Salty Seacock

Emirates Team New Zealand.

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1 hour ago, Guvacine said:

When a conventional multihull will do EVERYTHING better - what the hell is the point?

To my mind the verdict is still out but early signs for the AC75 are increasingly encouraging. They look to be absolute monsters upwind, ETNZ is already snap-tacking that boat very impressively even in the recent almost-hellish conditions out there. 
 

Would love to see an F50 try beat them to the top mark; my guess is that the F50 is faster uphill under only under a few wind and water state conditions 

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3 minutes ago, Stingray~ said:

To my mind the verdict is still out but early signs for the AC75 are increasingly encouraging. They look to be absolute monsters upwind, ETNZ is already snap-tacking that boat extremely impressively even in the recent almost-hellish conditions. 

The amount of whining that is happening, I’m half hoping whomever wins decides to go Luddite and make it slow as fuck requirement for ocean crossing, cotton sails and no battery or energy stores or instrumentation. 
 

“want to challenge the defender? Build the boat per rules and sail it here and be ready to race in 2 weeks”

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11 hours ago, terrafirma said:

So you don't have a gut feeling SBD? You gotta give me somethin....:huh:

Ah....Now that's a whole different question, mate.

Yes. My gut tells me ETNZ is looking formidable. 

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On 7/14/2020 at 11:14 PM, weta27 said:

And another fast pass by North Head at the end, heading for home.

RG will have some spectacular shots, he was even closer than me.

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Too bad there isn’t any seagulls in any of the shots for me to get some speed estimates.

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10 minutes ago, Miffy said:

The amount of whining that is happening, I’m half hoping whomever wins decides to go Luddite and make it slow as fuck requirement for ocean crossing, cotton sails and no battery or energy stores or instrumentation. 
 

“want to challenge the defender? Build the boat per rules and sail it here and be ready to race in 2 weeks”

:D

Could happen but it’s not gonna be while ETNZ holds the Cup and I applaud them for going with this basically-incredible design. 
 

Again, GD did an interview with Clean after Bermuda about the monohull options they were considering, ranging from ‘1 to 10 extremity-wise’ and suggested that ‘you won’t be disappointed.’ That got my hopes up a little, but man-oh-man did they over deliver on that promise. 
 

I guess the thing to do is to enjoy the spectacle, whether it’s what you’d choose or not, since this Class is the big deal this time round. 

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2 minutes ago, Stingray~ said:

:D

Could happen but it’s not gonna be while ETNZ holds the Cup and I applaud them for going with this basically-incredible design. 

At this point in the global chaos, I don’t even care who wins, I just want to see an event go well, good racing happens and if it brings the Italians or Brits or Kiwis or Americans a trophy to feel a little good - all good. If I could give everyone a trophy I would. 

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10 minutes ago, Stingray~ said:

To my mind the verdict is still out but early signs for the AC75 are increasingly encouraging. They look to be absolute monsters upwind, ETNZ is already snap-tacking that boat very impressively even in the recent almost-hellish conditions out there. 
 

Would love to see an F50 try beat them to the top mark; my guess is that the F50 is faster uphill under only under a few wind and water state conditions 

Stingray - it is just physics. The floppy gecko could never beat a vastly lighter and more stable foiling multihull with similar "power" (sail area to weight).

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3 minutes ago, Miffy said:

At this point in the global chaos, I don’t even care who wins, I just want to see an event go well, good racing happens and if it brings the Italians or Brits or Kiwis or Americans a trophy to feel a little good - all good. If I could give everyone a trophy I would. 

Nailed it! Me too

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1 minute ago, Guvacine said:

Stingray - it is just physics. The floppy gecko could never beat a vastly lighter and more stable foiling multihull with similar "power" (sail area to weight).

It’s to a big degree a battery-powered boat, giving it ginormous RM ability. That should more than offset the weight.

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On 7/15/2020 at 3:53 PM, Forourselves said:

We never saw any complete manoeuvres in their entirety from AM. Guess we’ll just take your word for it huh? 

Wrong again... just stop guessing.

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1 minute ago, Stingray~ said:

It’s to a big degree a battery-powered boat, giving it ginormous RM ability. That should more than offset the weight.

Can't beat physics. Mass is mass. If weight wasn't important you would not have performance car, boat, plane designers spending fortunes to develop materials to reduce weight. Making something HEAVIER to go faster is arcane.

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18 hours ago, terrafirma said:

I know it's early to be asking this question but who do we think has a chance of beating ETNZ when we only have 3 challengers? I still think one of these challengers will be a way off the pace. I also know we haven't seen B2's yet so I guess I'm asking which team do you think has the design competence to beat the Kiwis at their own game? So 2 of the boats began life without bustle's? The Kiwi's started with a bustle. The Italian's seem to have the fastest B1 not without it's problems off course but typically the Italian's beat themselves. The Poms are run by Grant Simmer who whilst experienced is the man who last lost the cup? That leaves the USA who will be driven by the man who lost the cup too? There isn't one challenger I believe is closer than 50:1 for my money that has a real chance in beating the Kiwi's? Am I too early and should we wait until B2's are out on the water?

I will take your 50:1 odds.  How much do you want to put up?

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6 minutes ago, Guvacine said:

Can't beat physics. Mass is mass. If weight wasn't important you would not have performance car, boat, plane designers spending fortunes to develop materials to reduce weight. Making something HEAVIER to go faster is arcane.

F18’s, with very heavy jet engines, put the speed of hang gliders to shame. Power matters too! 

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2 minutes ago, The_Alchemist said:

I will take your 50:1 odds.  How much do you want to put up?

Yikes, better put a max bet on that :) 

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11 minutes ago, The_Alchemist said:

Wrong again... just stop guessing.

Link?

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5 minutes ago, Stingray~ said:

F18’s, with very big jet engines, put hang gliders to shame. Power matters too! 

Stingray. That is a really bad example of false equivalence. Instead, take two F18s with the same engine power. One of the F18s is lighter - which one will be the fastest and most maneuverable?

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2 minutes ago, Guvacine said:

Stingray. That is a really bad example of false equivalence. Instead, take two F18s with the same engine power. One of the F18s is lighter - which one will be the fasted and most maneuverable?

Who cares. I can get in a jet and fly faster than any boat. Boom. Boats are now pointless. 

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1 minute ago, Guvacine said:

Stingray. That is a really bad example of false equivalence. Instead, take two F18s with the same engine power. One of the F18s is lighter - which one will be the fasted and most maneuverable?

For sure but the equivalence we are bantering about was, I thought, between a lower-powered but lightweight F50 versus a much higher-powered but much heavier AC75. The power to weight ratio may favor the AC75, the sheet loads are apparently close to 10t! 

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53 minutes ago, Guvacine said:

Oh I don't know. An AC50, or any multi developed with half of the funds spent on the spastic gecko.

A bespoke foiling wing sailed cat... yup dictionary definition of “conventional” 

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Just now, Stingray~ said:

For sure but the equivalence we are bantering about was, I thought, between a lower-powered but lightweight F50 versus a much higher-powered but much heavier AC75. The power to weight ratio may favor the AC75, the sheet loads are apparently close to 10t! 

The AC75 is 3X the weight of an AC50, but only has 2X the sail area. Therefore the AC50 will be faster all round - you can't beat physics.

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2 minutes ago, JALhazmat said:

A bespoke foiling windsailed cat... yup dictionary definition of “conventional” 

I’m so puzzled by the affection some have for the AC50s. They existed for what? 4 weeks of meaningful racing in the most isolated light air sound? Pitch pole and fairings were falling off left and right in 20 wind gusts. 
 

And the team that made the fastest boat didn’t even seem that fond of it afterwards. 
 

And all the apples and oranges comparison re speed - well I can sail an old 32 west sail across the Atlantic faster than the AC50s because they wouldn’t make it across. 
 

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1 minute ago, Guvacine said:

The AC75 is 3X the weight of an AC50, but only has 2X the sail area. Therefore the AC50 will be faster all round - you can't beat physics.

The massive battery-power enables massive RM, it’s where the enormous power gets derived from. 

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Posted (edited)
32 minutes ago, The_Alchemist said:

Too bad there isn’t any seagulls in any of the shots for me to get some speed estimates.

No super-sonic Solent seagulls out on the Waitemata, Aichy. They're all at the tip.

Unknown.jpeg

Edited by Sailbydate
Proof
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1 minute ago, Guvacine said:

The AC75 is 3X the weight of an AC50, but only has 2X the sail area. Therefore the AC50 will be faster all round - you can't beat physics.

It also has 5 times the righting moment but you don’t want to know About that do you.

fuck off to the f50 vs thread as you just trolling and you might find a mirror to chat to, it might even agree with you. 

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Just now, Stingray~ said:

The massive battery-power enables massive RM, it’s where the enormous power gets derived from. 

You are still ignoring the physics. Give the AC50 powered winches and controls too. It just gets worse for the spastic gecko in comparison. The AC50 is faster to foil, is more maneuverable, is more stable and has better power to weight.

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2 minutes ago, JALhazmat said:

It also has 5 times the righting moment but you don’t want to know About that do you.

fuck off to the f50 vs thread as you just trolling and you might find a mirror to chat to, it might even agree with you. 

Not trolling - just pointing out what is going to be really obvious to most people. Or use the AC72 as another multihull comparison - it has more sail area than the AC75, but weighs substantially less. The inescapable physics are that the AC72 would blitz the AC75.

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We will see how the numbers pan out, there are more physics going on than just weight and power.

Anyway, for something that looks on paper like it would have turned into a flailing tangle of sailcloth and strings in that breeze the other day, the over-riding impression as she flew past was of pure, taut, straining, groaning, frightening power.

Such an impressive machine.

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18 minutes ago, weta27 said:

We will see how the numbers pan out, there are more physics going on than just weight and power.

Anyway, for something that looks on paper like it would have turned into a flailing tangle of sailcloth and strings in that breeze the other day, the over-riding impression as she flew past was of pure, taut, straining, groaning, frightening power.

Such an impressive machine.

Until these boats have been in a real race, all of the claims about performance are meaningless. I am being down voted so fast that I will soon be in negative territory. There are clearly a lot of folks on this thread that are super touchy about the AC75 concept.

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Till they race it’s meaningless etc 

yet you are still trying to make a definitive statement about what’s best....

are AC 72s conventional too? haha! 

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39 minutes ago, Guvacine said:

Not trolling - just pointing out what is going to be really obvious to most people. Or use the AC72 as another multihull comparison - it has more sail area than the AC75, but weighs substantially less. The inescapable physics are that the AC72 would blitz the AC75.

Well, only one team has both an AC72 and an AC75... guess you're going to have to ask Dalts to recommission the 72 and do an exhibition race to replace his missing $3mil bucks.

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22 minutes ago, Guvacine said:

Until these boats have been in a real race, all of the claims about performance are meaningless. I am being down voted so fast that I will soon be in negative territory. There are clearly a lot of folks on this thread that are super touchy about the AC75 concept.

Ah, the downvoting tactic is just a KiWhingerTM pastime here. I think they think it means something.

sa_kiwis_feelings.png

Carry on old chap. Don't mind the KiwiTearsTM

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1 hour ago, Guvacine said:

You are still ignoring the physics. Give the AC50 powered winches and controls too. It just gets worse for the spastic gecko in comparison. The AC50 is faster to foil, is more maneuverable, is more stable and has better power to weight.

By ‘battery-power boat! I was referring to the ability to move the mains, the massive weight up to windward creating even more than what a wide tri can achieve. RM! 
 

But I agree, it’s very possible that F50’s, with their scary-powerful rudder differential, can eat up AC75’s in some conditions, the polars will show it. 
 

Nate O didn’t mention it but Artemis clocked the highest-recorded speed during racing in Bermuda, against Team Japan who recorded a close second, also in the high wind race during the CSS. Both were clocking at above 48 knots, right at cavitation, and he says the F50’s are now even faster. 

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1 hour ago, Guvacine said:

Not trolling - just pointing out what is going to be really obvious to most people. Or use the AC72 as another multihull comparison - it has more sail area than the AC75, but weighs substantially less. The inescapable physics are that the AC72 would blitz the AC75.

The 75 would kill a 72, especially upwind. The 72,s were still roll tacking where the 75’s are fully flying and accelerating much faster than the 72’s were.

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11 minutes ago, Forourselves said:

The 72,s were still roll tacking where the 75’s are fully flying and accelerating much faster than the 72’s were.

OR was pulling off flying tacks on SF Bay by the end of AC34, I wish RC had gone with an AC72 Version 2 for AC35. They were very-serious beasts, still on a fast up-cycle. 
 

Wings rock, departing from wings is the one disappointment I have with the AC75, even understanding the various pro’s and cons yakked about. 

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Actually I think the soft sail is interesting, perhaps safer than the wing if reefable, hopefully (but not sure) easier to control.

But a 75 foiling cat with softwing and foils oriented toward the exterior to increase the RM would be a killer.

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2 minutes ago, Tornado-Cat said:

But a 75 foiling cat with softwing and foils oriented toward the exterior to increase the RM would be a killer.

Agreed, but except for the ‘soft wing’ part. Solid wings are far superior, just as Vasco V, BA, and NO have said - repeatedly. 

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I agree with Guvacine to say that we would love a race between the AC75 and the F50 but we can already guess that the cat would be faster in light wind because much lighter therefore able to fly earlier, but in strong wind and waves the wide mono hull will violently hit the waves at 40 kts while multi finer hulls allow a much smoother fast run at 50 + kts.

 

 

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1 minute ago, Stingray~ said:

Agreed, but except for the ‘soft wing’ part. Solid wings are far superior, just as Vasco V, BA, and NO have said - repeatedly. 

Yes, more efficient, but IMO, it's a peace of mind to be able to reef on the water and adapt the boat to the wind and sea conditions.

Not sure it's possible on these AC wing sails though.

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2 hours ago, Guvacine said:

Oh I don't know. An AC50, or any multi developed with half of the funds spent on the spastic gecko.

AC50, pretty conventional, right.

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7 minutes ago, Tornado-Cat said:

Yes, more efficient, but IMO, it's a peace of mind to be able to reef on the water and adapt the boat to the wind and sea conditions.

Not sure it's possible on these AC wing sails though.

Not wing-related but I f’ing love this video

 

 

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F50s really want to be on calm water.  I think the AC75s can take a wider range of racing conditions than the cats.  

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21 minutes ago, Stingray~ said:

Not wing-related but I f’ing love this video

 

 

One of my favourite.

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4 hours ago, Guvacine said:

. When a conventional multihull will do EVERYTHING better - what the hell is the point? Oh right - there

Oh, except GETTING AROUND THE TRACK FIRST YOU MORONIC SOCK

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1 hour ago, Stingray~ said:

OR was pulling off flying tacks on SF Bay by the end of AC34, I wish RC had gone with an AC72 Version 2 for AC35. They were very-serious beasts, still on a fast up-cycle. 
 

Wings rock, departing from wings is the one disappointment I have with the AC75, even understanding the various pro’s and cons yakked about. 

Not consistently they weren’t. They were flying upwind in straight lines, doing about 28 knots, but they weren’t flying in tacks. Watch race 19. They were still getting down to 12/13 knots in a tack. The 75’s are barely slowing.

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That’s not the speed through tacks curve I remember but I will resurrect my AC34 and AC35 databases one of these days to show one way or the other. 
 

I wish the SailGP raw data was public but GD has promised that it will be made transparent for AC36, an excellent move that should be fun for many of us who drool over performance numbers. 

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4 minutes ago, Stingray~ said:

That’s not the speed through tacks curve I remember but I will resurrect my AC34 and AC35 databases one of these days to show one way or the other. 
 

I wish the SailGP raw data was public but GD has promised that it will be made transparent for AC36, an excellent move that should be fun for many of us who drool over performance numbers. 

Databases? It’s on video.

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21 minutes ago, Forourselves said:

Databases? It’s on video.

Agreed, but the raw data lets some folks here get deeper into the weeds than what the flash-fast summary graphics shown on TV demonstrated. 

The upwind speed curves through maneuvers they did show, but with little of the extra detail some of us here could bite into. I did like most of it though, like number s of tacks and jibes, ave speed broken down even to that level, etc. The changing tide graphics, especially on SF Bay, were freaking excellent too. 
 

For AC-heads, the graphics shown were good but they didn’t have enough screen-time for live-time deeper analysis like what proved to be the optimal path into a wicked-quick AC72 foiling tack by R17. 
 

Like it or not, some of us will have fun with the polars if as was promised that data is made public again. 

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26 minutes ago, Forourselves said:

Databases? It’s on video.

Oh dear lord. He really has no clue.

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Of course they will be faster through tacks and turns.. they are heavier and have more momentum. From seeing the video posted from 13/7, appears the AC75 will pretty much destroy an AC50 by some margin.

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Why not challenge an F50 to an exhibition race sometime? Not sure where they're parked up but surely Core has at least one lying around somewhere :)

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3 minutes ago, Tropical Madness said:

Of course they will be faster through tacks and turns.. they are heavier and have more momentum. From seeing the video posted from 13/7, appears the AC75 will pretty much destroy an AC50 by some margin.

And we don't even have a good idea of angles yet. After the first regatta when we see some hard data, it will be fork time for the nay sayers. FFS, etnz has long said these boats would destroy the AC 50 on the track, you'd think they would be conversant with angles that their design is capable of.

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4 hours ago, Guvacine said:

Can't beat physics. Mass is mass. If weight wasn't important you would not have performance car, boat, plane designers spending fortunes to develop materials to reduce weight. Making something HEAVIER to go faster is arcane.

It works for soap box derby cars....lol

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4 hours ago, Guvacine said:

The AC75 is 3X the weight of an AC50, but only has 2X the sail area. Therefore the AC50 will be faster all round - you can't beat physics.

The AC50's were way overpowered once they were up on the foils, so excess sail area didn't help.  Speed was limited by cavitation... can't beat physics.

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6 hours ago, Guvacine said:

I'm glad for those who are impressed by this folly.

Yeahhhh, somehow I really don't think you are....You're revisiting an old argument that's irrelevant now. The 75 is locked in for this cup, your ranting aint going to change that Angry Cat man. 

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Well, the financial shenanigans are coming into a bit more focus...

https://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=12348685

Quote

Businesses had to prove a 30 per cent revenue drop to secure the first round of wage subsidies and 40 per cent to qualify for the extension.

TNZ has secured both rounds, but questions are being raised over what revenue the syndicate actually lost as a result of the pandemic.

But it hasn't been keen to answer questions about its use of the Covid-19 wage subsidy.

Let's re-cap: Over $1M "lost" to a Hungarian bank scam, spies "leaking salaries" with "info coming back from Europe", no justification for the COVID subsidy, unwilling to say how much money has been lost, MBIE pulling funding from ACE, etc.

Piling this pandemic-plunder atop the $250M already pulled from NZ coffers????

GD! Say it isn't so!

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10 hours ago, Tornado-Cat said:

I was skeptic when the announced it would be a mono, enthousiast when they said they chose the most extreme version,

disappointed when I saw that they were inherently unstable because of their ballasted foils.

As a sailor a good boat is a boat with some basic stability

This could have been the perfect boat if stable, two solutions for that

1) the first Verdier version, with a small center weight or keel, but it is true it would have been slower

2) conceived like a trimaran with longer foil arms for same RM with less weight and small floats for safety. This, IMO, may represent the future of the boat. But we would have a boat looking like the hydroptere with different foils.

We would comeback to the old competition between tris and cats.

Anyway, it will be interesting to watch the AC75 compete and their sailing envelope in a race.

Your response is both Non Sensical and Contradictory.

So you want Extreme BUT you also want Stability.

This is the old Doug Lord school of thinking. One Foil to do everything - early take off (@ 3.5 or 4 Knots of TWS) AND and yet be high performance (+50 Knots Boat Speed)

I recall he was also dreaming of boats capable of armchair sailing, yet foiling, yet ultra fast........ This is the America's Cup - Not Geriatrics with Dementia Boating Trips Inc. Ltd.

Your comment As a sailor a good boat is a boat with some basic stability, alienates every Moth and Kite Foil sailor out there. 49er and I14 sailors would also take issue. In fact most high performance sailboat sailors would understand that you are talking nonsense.

You love of multihulls is not exactly Top Secret, but your commentary on anything that is not Multihull is just old. 

Your comment 1) the first Verdier version, with a small center weight or keel, but it is true it would have been slower, is describing that the America's Cup should be run in the YAC9F boats - and we have seen how relatively docile thay are compared to the AC75's or Testing Mules...... Just because you will never have the talent or skills to sail an AC75 does not make them an invalid proposition. 

This is like asking Formula 1 to be run in Saloon Cars or MotoGP to be run on 50cc scooters. That is complete Nonsense.

So as I previously said - when you have a new class of high performance and on the edge type of boats - and they are learning how to sail them and push them really hard, do not confuse a Boat handling error that leads to a bit of a slash down (that gets #Clown Pa all foaming at the mouth) or worse a capsize, with being grounds to condemn a boat type.

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5 hours ago, Guvacine said:

Stingray. That is a really bad example of false equivalence. Instead, take two F18s with the same engine power. One of the F18s is lighter - which one will be the fastest and most maneuverable?

Sheez, the idiots have been let out of the asylum early this weekend..........

You bitch about False equivalences, you claim that it is not suitable to compare Gliders with Jets; so to back yourself up by wanting to compare Two F18's but with different mass, yet revert to suggesting that comparing a 50ft catamaran with wing power against a 75ft monohull with sail power is a suitable equivalence........

Fuck me sideways, you are retarded (and here with your mates.........).

For the record, the designers of these boats and creators of the rule have already stated that the AC75's around a course will be faster than AC50, which has already been shown to be way in advance of an AC72 cat. Thats not some opinion by a ranty poster here on SA, that's smart people who earn great money by actually creating these boats. 

Claughton wrote an interesting article about these AC75's - the metrics for traditional performance indication are largely superceded. The amount of RM is massive. The sail area is c.250m2 - yet under traditional metrics the sail area should be between 500 and 1500m2 to achieve the performance required. 

The reality is that once airbourne, performance is more limited by induced drag, not just of both the hydrofoils and rig than by the power output, but also of the whole package. That is why Ineos is such a weird shape, the bustle of ETNZ and LR is a step forward (for multiple reasons) and why B1 of AM represents the laggard of the pack.

Only when we have seen B2's can we decide who is really in the game. If any team can find a way of raising the cavitation ceiling, then they too will have cracked the conundrum.

In the meantime you are excused from any further contributions.

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On 7/15/2020 at 9:02 PM, RMac said:

Thats pretty quickly sorted out.  The recovery mode from a miss on the foils is really interesting, this looks a lot slicker than earlier splahes like Ineos'.

Think they have a quick release on the mainsheet? That thing comes out _fast_. Interesting to see the leech bounce when they land too. 

The bearaway is epic.

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1 hour ago, Boink said:

Sheez, the idiots have been let out of the asylum early this weekend..........

You bitch about False equivalences, you claim that it is not suitable to compare Gliders with Jets; so to back yourself up by wanting to compare Two F18's but with different mass, yet revert to suggesting that comparing a 50ft catamaran with wing power against a 75ft monohull with sail power is a suitable equivalence........

Fuck me sideways, you are retarded (and here with your mates.........).

For the record, the designers of these boats and creators of the rule have already stated that the AC75's around a course will be faster than AC50, which has already been shown to be way in advance of an AC72 cat. Thats not some opinion by a ranty poster here on SA, that's smart people who earn great money by actually creating these boats. 

Claughton wrote an interesting article about these AC75's - the metrics for traditional performance indication are largely superceded. The amount of RM is massive. The sail area is c.250m2 - yet under traditional metrics the sail area should be between 500 and 1500m2 to achieve the performance required. 

The reality is that once airbourne, performance is more limited by induced drag, not just of both the hydrofoils and rig than by the power output, but also of the whole package. That is why Ineos is such a weird shape, the bustle of ETNZ and LR is a step forward (for multiple reasons) and why B1 of AM represents the laggard of the pack.

Only when we have seen B2's can we decide who is really in the game. If any team can find a way of raising the cavitation ceiling, then they too will have cracked the conundrum.

In the meantime you are excused from any further contributions.

So pleased that you have it all figured out Boink. If you say that the designers say that their boat is faster before its even been "around a course" - well I guess that's it then. I love how the Kiwis on these threads up vote each other, and down vote anyone who says anything bad about their spastic gecko.

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16 minutes ago, Guvacine said:

So pleased that you have it all figured out Boink. If you say that the designers say that their boat is faster before its even been "around a course" - well I guess that's it then. I love how the Kiwis on these threads up vote each other, and down vote anyone who says anything bad about their spastic gecko.

This proves your level of comprehension. I have stated many times that I am not a Kiwi. But your reading is up there with your understanding of Physics........

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Ouch. Are all of the Kiwis (and Boink) on these threads attending an elementary school somewhere?

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6 minutes ago, Hawke said:

I'm not so sure that that is the right approach. 

I recently got side-tracked on this forum when I read some posts on "ground effect."  What I was reading seemed absolute nonsense based on my practical experience and technical knowledge of what causes "ground effect."  My practical experience came from learning to fly light aircraft.  I started learning on a Piper Cherokee - a low wing aircraft.  In certain conditions you would experience "ground effect" after rounding out and the bloody thing would float for an age.  Which was particularly disconcerting when landing on the East-West runway which had a line of very large pine trees at the end!  Unfortunately just before going solo some locals hired the Cherokee, overloaded it and flew into rising land and wrote it and themselves off.  I then had to switch to a Cessna 172 - a high wing aircraft.  "Ground-effect" was no longer an issue but bloody cross winds were.

Anyway - my conclusion on "ground-effect" for the AC75 is it doesn't exist.  With a plane you have two parallel solid surfaces and a fluid in between.  One of the hard surfaces being an airfoil.  That isn't the situation with  a foiling boat - one hard surface and two fluids with an airfoil perpendicular to those fluids.  In my opinion the shape of the hull is only relevant in terms of reducing drag.  Which will also be influenced by ride height.  

Doing some refresh research on the physics of "ground-effect" I discovered that the conditions and parameters that induce it have some relevance to foil shape and depth.  However that is a lengthy subject for an entirely separate Topic Thread but it did lead me to airfoil cavitation.

In my opinion it is not pushing out the cavitation ceiling that is the crux but being able to manage cavitation oscillation (reduce the variation) and use cavitation to your advantage.  The fact is that cavitation on a foil surface up to a certain point will actually improve performance by reducing drag (less friction) and increasing lift.

I dont follow. Nowhere did I mention Ground Effect. I refer to the glass ceiling that Cavitation brings to top speed. The instability that a laminar flow foil experiences currently prevents these foils from continuing to accelerate. You reference supercavitating foil shapes - a real solution but inapplicable shape for boats with foils that need to fly in 6 knots of TWS. 

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Super cavitating foil sections don’t poses the lift Range required to operate in this application low 6/8kts -50plus well they do in that they will do SOMETHING but not get around a race course effectively. 

plus sticking an adjustable flap on the back edge of a super cavitating foil section instantly  stops it being what it’s supposed to be.
 

partial  cavitation is break down of flow and what non cavitating foils suffer from, hence all the effort to build a foil where that disruption point is raised and still retain use ability. 

 

 

 

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9 hours ago, Guvacine said:

Until these boats have been in a real race, all of the claims about performance are meaningless. I am being down voted so fast that I will soon be in negative territory. There are clearly a lot of folks on this thread that are super touchy about the AC75 concept.

Why don't you take some of your own advice and shut the fuck up then until you've seen an AC75 in a real race. Until then all of this bullshit spewing out of your mouth is meaningless !!

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24 minutes ago, Hawke said:

Is it fair to say that most of the testing to date has been in cold water?  Does temperature have an effect on foil performance?

There will be an 8 degree Celsius difference in sea temperature between now and race time.  Temperature does alter fluid dynamics considerably.  Just wondering if that will be a factor to consider.

Also is it within the rules to artificially heat/cool the foils?

No that’s speculation from you

yes it does but a large range, say Atlantic in winter vs Pacific summer   Another factor is salinity

probably but given the foils were being designed to work in the U.K., Sardinia and NewZeland its not that serious an issue 

highly doubtful and to what end? 

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21 hours ago, barfy said:

As I said before,deono will be shedding a quiet tear thinking "as long as I try hard and loose I'll be sweet". 

Suh Ben's wife will be drafting the "dear husband" letter.

Spitty will be saying "com'on boys here we go, it's come back time' , carefully practiced in Italian.

Meanwhile, etnz just keeps sailing

I think Ben's wife will be saying quote "Winning isn't everything Ben darling, and comeon honey you were paid a ridiculous amount of money for having fun" . And it could have been worse honey, they could have put you on a performance based contract? :D

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Seeing as his entire Olympic campaigns all had performance based clauses he should be just fine.. :)

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 Meanwhile:

Fuck NZ winter and quarantine - balmy weather, mild breeze, I think we’ll stay in Cagliari

2D96C9EB-6E3C-4ADD-9BE8-2169AB490138.png

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Does anyone own a video camera in Cagliari? Lots of pretty stills, but sweet fuck all video of the hand bag boat in motion.

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3 hours ago, Hawke said:

Sorry poor post on my part - my segue took too long to get to my point on cavitation.

How's that?  I'm not an expert just interested to hear the theories.  Isn't cavitation related to the speed of the boat rather than wind speed?  Or are you saying that the challenge of getting the boat to fly at low airspeeds means "supercavitation" can't be used?

I wasn't referring to true supercavitation.  I did read some research that partial cavitation up to a certain point has some advantages.

As others have written - Thanks @JALhazmat basically there are either laminar foils or cavitating foils - the latter deliberately entrain a bubble to surround the foil and enable it to run in a lower drag state. Partial cavitation is not a deliberate or desirable state to be in. It is unstable and can be destructive to the surface of the foils that can be quickly eroded and degraded - ask your local Moth sailor....... So cannot give the control that these boats at these speeds require.

What has not been designed is a Magic Silver Bullet of a foil section that can achieve High Lift at low velocities (the c.6.0 knots of TWS), yet not trip into very high drag, or cavitation at the high speeds that these boats quickly reach. This is what I hinted at earlier. AC50 could select Lift/Drag profiles by swapping between foils, But even they still ran into issues at the glass ceiling of cavitation. AC75's will have to use one set of foils for the actual cup. Big call as to what you run.........

But the knowledge base around here is generally low and largely misunderstood. 

The top guys with inside hydrodynamic knowledge that used to post here were chased away by the likes of DL and his ilk, and have remained absent with the shit spamming and trolling of some prize idiots who remain (and who clearly just get off on starting an argument because they like to provoke rather than learn). We are all poorer for their actions.

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10 hours ago, Boink said:

Sheez, the idiots have been let out of the asylum early this weekend..........

You bitch about False equivalences, you claim that it is not suitable to compare Gliders with Jets; so to back yourself up by wanting to compare Two F18's but with different mass, yet revert to suggesting that comparing a 50ft catamaran with wing power against a 75ft monohull with sail power is a suitable equivalence........

Fuck me sideways, you are retarded (and here with your mates.........).

For the record, the designers of these boats and creators of the rule have already stated that the AC75's around a course will be faster than AC50, which has already been shown to be way in advance of an AC72 cat. Thats not some opinion by a ranty poster here on SA, that's smart people who earn great money by actually creating these boats. 

Claughton wrote an interesting article about these AC75's - the metrics for traditional performance indication are largely superceded. The amount of RM is massive. The sail area is c.250m2 - yet under traditional metrics the sail area should be between 500 and 1500m2 to achieve the performance required. 

The reality is that once airbourne, performance is more limited by induced drag, not just of both the hydrofoils and rig than by the power output, but also of the whole package. That is why Ineos is such a weird shape, the bustle of ETNZ and LR is a step forward (for multiple reasons) and why B1 of AM represents the laggard of the pack.

Only when we have seen B2's can we decide who is really in the game. If any team can find a way of raising the cavitation ceiling, then they too will have cracked the conundrum.

In the meantime you are excused from any further contributions.

Pretty much agree with most of your comments.  A little confused why you would make such an offer, unless the sideways comment was an indication of frustration....lol

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On 7/15/2020 at 3:13 AM, Forourselves said:

 

This is the only one of the recent videos that I can really get any speed readings.

Time     Speed

0:15     27.9 knots

1:48     38.9 knots

3:08     31.4 knots - just before the second foil enters the water

4:33     34.7 knots

5:00     36.2 knots

6:50     25.1 knots

And of course, the precision is only to signify differences.  Actual reading are most likely within a few knots.

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47 minutes ago, The_Alchemist said:

This is the only one of the recent videos that I can really get any speed readings.

Time     Speed

0:15     27.9 knots

1:48     38.9 knots

3:08     31.4 knots - just before the second foil enters the water

4:33     34.7 knots

5:00     36.2 knots

6:50     25.1 knots

And of course, the precision is only to signify differences.  Actual reading are most likely within a few knots.

Yeah. Definitely can't see an AC50, F50 or AC72 staying with those numbers. Now I see why the spastic geckos were such a good idea and were worth the tremendous design and build investment.

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1 hour ago, The_Alchemist said:

This is the only one of the recent videos that I can really get any speed readings.

Time     Speed

0:15     27.9 knots

1:48     38.9 knots

3:08     31.4 knots - just before the second foil enters the water

4:33     34.7 knots

5:00     36.2 knots

6:50     25.1 knots

And of course, the precision is only to signify differences.  Actual reading are most likely within a few knots.

When we look at the F50 speed in a race on similar conditions their speed seem to be about 4 to 8 kts faster.

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22 hours ago, Guvacine said:

I'm glad your mind is blown, and I'm glad for those who are impressed by this folly. But to me it looks like a spastic gecko and is just embarrassing. When a conventional multihull will do EVERYTHING better - what the hell is the point? Oh right - there was no point. It was just some geezer had to have The Cup in a "Mono".

You are entitled to your opinion but, you can get your multi fix by watching Sail GP next year.

That's a polite way of saying, "fuck off".

Fuck off.

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7 hours ago, Xlot said:

 Meanwhile:

Fuck NZ winter and quarantine - balmy weather, mild breeze, I think we’ll stay in Cagliari

2D96C9EB-6E3C-4ADD-9BE8-2169AB490138.png

The best sailing in Auckland is had in winter.

Less idiots in power boats making wakes, less ferries with drunken skippers zig zagging around the harbour and way less SW days so, sailing back to the marina is possible.

Best of all, the winds are consistent. 

If it's a bit cold for you, get of the helm and grind a winch.

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1 hour ago, Tornado-Cat said:

When we look at the F50 speed in a race on similar conditions their speed seem to be about 4 to 8 kts faster.

Link? And since the F50 is still crashing in manoeuvres where the 75 isn’t, then No. It’s around the course that matters.

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1 hour ago, Tornado-Cat said:

When we look at the F50 speed in a race on similar conditions their speed seem to be about 4 to 8 kts faster.

Yeah if you look at the video closely you can see the heading/angle too, not to mention his verified speed numbers.. 

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1 hour ago, Forourselves said:

Link? And since the F50 is still crashing in manoeuvres where the 75 isn’t, then No. It’s around the course that matters.

Here's your link...

Screen_Shot_2020-07-14_at_10_01.51_AM.png

You are such an idiot.

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10 hours ago, Xlot said:

 Meanwhile:

Fuck NZ winter and quarantine - balmy weather, mild breeze, I think we’ll stay in Cagliari

2D96C9EB-6E3C-4ADD-9BE8-2169AB490138.png

That’s fantastic. It’s great to see that it managed to stay in one piece. 

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4 hours ago, The_Alchemist said:

This is the only one of the recent videos that I can really get any speed readings.

Time     Speed

0:15     27.9 knots

1:48     38.9 knots

3:08     31.4 knots - just before the second foil enters the water

4:33     34.7 knots

5:00     36.2 knots

6:50     25.1 knots

And of course, the precision is only to signify differences.  Actual reading are most likely within a few knots.

Is this actually serious? 
 

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