Tornado-Cat

AC75 vs F50 and Maxis

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And I wonder what the AC75 will be doing then? No doubt there will be the excuses new boat, crew learning etc, but there also might be smiling silence.....

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2 hours ago, RobG said:

No. Fuck off and stop paraphrasing to suit your case, which you seem to do very regularly. You take offense when your words are taken in any context other than literally and verbatim, why do you think it's OK to twist the meaning of other people's words so shamelessly?

"We" have arrived at the conclusion that you can't make a definitive statement either way based on results so far, but that the numbers are looking pretty good given the conditions and inexperience of the crews.

You, on the other hand, have decided to compare performance of AC50s in Bermuda after months of training and competitive sailing to F50s in their first event, in totally different conditions, with inexperienced crews and arrive at a definitive statement. And to relentlessly shout down anyone who doesn't agree with you.

You've made your case, endlessly repeating it and attacking anything that might be seen as contradictory just turns people away. I've stopped reading a number of threads here because of the intolerant bullshit being spruiked, I guess this is another one.

Total bullshit.

Plonk.

I asked a question Rob, and when I asked, it wasn't rhetorical... no one came to answer otherwise...I guess you don't have a contrary answer either...

Except you are now saying it's currently not definitive that the F50 is a quicker boat than the AC50... or do I have that wrong too?

I'm comparing the quickest public AC50 speeds with the fastest public F50 speeds...riddle me this... When exactly will these magical mystical boats finally realise the promise of being the fastest boats on the planet? Even if they have a theoretical top speed, if they can't be sailed well enough in the SGP races to achieve that speed then it's irrelevant, and frankly these guys seem miles away from sailing that well - there's a chance they might not even get there this year!

SGP themselves also appear to be wishy washy on whether cavitation will hold it at 48knots too... a speed already clocked by Artemis and co right?

I'll await to be proved wrong...

 

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3 hours ago, Monkey said:

ETNZ will always be the fastest AC50, but I’d still bet on the F50 to beat it by the end of this season. 

I’m not saying that as a slight to ETNZ in anyway, it’s just a less restricted, Gen II boat. 

If memory serves me correctly ETNZ's AC50 had three different tips for each of it's two foils.  The F50 having only two foils and no extra tips seems to be more restricted than the AC50. 

The flight control system of the F50's will be at least as good as Artemis which with an electric motor to drive the foils should not be too much behind ETNZ's set up.

That leaves the extra righting moment the foils will give on the F50 compared to the additional choices the AC50 have with the foils is likely to make the AC50 faster in light conditions and slower in stronger conditions.

 

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13 minutes ago, Terry Hollis said:

If memory serves me correctly ETNZ's AC50 had three different tips for each of it's two foils.  The F50 having only two foils and no extra tips seems to be more restricted than the AC50. 

The flight control system of the F50's will be at least as good as Artemis which with an electric motor to drive the foils should not be too much behind ETNZ's set up.

That leaves the extra righting moment the foils will give on the F50 compared to the additional choices the AC50 have with the foils is likely to make the AC50 faster in light conditions and slower in stronger conditions.

 

1) They don't need more tips: "For the F50 both the foil and rudder pitch will be actively controlled. This should make the flight of the boat through the manoeuvres significantly more efficient. "

2) Foil sections are finner

3) Righting moment is higher

 

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1 hour ago, Forourselves said:

America's Cup: AC75 - there's more to the rig than meets the eye

Interesting article. Expect to see some differences and innovations here. Also curious as to whether ETNZ's supplied design package contains all of ENTZ's tricks as well - you'd think they'd hold something back, at least for boat two. 

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^good background, and more to come......

 

 

So this ? is still undecided, after all this time?

On 4/8/2018 at 11:23 AM, nav said:

Faster than the AC50s

That is where small minds immediately went, but it was never a stated goal AFAIK.

But to indulge for a moment; 'faster' what? Reaching, VMG, up, down, time around the AC35 course, time around the AC36 course?? Pfft....

And now you shift the goal posts anyway and say they wont beat a secret class of modified boats that are clearly not AC50s - remember there's a rule that determines that.

You must mean the Spite Cup Class - modified also-ran carcases to indulge the expensive fantasies of those too timid to enter the AC

:D

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The AC could be raced in foiling bath tubs and it would still have more cachet than the Sailgp. Which to be honest, has very little, and is in no way enhanced by Slingers wanker comments about it being the worlds fastest dick boats. The AC need not make any such claims, does not need to sell or expouse its credentials, and can quite rightly view with contempt, Sailgp's whorish proclamations.

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6 hours ago, Horn Rock said:

The AC could be raced in foiling bath tubs and it would still have more cachet than the Sailgp. Which to be honest, has very little, and is in no way enhanced by Slingers wanker comments about it being the worlds fastest dick boats. The AC need not make any such claims, does not need to sell or expouse its credentials, and can quite rightly view with contempt, Sailgp's whorish proclamations.

I had a hard time deciphering that jibberish, but I think we agree. I was an Oracle fan, but view SailGP as a feeder series to the AC, which is a good thing. No one besides SClarke thinks they’re meant to go head to head. 

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As for SailGP competing with AC, Franck Cammas had the impression that LE thought it would back in early days. See interview

https://www.sailingscuttlebutt.com/2019/02/18/americas-cup-sailgp-france/

Even if that was part of the the intent, that does not mean it really DOES or WILL compete, lol. Thanks for the $$$$.

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I hope something, foiling, multihull? between the 18 foot skiff and Sydney to Hobart, in Australia. I thought the Super foilers would evolve into something good (but SailGP has put paid to that in the short term. There are foiling multihulls in NZ but it would have to be handicap as they are all different.  I guess internationally something will evolve from the many foiling multihull inner harbour alternatives.  But the ocean, round the world boats are amazing already.

I, like everyone would like to see Australia in the AC again! Put the image of "the sinking" behind them and go.

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2 hours ago, NeedAClew said:

Thanks for the $$$$.

Larry's bucks allowed Jimmy to run his mouth off, and boy did he run it off. One of the most satisfying aspects of Bermuda was the shutting up and humbling of the little aussie wanker and his big mouth.

 

28 minutes ago, Kiwing said:

I, like everyone would like to see Australia in the AC again! Put the image of "the sinking" behind them and go.

That was nearly 25 years ago. I really couldn't give a toss whether Oz is in the AC or not. You couldn't get any more fair weather fans than Aussies. If they're in it and contenders you'd hear all about it, if they're not, the event doesn't exist. Band-wagoners.

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3 hours ago, Monkey said:

I had a hard time deciphering that jibberish,

Really? Too many big words? Do you need me to tone it down? Simplify things?

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1 hour ago, Horn Rock said:

Larry's bucks allowed Jimmy to run his mouth off, and boy did he run it off. One of the most satisfying aspects of Bermuda was the shutting up and humbling of the little aussie wanker and his big mouth.

 

That was nearly 25 years ago. I really couldn't give a toss whether Oz is in the AC or not. You couldn't get any more fair weather fans than Aussies. If they're in it and contenders you'd hear all about it, if they're not, the event doesn't exist. Band-wagoners.

Horn, embrace the culture or fuck off back to NZ..  Its hypocritical to suck the teat of Aus by living there but at he same time denigrate the country every chance you get.

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1 hour ago, Horn Rock said:

Larry's bucks allowed Jimmy to run his mouth off, and boy did he run it off. One of the most satisfying aspects of Bermuda was the shutting up and humbling of the little aussie wanker and his big mouth

As someone said in one of these threads, yes people can choose how to spend their money.

However, I was not thrilled that OTAUS chose to defend in a foreign country. But it turned out for the best. It would have been too sad watching OTAUS lose in the USA.

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1 hour ago, trt131 said:

Horn, embrace the culture or fuck off back to NZ..  Its hypocritical to suck the teat of Aus by living there but at he same time denigrate the country every chance you get.

I contribute generously to the cause in Australia, and feel not the need for supplication nor compliance in matters relating to sporting contests between the two nations.

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19 hours ago, Horn Rock said:

Interesting article. Expect to see some differences and innovations here. Also curious as to whether ETNZ's supplied design package contains all of ENTZ's tricks as well - you'd think they'd hold something back, at least for boat two. 

 

20 hours ago, Forourselves said:

https://www.sail-world.com/news/214640/Americas-Cup-AC75-rig-concept-took-20-minutes

America's Cup: AC75 - there's more to the rig than meets the eye

Yes, good stuff from Burns Fallow and RG, although I'm surprised RG left stand Fallow's contention that “The general concept of double skinned mainsails was invented there (in Bermuda)"!  That novelty has bedevilled designers for decades.

You'd have to believe that ETNZ won't be sharing its double-skinned mainsail developments as part of the supplied design package.  The article says as much.

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1 hour ago, KiwiJoker said:

 

Yes, good stuff from Burns Fallow and RG, although I'm surprised RG left stand Fallow's contention that “The general concept of double skinned mainsails was invented there (in Bermuda)"!  That novelty has bedevilled designers for decades.

 

Yes KJ, you are right to be surprised of RG quote of Fallow's contention ;)

There have been many previous double skin concept, one being the Gallant rig, not to mention sailboard double skins.

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4 hours ago, trt131 said:

Horn, embrace the culture or fuck off back to NZ..  Its hypocritical to suck the teat of Aus by living there but at he same time denigrate the country every chance you get.

Talk about walking into a room and shutting your junk in the drawer...

Why the fuck does anyone in Australia (Australian or not) have to like every Australian?

Fucking Jesus what a retarded notion

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51 minutes ago, Forourselves said:

Compared to what we saw in Bermuda, this is a rubbish gybe.

 

again comparing apples and oranges there champ. team Australia's what 15 something day in the yacht, and ETNZ what? not to mention you didnt actually post an ETNZ VMG gybe, it was a kiwi(mexican).

I agree though it wasnt one of the best gybes thats for sure, but impressive catch of the foils, with minimal touchdown.     

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10 minutes ago, agk470 said:

again comparing apples and oranges there champ. team Australia's what 15 something day in the yacht, and ETNZ what? not to mention you didnt actually post an ETNZ VMG gybe, it was a kiwi(mexican).

I agree though it wasnt one of the best gybes thats for sure, but impressive catch of the foils, with minimal touchdown.     

Huh? The Australian boat was launched in Whangarei last year. They had at least a week in Whangarei, on top of at least three weeks of training in Australia. 

This was literally straight out of the box...

 

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22 minutes ago, Forourselves said:

Huh? The Australian boat was launched in Whangarei last year. They had at least a week in Whangarei, on top of at least three weeks of training in Australia. 

This was literally straight out of the box...

 

they teams have said that they had to share the yachts in NZ and only had 2 weeks so put in maintenance days and bad weather they had max 5 days, and then sydney the boats were all staggered on the water not sailing all together on each day, they were not allowed to sail wednesday afternoons and saturday/sundays so out of your 3 weeks thats a possible 13.5 days and they didnt sail everyday so yeah mate simple maths says that would have been around 18.5 days available, now the video you showed obviously isnt a race day so theres another 2 days off so yep say a max 16.5 days. 

I cannot 100% confirm but all the original videos i saw of the ETNZ sailing the AC50 they did not have the centre pod fairing on so i'm not sure your so accurate there but i cannot say that for fact so have to take your word. also still doesnt show a gybe. ha. (joking i know it shows a foil tack) 

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47 minutes ago, agk470 said:

they teams have said that they had to share the yachts in NZ and only had 2 weeks so put in maintenance days and bad weather they had max 5 days, and then sydney the boats were all staggered on the water not sailing all together on each day, they were not allowed to sail wednesday afternoons and saturday/sundays so out of your 3 weeks thats a possible 13.5 days and they didnt sail everyday so yeah mate simple maths says that would have been around 18.5 days available, now the video you showed obviously isnt a race day so theres another 2 days off so yep say a max 16.5 days. 

I cannot 100% confirm but all the original videos i saw of the ETNZ sailing the AC50 they did not have the centre pod fairing on so i'm not sure your so accurate there but i cannot say that for fact so have to take your word. also still doesnt show a gybe. ha. (joking i know it shows a foil tack) 

The video below was published 18th of October 2018, so one would think there would be maybe a couple of weeks before the video was actually published online. That gives them 3 months. October, November and December in Whangarei. On top of the simulation time, plus the 3 weeks training time in Sydney. 

The video below, was Posted Feb 15th, 2017, ETNZ AC50 was splashed Feb 14th. So this is one day after launch. Definitely cleaner and sharper than day one on the F50 thats for sure! Probably cleaner and sharper than Race day 2 of the SailGP first event!

https://www.catsailingnews.com/2017/02/team-new-zealanda-ac50-cycling-cup-by.html

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2 hours ago, Forourselves said:

The video below was published 18th of October 2018, so one would think there would be maybe a couple of weeks before the video was actually published online. That gives them 3 months. October, November and December in Whangarei. On top of the simulation time, plus the 3 weeks training time in Sydney. 

The video below, was Posted Feb 15th, 2017, ETNZ AC50 was splashed Feb 14th. So this is one day after launch. Definitely cleaner and sharper than day one on the F50 thats for sure! Probably cleaner and sharper than Race day 2 of the SailGP first event!

https://www.catsailingnews.com/2017/02/team-new-zealanda-ac50-cycling-cup-by.html

the F50 video you have posted there is a mixed crew, Nathan Outteridge, Luke Parkingson (kyle or Iain, draper (Unsure) and cant find the details) Sam Newton and Ky Hurst, they were the commissioning team that was released in an interview with ky i think. and quite sure that was day 2 or 3 from memory. 

each team had 2 weeks, split with a second team, Tom has confirmed this in multiple interviews. the boats were commissioned first with the above crew so no one   was meant to get an advantage during commissioning. October was to be commissioning then november through december was to be teams training.

 

fair call on ETNZ, i thought that they sailed with the 45 boards for quite a while after damaging the 50 boards strait up on day 1?

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no team sailed the f50 for more than 15 days (i do not know the exact number) before the sydney regatta, it was part of the planning. outerridge or slingsby have sailed a bit more for systems developement, but not with their gp team.

 

 

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With the AC 50's in Bermuda didn't all of the teams put significant time into getting their foil  presets  programmed in for tacks and gybes ?

I would have to wonder if the crews on the F 50's  have had enough time in the boats to get that right .

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Except that here it's collaborative so they each get 6x the data, each time the fleet is out....right?

Plus no one has to work very hard on these electric boats so the crew can concentrate on refining anything the computers haven't already got covered - easy as...

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OR won AC34 thanks to their altitude control system (I didn't say Herbie), TNZ won AC35 thanks to their computer assist altitude control system. IMO, even though considered legal both were in the grey zone.

I hope the F50 don't have it, a sail boat should not have to be controlled directly or indirectly by a computer to be able to sail, the F50 will be faster any way, it is already faster, which explains why some here try to compare the F50 sailing in irregular 6-8 kts wind to stable 15 kts Bermudas breeze conditions.

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57 minutes ago, Tornado-Cat said:

OR won AC34 thanks to their altitude control system (I didn't say Herbie), TNZ won AC35 thanks to their computer assist altitude control system. IMO, even though considered legal both were in the grey zone.

I hope the F50 don't have it, a sail boat should not have to be controlled directly or indirectly by a computer to be able to sail, the F50 will be faster any way, it is already faster, which explains why some here try to compare the F50 sailing in irregular 6-8 kts wind to stable 15 kts Bermudas breeze conditions.

It's posts like these that make me realise we must be living in two different reality dimensions that happen to share the same forum.

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5 minutes ago, rh2600 said:

It's posts like these that make me realise we must be living in two different reality dimensions that happen to share the same forum.

:wub: Perfect!

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26 minutes ago, rh2600 said:

It's posts like these that make me realise we must be living in two different reality dimensions that happen to share the same forum.

Yep, you are the one who endlessly compare the AC50 in Bermudas conditions with the F50 in Sydney conditions :)

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8 minutes ago, Tornado-Cat said:

Yep, you are the one who endlessly compare the AC50 in Bermudas conditions with the F50 in Sydney conditions :)

Sorry, but I haven't seen the wind data for Sydney - can you share? :-)

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8 hours ago, 17mika said:

no team sailed the f50 for more than 15 days (i do not know the exact number) before the sydney regatta, it was part of the planning. outerridge or slingsby have sailed a bit more for systems developement, but not with their gp team.

 

 

Do you reckon this is part of the business model? Keep all the teams fresh, as it were, and the sailing scrappy? Certainly keeps crew and base costs and maintenance down.

11 hours ago, agk470 said:

they had max 5 days, and then sydney the boats were all staggered on the water not sailing all together on each day, they were not allowed to sail wednesday afternoons and saturday/sundays so out of your 3 weeks thats a possible 13.5 days and they didnt sail everyday so yeah mate simple maths says that would have been around 18.5 days available,

And this was in the light air Sydney, SF might be fresh every afternoon...10 days training, the rich will just get richer, and the rest of the flock still floundering. Maybe next year.

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17 minutes ago, barfy said:

Do you reckon this is part of the business model? Keep all the teams fresh, as it were, and the sailing scrappy? Certainly keeps crew and base costs and maintenance down.

And this was in the light air Sydney, SF might be fresh every afternoon...10 days training, the rich will just get richer, and the rest of the flock still floundering. Maybe next year.

Yep, I heard both russell an dylan fletcher (gbr helm) talking about very limited and controlled time on the water. I suspect it it is both a business case decision and a one design decision.

Probably the data sharing opportunities are also intended to maximise catch-up opportunities for the new teams in the limited training time they have. But Definitely if it is very  breezy in frisco aus and jap will dominate again... it will take 2-3 regattas for other teams to get good hours on the water to catch up

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59 minutes ago, 17mika said:

Probably the data sharing opportunities are also intended to maximise catch-up opportunities for the new teams in the limited training time they have

I'm not really sure how effective looking at polars will be in taming the beasts and sharpening maneuvers.

Bit like my fav line from 35, slingers to spitty, " gotta be a bit faster through this part Jimmy".

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3 hours ago, barfy said:

I'm not really sure how effective looking at polars will be in taming the beasts and sharpening maneuvers.

Bit like my fav line from 35, slingers to spitty, " gotta be a bit faster through this part Jimmy".

Ahahh right. Boat spees makes u always a better sailor :)

But I think they have full telemetry data. Foil angles, rudder angle, wing aoa, wing camber etc. See how the aussies operate foils ans wing in the transitions I guess it is helpful for the newer teams.

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True, could be the most "open" part of the class then, developing your cheat sheets of optimum settings.

Then getting them "borrow ed" after the regatta.

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6 hours ago, Tornado-Cat said:

I posted a sail data graph from Scott Babbage of SailGP

But TC that tells us nothing about the conditions, let alone comparative performance in wind angles. I'm still not sure what empirical data we have to indicate that Sydney's conditions were somehow 'worse' than in Bermuda.

Without polars, or windspeed data, visually the boats looked significantly slower, and flew a lot less, that much is certain, and this was even noted in the article you shared with the speed graph.

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3 hours ago, rh2600 said:

But TC that tells us nothing about the conditions, let alone comparative performance in wind angles. I'm still not sure what empirical data we have to indicate that Sydney's conditions were somehow 'worse' than in Bermuda.

Without polars, or windspeed data, visually the boats looked significantly slower, and flew a lot less, that much is certain, and this was even noted in the article you shared with the speed graph.

I agree that we need more data, just a quick search gave that for Sydney arbour and Little Bay

On Feb 15 we had an average of about 6 kts and max of 14 kts, which means probable lulls of 2kts  which is pretty low. Let's SailGP will give us more data in SF,  but we can check the wind of the day in SF if I remember correctly  from AC34.

Capture.PNG

Capture2.PNG

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5 minutes ago, Tornado-Cat said:

I agree that we need more data, just a quick search gave that for Sydney arbour and Little Bay

On Feb 15 we had an average of about 6 kts and max of 14 kts, which means probable lulls of 2kts  which is pretty low. Let's SailGP will give us more data in SF,  but we can check the wind of the day in SF if I remember correctly  from AC34.

Capture.PNG

Capture2.PNG

Those days look pretty bad. It would be great for SGP provide more data so that a comparison can be made... 

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Following the excellent article of Sailworld from RG: https://www.sail-world.com/photo/240215

TH considers the mule as fast as an AC50 upwind the AC75 will be impressively fast:

“Yet the guys with the AC50 experiences who are on board say the Mule is matching those boats' performance upwind. “

TH also feels like the mono is safer than the multi:

"Yet it feels quite a bit safer than the multihull - even though my multihull experience was with a non-foiling AC72 for about 10 days and the AC45's prior to them foiling. In that regard this platform feels night and day different and safer. "

If YH is right the AC75 could be demonstrate faster and safer than foiling cats but very unstable and unpredictable in displacement mode, I had already commented on that months ago.

However the test boats are pretty narrow, my guess is the the width and stability of the AC75 hull will be key for success, knowing the wider = safer but wider = more drag.

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18 hours ago, Tornado-Cat said:

Following the excellent article of Sailworld from RG: https://www.sail-world.com/photo/240215

TH considers the mule as fast as an AC50 upwind the AC75 will be impressively fast:

“Yet the guys with the AC50 experiences who are on board say the Mule is matching those boats' performance upwind. “

TH also feels like the mono is safer than the multi:

"Yet it feels quite a bit safer than the multihull - even though my multihull experience was with a non-foiling AC72 for about 10 days and the AC45's prior to them foiling. In that regard this platform feels night and day different and safer. "

If YH is right the AC75 could be demonstrate faster and safer than foiling cats but very unstable and unpredictable in displacement mode, I had already commented on that months ago.

However the test boats are pretty narrow, my guess is the the width and stability of the AC75 hull will be key for success, knowing the wider = safer but wider = more drag.

Yes, safer in that when the boat nose dives it will just pop back up with the added volume.  It is a strange beast, much different than anything they have ever sailed before.

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4 hours ago, Herfy said:

Yes, safer in that when the boat nose dives it will just pop back up with the added volume.  It is a strange beast, much different than anything they have ever sailed before.

You don't know if that's the only reason Terry feels safer. After all, he does state he hardly foiled at all. Could be better protection in a bigger cockpit, not crossing the tramp, not having rudder and associated wings on both sides waiting for a MOB. all discussed here I believe.

It is a damn strange beast, why I remember many a pundit here saying it would never sail.

Strange that AM hasn't tacked or gybed yet, when we saw team Ben throwing some nice tacks within a month. Just shy? Deano a bit timid?

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6 hours ago, barfy said:

You don't know if that's the only reason Terry feels safer. After all, he does state he hardly foiled at all. Could be better protection in a bigger cockpit, not crossing the tramp, not having rudder and associated wings on both sides waiting for a MOB. all discussed here I believe.

It is a damn strange beast, why I remember many a pundit here saying it would never sail.

Strange that AM hasn't tacked or gybed yet, when we saw team Ben throwing some nice tacks within a month. Just shy? Deano a bit timid?

Maybe not the only one but it is the one he mentions.  Here is a quote directly from the article:

“You learn to respect the boat very quickly for what it is capable of doing. Yet it feels quite a bit safer than the multihull - even though my multihull experience was with a non-foiling AC72 for about 10 days and the AC45's prior to them foiling. In that regard this platform feels night and day different and safer.

“We've had a couple of good nosedives and the boat pops right back out and away you go. I suspect that with the AC75, while people might be a bit nervous about it right now, I would think that it is going to be quite a bit safer than the multihull - because of the ample volume that you have in the hull form.

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To give you your point, the first paragraph is not that clear.

Respect the boat - perhaps apprehensive

Safer than cat - but not much foiling to compare it to

But with regards to not foiling the boat is night and day safer?

 any way, I see the article as a pretty positive reaction to his experience sailing something close to what the AC36 rule will produce. 

Small crowd right now have been down that road, respect.

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On 3/10/2019 at 9:03 AM, Tornado-Cat said:

Following the excellent article of Sailworld from RG: https://www.sail-world.com/photo/240215

It makes a questionable claim though:

"In the AC75 class rule there is no beam or depth restrictions on the hull…"

Which is just wrong. The beam is fairly tightly controlled by rules 11.5 and 11.6 such that beam at the transom must be at least 4m and maximum beam must be between 4.8 and 5.0m. Figure 13.1 shows the beam where the foils are mounted (roughly abeam the mast?) must be at least 4.1m. There are also measurements to effectively prevent a scow bow, though it can be pretty blunt. Rule 11.4 prevents any kind of "coke bottle" effect to reduce beam between the specified station widths.

So while aerodynamic drag will be looked at very closely, there isn't a lot that can be done in terms of gross hull shape other than keeping it as small as practical.

In regard to safety, the issue is not crashes but the foils from other boats. There were some pretty close passes in the multis, it will be interesting to see how safe it feels in a mono with 1.5 ton of steel foil passing at a closing speed of 80km/h just a few metres away. I don't think it will be an issue for AC–class sailors, but not really suitable for weekend warriors.

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11 hours ago, RobG said:

It makes a questionable claim though:

"In the AC75 class rule there is no beam or depth restrictions on the hull…"

Which is just wrong. The beam is fairly tightly controlled by rules 11.5 and 11.6 such that beam at the transom must be at least 4m and maximum beam must be between 4.8 and 5.0m. Figure 13.1 shows the beam where the foils are mounted (roughly abeam the mast?) must be at least 4.1m. There are also measurements to effectively prevent a scow bow, though it can be pretty blunt. Rule 11.4 prevents any kind of "coke bottle" effect to reduce beam between the specified station widths.

So while aerodynamic drag will be looked at very closely, there isn't a lot that can be done in terms of gross hull shape other than keeping it as small as practical.

In regard to safety, the issue is not crashes but the foils from other boats. There were some pretty close passes in the multis, it will be interesting to see how safe it feels in a mono with 1.5 ton of steel foil passing at a closing speed of 80km/h just a few metres away. I don't think it will be an issue for AC–class sailors, but not really suitable for weekend warriors.

The perimeter line shall:
(a) have a point on TRP that is at least 2.000 m from LCP;
(b) at its greatest distance from LCP, be between 2.400 m and 2.500 m from LCP;

the angle between LCP and the flotation waterplane shall be no more than 5°.

 

You are right, the restrictions on the hull are pretty tight and that is sad because the 2 points where design could make a difference IMO are the foils and the width of the hull.

Pre foiling maneuvers and tactics to make them fall of their foils will be very interesting and different hull would have made a difference.

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5 hours ago, Tornado-Cat said:

The perimeter line shall:
(a) have a point on TRP that is at least 2.000 m from LCP;
(b) at its greatest distance from LCP, be between 2.400 m and 2.500 m from LCP;

the angle between LCP and the flotation waterplane shall be no more than 5°.

 

You are right, the restrictions on the hull are pretty tight and that is sad because the 2 points where design could make a difference IMO are the foils and the width of the hull.

Pre foiling maneuvers and tactics to make them fall of their foils will be very interesting and different hull would have made a difference.

Those dimensions are one way to ensure the thing self-rights. Taken away and we'd be back to some accusing the boat of being unsafe and not-self righting..

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11 hours ago, rh2600 said:

Those dimensions are one way to ensure the thing self-rights. Taken away and we'd be back to some accusing the boat of being unsafe and not-self righting..

Width is part of the equation but not the key variable, length of the arm, weight of the foil, length of the mast, position vs the wind, and mainly weight of the sail if it takes water are more important.

They did not have to eliminate the rule, they could have made it more open, the interest of the AC is to have a more open design.

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17 minutes ago, Tornado-Cat said:

Width is part of the equation but not the key variable, length of the arm, weight of the foil, length of the mast, position vs the wind, and mainly weight of the sail if it takes water are more important.

They did not have to eliminate the rule, they could have made it more open, the interest of the AC is to have a more open design.

Yes, bit if they didn't have fixed dimensions for those items they'd be back to not having a self-righting spec... in short in order to know the boat is self righting, the equation needs to know some set variables... given the current arm length is x, foil weight is y , mast length is x then the width needs to be a.

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8 hours ago, rh2600 said:

Yes, bit if they didn't have fixed dimensions for those items they'd be back to not having a self-righting spec... in short in order to know the boat is self righting, the equation needs to know some set variables... given the current arm length is x, foil weight is y , mast length is x then the width needs to be a.

No, you can also calculate the other way around. All the hype was a bout a mono free design and we end up with pretty much a one design that may not even be self righting.

Anyway, I hope the boat will be stable enough not to have to self right and that teams will present different kind of boats to make it interesting.

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8 hours ago, Tornado-Cat said:

Width is part of the equation but not the key variable, length of the arm, weight of the foil, length of the mast, position vs the wind, and mainly weight of the sail if it takes water are more important.

They did not have to eliminate the rule, they could have made it more open, the interest of the AC is to have a more open design.

The position of the arms and ballast is not fixed so the boats need the operating mechanism of the foils to continue to work while the boat is upside down or lying on it's side.

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2 hours ago, Tornado-Cat said:

No, you can also calculate the other way around. All the hype was a bout a mono free design and we end up with pretty much a one design that may not even be self righting.

Anyway, I hope the boat will be stable enough not to have to self right and that teams will present different kind of boats to make it interesting.

Sorry, how can you calculate it the other way round?

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2 minutes ago, rh2600 said:

Sorry, how can you calculate it the other way round?

You decide the length of arm, or the weight of the foil, or the length of the mast, depending on the width.

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1 hour ago, Terry Hollis said:

The position of the arms and ballast is not fixed so the boats need the operating mechanism of the foils to continue to work while the boat is upside down or lying on it's side.

So ?

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22 hours ago, rh2600 said:

Those dimensions are one way to ensure the thing self-rights. Taken away and we'd be back to some accusing the boat of being unsafe and not-self righting..

They are not accusations, it is the information coming from the AM Mule.  They say the hull feels safer because it pops back out during a nose dive (compared to the Multis that flipped) and the hull design may be self righting, but it certainly isn't with the sail.  Of course there will be changes in the hull design for the AC75, but AM is using scaled down rigging and foils.  

Another interesting tit-bit from the AM Mule update is that it looks like they are seeing good results with the dual sail and expect to make some significant gains.

Remember when they used to sail monohulls that didn't NEED to be self-righting? lol...  I think the design will lead to some very interesting races with good speed on the foils, but the hull in the water may be too tricky for a very broad trickle down use.

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59 minutes ago, Tornado-Cat said:

You decide the length of arm, or the weight of the foil, or the length of the mast, depending on the width.

Yeah, but haven't you just locked in all the other variables and left hull width as the open one? That's my point... some dimensions need to be known and fixed in order to ensure self righting... we're now just debating which elements are fixed...

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34 minutes ago, Herfy said:

They are not accusations, it is the information coming from the AM Mule.  They say the hull feels safer because it pops back out during a nose dive (compared to the Multis that flipped) and the hull design may be self righting, but it certainly isn't with the sail.  Of course there will be changes in the hull design for the AC75, but AM is using scaled down rigging and foils.  

Another interesting tit-bit from the AM Mule update is that it looks like they are seeing good results with the dual sail and expect to make some significant gains.

Remember when they used to sail monohulls that didn't NEED to be self-righting? lol...  I think the design will lead to some very interesting races with good speed on the foils, but the hull in the water may be too tricky for a very broad trickle down use.

But why do you keep considering the AM mule has any meaningful relationship to the AC75 in terms of righting physics and geometry?

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1 hour ago, Tornado-Cat said:

So ?

So the movable ballast can be positioned to right the hull but if it cannot be moved it's position might prevent self righting.

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13 hours ago, Terry Hollis said:

So the movable ballast can be positioned to right the hull but if it cannot be moved it's position might prevent self righting.

Probably....

The one tricky variable will be how quickly water ingresses into the sail and associated cavities, and how easily it drains. This will be different for every team as the sail design is quite open.

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13 hours ago, Terry Hollis said:

So the movable ballast can be positioned to right the hull but if it cannot be moved it's position might prevent self righting.

Why not let teams do their work depending on the type of hull ? Or do they want a kind one design based on their foil arm ?

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35 minutes ago, Tornado-Cat said:

Why not let teams do their work depending on the type of hull ? Or do they want a kind one design based on their foil arm ?

Because safety will always give way to speed in the AC !

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17 hours ago, rh2600 said:

But why do you keep considering the AM mule has any meaningful relationship to the AC75 in terms of righting physics and geometry?

Possibly because they designed it to be in scale, why do you assume is doesn't?

“Everything is to scale with the AC75,” says Hutchinson. “As the project grew, we made the conscious decision that when we were comparing the 38 ft apple to the 75ft apple, that we were doing it as close as we can.”

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7 minutes ago, Herfy said:

Possibly because they designed it to be in scale, why do you assume is doesn't?

“Everything is to scale with the AC75,” says Hutchinson. “As the project grew, we made the conscious decision that when we were comparing the 38 ft apple to the 75ft apple, that we were doing it as close as we can.”

And yet they used an MC 38 Hull, which barring the use of time traveling Deloreans, probably wasn’t designed to the rule. 

Not everything with the mule scales correctly, and I’ll give the Kiwi’s benefit of doubt until we see an AC75 pinned on its side. 

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It will be certainly fun if righting is part of measurement, as every hull will have different characteristics beyond shape, like compartment flooding, surface effects...be fun to see the boats pulled over in downtown Auckland to test.

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2 hours ago, Herfy said:

Possibly because they designed it to be in scale, why do you assume is doesn't?

“Everything is to scale with the AC75,” says Hutchinson. “As the project grew, we made the conscious decision that when we were comparing the 38 ft apple to the 75ft apple, that we were doing it as close as we can.”

Fair point...I thought the foils in the mule weren't ballasted though?

I wonder if AC75 will have some form of flotation on mast-head...

 

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4 hours ago, Monkey said:

And yet they used an MC 38 Hull, which barring the use of time traveling Deloreans, probably wasn’t designed to the rule. 

Not everything with the mule scales correctly, and I’ll give the Kiwi’s benefit of doubt until we see an AC75 pinned on its side. 

The hull will make some differences, but the majority of the self righting comes from the ability in the design to move the ballasted foils.  AM thinks the Mule hull, by itself, could be self righting, but it is the weight of the water and such in the sail that stops it from working.

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7 hours ago, Kiwing said:

Because safety will always give way to speed in the AC !

Well, I think we should remember your assertion :)

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On 3/14/2019 at 10:13 AM, rh2600 said:

I wonder if AC75 will have some form of flotation on mast-head...

It's a certainty: rule 20.24.

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59 minutes ago, RobG said:

It's a certainty: rule 20.24.

Welp, @Herfy at least there goes the issue with submerged mast/sails preventing self-righting.

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On 3/16/2019 at 7:21 PM, rh2600 said:

Welp, @Herfy at least there goes the issue with submerged mast/sails preventing self-righting.

It could be just as simple as that.  Most of the pictures of AM Mule don't show the top of the mast, but the ones I could find look like they are not using a float on the mast-head.

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A dangerous boat ?

"Spithill suggested the boats would be beasts when the class rule was first revealed, and Sirena warned the AC75 lacked the stability of the catamarans.

"This is a monohull without a keel, with appendages that weigh little. A hyper-powerful boat, very light, with little stability. There are fractions of a second that there is zero stability, if the helmsman and the trimmer cannot anticipate this zero moment, you fall back … go from 30-40 knots to zero, you have a g-force that shoots you in the air," he told La Stampa."

https://www.nzherald.co.nz/sailing/news/article.cfm?c_id=106&objectid=12214523

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45 minutes ago, Tornado-Cat said:

A dangerous boat ?

"Spithill suggested the boats would be beasts when the class rule was first revealed, and Sirena warned the AC75 lacked the stability of the catamarans.

"This is a monohull without a keel, with appendages that weigh little. A hyper-powerful boat, very light, with little stability. There are fractions of a second that there is zero stability, if the helmsman and the trimmer cannot anticipate this zero moment, you fall back … go from 30-40 knots to zero, you have a g-force that shoots you in the air," he told La Stampa."

https://www.nzherald.co.nz/sailing/news/article.cfm?c_id=106&objectid=12214523

Depends who you ask apparently...

Of course ETNZ went from 30 knots to 0 in an AC50 too... ;-)

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Spitty should know,  in one of those fractions of a second of instability he found the second most stable position of a cat in pre AC34. then the bits remained stable as they got flushed under the Golden gate Bridge.

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