the last monohulls who sailed for the canteen in Valencia ten years ago. Their difference shows the rapid development that the sailing sport has accomplished during this time. The Briton stresses that it was very important to develop something close to the club sailor. This statement looks funny in view of the extreme design. On the other hand, more and more boats are actually lifting out of the water. And a Quant 23 might look like the future Cupper when sailing, even though the system with the curved DSS Foil works completely different than the T-Foils of the AC75. The Moth sailing, each with a wing on the rudder and sword is much closer. Optical proximity to "normal" yachts Mostly Bernasconi is concerned with the rig, of which not much is known, except that it should not be set by crane every day. But the ship in the harbor with foils folded down is then at least visually closer to the normal yacht than the flying catamarans.     Bernasconi says: "Of course we did a lot of simulation work in the cumputer and know exactly how the boat will behave. But of course we will not fully understand it until it's on the water. " For the expected speed, the designer says: "At 20 knots of wind, the boat will sail at a similar speed as the AC50. But the AC75 is bigger, has a higher rigging (90 feet) and develops more righting momentum. "This remains constant over all wind ranges, so the monohull has the potential to be between 9 to 15 knots faster than the AC50 in the foiling range , The more wind there is, the closer the speed will be. Because in strong winds, the AC75 lack the ability of the catamarans with the down-hired T-Foil Luvruders to develop further righting moment. Cyclists banished The engineer confirms that a crew of twelve is planned. It will not sit on wheels - that's not allowed - but use classic arm grinders. The use of hydraulic systems is limited and energy may only be stored for trimming the side swords. The pods are served by winch again.

While the AC50 Kats changed the angle of attack of the entire Lee foil, Bernasconi expects a movable trim flap like the tail of a Moth wing. In the case of the Moth, it is automatically trimmed by a sensor and thus the altitude adjusted, in the AC75 a sailor should be responsible. Also, the T-Foil at the helm is as the AC50 adjustable The swords function as a wing when they are tilted into the water at leeward, and in luff as a lever arm by their weight of up to 1.5 tons. It may be that a hydraulic pump is operated by batteries that allow the swords to tilt. This would eliminate the permanent crank operation of the grinder. When rigging, it looks as if the AC75 could not do without the advantageous shape of the wing. But it is being worked on to develop a system that allows conventional setting and recovery.

Foil from 9 knots   Even the AC75 should be operational even at the lowest wind speeds. This is essential if the races are to meet TV requirements. The AC50 reached four times the wind speed even at 6 knots of wind. The AC75 will not be that effective, but a big code zero roll sail will compensate for this shortcoming. Presumably, the new Cupper will not foilen at 6 knots wind. They are much heavier due to the ballast and the larger crew. But from 9 knots they should take off with the code Zero and then turn on their wings and jibe. It may then be rolled away again to reduce wind resistance. The conditions before Auckland - when the Cup actually takes place there - with often 18 to 20 knots of wind and a wave up to 1.5 meters against the Tide are much more demanding than in Bermuda. But Bernasconi believes that the new designs will cope with it. Maybe it would then be necessary in addition to tilt the windward foil into the water to increase stability.   However, the hull with the rigging and larger volume at the far end was much seaworthy than the configuration of the AC50 Kats. However, it is clear that these ships will be a big challenge for all teams.

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"While the AC50 Kats changed the angle of attack of the entire Lee foil, Bernasconi expects a movable trim flap like the tail of a Moth wing"

This is obvious in light of the length of races and banishment of cyclors, but nice to see it clarified.

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18 hours ago, Boybland said:

It was argued and proven to be legal and used in the Alinghi v Oracle deed of gift match.

It was only legal then because SNG had waived the parts of the racing rules that prohibited stored energy.  Had they sailed under the normal racing rules, the engines would not have been legal.  The trimaran was originally designed, built, and tested using manual power alone.  It was only after Alinghi opted for powered controls that BMW Oracle ripped out the cockpit of the trimaran and installed a BMW turbo diesel to power the hydraulics.  Keep your eye on the racing rules for this edition to see what will be allowed.

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7 hours ago, ~Stingray~ said:

Almost looks like, for absolutely max RM, you’d want to fly the ww foil below the limit. Right? The aero could be better too.

No, with the foil out of the water the only RM comes from the weight of the foil.  With the foil in the water, the RM comes from negative lift on the foil.  The latter can be far greater than the former.  After all, the foil is capable of creating enough lift to equal the weight of the entire boat.  What you could end up with is the lee foil operating at maximum positive lift and sails will be cranked on as hard as possible all the time.  The heeling moment will then be balanced by negative lift on the windward foil.  So it could be the windward foil that gets actively controlled, rather than the leeward foil.

The one advantage that does accrue to holding the foil above the water is the saving of hydrodynamic drag.  So the question becomes, "Does the extra righting moment improve the performance of the boat more than the associated drag degrades it?"  That's a question for the VPP.  I think there's a good chance the answer is, "Yes."  Only if the answer is, "No," would it make sense to hold the foil above the water.

Holding the foil in the raised position has some aerodynamic drag associated with it, too.  The apparent wind angles will be on the order of 20 deg, and there's no way the airflow will be attached on the lee side of the T foil at that angle of attack.  And any lift produced by the raised foil has to be countered by side force on the other foil, resulting in more drag.

Perhaps Mr. Bernasconi would like to share the results of VPP studies so we can appreciate the full brilliance of the concept?

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1 hour ago, Basiliscus said:

No, with the foil out of the water the only RM comes from the weight of the foil.  With the foil in the water, the RM comes from negative lift on the foil.  The latter can be far greater than the former.  After all, the foil is capable of creating enough lift to equal the weight of the entire boat.  What you could end up with is the lee foil operating at maximum positive lift and sails will be cranked on as hard as possible all the time.  The heeling moment will then be balanced by negative lift on the windward foil.  So it could be the windward foil that gets actively controlled, rather than the leeward foil.

The one advantage that does accrue to holding the foil above the water is the saving of hydrodynamic drag.  So the question becomes, "Does the extra righting moment improve the performance of the boat more than the associated drag degrades it?"  That's a question for the VPP.  I think there's a good chance the answer is, "Yes."  Only if the answer is, "No," would it make sense to hold the foil above the water.

Holding the foil in the raised position has some aerodynamic drag associated with it, too.  The apparent wind angles will be on the order of 20 deg, and there's no way the airflow will be attached on the lee side of the T foil at that angle of attack.  And any lift produced by the raised foil has to be countered by side force on the other foil, resulting in more drag.

Perhaps Mr. Bernasconi would like to share the results of VPP studies so we can appreciate the full brilliance of the concept?

basilicus, would you mind sharing a few words on how vpp simulations are structured, what typical variables are, and what data feeds them?

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16 minutes ago, buckdouger said:

basilicus, would you mind sharing a few words on how vpp simulations are structured, what typical variables are, and what data feeds them?

A VPP solves for the equilibrium forces and moments, so you need aero and hydro force models and a means of iterating to find the solution.  You can do it all in a spreadsheet, using Excel's Solver add-in.  The force models are typically in the form of look-up tables.  

The real grunt work is in generating the look-up tables.  You can use any aero/hydro method you want.  For conceptual design, you might use a vortex lattice method like AVL, or even a simple lifting line method, plus 2D section data from XFOIL or MSES.  If you don't have MSES, you could use Javafoil for multielement wingsail sections.  For more fidelity, you can use a panel code.  A panel code is the simplest method that can show the areas susceptible to cavitation on a 3D foil.  For higher fidelity work you'd go to Reynolds averaged Navier Stokes (RANS) CFD codes.

The kicker is the number of independent variables.  For a wingsail, you're going to need angle of attack (apparent wind angle - mast rotation), flap deflection, twist at a minimum.  For a foil, you're going to need cant, rake, leeway, flying height at a minimum.  Every independent variable you add multiplies the number of points in the table by the number of values for that independent variable.  It's easy for the tables to grow to many thousands of points.

You'll assign fixed values for some of the independent variables.  For example, you may fix the flying height and heel angle.  On a wingsail, whether you'd fix the flap deflection or twist would depend on how you intend to trim the sail.  Foil cant would be fixed.  You'd also specify the true wind angle if you were trying to generate a polar diagram.  Some variables you'd use as controls to let the VPP vary to find the equilibrium, such as mast rotation or wingsail twist (depending on your approach for trimming the wing), foil rake, rudder angle, leeway, pitch attitude.  Then chose some variable to maximize - typically based on boat speed.  You'd leave true wind angle free if you were trying to maximize Vmg.

Finally, you'd write the equations for summing all of the forces and moments in each of the six degrees of freedom.  When you add up all the forces for one degree of freedom, the result will not necessarily add to zero. This is called the residual.  To find the equilibrium a common method is to create a cost function as the weighted sum of the squares of the residuals.  Then you let your solver loose to minimize the cost function.  Ideally, all of the residuals will be driven to zero, but numerical errors will probably leave you with a small value.  

If you want to build a dynamic simulation, you need twice as many force and moment tables, because you now have to include the forces and moments due to angular rates.  These were assumed to be zero for the static equilibrium used in a performance analysis.  You also have more independent variables.  For example, with the boat flying straight and level, the angle of attack of the foils is only due to the rake of the foil and the pitch attitude of the boat.  But in a dynamic situation, the boat can be moving vertically, which changes the angle of attack.  Rolling of the boat changes the angle of attack differently for the port and starboard foils.  So the force models for a dynamic simulation have to be built with the appropriate assumptions in mind.  

Instead of solving for equilibrium, in a dynamic simulation what were the residual forces and moments become the accelerations used in the equations of motion.  The equations of motion are integrated to time-step the simulation.

If you poke around the net, you can probably find a Moth VPP to use as an example.  Here's a bare-bones landyacht VPP that I wrote eons ago.  It's very simple, but it has force models, solves for the equilibrium, and steps through the true wind angles to build a polar.

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On 11.9.2017 at 3:03 PM, SeaGul said:

If you take a unballasted flat very light  but wide mono - and put a foil on each side (dual rudders too) the leeward foil and rudder gives lift - the windward gives downforce - they are also in the water - but flaps make them pulling the boat upright.  In light winds all 4 foils can help lift the boat  out of the water. 

 

Basically in a match-race it will be the same as with the cats - wingmast and 1 or two other sails.

My first post in this tread....   ref using all 4 foils to lift out the hull at low speeds. The control will be to to keep the thing level - sideways and longitude...

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11 hours ago, See Level said:

I think Doug took his toys and went home.

Could we be that lucky?

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3 hours ago, Basiliscus said:

It was only legal then because SNG had waived the parts of the racing rules that prohibited stored energy.  Had they sailed under the normal racing rules, the engines would not have been legal.  The trimaran was originally designed, built, and tested using manual power alone.  It was only after Alinghi opted for powered controls that BMW Oracle ripped out the cockpit of the trimaran and installed a BMW turbo diesel to power the hydraulics.  Keep your eye on the racing rules for this edition to see what will be allowed.

This.

As I understand - the AC50s and the 72s didnt use a lot stored energy to operate the boats - they could probably have made that energy by using systems that developed the energy while they where sailing. 

 

But now they have some ballasted foils that will need a lot of energi - and the will have to use motor or a big battery charged before they sail.

 

And now Macif -  do they have a motor to make energy - or do the use solarpanels or some other energy systems while hes sailing?

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12 minutes ago, Sailbydate said:

Could we be that lucky?

Unlikely. He HAS disappeared for weeks at a time before. Doug Lord Xenu will return, rest assured. 

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Just now, jaysper said:

Unlikely. He HAS disappeared for weeks at a time before. Doug Lord Xenu will return, rest assured. 

Bugger!

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1 minute ago, Sailbydate said:

Bugger!

Sorry dude. Unless he got lost at sea on one of his remote control toys (Its called Arse Fire right?), them he will be back to annoy one and all! LOL!

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One existing boat that has the system with downforce is the old Windrider Rave - using magic wands on both ama foils - very simple system that seems to be usable for the not so advanced sailor.  

 

By using all foils to get the boat out of the water - all foils can be smaller and slimmer - better dynamics when going fast too. 

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3 hours ago, Basiliscus said:

A VPP solves for the equilibrium forces and moments, so you need aero and hydro force models and a means of iterating to find the solution.  You can do it all in a spreadsheet, using Excel's Solver add-in.  The force models are typically in the form of look-up tables.  

The real grunt work is in generating the look-up tables.  You can use any aero/hydro method you want.  For conceptual design, you might use a vortex lattice method like AVL, or even a simple lifting line method, plus 2D section data from XFOIL or MSES.  If you don't have MSES, you could use Javafoil for multielement wingsail sections.  For more fidelity, you can use a panel code.  A panel code is the simplest method that can show the areas susceptible to cavitation on a 3D foil.  For higher fidelity work you'd go to Reynolds averaged Navier Stokes (RANS) CFD codes.

The kicker is the number of independent variables.  For a wingsail, you're going to need angle of attack (apparent wind angle - mast rotation), flap deflection, twist at a minimum.  For a foil, you're going to need cant, rake, leeway, flying height at a minimum.  Every independent variable you add multiplies the number of points in the table by the number of values for that independent variable.  It's easy for the tables to grow to many thousands of points.

You'll assign fixed values for some of the independent variables.  For example, you may fix the flying height and heel angle.  On a wingsail, whether you'd fix the flap deflection or twist would depend on how you intend to trim the sail.  Foil cant would be fixed.  You'd also specify the true wind angle if you were trying to generate a polar diagram.  Some variables you'd use as controls to let the VPP vary to find the equilibrium, such as mast rotation or wingsail twist (depending on your approach for trimming the wing), foil rake, rudder angle, leeway, pitch attitude.  Then chose some variable to maximize - typically based on boat speed.  You'd leave true wind angle free if you were trying to maximize Vmg.

Finally, you'd write the equations for summing all of the forces and moments in each of the six degrees of freedom.  When you add up all the forces for one degree of freedom, the result will not necessarily add to zero. This is called the residual.  To find the equilibrium a common method is to create a cost function as the weighted sum of the squares of the residuals.  Then you let your solver loose to minimize the cost function.  Ideally, all of the residuals will be driven to zero, but numerical errors will probably leave you with a small value.  

If you want to build a dynamic simulation, you need twice as many force and moment tables, because you now have to include the forces and moments due to angular rates.  These were assumed to be zero for the static equilibrium used in a performance analysis.  You also have more independent variables.  For example, with the boat flying straight and level, the angle of attack of the foils is only due to the rake of the foil and the pitch attitude of the boat.  But in a dynamic situation, the boat can be moving vertically, which changes the angle of attack.  Rolling of the boat changes the angle of attack differently for the port and starboard foils.  So the force models for a dynamic simulation have to be built with the appropriate assumptions in mind.  

Instead of solving for equilibrium, in a dynamic simulation what were the residual forces and moments become the accelerations used in the equations of motion.  The equations of motion are integrated to time-step the simulation.

If you poke around the net, you can probably find a Moth VPP to use as an example.  Here's a bare-bones landyacht VPP that I wrote eons ago.  It's very simple, but it has force models, solves for the equilibrium, and steps through the true wind angles to build a polar.

Thanks!!! Verey informative (although I didn't catcha a word) Really, I'd always wanted to know how an VPP was made. Thanks again.

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13 hours ago, Rennmaus said:

Am I blind? Where is the thread "The Next Boat----2020"?

Perhaps someone felt touched by too much criticism? Or there was something very intelligent posted that we did not notice and someone did? Nah discard the latter...

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2 hours ago, jorge said:

Perhaps someone felt touched by too much criticism? Or there was something very intelligent posted that we did not notice and someone did? Nah discard the latter...

I thought I was going mad - glad it's not just me that can't see the other thread.....

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8 hours ago, Basiliscus said:

A VPP solves for the equilibrium forces and moments, so you need aero and hydro force models and a means of iterating to find the solution.  You can do it all in a spreadsheet, using Excel's Solver add-in.  The force models are typically in the form of look-up tables.  

The real grunt work is in generating the look-up tables.  You can use any aero/hydro method you want.  For conceptual design, you might use a vortex lattice method like AVL, or even a simple lifting line method, plus 2D section data from XFOIL or MSES.  If you don't have MSES, you could use Javafoil for multielement wingsail sections.  For more fidelity, you can use a panel code.  A panel code is the simplest method that can show the areas susceptible to cavitation on a 3D foil.  For higher fidelity work you'd go to Reynolds averaged Navier Stokes (RANS) CFD codes.

The kicker is the number of independent variables.  For a wingsail, you're going to need angle of attack (apparent wind angle - mast rotation), flap deflection, twist at a minimum.  For a foil, you're going to need cant, rake, leeway, flying height at a minimum.  Every independent variable you add multiplies the number of points in the table by the number of values for that independent variable.  It's easy for the tables to grow to many thousands of points.

You'll assign fixed values for some of the independent variables.  For example, you may fix the flying height and heel angle.  On a wingsail, whether you'd fix the flap deflection or twist would depend on how you intend to trim the sail.  Foil cant would be fixed.  You'd also specify the true wind angle if you were trying to generate a polar diagram.  Some variables you'd use as controls to let the VPP vary to find the equilibrium, such as mast rotation or wingsail twist (depending on your approach for trimming the wing), foil rake, rudder angle, leeway, pitch attitude.  Then chose some variable to maximize - typically based on boat speed.  You'd leave true wind angle free if you were trying to maximize Vmg.

Finally, you'd write the equations for summing all of the forces and moments in each of the six degrees of freedom.  When you add up all the forces for one degree of freedom, the result will not necessarily add to zero. This is called the residual.  To find the equilibrium a common method is to create a cost function as the weighted sum of the squares of the residuals.  Then you let your solver loose to minimize the cost function.  Ideally, all of the residuals will be driven to zero, but numerical errors will probably leave you with a small value.  

If you want to build a dynamic simulation, you need twice as many force and moment tables, because you now have to include the forces and moments due to angular rates.  These were assumed to be zero for the static equilibrium used in a performance analysis.  You also have more independent variables.  For example, with the boat flying straight and level, the angle of attack of the foils is only due to the rake of the foil and the pitch attitude of the boat.  But in a dynamic situation, the boat can be moving vertically, which changes the angle of attack.  Rolling of the boat changes the angle of attack differently for the port and starboard foils.  So the force models for a dynamic simulation have to be built with the appropriate assumptions in mind.  

Instead of solving for equilibrium, in a dynamic simulation what were the residual forces and moments become the accelerations used in the equations of motion.  The equations of motion are integrated to time-step the simulation.

If you poke around the net, you can probably find a Moth VPP to use as an example.  Here's a bare-bones landyacht VPP that I wrote eons ago.  It's very simple, but it has force models, solves for the equilibrium, and steps through the true wind angles to build a polar.

Thanks Basilicus, that's very informative and interesting. It's a term that gets referred to a lot, yet I have never come across a detailed description before. Much appreciated!

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Thanks, basilicus! Please keep it coming.

I was curious in my q above simply about if the max rm lever arm would be achieved by flying the airborn ww foil arm at an angle just below what the max appears to be; someone pointed out there is little difference and that the boat may heel to windward anyway.

You pointed out the much larger question about if you’d fly it airborn at all, if the rm created by negative attack while submerged superseded the drag effects; which for the AC50 ww rudder was certainly true - to the point teams were even wracking the hulls to maximize that effect. Could the Rule simply outlaw negative attack?

Here’s another probably-silly question:

At about what ‘configuration’ of the two foil arms would you want to lose positive lift on the ww foil?  The diagrams depict the optimal  ‘stable’ sailing and ‘foiling’ sailing modes but there must be an enormous amount to think about for the in-betweens.

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The "stable" mode will be used when its wind  to overpower the "normal" mode. Wonder if it will be possible to have several sets of foils - for different conditions?

    

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Leaving aside the design issues, in practical terms and the dreaded 'elf'nsafety then the SI's are going to need some rules of engagement in place to avoid potentially lethal close proximity manouevering.

Underwater issues were one thing but airborne contraptions flying in towards each other really are a serious issue.

No doubt that has been considered...or has it??    Can see the legal beagles having a field day on that one if there is an incident with subsequent human damage, and that would roll right back and directly into the people that designed the rule.

Whatever, if say there is a 2 or 3 boat length circle required around the protagonists then what does that do for the match racing element?

Overall I really don't get the impression this has been fully thought through

 

 

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52 minutes ago, GBH said:

Leaving aside the design issues, in practical terms and the dreaded 'elf'nsafety then the SI's are going to need some rules of engagement in place to avoid potentially lethal close proximity manouevering.

Underwater issues were one thing but airborne contraptions flying in towards each other really are a serious issue.

No doubt that has been considered...or has it??    Can see the legal beagles having a field day on that one if there is an incident with subsequent human damage, and that would roll right back and directly into the people that designed the rule.

Whatever, if say there is a 2 or 3 boat length circle required around the protagonists then what does that do for the match racing element?

Overall I really don't get the impression this has been fully thought through

There has been mention of ‘an electronic diamond’ boundary (hopefully a pretty big one!) to help address the very-obvious safety issues. Perhaps they will have flashing light indicators on board to warn them as they approach that diamond’s boundary.

Unlike the Cats the crew on this boat will probably not be traversing the boat while under G loads, so MOB probabilities are greatly reduced.

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And then you get ?time? penalties for infringing the boundary??  It's going to have to be a pretty big area to surround the craft, and so we've now lost the close quarters action that is and should be part of the match racing.  

Frankly I reckon they've lost the plot on the whole thing, as this is so far removed from having any trickledown to the rest of the sailing world - massive battery pack to power the foils or do you simply have a set number of raise/lower and have to use as you see fit?  That's getting too close to the F1 world where most of the time the drivers are in fuel and/or tyre saving modes, and can see how that is losing out big time to MotoGP

And if time penalties, then going to have to work out when it's worth taking one. Try explaining that to the masses!

 

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28 minutes ago, GBH said:

And then you get ?time? penalties for infringing the boundary??  It's going to have to be a pretty big area to surround the craft, and so we've now lost the close quarters action that is and should be part of the match racing.  

Frankly I reckon they've lost the plot on the whole thing, as this is so far removed from having any trickledown to the rest of the sailing world - massive battery pack to power the foils or do you simply have a set number of raise/lower and have to use as you see fit?  That's getting too close to the F1 world where most of the time the drivers are in fuel and/or tyre saving modes, and can see how that is losing out big time to MotoGP

And if time penalties, then going to have to work out when it's worth taking one. Try explaining that to the masses!

 

You must be fun to have at parties...

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19 minutes ago, sclarke said:

You must be fun to have at parties...

 

48 minutes ago, GBH said:

And then you get ?time? penalties for infringing the boundary??  It's going to have to be a pretty big area to surround the craft, and so we've now lost the close quarters action that is and should be part of the match racing.  

Frankly I reckon they've lost the plot on the whole thing, as this is so far removed from having any trickledown to the rest of the sailing world - massive battery pack to power the foils or do you simply have a set number of raise/lower and have to use as you see fit?  That's getting too close to the F1 world where most of the time the drivers are in fuel and/or tyre saving modes, and can see how that is losing out big time to MotoGP

And if time penalties, then going to have to work out when it's worth taking one. Try explaining that to the masses!

 

Enforst splashdown wood do it, praps

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So just throwing this out there. No definative plans for the rig/wing/main shown. Could it be that the rig could be canted to provide lift? Been done before, so why not? 

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37 minutes ago, Woolfy said:

So just throwing this out there. No definative plans for the rig/wing/main shown. Could it be that the rig could be canted to provide lift? Been done before, so why not? 

Been wondering the same. In the ‘Normal’ sailing mode (pic above) then compared to a much lighter AC50 there’s going to otherwise be a sh*tload of lift required by the one submerged main foil. 

I forget, does weight (extra attack/lift required) necessarily also lower the speed at which water cavitation will start? Perhaps at this scale it is not too significant and top speeds could still reach 47knts+?

Hydroprere’s 2008 500m speed record was something like 51.5knts but that boat, like the AC50, must have been much lighter than this AC75 - even if it comes in at the 5T lower end of the weight range guesses we’ve seen and even given the flying-arm’s ballast.

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On 24/11/2017 at 10:16 AM, ~Stingray~ said:

Any guesses as to the size of the track as depicted in the video?

6143CF2B-C041-4C4C-97AB-071F8780CAAF.thumb.jpeg.7dd9081d1e6c50bd71bc4eac6ed3699c.jpeg

 

By using map measure I get 6km (3.7m) x 1.75km (1.1m)

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19 minutes ago, yl75 said:

Cammas interview about the the new "boat"/concept :

http://voileactu.blog.lemonde.fr/2017/11/21/americas-cup-les-neo-zed-devoilent-leur-ac75/

Not overly impressed somehow.

Very few AC designers are impressed either so far.

Grant Simmer who signed only a week ago with BAR is the only designer to have commented and even with all his obvious reasons to promote it he emphasized a strong desire to be included, starting asap, in how this thing goes down.. The response has for sure been tepid so far.

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Cammas:

- Maintenant on sait que ces bateaux seront plus lents que les AC50.

Ce n’est pas ce que dit Grant Dalton.

- Je ne sais pas comment il peut affirmer ça. Rien qu’avec les chiffres, on sait que c’est impossible. Quand on prend trois données : poids, raideur et trainées, on sait que cet AC75 est au-dessus de l’AC50. Donc on sait que les AC75 seront plus lents.

- Now we know that these boats will be slower

This is not what GD says

- I don't know how he can tell that. Just reading the figures we know it's not possible. I we take 3 figures: wight, stiffness, drag, we know it is above the AC50. So we know that AC75 will be slower.

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2 minutes ago, ~Stingray~ said:

Nice. Is it pointed NE/SW?

From the points of the diamond align fairly close to NE, maybe slightly east of NE. 

Auckland's wind is most typically SW, but in summer the sea breeze can reverse this, which is why there is often a visible convergence zone where you can see breeze to the west and breeze to the east and nil in the middle.. 

Not as familiar with the northern side of Rangitoto, but I assume they chose it partly for more stable breeze as well as clear sailing room. 

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20 minutes ago, ~Stingray~ said:

Very few AC designers are impressed either so far.

Grant Simmer who signed only a week ago with BAR is the only designer to have commented and even with all his obvious reasons to promote it he emphasized a strong desire to be included, starting asap, in how this thing goes down.. The response has for sure been tepid so far.

There has been a deafening silence from RC. It would be interesting to get his take.. Although, given the strained history, it would be hard to comment objectively. 

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9 hours ago, ~Stingray~ said:

...Could the Rule simply outlaw negative attack?

Here’s another probably-silly question:

At about what ‘configuration’ of the two foil arms would you want to lose positive lift on the ww foil?  The diagrams depict the optimal  ‘stable’ sailing and ‘foiling’ sailing modes but there must be an enormous amount to think about for the in-betweens.

If the section shape is left for the teams to define, there's no point in trying to limit the angle of attack because the section shape can be designed to produce the desired down force even with a positive incidence on the foil.  

I've no idea what the optimum angle would be for the arms - that's another VPP question.  Say both foils were angled down at the same angle as the lee foil in the normal sailing mode.  Positive lift on the leeward foil would have a vertical component to support the boat and a horizontal component that provides side force to counter the rig.  Negative lift on the windward foil would have a vertical component that provides righting moment and a horizontal component that also helps to counter the rig.  Because of the down load on the windward foil, the leeward foil has to support both the weight of the boat and the down load from the windward foil, so it needs more of a vertical component than it did when the windward foil was retracted.  It may be that the best position for the two foils would be a little lower than shown for the normal sailing mode, but higher than shown for the stable mode.

If the foils were positioned flat as shown in the stable mode, then the side force needs to come from leeway acting on the struts (assuming there are no flaps on the curved struts).  The spanwise load distribution on the horizontal foils will have a discontinuity at the junction.  They will need to have independently articulated flaps on either side of the strut to minimize the drag.  I would expect there to be port and starboard flaps on each foil regardless of how they operate, because of the interference effects of the strut.  There may also be flaps on the strut, and it would make sense for the strut to have a sharper elbow than is shown on the concept sketches so there could be a longer straight segment for the flap.

It could also make sense to put some angle into the cant axis instead of having it straight fore-aft.  This might be used to toe the foils in or out when fully down.  It's not obvious to me whether you'd want all the side force to come evenly from both foils or to be shifted to either the leeward or windward foil.  Since the leeward foil literally does the heavy lifting, it might be desirable to have the windward foil generate the side force so the leeward foil can be optimized for vertical lift with minimum drag.

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