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#101 Sean

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Posted 18 September 2013 - 05:01 PM

Safe to say none of the wives and children of the sailors are clamoring to raise the limits.

#102 NewDogBalls

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Posted 18 September 2013 - 05:06 PM

 

Even when I sailed the 2.4mR , a boat with 1ft of freeboard, we sailed if we did not have sustained winds above 22knts. Not 30 seconds above but it must be sustained. Then if the winds increased during the race, too bad, the race has been started.
 
This is why the AC is not a Marketable Event and thus all of sailing is hurt by the Premier Event in Sailing being non-sailable in such a low wind range.
 
Thanks Larry, even disabled sailors in the 2.4mR got more balls than you and RC.

Dave, you're talking about a boat that does 45 kts. In today's conditions, with an ebb chop that was shoulder high, ands gusting to mid-high 30s at the bottom of the course, it wouldn't have been racing, it would have been survival. Even ETNZ said on their FB page that Murray made the right call.

Now, why don't you write NASCAR and tell them to remove the restrictor plates at Daytona and talledega so you can see cars hit 240 mph? I mean clearly they must have balls smaller than yours, because keeping drivers alive is a priority.

You've really been behaving like a petulant child lately. I'm willing to bet that most disabled sailors are embarrassed by your outbursts.

I have often been a proponent of "Unleashing the Dogs of War" when it  comes to motor racing.

Lets see some real banked corners and hairpins. POD RACING if you will.

 

If you're gonna charge outrageous fees to watch an event, GodDamnit there had better be some exciting and entertaining moments.

There are too many humans on this planet to worry about death.

 

Who cares when a disabled person passes? Why care when a professional doing what they love and get paid for passes?

 

GODDAMNIT, THAT IS WHAT LIFE IS ABOUT.

 

FUCK, I am tired of PUSSIES.

Sounds like you have some serious issues.  Were you dropped on your head as a baby, bullied at school, given wedgies by the football players?



#103 chuso007

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Posted 18 September 2013 - 05:16 PM

Even when I sailed the 2.4mR , a boat with 1ft of freeboard, we sailed if we did not have sustained winds above 22knts. Not 30 seconds above but it must be sustained. Then if the winds increased during the race, too bad, the race has been started.

 

This is why the AC is not a Marketable Event and thus all of sailing is hurt by the Premier Event in Sailing being non-sailable in such a low wind range.

 

Thanks Larry, even disabled sailors in the 2.4mR got more balls than you and RC.

 

Well, for some reason I think you would shit yourself just riding on one of these beast at say, 15 kn TWS...



#104 RHough

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Posted 18 September 2013 - 05:39 PM

 

FFS before the limit was set so low NZ and USA wanted it higher. The two most credible teams weren't making a case for 22-23. Now that is set, I think I'm allowed to offer opinion and a bit of data in hopes that someone can outline the objective considerations that support the limit. I want to learn something.

You DO realize don't you that a steady state breeze of 30-33 kts is going to be accompanied by gusts coming off the Presidio of 38-40? Thats a perfect place for 55 kts of apparent when you're making the turn downwind eh?

BTW, Your claims that the IOR boats weren't "survival sailing" in 30 kts tells me a lot, and there are hundreds of pics that prove you wrong that were taken at 20-25 kts.

To me the measure of the wind limits is the quality of the racing. I think the current wind limits bear that out. I have no desire to see either boat upside down just because someone wants to crow about having bigger balls.

I have never argued for 33 as being safe or reasonable. I only point out that the same people that every claims to support 22 once agreed to design for 33. I thought it was ambitious when I first heard it. I have not been able to accept that the teams and their designers all agree that they missed the target so badly that the dynamic wind strength had to be reduced by 50%.

 

After dogwatch called me out for not having any statement from the teams to support mu claim that they were not behind the extremely low limit the first post I could find (SA's search function is broken) was dogwatch claiming that PB and LR once stated they would refuse to accept a reduction in the upper limit.

 

I'm not making this stuff up. The tune has changed from May to now. I can't find objective statement to support it. Your photos of boats struggling and my experiences do not count for much other than to show I'm not posting from a vacuum of knowledge or experience. I'm not trying to make anyone wrong. 

 

If indeed the designers missed it by that much I'm cool with that. I just can't find anything to support that conclusion. That Juan K and or the Artemis build team missed it and the boat folded is evident. It is obvious that no one wants to have an abstract discussion about it on this forum.

 

The objective conclusion I reach is that when the rule was written no one knew that 33 knots sustained would require ability to bear off in 55 apparent so they made an error. If this is true there would be no debate about lowering the limit. I did not see those statements. I hate to think that none of the rule writers that happen to be respected multihull designers could not have known what the speed and loads would be. If that is true they should not be so well respected.

 

I was not following the safety rules shit fight after the Artemis disaster, so I don't know where to start looking for statements made at the time to support my gut feeling that IM wanted to impose a limit lower than suggested by USA and NZ.

 

Does anyone deny that one of the stated goals was a design rule that would not require abandonment or postponement for normal expected SF Cityfront conditions? Did the rule miss and the designers miss? Are we to believe that it is unsafe to race multihulls in the mid 20's in AF?

 

All I'm trying to do is assemble a logical set of facts that supports the wind limits that also fits with the facts of my experience. For that I'm getting trashed left and right with emotion and opinion. That is part of SA, but I surrender. I'll wait for the book.

 

Cheers,

 

Randy



#105 dogwatch

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Posted 18 September 2013 - 06:03 PM

After dogwatch called me out for not having any statement from the teams to support mu claim that they were not behind the extremely low limit the first post I could find (SA's search function is broken) was dogwatch claiming that PB and LR once stated they would refuse to accept a reduction in the upper limit.

 

Nope. I've already said once that is incorrect. That statement from PB was about changes to class rules. The wind limit is not a class rule, it's a protocol clause. That was a critical distinction at that point. Protocol changes = majority vote, class rules = unanimity.



#106 NoStrings

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Posted 18 September 2013 - 06:07 PM

You're being pelted with opinion, because OPINION and ANECDOTES is what you have offered in support of your argument for higher limits.

Now, could the rule and spec writers and designers have been overly optimistic? Are you serious? You're not an engineer are you? FFS man, this kind of shit happens daily.

Almost every form of racing, save horse racing, has some kind of limits. Some are in place to enhance safety, some (like restrictor plates) were put in place both for safety and to make the competition closer and more appealing to the audience.

I guess I'll ask you this: Specifically what are you not seeing, in the AC Finals to date, that has left you feeling dissatisfied?

#107 Lysistrata

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Posted 18 September 2013 - 06:14 PM


Almost every form of racing, save horse racing, has some kind of limits.

 

In Australia horse racing has safety restrictions too.

Races are cancelled if the track is too boggy or if the weather is too inclement.

Horses can be banned if they are a danger to themselves or other horses and jockeys.



#108 RHough

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Posted 18 September 2013 - 06:15 PM

After dogwatch called me out for not having any statement from the teams to support mu claim that they were not behind the extremely low limit the first post I could find (SA's search function is broken) was dogwatch claiming that PB and LR once stated they would refuse to accept a reduction in the upper limit.

 

Nope. I've already said once that is incorrect. That statement from PB was about changes to class rules. The wind limit is not a class rule, it's a protocol clause. That was a critical distinction at that point. Protocol changes = majority vote, class rules = unanimity.

I stand corrected. I admit I have not read the class rules to separate the design rule and goals from the protocol and SI's.

 

I now freely admit that the designers of the boats and the people that wrote the rule had their heads up their asses and should have known the boats were unsafe in over 22 knots when they wrote the protocol.

 

Lets enjoy the races. May the better boat win ... the crews are all kiwi so NZ should be happy either way!  :-)



#109 Lysistrata

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Posted 18 September 2013 - 06:25 PM

Lets enjoy the races. May the better boat win ... the crews are all kiwi so NZ should be happy either way!  :-)

Australia too.
We have representation in both teams and NZ is mentioned in the first
version of our Constitution, so they're virtually a colony.
 



#110 RHough

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Posted 18 September 2013 - 06:57 PM


I guess I'll ask you this: Specifically what are you not seeing, in the AC Finals to date, that has left you feeling dissatisfied?

I never said I was not satisfied. Not satisfied or disappointed gets indifference not passion.

 

I have offered a bit of basic math that shows the new wind limit is about 50% of the force targeted in either the class rule, the design, brief or protocol. IIRC the loads are a 3rd or 4th level exponent of force. So the the reduction is a about 75% reduction in loads. If all of my posts are based on opinion and anecdotes there has been no rebuttal with anything else.

 

I just have difficulty accepting that the design concept, class rule and protocol were all that far wrong. A single designer missing by that much, certainly. For the entire AC34 team from concept to rule to execution to have made that large an error beggars belief.

 

This very much says that M&M didn't know what they were doing when the wrote the rule and CCYC didn't know what they were doing when they wrote the protocol. It also vindicates the teams that cited safety as the reason for not competing. It means that GD and RC and PC and PB unknowingly put their people at risk or they would not have agree to the protocol or whatever document contains the original limit. This paints a picture of gross incompetence at what is supposed to be the top level of sailing sport. 

 

The above might be true, I was trying to convince myself that it is not.

 

I think the racing is great and the boats are spectacular. For all this good to come from a management system and designers that missed the wind limit so badly must be an act of DoG.

 

Thank goodness IM got them to agree to the lower limit before more sailors died.



#111 Mark K

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Posted 18 September 2013 - 06:59 PM



#112 burbanite

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Posted 18 September 2013 - 07:07 PM



Almost every form of racing, save horse racing, has some kind of limits. Some are in place to enhance safety, some (like restrictor plates) were put in place both for safety and to make the competition closer and more appealing to the audience.

 

 

Now, I'm on your side in this argument discussion but this is my territory. Restrictor plates were introduced because of liability concerns, they had to keep the cars under 200 for insurance reasons. The competition isn't closer but the cars are and it appeals to the audience because the likelihood of a crash is actually increased as a result...

 

NASCAR mentality. I don't like it when the AC is compared to that organization.



#113 jorgensen-online

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Posted 18 September 2013 - 07:14 PM

I have never argued for 33 as being safe or reasonable. I only point out that the same people that every claims to support 22 once agreed to design for 33. I thought it was ambitious when I first heard it. I have not been able to accept that the teams and their designers all agree that they missed the target so badly that the dynamic wind strength had to be reduced by 50%.

 

Early on, there were to be two rig sizes, I do not know what windspeed was anticipated to be the conditions to start to utilize the smaller rig, but it was conceived to be at some point. So, someone had done estimates on loads. When the decision to only go with one rig was made there appeared to me the beginnings of a disconnect of what all would have and the conditions all or most all knew be probable.

 

Even assuming that two rigs were on hand, the Teams I would assume would have to make that decision prior to racing, and that decision would be theirs.



#114 Mark K

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Posted 18 September 2013 - 07:19 PM



Almost every form of racing, save horse racing, has some kind of limits. Some are in place to enhance safety, some (like restrictor plates) were put in place both for safety and to make the competition closer and more appealing to the audience.

 

 

Now, I'm on your side in this argument discussion but this is my territory. Restrictor plates were introduced because of liability concerns, they had to keep the cars under 200 for insurance reasons. The competition isn't closer but the cars are and it appeals to the audience because the likelihood of a crash is actually increased as a result...

 

NASCAR mentality. I don't like it when the AC is compared to that organization.

 

    "The competition isn't closer but the cars are" ?  



#115 burbanite

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Posted 18 September 2013 - 07:22 PM

 



Almost every form of racing, save horse racing, has some kind of limits. Some are in place to enhance safety, some (like restrictor plates) were put in place both for safety and to make the competition closer and more appealing to the audience.

 

 

Now, I'm on your side in this argument discussion but this is my territory. Restrictor plates were introduced because of liability concerns, they had to keep the cars under 200 for insurance reasons. The competition isn't closer but the cars are and it appeals to the audience because the likelihood of a crash is actually increased as a result...

 

NASCAR mentality. I don't like it when the AC is compared to that organization.

 

    "The competition isn't closer but the cars are" ?  

 

Cars that are artificially close does not equal close competition.



#116 BrownTrout

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Posted 18 September 2013 - 07:39 PM

I was out there this past weekend. and these boats are awesome. It is amazing to watch this event live, as it has been on tv.  These things are simply really cool to see. The venue provides for the first time the ability for spectators to watch from shore, the boats provide for incredibly dramatic sights. However disorganized this event is, it is simply awesome. Could there be improvements? Absolutely. But I would hate to be sitting and watching AICC mono hulls going around a course again. They have moved it forward and good for them. Will the next one be in foiling 55ft winged cats? I hope so. If only to get 10 teams in next time. But no matter what, this was fucking cool. I hope the kiwis win to get the boats to a more non-billionaire scale, but I hope oracle wins to keep it in San Fran so I can go out and see it again next time. and no matter what I hope that the old AICC's remain tourist attractions for a "day on the bay". This has been a huge step forward and good for us to be able to watch it. Next, maybe a little step back to make it even better.



#117 Mark K

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Posted 18 September 2013 - 07:50 PM

 

 



Almost every form of racing, save horse racing, has some kind of limits. Some are in place to enhance safety, some (like restrictor plates) were put in place both for safety and to make the competition closer and more appealing to the audience.

 

 

Now, I'm on your side in this argument discussion but this is my territory. Restrictor plates were introduced because of liability concerns, they had to keep the cars under 200 for insurance reasons. The competition isn't closer but the cars are and it appeals to the audience because the likelihood of a crash is actually increased as a result...

 

NASCAR mentality. I don't like it when the AC is compared to that organization.

 

    "The competition isn't closer but the cars are" ?  

 

Cars that are artificially close does not equal close competition.

 

 I don't know what you're smoking, but where can I get some?  



#118 WetHog

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Posted 18 September 2013 - 08:23 PM

Well, for some reason I think you would shit yourself just riding on one of these beast at say, 15 kn TWS...

 

Talk about a blast from the past. A good blast from the past at that.

 

Hope all is well Chuso. ;)

 

WetHog :ph34r:



#119 WetHog

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Posted 18 September 2013 - 08:31 PM

 

Not sure why you posted that video, but because you did:

 

24pjgu8.jpg

 

WetHog :ph34r:



#120 Mark K

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Posted 18 September 2013 - 08:44 PM

 

Not sure why you posted that video, but because you did:

 

24pjgu8.jpg

 

WetHog :ph34r:

  It's an example of striving for a foolish consistency in scheduling.  



#121 chuso007

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Posted 18 September 2013 - 09:26 PM

Well, for some reason I think you would shit yourself just riding on one of these beast at say, 15 kn TWS...

 
Talk about a blast from the past. A good blast from the past at that.
 
Hope all is well Chuso. ;)
 
WetHog :ph34r:

Hi Wethog, I've been a bit busy having kids and all that... I come every once in a while in lurking mode.

#122 Wish I had a boat

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Posted 18 September 2013 - 09:30 PM

 

Well, for some reason I think you would shit yourself just riding on one of these beast at say, 15 kn TWS...

 
Talk about a blast from the past. A good blast from the past at that.
 
Hope all is well Chuso. ;)
 
WetHog :ph34r:

Hi Wethog, I've been a bit busy having kids and all that... I come every once in a while in lurking mode.

 

Kids sure do have a way of cutting into your internet time. But they are worth it.



#123 NoStrings

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Posted 18 September 2013 - 09:53 PM


 



Almost every form of racing, save horse racing, has some kind of limits. Some are in place to enhance safety, some (like restrictor plates) were put in place both for safety and to make the competition closer and more appealing to the audience.
 

 
Now, I'm on your side in this argument discussion but this is my territory. Restrictor plates were introduced because of liability concerns, they had to keep the cars under 200 for insurance reasons. The competition isn't closer but the cars are and it appeals to the audience because the likelihood of a crash is actually increased as a result...
 
NASCAR mentality. I don't like it when the AC is compared to that organization.
 
    "The competition isn't closer but the cars are" ?  
 
Cars that are artificially close does not equal close competition.

Ok, that's just a ridiculous statement. I just displayed my B flag for violation of the Common Sense rule. Please do your 720.

#124 floater

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Posted 19 September 2013 - 12:12 AM


Lets enjoy the races. May the better boat win ... the crews are all kiwi so NZ should be happy either way!  :-)

Australia too.
We have representation in both teams and NZ is mentioned in the first
version of our Constitution, so they're virtually a colony.
 
i didn't know that. Did your ever ship your felons there?

#125 burbanite

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Posted 19 September 2013 - 04:56 AM

 

 


 



Almost every form of racing, save horse racing, has some kind of limits. Some are in place to enhance safety, some (like restrictor plates) were put in place both for safety and to make the competition closer and more appealing to the audience.
 

 
Now, I'm on your side in this argument discussion but this is my territory. Restrictor plates were introduced because of liability concerns, they had to keep the cars under 200 for insurance reasons. The competition isn't closer but the cars are and it appeals to the audience because the likelihood of a crash is actually increased as a result...
 
NASCAR mentality. I don't like it when the AC is compared to that organization.
 
    "The competition isn't closer but the cars are" ?  
 
Cars that are artificially close does not equal close competition.

Ok, that's just a ridiculous statement. I just displayed my B flag for violation of the Common Sense rule. Please do your 720.

 

In my business we do know the difference between reality and contrived situations. 720's are what the NASCAR fans are all about...



#126 dogwatch

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Posted 19 September 2013 - 06:11 AM

I just have difficulty accepting that the design concept, class rule and protocol were all that far wrong. A single designer missing by that much, certainly. For the entire AC34 team from concept to rule to execution to have made that large an error beggars belief.

 

This very much says that M&M didn't know what they were doing when the wrote the rule and CCYC didn't know what they were doing when they wrote the protocol. It also vindicates the teams that cited safety as the reason for not competing. It means that GD and RC and PC and PB unknowingly put their people at risk or they would not have agree to the protocol or whatever document contains the original limit. This paints a picture of gross incompetence at what is supposed to be the top level of sailing sport.

 

A couple of comments. One, as someone else as pointed out, there was originally going to be a second smaller wing. Dropped by competitor agreement for cost reasons.

 

Secondly, if you haven't read it, read http://www.sailingwo...riting-the-rule Amongst other things, it makes it clear how the rule was a compromise developed to satisfy several influencers.



#127 chuso007

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Posted 19 September 2013 - 06:29 AM

 

 

Well, for some reason I think you would shit yourself just riding on one of these beast at say, 15 kn TWS...

 
Talk about a blast from the past. A good blast from the past at that.
 
Hope all is well Chuso. ;)
 
WetHog :ph34r:

Hi Wethog, I've been a bit busy having kids and all that... I come every once in a while in lurking mode.

 

Kids sure do have a way of cutting into your internet time. But they are worth it.

That is a big truth there...

 

Anyway, the little time I get to surf the web I use an Ipad, and it is HELL to go through SA forums with it...



#128 Black Sox

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Posted 19 September 2013 - 12:33 PM

 


Lets enjoy the races. May the better boat win ... the crews are all kiwi so NZ should be happy either way!  :-)

Australia too.
We have representation in both teams and NZ is mentioned in the first
version of our Constitution, so they're virtually a colony.
 
i didn't know that. Did your ever ship your felons there?

Ehm,  how would a felon be distinguishable from all the other felons Australians?

 

Just curious...



#129 christom

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Posted 19 September 2013 - 12:54 PM


Lets enjoy the races. May the better boat win ... the crews are all kiwi so NZ should be happy either way!  :-)

Australia too.
We have representation in both teams and NZ is mentioned in the first
version of our Constitution, so they're virtually a colony.
 
i didn't know that. Did your ever ship your felons there?

One thing that I didn't know until recently was the reason we became a penal colony was because of the US war of independence which the US won so the British could not send the convicts there anymore so the alternative was Australia. So I think we all might have a bit of convict in us.

#130 RHough

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Posted 19 September 2013 - 02:53 PM

I just have difficulty accepting that the design concept, class rule and protocol were all that far wrong. A single designer missing by that much, certainly. For the entire AC34 team from concept to rule to execution to have made that large an error beggars belief.

 

This very much says that M&M didn't know what they were doing when the wrote the rule and CCYC didn't know what they were doing when they wrote the protocol. It also vindicates the teams that cited safety as the reason for not competing. It means that GD and RC and PC and PB unknowingly put their people at risk or they would not have agree to the protocol or whatever document contains the original limit. This paints a picture of gross incompetence at what is supposed to be the top level of sailing sport.

 

A couple of comments. One, as someone else as pointed out, there was originally going to be a second smaller wing. Dropped by competitor agreement for cost reasons.

 

Secondly, if you haven't read it, read http://www.sailingwo...riting-the-rule Amongst other things, it makes it clear how the rule was a compromise developed to satisfy several influencers.

I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong.

 

The boats ended up being faster than they predicted, i.e. the designs were too good. :-)  This put them dangerously close to putting the foils into cavitation speeds (~50+) that could have lead to real control problems.

 

Basically they want to limit boat speed to under 50 knots to stay safely out of foil cavitation speeds. The boats can sail over 2x wind speed and in some ranges are close to or at 3x wind speed the TWS needed to keep them below 50 knots is in the 22-24 knot range.

 

The wind limit for safety was not a reaction to the Artemis disaster as I assumed incorrectly. I had assumed the limit was for structural concerns not an unforeseen design challenge.

 

If they want higher wind speed limits they have to lose the foiling to remove the "50 knot barrier"  or they can lose the wing to reduce the top speed of the boats to under 3x wind speed.

 

If they want to keep the full foiling and hard wings they are stuck with a low wind speed limit until they solve the cavitation issue. Sort of ironic that the faster the boat is relative to wind speed the lower the safe wind speed becomes. If indeed the wind limit was lowered due to concerns about foil cavitation then they got it right and the engineering math supports it.

 

It is not about being pansies, or poor design, or reaction to the Artemis disaster. It is about unforeseen design success.

 

Stop bitching about the boats being to fragile to sail in 30+

Start celebrating that they are too fast to sail in over 25.

 

I'm surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.

 

Cheers,

 

Randy



#131 jorgensen-online

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Posted 19 September 2013 - 03:06 PM

So Randy, the question might be what would be the "right" sized boat (or attributes) to approach 50 kt. but not exceed it off Auckland.

 

Others have here and there mentioned the cavitation issue but none has placed it in the terms you did. 



#132 floater

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Posted 19 September 2013 - 03:17 PM



Lets enjoy the races. May the better boat win ... the crews are all kiwi so NZ should be happy either way!  :-)

Australia too.
We have representation in both teams and NZ is mentioned in the first
version of our Constitution, so they're virtually a colony.
 
i didn't know that. Did your ever ship your felons there?
One thing that I didn't know until recently was the reason we became a penal colony was because of the US war of independence which the US won so the British could not send the convicts there anymore so the alternative was Australia. So I think we all might have a bit of convict in us.
we got the Puritans - you got the criminals. Both sets expelled by mother Britain.

Far from certain which heritage more desirable

#133 RHough

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Posted 19 September 2013 - 03:40 PM

So Randy, the question might be what would be the "right" sized boat (or attributes) to approach 50 kt. but not exceed it off Auckland.

 

Others have here and there mentioned the cavitation issue but none has placed it in the terms you did. 

 

I don't think there is a good answer for that. The answer to keeping the boats under 50 knots might be writing a rule that requires larger foils (increase drag) and soft sails (reduce rig efficiency). Then scale the boats to fit projected budgets.

 

65 feet would fit the traditional AC lower limit.



#134 catsailordude

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Posted 19 September 2013 - 03:41 PM

The wind limits are definitely necessary but the way they are applied has caused a great deal of disappointment for the viewers.  It's unfortunate that a race can be cancelled during the pre-start because of a 15 second gust.  Given that the races last only 20 minutes or so, I think that once the pre-start has commence (at 2:10) there should be no cancellations.  The wind limits should have had some cushion built into them to allow for the fact that wind could increase by a knot or two during a 20 minute race.  

 

As for anyone being pussies, people sailing non-self-righting boats that foil at over 40 knots are not pussies.  Sailing a fast boat in 12 knots TWS is much more on-the-edge than sailing a ballasted boat in anything.  Calling these guys pussies would be like calling an F1 driver a pussy because he only drives on smooth pavement and doesn't go off-roading.  

 

The mistake of this America's Cup is not that it's in fast catamarans, it's that the rig is just a little bit too tall for the conditions of San Francisco.  Had they gone with the 110 foot rig, the boats would have less weight and power up high and the wind limit could have been set at 25 or 26 knots, which would have meant few if any cancellations.  It also might have meant that you would see the code zeros come out in 12 knots instead of 9 knots.   Hopefully ETNZ runs the next cup in catamarans, but with a rule that is more accurately calibrated to the prevailing local conditions.  

 

But this is only version 1 of this type of boat in the Americas Cup and despite a few cancelled races, this is by far the best sailboat racing I have ever seen broadcast, and not just because of the speed--it's more because the upwind legs.  It is certainly much better racing than anything we saw in 1992 or 1958.  Let's face it, the only competitive America's Cup finals prior to this one were in 1983 and 2007.  

 

Even with the 131 foot rig, these boats and crews are handling the big breeze better than just about any AC boats in the past.  They are certainly handling the breeze much better than any prior AC boat capable of powering up in 6 knots of wind.



#135 tractorbeam

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Posted 19 September 2013 - 03:57 PM

Dumbass. It's a 5 minute average "Sailing Wind Speed" that determines the limit.



#136 RHough

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Posted 19 September 2013 - 04:02 PM

Dumbass. It's a 5 minute average "Sailing Wind Speed" that determines the limit.

LMAO

 

The limit is set ...  the sailing wind speed is compared to the limit

 

who were you calling dumbass?



#137 maskirovka

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Posted 19 September 2013 - 04:08 PM

Even when I sailed the 2.4mR , a boat with 1ft of freeboard, we sailed if we did not have sustained winds above 22knts. Not 30 seconds above but it must be sustained. Then if the winds increased during the race, too bad, the race has been started.
 
This is why the AC is not a Marketable Event and thus all of sailing is hurt by the Premier Event in Sailing being non-sailable in such a low wind range.
 
Thanks Larry, even disabled sailors in the 2.4mR got more balls than you and RC.


You would not last 10" upright in 15 knots TWS on those boats. Definitely you don't know what you are talking about!

Pass your way and go watch crickets, there is no postponement.
Mechanical sports have all their limits, if you don't like it, just move your fat body on a bike next WE, you'll find some limit quickly :-))

#138 maskirovka

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Posted 19 September 2013 - 04:09 PM

So what happens when Oracle asks ETNZ to agree to raise the wind limits, and they say no. Does that make them pussies who dont want to race in conditions where they might lose, or heroes who are doing what it takes to win the series? Look at the email exchange below and decide for yourself


From: Richard Slater (Oracle)
Sent: Monday, 16 September 2013 11:59 a.m.
To: Russell Green (ETNZ)
Subject: Proposed Protocol Amendment

Gday Russell,
Attached is a proposed protocol amendment in relation to wind limits. The proposed changes are to:
1. Increase the wind limit to start a race from 23 to 24 knots.
and
2. Removed the fixed wind speed limit after starting.
The wind limits set by Iain have increased each month as the teams gained more experience. We now believe that both teams are capable to start races in conditions that are 1 knot higher. So this is in line with the safety committee proposals of increasing the limits over time.
Once a race is started, it makes no sense to abandon it. Removing this requirement still allows ACRM to abandon for safety reasons but no longer provides such a hard limit. If we can agree on this we can talk to Iain about amending the event permit.
I look forward to your comments.
Regards
Richard
From: Russell Green
Date: 16 September 2013 18:40:33 PDT
To: Richard Slater
Subject: RE: Proposed Protocol Amendment

Hi Richard
Our guys have talked about your proposal and would have considered it before racing started but now that a substantial number of races have been sailed and one abandoned we think it is no longer appropriate to make changes.
Cheers
Russell

#139 pqbon

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Posted 19 September 2013 - 04:52 PM

So baiscally you are saying that the teams all failed to design for the 33kts wind limit?

When M&M deisgned foiling ENTZ boat they blew the design parameters and designed a boat that was unsafe at 66% of the speed?

 

The Prada team was the first ones to figure it out? Remember they set the wind limits right after the accident with their threat to walk if the wind limit was not lowered.



#140 TornadoSail2016

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Posted 19 September 2013 - 04:55 PM

The boats ended up being faster than they predicted, i.e. the designs were too good. :-)  This put them dangerously close to putting the foils into cavitation speeds (~50+) that could have lead to real control problems.

 

Basically they want to limit boat speed to under 50 knots to stay safely out of foil cavitation speeds. The boats can sail over 2x wind speed and in some ranges are close to or at 3x wind speed the TWS needed to keep them below 50 knots is in the 22-24 knot range.

 

The wind limit for safety was not a reaction to the Artemis disaster as I assumed incorrectly. I had assumed the limit was for structural concerns not an unforeseen design challenge.

Start celebrating that they are too fast to sail in over 25.

 

I'm surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.

 

Cheers,

 

Randy

This was the big issue that Paul Larson and the Speed Rocket Team dealt with for years.  I think it took them 10-12 years with many attempts to get to their record breaking runs last year.  If you look at the foil design they chose they are far different affairs than these foils are and they were designed with cavitation in mind and a part of how they worked. Thanks, TTS



#141 Kanting_Kid

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Posted 19 September 2013 - 04:59 PM

You are totally wrong to think cavitation is a safety issue. It is a total speed limiter- but NOT a safety problem. If anything it saves the crew just like a turbo restrictor plate in the WRC .

#142 RHough

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Posted 19 September 2013 - 05:02 PM

So baiscally you are saying that the teams all failed to design for the 33kts wind limit?

When M&M deisgned foiling ENTZ boat they blew the design parameters and designed a boat that was unsafe at 66% of the speed?

 

The Prada team was the first ones to figure it out? Remember they set the wind limits right after the accident with their threat to walk if the wind limit was not lowered.

Judging from the math from foiling speeds and the public comments about what they thought the top speeds would be the rule was fine. When they started designing the foils for the AC72 they exceeded their own estimates.

 

I can't fault anyone for not having a crystal ball. You can bet that if the rule was written today it would be different.

 

What I'm saying is that the 33 knot wind limit became absurd once the foiling challenger was met and the boats started cracking 45 knots.

 

To foil safely in 33 knots you need to have control at 50+ boat speeds. AFAIK very few people have that design ability and budget.

 

Isn't nice when you exceed your own expectations and your design success requires a reset of rules?



#143 RHough

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Posted 19 September 2013 - 05:08 PM

You are totally wrong to think cavitation is a safety issue. It is a total speed limiter- but NOT a safety problem. If anything it saves the crew just like a turbo restrictor plate in the WRC .

Wrong.

Cavitation (as opposed to ventilation) destroys foils.  If you think catastrophic foil failure at 50+ knots is not a safety concern you are living in an alternate reality. 



#144 ibsailn

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Posted 19 September 2013 - 05:13 PM

 

I just have difficulty accepting that the design concept, class rule and protocol were all that far wrong. A single designer missing by that much, certainly. For the entire AC34 team from concept to rule to execution to have made that large an error beggars belief.

 

This very much says that M&M didn't know what they were doing when the wrote the rule and CCYC didn't know what they were doing when they wrote the protocol. It also vindicates the teams that cited safety as the reason for not competing. It means that GD and RC and PC and PB unknowingly put their people at risk or they would not have agree to the protocol or whatever document contains the original limit. This paints a picture of gross incompetence at what is supposed to be the top level of sailing sport.

 

A couple of comments. One, as someone else as pointed out, there was originally going to be a second smaller wing. Dropped by competitor agreement for cost reasons.

 

Secondly, if you haven't read it, read http://www.sailingwo...riting-the-rule Amongst other things, it makes it clear how the rule was a compromise developed to satisfy several influencers.

I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong.

 

The boats ended up being faster than they predicted, i.e. the designs were too good. :-)  This put them dangerously close to putting the foils into cavitation speeds (~50+) that could have lead to real control problems.

 

Basically they want to limit boat speed to under 50 knots to stay safely out of foil cavitation speeds. The boats can sail over 2x wind speed and in some ranges are close to or at 3x wind speed the TWS needed to keep them below 50 knots is in the 22-24 knot range.

 

The wind limit for safety was not a reaction to the Artemis disaster as I assumed incorrectly. I had assumed the limit was for structural concerns not an unforeseen design challenge.

 

If they want higher wind speed limits they have to lose the foiling to remove the "50 knot barrier"  or they can lose the wing to reduce the top speed of the boats to under 3x wind speed.

 

If they want to keep the full foiling and hard wings they are stuck with a low wind speed limit until they solve the cavitation issue. Sort of ironic that the faster the boat is relative to wind speed the lower the safe wind speed becomes. If indeed the wind limit was lowered due to concerns about foil cavitation then they got it right and the engineering math supports it.

 

It is not about being pansies, or poor design, or reaction to the Artemis disaster. It is about unforeseen design success.

 

Stop bitching about the boats being to fragile to sail in 30+

Start celebrating that they are too fast to sail in over 25.

 

I'm surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.

 

Cheers,

 

Randy

RHough -- is it really "cavitation" that is the problem or air ingestion, or something else?  Cavitation is the "boiling" of water due to low pressure.  Traditionally this is the domain of Propellers and this is where my knowledge comes from. cavitation is usually caused be extremely high loading of an water borne foil.  In propellers the solution is to adjust the pitch and use a bigger area propeller to distribute the load over a bigger area.  If it is truly cavitation, I would think they could solve the problem by using lower angle of attack, reducing loading on the foils, and avoiding cavitation.  This may actually require larger areas to get the same total lift with lower pressures, but not exactly sure.

 

Air ingestion, caused from surface tension of water, and the air feeding along the foil surface is a different issue, but causes the same problem of the foil operating in a gas instead of a liquid.

 

Maybe I am missing something as cavitation of non-rotating foils is not my forte, but in theory it is all the same thing.

 

Thanks.



#145 SailHigh

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Posted 19 September 2013 - 05:13 PM

You are totally wrong to think cavitation is a safety issue. It is a total speed limiter- but NOT a safety problem. If anything it saves the crew just like a turbo restrictor plate in the WRC .

Wrong.

Cavitation (as opposed to ventilation) destroys foils.  If you think catastrophic foil failure at 50+ knots is not a safety concern you are living in an alternate reality. 

but teams should know this.  so when winds are up to 25+, they should either a) slow down (sail more DDW), or b ) stop foiling.  not cancel the race.  it would be more interesting to see how they would handle the situation to avoid cavitation no?



#146 ssi

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Posted 19 September 2013 - 05:16 PM

What a pile of apologetic socialist bullshit.

 

They were told of the wind limits and were given a box design rule.  At that point their job was to design a boat that can race in given wind limits and fits within the rule.

 

SOME of them failed in the first respect.  You can make the wing flatter, take off the jib, run deeper, you can take the foils off so that nothing cavitates, you can do WHATEVER THE FUCK YOU WANT so that YOU race in GIVEN wind range.  You can also slow down the boat while you are sailing.

 

THE END

 

Stop bitching about the boats being to fragile to sail in 30+

Start celebrating that they are too fast to sail in over 25.

 

I'm surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.



#147 RHough

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Posted 19 September 2013 - 05:22 PM

What a pile of apologetic socialist bullshit.

 

They were told of the wind limits and were given a box design rule.  At that point their job was to design a boat that can race in given wind limits and fits within the rule.

 

SOME of them failed in the first respect.  You can make the wing flatter, take off the jib, run deeper, you can take the foils off so that nothing cavitates, you can do WHATEVER THE FUCK YOU WANT so that YOU race in GIVEN wind range.  You can also slow down the boat while you are sailing.

 

THE END

 

Stop bitching about the boats being to fragile to sail in 30+

Start celebrating that they are too fast to sail in over 25.

 

I'm surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.

Or you can agree to a lower wind limit that allows you to race the boats safely and take the heat from people that are pissed of about the limit.



#148 bruno

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Posted 19 September 2013 - 05:28 PM

What a pile of apologetic socialist bullshit.
 
They were told of the wind limits and were given a box design rule.  At that point their job was to design a boat that can race in given wind limits and fits within the rule.
 
SOME of them failed in the first respect.  You can make the wing flatter, take off the jib, run deeper, you can take the foils off so that nothing cavitates, you can do WHATEVER THE FUCK YOU WANT so that YOU race in GIVEN wind range.  You can also slow down the boat while you are sailing.
 
THE END
 

Stop bitching about the boats being to fragile to sail in 30+
Start celebrating that they are too fast to sail in over 25.
 
I'm surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.


dear the end,

thanks for the new definition of socialism: limiting the costly damage that teams financed by wealthy individuals can do to themselves in pursuit of status in perhaps the most exclusive and expensive veblen good existing.

#149 NoStrings

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Posted 19 September 2013 - 05:29 PM

In the scientific world you don't get to take the podium and present your hypothesis without showing how to got there. Stating, "I did the math" without actually showing the math isn't sufficient. Please cite your sources and show how you arrived at this conclusion.

#150 Kanting_Kid

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Posted 19 September 2013 - 05:35 PM

You are totally wrong to think cavitation is a safety issue. It is a total speed limiter- but NOT a safety problem. If anything it saves the crew just like a turbo restrictor plate in the WRC .

Wrong.

Cavitation (as opposed to ventilation) destroys foils.  If you think catastrophic foil failure at 50+ knots is not a safety concern you are living in an alternate reality. 

On what authority or source do you think this? If you think I am living in a alternate reality then I must have been eating magic mushrooms for the past 12 months... Whats your day job? I bet it has nothing to do with anything or anyone close to the AC.  Therefore, YOU are living in a internet playground and influencing all the other desktop designers about shit you dont know half what you think you do.  If you doubt me, listen to yesturdays after race presser. JS talks about it. And no I don't listen to pressers then come on here pretending to have crunched numbers.  ;)  



#151 bruno

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Posted 19 September 2013 - 05:37 PM



Lets enjoy the races. May the better boat win ... the crews are all kiwi so NZ should be happy either way!  :-)

Australia too.
We have representation in both teams and NZ is mentioned in the first
version of our Constitution, so they're virtually a colony.
 
i didn't know that. Did your ever ship your felons there?
One thing that I didn't know until recently was the reason we became a penal colony was because of the US war of independence which the US won so the British could not send the convicts there anymore so the alternative was Australia. So I think we all might have a bit of convict in us.
we got the Puritans - you got the criminals. Both sets expelled by mother Britain.
Far from certain which heritage more desirable
At a time when insolvency was considered criminal, most of the indentured servants in NA were debtors sold to satisfy their debts. As Sabatini described, there also were criminals and traitors condemned to slavery and servitude on the plantations. Puritans were typically middle to upper class religious dissenters who followed the Pilgrims over, perhaps to the detriment of the locals. So American exceptionalism was in part founded on the backs of debtors and cultists from thenperspective of the mother country.

Australia was where the overflow of the Industrial age were consigned, and NZ was an outpost which received most of its 19th c. population naturally enough from there. Though the psuedo poms deny it today.

#152 Wild honey

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Posted 19 September 2013 - 05:39 PM

I don't subscribe to RHough's cavitation hypothesis as pronounced in the SA homepage.

I don't believe that these boats are capable of attaining 50 kts in any wind speed other than (possibly) in ideal and artificial conditions in flat water. They are peaking out at approx 43 kts, and I don't think that by increasing the wind speed max by 7 kts or so will produce another 7 kts max boat speed. The wind speed to boat speed graph is not a straight line, it is a curve with a limit.

#153 JMOD

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Posted 19 September 2013 - 05:44 PM

for the people who haven't seen it yet, a very nice interview with MM, especially on the foils and foilingpart. 

 

http://www.cupinfo.c...hulls-13146.php



#154 RHough

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Posted 19 September 2013 - 05:47 PM

 

 

I just have difficulty accepting that the design concept, class rule and protocol were all that far wrong. A single designer missing by that much, certainly. For the entire AC34 team from concept to rule to execution to have made that large an error beggars belief.

 

This very much says that M&M didn't know what they were doing when the wrote the rule and CCYC didn't know what they were doing when they wrote the protocol. It also vindicates the teams that cited safety as the reason for not competing. It means that GD and RC and PC and PB unknowingly put their people at risk or they would not have agree to the protocol or whatever document contains the original limit. This paints a picture of gross incompetence at what is supposed to be the top level of sailing sport.

 

A couple of comments. One, as someone else as pointed out, there was originally going to be a second smaller wing. Dropped by competitor agreement for cost reasons.

 

Secondly, if you haven't read it, read http://www.sailingwo...riting-the-rule Amongst other things, it makes it clear how the rule was a compromise developed to satisfy several influencers.

I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong.

 

The boats ended up being faster than they predicted, i.e. the designs were too good. :-)  This put them dangerously close to putting the foils into cavitation speeds (~50+) that could have lead to real control problems.

 

Basically they want to limit boat speed to under 50 knots to stay safely out of foil cavitation speeds. The boats can sail over 2x wind speed and in some ranges are close to or at 3x wind speed the TWS needed to keep them below 50 knots is in the 22-24 knot range.

 

The wind limit for safety was not a reaction to the Artemis disaster as I assumed incorrectly. I had assumed the limit was for structural concerns not an unforeseen design challenge.

 

If they want higher wind speed limits they have to lose the foiling to remove the "50 knot barrier"  or they can lose the wing to reduce the top speed of the boats to under 3x wind speed.

 

If they want to keep the full foiling and hard wings they are stuck with a low wind speed limit until they solve the cavitation issue. Sort of ironic that the faster the boat is relative to wind speed the lower the safe wind speed becomes. If indeed the wind limit was lowered due to concerns about foil cavitation then they got it right and the engineering math supports it.

 

It is not about being pansies, or poor design, or reaction to the Artemis disaster. It is about unforeseen design success.

 

Stop bitching about the boats being to fragile to sail in 30+

Start celebrating that they are too fast to sail in over 25.

 

I'm surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.

 

Cheers,

 

Randy

RHough -- is it really "cavitation" that is the problem or air ingestion, or something else?  Cavitation is the "boiling" of water due to low pressure.  Traditionally this is the domain of Propellers and this is where my knowledge comes from. cavitation is usually caused be extremely high loading of an water borne foil.  In propellers the solution is to adjust the pitch and use a bigger area propeller to distribute the load over a bigger area.  If it is truly cavitation, I would think they could solve the problem by using lower angle of attack, reducing loading on the foils, and avoiding cavitation.  This may actually require larger areas to get the same total lift with lower pressures, but not exactly sure.

 

Air ingestion, caused from surface tension of water, and the air feeding along the foil surface is a different issue, but causes the same problem of the foil operating in a gas instead of a liquid.

 

Maybe I am missing something as cavitation of non-rotating foils is not my forte, but in theory it is all the same thing.

 

Thanks.

It is my understanding that the cavitation is "boiling" water on the foil before it stalls. This can damage the foil as well as reducing lift similar to instantaneous loss of lift in a violent stall if separation is massive.

 

Foils exist that operate while cavitating, but they are poor below that speed.

 

The point I am trying to make is the only failure here is they underestimated their own success. If the boats only lifted 80-90% of their weight out of the water, the speeds they could reach in 30+ would be "safe".

 

It was only after the boats were fully flying that they ran into a new set of challenges that required either a solution to cavitation or a reduction in the wind speed limit or accepting that the boats would have to stop racing and sail the course slowly in stronger breeze.

 

In a match race expecting the crews to NOT push that limit until a big gust put them over and the foil explodes is asking too much of the sailors IMO.

There was not enough time and it likely the rules would prevent designing foils to operate at near cavitation speeds. There was a limit to number of foils the teams could build.

That leaves the unpopular expedient of reducing the wind limit to allow the boats to race safely with designs evolved as much as possible within the existing time constraints.

 

If the rule was to remain, foil development would continue and the practical wind limit safe to race in would be higher.

 

If the goal is a requirement to *race* (not just sail) in higher breeze, that is simple. Change the rule to reduce the high lift/drag ratios that allow sailing so much faster than the wind. That means decide to chose slower boats.

 

For now the wind limit is justified as a solution to design success beyond expectation. It shows that the boats have entered a new performance envelope that was unforeseen when the rule was written. Driving design to explore new challenges fits the spirit of the AC perfectly.



#155 RHough

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Posted 19 September 2013 - 05:59 PM

I don't subscribe to RHough's cavitation hypothesis as pronounced in the SA homepage.

I don't believe that these boats are capable of attaining 50 kts in any wind speed other than (possibly) in ideal and artificial conditions in flat water. They are peaking out at approx 43 kts, and I don't think that by increasing the wind speed max by 7 kts or so will produce another 7 kts max boat speed. The wind speed to boat speed graph is not a straight line, it is a curve with a limit.

It won't, I agree.

 

However it is quite likely that a foil will reach cavitation conditions during a manoeuvre. The result of a foil failure at maximum load would end the match.

 

The bottom line is the boats are much faster than thought possible when the rule was written for a 33 knot limit. There is not enough development time to know for certain what the safe wind limit is. They were designed for sub 40 knot speeds not 45-50.



#156 CapSizer

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Posted 19 September 2013 - 06:08 PM

RHough -- is it really "cavitation" that is the problem or air ingestion, or something else?  Cavitation is the "boiling" of water due to low pressure.  Traditionally this is the domain of Propellers and this is where my knowledge comes from. cavitation is usually caused be extremely high loading of an water borne foil.  In propellers the solution is to adjust the pitch and use a bigger area propeller to distribute the load over a bigger area.  If it is truly cavitation, I would think they could solve the problem by using lower angle of attack, reducing loading on the foils, and avoiding cavitation.  This may actually require larger areas to get the same total lift with lower pressures, but not exactly sure.

 

Air ingestion, caused from surface tension of water, and the air feeding along the foil surface is a different issue, but causes the same problem of the foil operating in a gas instead of a liquid.

 

Maybe I am missing something as cavitation of non-rotating foils is not my forte, but in theory it is all the same thing.

 

Thanks.

 

I've run the simple math on this, and it turns out that at around 46 knots, even a straightforward symmetric NACA 0012 style foil at zero angle of attack will produce pressures that are low enough for cavitation to start happening.  So any lifting foil, even a far more suitable cambered profile, will start to get into cavitating conditions at around 46 knots.  Cavitation is definitely an issue, and even a lightly loaded surface will run into difficulties.   It is probably no coincidence that the boats accelerate very easily to around 45 knots, but not significantly more, and that the sailing speed record got stuck at around that level until ski-type (ie. no liquid on the low-pressure side) lifting surfaces were made to work.



#157 Kanting_Kid

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Posted 19 September 2013 - 06:13 PM

I don't subscribe to RHough's cavitation hypothesis as pronounced in the SA homepage.

I don't believe that these boats are capable of attaining 50 kts in any wind speed other than (possibly) in ideal and artificial conditions in flat water. They are peaking out at approx 43 kts, and I don't think that by increasing the wind speed max by 7 kts or so will produce another 7 kts max boat speed. The wind speed to boat speed graph is not a straight line, it is a curve with a limit.

It won't, I agree.

 

However it is quite likely that a foil will reach cavitation conditions during a manoeuvre. The result of a foil failure at maximum load would end the match.

 

The bottom line is the boats are much faster than thought possible when the rule was written for a 33 knot limit. There is not enough development time to know for certain what the safe wind limit is. They were designed for sub 40 knot speeds not 45-50.

Not trying to start a arguement, but your wrong again. Designing foils trying to AVOID cavitation might end in disaster. Such as reducing the chord thickness especially around the tip to board joint.  And think about it after taking a deep breath. 33 knots? How fast does a Volvo 70 go in 33 knots? How fast does a MOD 70 go in 33 knots? Then think how fast a 72 ft wing sailed cat would possibly go? Full foiling or not.   I'm signing out of this now. I don't have the motivation for a all out forum shit fight. The one thing they didnt foresee would be going 32-34knts UPWIND. That is the big surprise.



#158 RHough

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Posted 19 September 2013 - 06:14 PM

RHough -- is it really "cavitation" that is the problem or air ingestion, or something else?  Cavitation is the "boiling" of water due to low pressure.  Traditionally this is the domain of Propellers and this is where my knowledge comes from. cavitation is usually caused be extremely high loading of an water borne foil.  In propellers the solution is to adjust the pitch and use a bigger area propeller to distribute the load over a bigger area.  If it is truly cavitation, I would think they could solve the problem by using lower angle of attack, reducing loading on the foils, and avoiding cavitation.  This may actually require larger areas to get the same total lift with lower pressures, but not exactly sure.

 

Air ingestion, caused from surface tension of water, and the air feeding along the foil surface is a different issue, but causes the same problem of the foil operating in a gas instead of a liquid.

 

Maybe I am missing something as cavitation of non-rotating foils is not my forte, but in theory it is all the same thing.

 

Thanks.

 

I've run the simple math on this, and it turns out that at around 46 knots, even a straightforward symmetric NACA 0012 style foil at zero angle of attack will produce pressures that are low enough for cavitation to start happening.  So any lifting foil, even a far more suitable cambered profile, will start to get into cavitating conditions at around 46 knots.  Cavitation is definitely an issue, and even a lightly loaded surface will run into difficulties.   It is probably no coincidence that the boats accelerate very easily to around 45 knots, but not significantly more, and that the sailing speed record got stuck at around that level until ski-type (ie. no liquid on the low-pressure side) lifting surfaces were made to work.

Thanks, that is what I suspected also.

 

Conventional hydrofoil craft have a number of problems which make them difficult or impractical to operate at high speeds. A first problem is cavitation, which is a phenomenon in which vapor bubbles form along the upper surface of a foil due to a low fluid pressure on this surface. Cavitation invariably occurs in conventional hydrofoil craft above a certain operating speed (typically around 50 knots). When the vapor bubbles caused by cavitation collapse in the water, they produce strong shock waves. If the collapse occurs in the vicinity of the foil, the shock waves not only produce unpleasant noise and vibrations, but can also physically damage the foil of the craft by pitting.

In order to prevent damage by cavitation, foils referred to as supercavitating foils have been developed. With a supercavitating foil, a large vapor-filled cavity, referred to as a separation bubble, is formed over substantially the entire upper surface of the foil. Vapor bubbles in the cavity are carried beyond the trailing edge of the foil and collapse in the water aft of the foil, so that shock waves produced by the collapse of the bubbles have much less effect on the foil than in a normal cavitating foil.

While a supercavitating foil prevents the collapse of air bubbles in the vicinity of the foil which could damage the foil, in order to prevent the separation bubble from collapsing, it is necessary to maintain the foil at an extremely high angle of incidence. This high angle of incidence results in a great deal of drag, so that the lift/drag ratio of a conventional supercavitating foil is so low as to make such a foil impractical. For this reason, supercavitating foils are not used in practice, and hydrofoil craft must rely onicon1.png conventional cavitating foils, which as described above are unsatisfactory.

LINK



#159 RHough

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Posted 19 September 2013 - 06:20 PM

 

I don't subscribe to RHough's cavitation hypothesis as pronounced in the SA homepage.

I don't believe that these boats are capable of attaining 50 kts in any wind speed other than (possibly) in ideal and artificial conditions in flat water. They are peaking out at approx 43 kts, and I don't think that by increasing the wind speed max by 7 kts or so will produce another 7 kts max boat speed. The wind speed to boat speed graph is not a straight line, it is a curve with a limit.

It won't, I agree.

 

However it is quite likely that a foil will reach cavitation conditions during a manoeuvre. The result of a foil failure at maximum load would end the match.

 

The bottom line is the boats are much faster than thought possible when the rule was written for a 33 knot limit. There is not enough development time to know for certain what the safe wind limit is. They were designed for sub 40 knot speeds not 45-50.

Not trying to start a arguement, but your wrong again. Designing foils trying to AVOID cavitation might end in disaster. Such as reducing the chord thickness especially around the tip to board joint.  And think about it after taking a deep breath. 33 knots? How fast does a Volvo 70 go in 33 knots? How fast does a MOD 70 go in 33 knots? Then think how fast a 72 ft wing sailed cat would possibly go? Full foiling or not.   I'm signing out of this now. I don't have the motivation for a all out forum shit fight. The one thing they didnt foresee would be going 32-34knts UPWIND. That is the big surprise.

The designers and writers of the rule are on record as not anticipating either full foiling or speeds so high. Feel free to talk with them.



#160 pwormwood

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Posted 19 September 2013 - 06:25 PM

The mistake was not reducing the size of the tall rig when they eliminated the second, small rig...they would still be able to fly the hull at low wind speeds with the Code 0.  Isn't 20/20 hindsight wonderful!



#161 Edu-Rio

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Posted 19 September 2013 - 06:28 PM

Hello!

I think we're missing an iportant point here. No matter if the issue is cavitation or not. We 're talking about sail boats. Ok, hight tech ones! But still boats. And, boats has options to handle with strong winds. Even windsurf do it. Change the sails(wings) big ones for light and small ones for heavy. This is "tip", for who spent +$100m.  :D 

At least we would see some momentum on teams to work around the clock to make the changes, and, of course they should keep the match safe and running.



#162 jjhplus9

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Posted 19 September 2013 - 06:40 PM


The boats ended up being faster than they predicted, i.e. the designs were too good. :-)  This put them dangerously close to putting the foils into cavitation speeds (~50+) that could have lead to real control problems.

 

Basically they want to limit boat speed to under 50 knots to stay safely out of foil cavitation speeds. The boats can sail over 2x wind speed and in some ranges are close to or at 3x wind speed the TWS needed to keep them below 50 knots is in the 22-24 knot range.

 

The wind limit for safety was not a reaction to the Artemis disaster as I assumed incorrectly. I had assumed the limit was for structural concerns not an unforeseen design challenge.

Start celebrating that they are too fast to sail in over 25.

 

I'm surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.

 

Cheers,

 

Randy

 

 

OMFG this is LAME....

if they want to sail above 50kts - they need to adopt cavitating foil designs.

 

it is - in a very literal sense - not rocket science.

 

They can always give Paul Larsen a ring, for a few quid he will hook them up.



#163 Lysistrata

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Posted 19 September 2013 - 06:42 PM

I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong.


Where "cracked the books" means using other people's calculations without attribution?

 


 



#164 Daiquiri

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Posted 19 September 2013 - 06:47 PM

I am sorry guys, but I feel angry and I want to inform you where you can find the original source of the cavitation as speed limit: http://www.boatdesig...html#post652542 . It is complete with explanatory graphs and arguments.

 

That post was my reply to RHough's inquiry about possible reasons for the speed limit of 23 kts (visible here: http://www.boatdesig...html#post652532)

 

For more number crunching, take a look here: http://www.boatdesig...html#post652615

 

It was a really bitter feeling, to come here at Sailing Anarchy and discover other's name in the signature of an idea of mine. I even feel bad and sad that I had to write this, but the sense of injustice was too big. Sorry again for this moment. If anything, it fits well with the title of the thread...

 

Cheers to all and keep up the good discussion.



#165 RHough

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Posted 19 September 2013 - 06:57 PM

 

I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong.


Where "cracked the books" means using other people's calculations without attribution?

 


 

I opined that this was the reason. I made such a post on boatdesign.net.  I asked for other opinions and did not use anything from Daiquiri's excellent post. I also posted my basic train of thought that lead me to ask the questions.

 

I have been trying to get this topic started in this thread for some time. Daiquiri could have jumped in at any time.

 

I didn't get the thing put on the front page.

 

I had no idea that "credit" was an issue, I am willing to take the heat for my opinions. If I wanted to support a conclusion with a response on the same subject I'd have asked Daiquiri before citing it here.



#166 MR.CLEAN

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Posted 19 September 2013 - 07:02 PM

I don't subscribe to RHough's cavitation hypothesis as pronounced in the SA homepage.

I don't believe that these boats are capable of attaining 50 kts in any wind speed other than (possibly) in ideal and artificial conditions in flat water. They are peaking out at approx 43 kts, and I don't think that by increasing the wind speed max by 7 kts or so will produce another 7 kts max boat speed. The wind speed to boat speed graph is not a straight line, it is a curve with a limit.

It won't, I agree.

 

However it is quite likely that a foil will reach cavitation conditions during a manoeuvre. The result of a foil failure at maximum load would end the match.

 

The bottom line is the boats are much faster than thought possible when the rule was written for a 33 knot limit. There is not enough development time to know for certain what the safe wind limit is. They were designed for sub 40 knot speeds not 45-50.

No, Rule developers expected these to be at least a few ticks faster than the MOD downwind, and those can hit about 40 in big breeze and flat water. As KK said, it's the upwind speeds that have really blown away the designers.  Designers always seem to think they know what they designed, and then sailors always seem to prove them wrong ;)



#167 Daiquiri

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Posted 19 September 2013 - 07:03 PM

I have already asked you too pardon me back on BD.net Randy, and I am doing it here too.

I am sorry, it was an instantaneous sense of bitterness in seeing my idea presented as someone's else which has probably made me over-react.

You have always left me an impression of a honest person in the old-style way, and I am very sure that this was just an unwanted incident. I beg for your pardon again. It happens.

 

However, the important note remains: it is always a good and fair practice to cite the original source of your info. 

 

Cheers



#168 Lysistrata

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Posted 19 September 2013 - 07:11 PM

 

 

I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong.


Where "cracked the books" means using other people's calculations without attribution?

 


 

I opined that this was the reason. I made such a post on boatdesign.net.  I asked for other opinions and did not use anything from Daiquiri's excellent post. I also posted my basic train of thought that lead me to ask the questions.

 

I have been trying to get this topic started in this thread for some time. Daiquiri could have jumped in at any time.

 

I didn't get the thing put on the front page.

 

I had no idea that "credit" was an issue, I am willing to take the heat for my opinions. If I wanted to support a conclusion with a response on the same subject I'd have asked Daiquiri before citing it here.

 

No worries, mate! :)

I just saw an opportunity to have some fun with somebody who is

so vehemently (and correctly) opposed to Oracle's culture of cheating.



#169 RHough

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Posted 19 September 2013 - 07:14 PM

I am sorry guys, but I feel angry and I want to inform you where you can find the original source of the cavitation as speed limit: http://www.boatdesig...html#post652542 . It is complete with explanatory graphs and arguments.

 

That post was my reply to RHough's inquiry about possible reasons for the speed limit of 23 kts (visible here: http://www.boatdesig...html#post652532)

 

For more number crunching, take a look here: http://www.boatdesig...html#post652615

 

It was a really bitter feeling, to come here at Sailing Anarchy and discover other's name in the signature of an idea of mine. I even feel bad and sad that I had to write this, but the sense of injustice was too big. Sorry again for this moment. If anything, it fits well with the title of the thread...

 

Cheers to all and keep up the good discussion.

I'm sorry, it never crossed my mind that you would feel this way.

 

I have posted this apology on boatdesign.net:

I absolutely had no idea that anyone would take exception. None.

I did not cite this post and given the cesspool SA is I would not without permission.

I will do anything within my power to right any wrong is have done. 

Please trust me that getting on the front page of SA was done without my knowledge or permission.

Putting Daiquiri's actual post up means that all the people that are/will debate with what I posted as my opinion "I think" will attack Daiquiri. He has taken credit for it on SA and I will post that yes his post confirmed my basic premise, that it was not pure design error or knee jerk reaction that is behind the wind limit.

I also asked the same questions on SA and no one responded. The first stage guesses that the wind limit change reduced force by 50% or so are weeks old.

If anyone wanted what ever credit posting in SA gets, they were free to engage at that point.

I have been hammered and insulted over trying to get unemotional discussion going on this topic since the first postponement.

I sincerely apologize to you Daiquiri. I had no intention of taking credit for ideas not my own and certainly would not have quoted your work without attribution and permission.

Sincerely
Randy



#170 Zissou

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Posted 19 September 2013 - 07:22 PM

In iceboat regattas we have a wind limit around 20 knots since the most efficient vessels approach speeds 5 times the speed of the wind over the ice. I'm guessing this helps to prevent low earth orbit (LEO).  Also it has to be warmer than 10 degrees. Figure out the wind chill yourself.

 

Photo by Gretchen Dorian

Attached Files



#171 Daiquiri

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Posted 19 September 2013 - 07:23 PM

As I replied to you back on BD.net - a good beer will fix everything, if we ever happen to meet in person. Up till then, I apologize again for all this fuss. You seem to be a good person, Randy. Let's carry on with the discussion about sailboats and the AC.  :)

All the best,

 

Slavi



#172 dogwatch

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Posted 19 September 2013 - 07:41 PM

 

I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong.


Where "cracked the books" means using other people's calculations without attribution?

 


 

 

 

First thing, those words are RHough's not mine. Your moral outrage is a little strained when it carelessly puts someone else's words in my mouth.  Second thing, see his post #169.



#173 ibsailn

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Posted 19 September 2013 - 07:53 PM

RHough -- is it really "cavitation" that is the problem or air ingestion, or something else?  Cavitation is the "boiling" of water due to low pressure.  Traditionally this is the domain of Propellers and this is where my knowledge comes from. cavitation is usually caused be extremely high loading of an water borne foil.  In propellers the solution is to adjust the pitch and use a bigger area propeller to distribute the load over a bigger area.  If it is truly cavitation, I would think they could solve the problem by using lower angle of attack, reducing loading on the foils, and avoiding cavitation.  This may actually require larger areas to get the same total lift with lower pressures, but not exactly sure.

 

Air ingestion, caused from surface tension of water, and the air feeding along the foil surface is a different issue, but causes the same problem of the foil operating in a gas instead of a liquid.

 

Maybe I am missing something as cavitation of non-rotating foils is not my forte, but in theory it is all the same thing.

 

Thanks.

 

I've run the simple math on this, and it turns out that at around 46 knots, even a straightforward symmetric NACA 0012 style foil at zero angle of attack will produce pressures that are low enough for cavitation to start happening.  So any lifting foil, even a far more suitable cambered profile, will start to get into cavitating conditions at around 46 knots.  Cavitation is definitely an issue, and even a lightly loaded surface will run into difficulties.   It is probably no coincidence that the boats accelerate very easily to around 45 knots, but not significantly more, and that the sailing speed record got stuck at around that level until ski-type (ie. no liquid on the low-pressure side) lifting surfaces were made to work.

Interesting....I am surprised that there is enough taper on a 0012 foil to create that low of a pressure without any angle of attack.....Seems counter intuitive to me since local velocities of propellers are much higher than 46 knots and can operate in sub-cavitation regions while still providing significant lift (i.e angle of attack)....As far as cavitation causing catastrophic failure goes, most propellers are designed to operate with 5-10% tip cavitation for their entire lives.  It will cause some minor errosion, but the alternative is larger propellers and much more expensive reduction gears.  A little bit of cavitation on these foils would not be a problem....Lots of cavitation, particularly on the rudders could cause control issues.

 

My company does have a few boats capable of 50 kts with traditional lifting foils (foil assisted power cats).  The foils aren't strictly naca shapes as they have been adjusted a bit, but are pretty close, and I am not aware of cavitation problems on those boats.



#174 Topmast

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Posted 19 September 2013 - 07:58 PM

"Since the shock waves formed by collapse of the voids are strong enough to cause significant damage to moving parts, cavitation is usually an undesirable phenomenon. It is very often specifically avoided in the design of machines such as turbines or propellers, and eliminating cavitation is a major field in the study of fluid dynamics."

 

Airplane crash because of cavitation and they are designed to fly faster than 50 knots... High frequency vibration can be very bad...



#175 dogwatch

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Posted 19 September 2013 - 08:00 PM

Airplane crash because of cavitation

 

Huh?

 

Cavitation is the formation of vapour cavities in a liquid – i.e. small liquid-free zones ("bubbles" or "voids") http://en.wikipedia....wiki/Cavitation



#176 Lysistrata

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Posted 19 September 2013 - 08:03 PM

 

 

I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong.


Where "cracked the books" means using other people's calculations without attribution?

 


 

 

 

First thing, those words are RHough's not mine. Your moral outrage is a little strained when it carelessly puts someone else's words in my mouth.  Second thing, see his post #169.

 

Calm down, pussy.

See my post #168.



#177 CorrosionX

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Posted 19 September 2013 - 08:59 PM

The best part of this whole argument is looking forward to what might be possible in v 2.0 of these boats as more time and testing develops better foils. I've told my pals in Aukland to start stocking up their liquor cabinets...



#178 'moondance44

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Posted 19 September 2013 - 09:18 PM

So what happens when Oracle asks ETNZ to agree to raise the wind limits, and they say no. Does that make them pussies who dont want to race in conditions where they might lose, or heroes who are doing what it takes to win the series? Look at the email exchange below and decide for yourself
From: Richard Slater (Oracle)
Sent: Monday, 16 September 2013 11:59 a.m.
To: Russell Green (ETNZ)
Subject: Proposed Protocol Amendment
Gday Russell,
Attached is a proposed protocol amendment in relation to wind limits. The proposed changes are to:
1. Increase the wind limit to start a race from 23 to 24 knots.
and
2. Removed the fixed wind speed limit after starting.
The wind limits set by Iain have increased each month as the teams gained more experience. We now believe that both teams are capable to start races in conditions that are 1 knot higher. So this is in line with the safety committee proposals of increasing the limits over time.
Once a race is started, it makes no sense to abandon it. Removing this requirement still allows ACRM to abandon for safety reasons but no longer provides such a hard limit. If we can agree on this we can talk to Iain about amending the event permit.
I look forward to your comments.
Regards
Richard
Rding to Gary From: Russell Green
Date: 16 September 2013 18:40:33 PDT
To: Richard Slater
Subject: RE: Proposed Protocol Amendment
Hi Richard
Our guys have talked about your proposal and would have considered it before racing started but now that a substantial number of races have been sailed and one abandoned we think it is no longer appropriate to make changes.
Cheers
Russell


According to Jobbo moments ago, who spoke withe the judges, this exchange is irrelevant. They've been told the USCG will not allow an increase in the wind speed cap due to the Artemis tragedy. This is unbelievable and I blame it on Obama who as Commander in Chief heads the USCG.

#179 catsailordude

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Posted 19 September 2013 - 09:47 PM

Dumbass. It's a 5 minute average "Sailing Wind Speed" that determines the limit.

LMAO

 

The limit is set ...  the sailing wind speed is compared to the limit

 

who were you calling dumbass?

 

Prior to the start it is a 30 second average.  It becomes a 5 minute average only after the start.

 

A wind limit is necessary but the 30 second average is just ridiculous.  The wind was averaging 17 knots today--perfect conditions for these boats--when racing was cancelled due to a tiny little blip in the wind speed.  

 

Very unfortunate.  



#180 phlegmatic

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Posted 19 September 2013 - 10:30 PM

There's a great sailrocket article in wired that talks about how they built a foil that uses air to simulate the foil shape and avoid cavitation at 50 knots. I might not 100% get it but it's a great article.

 

I'm quoting the article:

 

"Larsen’s trick foil—the one we have just rammed into the ground—is different. It is V-shaped in cross section. It’s a simple wedge. At low speed, water generally flows around it just as one might expect. The seas are parted by the foil’s leading edge and then collapse again into a turbulent mess once it passes. At higher speeds, however, something interesting starts to happen. The foil actually digs a trench, creating, just for a split second, a hole in the water. The faster it goes, the deeper the hole.

The hole is important, because the water flows around it. The funny-looking wedge foil now has a tail—made of air. In cross section it suddenly takes on the familiar teardrop shape. But cavitation can’t take hold of this teardrop, because its trailing edge is made of nothing. That’s the theory, at least."

http://www.wired.com...sailrocket/all/



#181 Kanting_Kid

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Posted 19 September 2013 - 11:28 PM

The designers and writers of the rule are on record as not anticipating either full foiling or speeds so high. Feel free to talk with them.

I do talk to them everyday ;)

Its obvious now that your ideas were not your own. It confirms what I first thought as you can see from my first replies to your 'hypothesis'.

Good onya for being enthusiastic about it. But get your facts right before you claim it as gospel. There is too many dumb people and journalists on these forums that will eat that shit up.

Both teams have done 50knots+ in their own time and conditions. Don't worry about cavitation. Worry about a hydraulic or rigging failure. Much more risk and huge consequences if the worst happened. 



#182 Chris 249

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Posted 19 September 2013 - 11:29 PM

Vee-foils are far from new; for example they were used on Rob Brown's 18s in the mid '80s, IIRC. The issue, as I understand it, is that they are less efficient at lower speeds and therefore probably not the sort of thing an AC72 would use.



#183 ~Stingray~

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Posted 19 September 2013 - 11:34 PM

+1
The Apparent Wind is the issue on these boats, not the '33.'

#184 Abbo

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Posted 20 September 2013 - 12:10 AM

 

I just have difficulty accepting that the design concept, class rule and protocol were all that far wrong. A single designer missing by that much, certainly. For the entire AC34 team from concept to rule to execution to have made that large an error beggars belief.

 

This very much says that M&M didn't know what they were doing when the wrote the rule and CCYC didn't know what they were doing when they wrote the protocol. It also vindicates the teams that cited safety as the reason for not competing. It means that GD and RC and PC and PB unknowingly put their people at risk or they would not have agree to the protocol or whatever document contains the original limit. This paints a picture of gross incompetence at what is supposed to be the top level of sailing sport.

 

A couple of comments. One, as someone else as pointed out, there was originally going to be a second smaller wing. Dropped by competitor agreement for cost reasons.

 

Secondly, if you haven't read it, read http://www.sailingwo...riting-the-rule Amongst other things, it makes it clear how the rule was a compromise developed to satisfy several influencers.

I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong.

 

The boats ended up being faster than they predicted, i.e. the designs were too good. :-)  This put them dangerously close to putting the foils into cavitation speeds (~50+) that could have lead to real control problems.

 

Basically they want to limit boat speed to under 50 knots to stay safely out of foil cavitation speeds. The boats can sail over 2x wind speed and in some ranges are close to or at 3x wind speed the TWS needed to keep them below 50 knots is in the 22-24 knot range.

 

The wind limit for safety was not a reaction to the Artemis disaster as I assumed incorrectly. I had assumed the limit was for structural concerns not an unforeseen design challenge.

 

If they want higher wind speed limits they have to lose the foiling to remove the "50 knot barrier"  or they can lose the wing to reduce the top speed of the boats to under 3x wind speed.

 

If they want to keep the full foiling and hard wings they are stuck with a low wind speed limit until they solve the cavitation issue. Sort of ironic that the faster the boat is relative to wind speed the lower the safe wind speed becomes. If indeed the wind limit was lowered due to concerns about foil cavitation then they got it right and the engineering math supports it.

 

It is not about being pansies, or poor design, or reaction to the Artemis disaster. It is about unforeseen design success.

 

Stop bitching about the boats being to fragile to sail in 30+

Start celebrating that they are too fast to sail in over 25.

 

I'm surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.

 

Cheers,

 

Randy

You are right about the foils approaching stall speed being very dangerous. But that has nothing to do with the wind limits. The wind limits were reduced immediately after the Artemis tragedy. They were put in place because of the bear away maneuver being so dangerous with the boats general tendency to nose dive. They nose dive because the rig height is double the length of the hull. It really IS that simple. Coutts and Ellison were stupid for putting such massive rigs on these boats when everyone knows it blows 20-25 in Sanfran about 95% of the time. Remember the preaching about having a boat where the racing would rarely need to be a called off? A hundred foot rig would have been more than enough.

 

The other reason to lower the limits was to keep the loads under control. As wind speed increases the loads go up exponentially. The difference in load between 20 and 25 knots is massive. It was excessive load which was the root cause of the Artemis tragedy. Before we go slapping Coutts and Ellison on the back for their vision and foresight let's not forget about the fact that someone died in this AC. Formula one hasn't had a death since Senna in 1994. These boats are far too dangerous to have any future in our sport. These guys are human and have wives and families. Their lives should not be at risk just for going to work.

 

Abbo.



#185 RHough

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Posted 20 September 2013 - 12:39 AM

The designers and writers of the rule are on record as not anticipating either full foiling or speeds so high. Feel free to talk with them.

I do talk to them everyday ;)

Its obvious now that your ideas were not your own. It confirms what I first thought as you can see from my first replies to your 'hypothesis'.

Good onya for being enthusiastic about it. But get your facts right before you claim it as gospel. There is too many dumb people and journalists on these forums that will eat that shit up.

Both teams have done 50knots+ in their own time and conditions. Don't worry about cavitation. Worry about a hydraulic or rigging failure. Much more risk and huge consequences if the worst happened. 

I didn't claim anything as gospel I said "I think I have a good reason for the wind speed limit being set where it is."

 

What my friend on boatdesign.net posted was about foil cavitation and the "50 knot barrier" I had already done enough basic math to have a general idea. I hardly think anyone that has followed Hdroptre and speed sailing would find the idea of cavitation at or near 50 knots as news. For it to become a consideration for these boats is as feasible as any other objective reason for the reduced speed limit.

 

The gospel as near as I can tell is the unforeseen top speed of the boats (as published by the rule writers) has created design challenges. The loads at the higher speed have likely used much of the safety margin that was built into the design with a lower top speed.

 

Would you agree with that broad stroke?

 

Would you agree that my characterization of the lower wind limit being driven by unexpected design success?

 

I think it is pretty funny that no one wanted to enter into a discussion of objective of reasons for the wind limit reduction, but no sooner than I stick out my neck with my opinion then we have people with enough knowledge to say I'm wrong jumping in.

 

We used to have folk with knowledge that would engage in friendly technical discussion. People that knew more were happy to suffer those of us that know less. I was wrong again to think that I could get one started here as we could in 2009.

 

I'll ask one favor, Do you think an objective case for the 23 knot limit can be made?

 

Thanks,

 

Randy 



#186 White Cracker

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Posted 20 September 2013 - 12:52 AM

You are totally wrong to think cavitation is a safety issue. It is a total speed limiter- but NOT a safety problem. If anything it saves the crew just like a turbo restrictor plate in the WRC .

Wrong.

Cavitation (as opposed to ventilation) destroys foils.  If you think catastrophic foil failure at 50+ knots is not a safety concern you are living in an alternate reality. 

Just ask anyone who has fully loaded a foil on a sailboard in high wind and then had full cavitation - in traffic (i.e. The Gorge). It is a scary moment when full cavitation occurs.



#187 Amati

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Posted 20 September 2013 - 01:29 AM

This AC is as good as it will ever get. The crew work is at the pinacle of human capability,
without degenerating into a rerun of the TV show Jackass. The chance of death in a team sport
that depends on optimum performance of all involved requires peak performance.
Yet the AC has evolved as the sport of gentlemen, and the first rule of command is:
look out for the welfare of your troups.


To paraphrase Falstaff, right....

#188 Abbo

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Posted 20 September 2013 - 02:53 AM

The gospel as near as I can tell is the unforeseen top speed of the boats (as published by the rule writers) has created design challenges. The loads at the higher speed have likely used much of the safety margin that was built into the design with a lower top speed.

 

Would you agree with that broad stroke?

 

Would you agree that my characterization of the lower wind limit being driven by unexpected design success?

 

 

 

I'll ask one favor, Do you think an objective case for the 23 knot limit can be made?

 

Thanks,

 

Randy 

 

Nope, nope and nope. I don't agree with any of that. A 72 footer with a 140 foot rig (hard or soft) was always going to nose dive in 25 +. The 33 knot wind limits were laughable to me right from the very beginning. Blind Freddy could see that they were going to be on the ragged edge of control in 22-25. 33? Give me a break. The AC72's look like they were designed for a Valencian winter, or summer on Long Island Sound, not San Francisco in summer.

 

I agree that more than likely the first Oracle boat the Artemis boats were not designed or engineered with foiling speeds in mind. So for them you could make a case that the design success of TNZ has caused all sorts of strength and structural issues for their competition as they tried to keep up. Team NZ were hitting 40+ knots within days of beginning to foil so they knew exactly how fast they were going to be going a very long time ago.

 

Abbo.



#189 RHough

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Posted 20 September 2013 - 03:33 AM

The gospel as near as I can tell is the unforeseen top speed of the boats (as published by the rule writers) has created design challenges. The loads at the higher speed have likely used much of the safety margin that was built into the design with a lower top speed.

 

Would you agree with that broad stroke?

 

Would you agree that my characterization of the lower wind limit being driven by unexpected design success?

 

 

 

I'll ask one favor, Do you think an objective case for the 23 knot limit can be made?

 

Thanks,

 

Randy 

 

Nope, nope and nope. I don't agree with any of that. A 72 footer with a 140 foot rig (hard or soft) was always going to nose dive in 25 +. The 33 knot wind limits were laughable to me right from the very beginning. Blind Freddy could see that they were going to be on the ragged edge of control in 22-25. 33? Give me a break. The AC72's look like they were designed for a Valencian winter, or summer on Long Island Sound, not San Francisco in summer.

 

I agree that more than likely the first Oracle boat the Artemis boats were not designed or engineered with foiling speeds in mind. So for them you could make a case that the design success of TNZ has caused all sorts of strength and structural issues for their competition as they tried to keep up. Team NZ were hitting 40+ knots within days of beginning to foil so they knew exactly how fast they were going to be going a very long time ago.

 

Abbo.

Good point. The designers did say that after the first boat was foiling they changed the design of boat 2 with full foiling in mind. I would assume the second gen boat would have a hull and rig designed for the 45+ knot speeds that the foils allowed. I'd assume Oracles #2 boat is also designed for the 45+ knot sailing speeds.

 

If the boats were indeed designed for 45+ knot speeds what concerns are there that would justify the lower wind speed limit?

 

I don't agree with Blind Freddy unless everyone that agreed to the rules also missed something that is so obvious to you. They could have agreed to the shorter rig instead of the taller rig in that case.

 

Randy



#190 In the Jailhouse Now

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Posted 20 September 2013 - 03:48 AM

If the boats can handle more wind but the sailors cannot handle the boats.

 

Why not do what F1 did at Indy a few years back and just call the Race as a JOKE?

If the drivers cannot handle the boat/cars, IT"S OVER.

 

Larry said he wanted the AC to be more F1 like.



#191 justinnyc

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Posted 20 September 2013 - 03:56 AM

 

I just have difficulty accepting that the design concept, class rule and protocol were all that far wrong. A single designer missing by that much, certainly. For the entire AC34 team from concept to rule to execution to have made that large an error beggars belief.

 

This very much says that M&M didn't know what they were doing when the wrote the rule and CCYC didn't know what they were doing when they wrote the protocol. It also vindicates the teams that cited safety as the reason for not competing. It means that GD and RC and PC and PB unknowingly put their people at risk or they would not have agree to the protocol or whatever document contains the original limit. This paints a picture of gross incompetence at what is supposed to be the top level of sailing sport.

 

A couple of comments. One, as someone else as pointed out, there was originally going to be a second smaller wing. Dropped by competitor agreement for cost reasons.

 

Secondly, if you haven't read it, read http://www.sailingwo...riting-the-rule Amongst other things, it makes it clear how the rule was a compromise developed to satisfy several influencers.

I cracked the books a bit and ran some numbers yesterday. I think I have a good reason for the wind speed limit being set where it is. Wow was I wrong.

 

The boats ended up being faster than they predicted, i.e. the designs were too good. :-)  This put them dangerously close to putting the foils into cavitation speeds (~50+) that could have lead to real control problems.

 

Basically they want to limit boat speed to under 50 knots to stay safely out of foil cavitation speeds. The boats can sail over 2x wind speed and in some ranges are close to or at 3x wind speed the TWS needed to keep them below 50 knots is in the 22-24 knot range.

 

The wind limit for safety was not a reaction to the Artemis disaster as I assumed incorrectly. I had assumed the limit was for structural concerns not an unforeseen design challenge.

 

If they want higher wind speed limits they have to lose the foiling to remove the "50 knot barrier"  or they can lose the wing to reduce the top speed of the boats to under 3x wind speed.

 

If they want to keep the full foiling and hard wings they are stuck with a low wind speed limit until they solve the cavitation issue. Sort of ironic that the faster the boat is relative to wind speed the lower the safe wind speed becomes. If indeed the wind limit was lowered due to concerns about foil cavitation then they got it right and the engineering math supports it.

 

It is not about being pansies, or poor design, or reaction to the Artemis disaster. It is about unforeseen design success.

 

Stop bitching about the boats being to fragile to sail in 30+

Start celebrating that they are too fast to sail in over 25.

 

I'm surprised that none of the SA techies from AC33 had done the figures to reach this conclusion.

 

Cheers,

 

Randy

doesnt seem like we'd see it this cup, but with interchangeable foil tips, a fence doesn't seem out of the question? 



#192 rosco08

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Posted 20 September 2013 - 04:19 AM

ahhhh......TNZ built a foiler to to rule as in the inital wind limits!! wasnt that 30 odd knots. I think they were prepared and happy to race up to the limit.. watching them heading out the harbour in auckland in very fresh winds id say they were up for it and could sail in that wind....the boat and foils were set up for it OR not so much. I think youd find TNZ would race round a course in 30+ OR would not. Build a boat for the rules and your ok.



#193 us772

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Posted 20 September 2013 - 04:36 AM

Safe to say none of the wives and children of the sailors are clamoring to raise the limits.

I imagine the shore crews are good with the wind limits as they stand.

 A look back - 



#194 gliderguider

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Posted 20 September 2013 - 04:37 AM

If the AC goes to NZ they get to set the limits. If they choose 33 kts your going to end up with reef-able sails, or smaller wings, or broken boats. THere is no magic here, except the stunning sight of a foiling sailboat nearly setting world records while dueling with a competitor, and the TV coverage to bring it to life. The later is something NZ just won't have the resources to duplicate.

 

I'm unsure what it is that NZ is supposed not to have the resources for.

 

They can clearly field an entry.

Running a regatta doesn't depend a lot on what boats are sailing in it.

The TV coverage software *is* NZ made.

Getting a couple of choppers to fly around taking video isn't a big deal and has been done, by the way, for the obscure sport of glider racing: 

 



#195 bmyers

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Posted 20 September 2013 - 04:53 AM

breaking the cavitation barrier seems like a good challenge that these well funded teams could solve for the rest of us.



#196 RHough

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Posted 20 September 2013 - 05:01 AM

You are totally wrong to think cavitation is a safety issue. It is a total speed limiter- but NOT a safety problem. If anything it saves the crew just like a turbo restrictor plate in the WRC .

<iframe width="640" height="390" src="//www.youtube.com/embed/H7hhf9Xj550" frameborder="0" allowfullscreen></iframe>

 

JS mentioned the boats were close to or up against a cavitation limit for speed about 20 minutes in

 

Are you saying that when the the profile that Oracle is using started to cavitate it is a non violent event similar to a foil profile that has a soft progressive stall and quick reattachment? That fits with the foils and cavitation being a soft limit of speed. Not all foils are so forgiving.

 

There is lots of evidence that cavitation can cause physical damage to the foil that has lead to the foils failing. If you say this is not an Issue with Oracles foils I cannot dispute it.

 

Since the first boats were foiling well before the second boats were built, is it safe to assume the second gen boats were built with 45+ knot speeds in mind?

 

If that is true, what would require such a low wind speed limit?

 

Sorry we got off on the wrong foot.

Randy



#197 dogwatch

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Posted 20 September 2013 - 06:58 AM

I'll ask one favor, Do you think an objective case for the 23 knot limit can be made?

 

An objective case can be made for a limit (and I don't feel the need to repeat that well-rehearsed argument). I don't think that an objective case can be made for any particular figure, however a limit requires a figure.



#198 dogwatch

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Posted 20 September 2013 - 07:04 AM

Just ask anyone who has fully loaded a foil on a sailboard in high wind and then had full cavitation - in traffic (i.e. The Gorge). It is a scary moment when full cavitation occurs.

 

Stall or entrained air on a fin ("spinout") is not cavitation. "Spinout" has been an issue since the year dot, when we thought 15 knots on a sailboard was pretty quick.



#199 Daiquiri

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Posted 20 September 2013 - 07:45 AM

The point about the cavitation was not the possible damage to the foils. Although, since I work a lots with boatyards and see a lots of stuff around, I can assure you that cavitation does create very visible damage to overloaded propeller blades and hull plating near prop tips.

 

The point was that an extensive cavitation can be potentially catastrophic if it happens on the rudder elevator, because cavitation degrades the lift force generated by the foil. If it happens to the elevator, the boat is left with no means to counter the pitch-down moment from the wing sails. Hence, a pitch-pole.

 

The same is valid for the ventilation (which causes a much more abrupt decrease of lift), although it is a completely different physical problem.



#200 mili

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Posted 20 September 2013 - 08:44 AM

So baiscally you are saying that the teams all failed to design for the 33kts wind limit?

When M&M deisgned foiling ENTZ boat they blew the design parameters and designed a boat that was unsafe at 66% of the speed?

 

The Prada team was the first ones to figure it out? Remember they set the wind limits right after the accident with their threat to walk if the wind limit was not lowered.

Judging from the math from foiling speeds and the public comments about what they thought the top speeds would be the rule was fine. When they started designing the foils for the AC72 they exceeded their own estimates.

 

I can't fault anyone for not having a crystal ball. You can bet that if the rule was written today it would be different.

 

What I'm saying is that the 33 knot wind limit became absurd once the foiling challenger was met and the boats started cracking 45 knots.

 

To foil safely in 33 knots you need to have control at 50+ boat speeds. AFAIK very few people have that design ability and budget.

 

Isn't nice when you exceed your own expectations and your design success requires a reset of rules?

IMO you're right. They exceeded their expectations. Originally the rule was written not having foiling in mind, but voila.






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