Isn't it just above 50kts where they start cavitating? I don't think they're getting near that upwind?
Emirates Team New Zealand.
- Thread starter Salty Seacock
- Start date
enigmatically2
Super Anarchist
That's where I am not sure when it hits. So foil drag is the limiting factor upwind, but cavitation down? Not sure of either
robingimblett
Member
- 59
- 77
The deeper foil box for AC37 gives approx 100mm longer lever from foil centreline to hull centreline when the foil arm's at 64 degrees. That's about 1.7% longer lever but a 20+% drop in hull & mast weight. If the foil flaps will allow the centre of lift to be moved to midway along the leeward half of the foil, the lever length increases by another metre......
JALhazmat
Super Anarchist
You can get cav at much lower speed if the flow detaches from a surface thats causing a massive pressure differential tripping from laminar to detached flow
on a propeller where the angle of attack is steeper at the root you can have cavitation occuring at sub 15 kts, where as at the tip of the propeller it would be much higher
So you can’t just say it happens at a specific speed as there are nearly infinite variables. Taken into account in the foil selection, the junction to the arm etc.
it’s easier for the teams to talk about it in a general term than the actual detail as 99% of the audience find it a hard concept to grasp let alone that it can happen at low speed In a specific location let alone just when doing 50..
I remember the good old days when people thought it happened at 40 knts and now that is seen as pretty pedestrian
on a propeller where the angle of attack is steeper at the root you can have cavitation occuring at sub 15 kts, where as at the tip of the propeller it would be much higher
So you can’t just say it happens at a specific speed as there are nearly infinite variables. Taken into account in the foil selection, the junction to the arm etc.
it’s easier for the teams to talk about it in a general term than the actual detail as 99% of the audience find it a hard concept to grasp let alone that it can happen at low speed In a specific location let alone just when doing 50..
I remember the good old days when people thought it happened at 40 knts and now that is seen as pretty pedestrian
I agree with Jal, 50kts is regarded as the area cavitation starts to rear it's ugly head but it is dependant on the foil design, some earlier others later. It does appear that the boundry is now higher than some originally thought and it maybe possible to push it even further before it's a problem. I still think it will not be a issue this cup, early lift off in waves will probably be a lot more important than peak speed and you maybe able to nearly have your cake and eat it, with something thats does both pretty well as claims of 50kts are already common place.
enigmatically2
Super Anarchist
So even as a GB supporter, with what we know the re-birth of the w does seem odd. They aren't dumb or lacking in expertise as some of our more intellectually challenged fellow think, so what is it they think is worth going after?
Is it purely that ability to lift out at the very light end of the spectrum? Will it really have gains because of the waves? Can they re-engineer.a w to a thin foil and get the best of both?Or is it something else I'm missing?
Is it purely that ability to lift out at the very light end of the spectrum? Will it really have gains because of the waves? Can they re-engineer.a w to a thin foil and get the best of both?Or is it something else I'm missing?
buckdouger
Anarchist
- 916
- 412
nav
Super Anarchist
- 14,165
- 637
You talk as if there's a proven upside to this 'thing'.....where do you take that from?
You even speculate about where it works best.....based on what info?
As to the non-intelligence of the commentators and the non-dumbness of the team's (latest and fast-fading) set of experts, one has to say a) look at the record b) look (if your eyes can stand the pain) at the latest examples of their desperation combined with bad engineering; foredeck cockroach, or the foil that looks like a skiing accident x-ray, take your pick.....
Neither will be on the next RB
edit: sorry for the thread pollution
Last edited:
Forourselves
Super Anarchist
2003, the Hula. That design team weren't dumb, it was the idea that indeed was dumb, hence it got removed and the boat reinforced after the 2003 cup because that boat was a failure, designed by guys considered experts in their fields, and everyone raved about the Hula being some revolutionary new concept, when in fact it was rubbish.
But they had to be after something too right? No one knew what it was exactly that they thought they were after, but it doesn't matter at the end of the day. The hula was a dumb idea and it produced dumb results. The entire boat, again, designed by experts, was a failure.
Dumb ideas are dumb ideas whether they're designed by experts or not.
enigmatically2
Super Anarchist
I doubt there are many people on here capable of deciding what is a dumb before the design teams. And 4braincells certainly isn't the one.
It maybe a bad idea or it may not. Time will tell
It maybe a bad idea or it may not. Time will tell
Forourselves
Super Anarchist
Sticks and stones my friend, but at the moment, you're the one howling at the moon while I'm the one that has something to base my argument on.
Your entire argument is "they're experts so they know what they're doing".
2 words... The Hula.
enigmatically2
Super Anarchist
They must have some good reason. But not all good ideas in engineering work. We will see. Your argument (as your view on every argument) is that if GD or NZ do it, then it's right. If not then it's wrong. And that NZ are best at everything and "dominate" all sailing, cricket and rugby competitions.
And when proved wrong deny ever having said anything of the sort.
That is not a sound basis
Still waiting for your strategy expertise
JALhazmat
Super Anarchist
Holy fuck, don’t read the forum when your not logged in.., actually grateful to have been bitch blocked if the recent contributions are anything to go by
Sailbydate
Super Anarchist
RD: "We have to put our big boy pants on - Barcelona is going to be bumpy"
jaysper
Super Anarchist
In fairness to that design team, the challengers pressured the shit out of the measurers to force ETNZ to increase the gap, which dropped its effectiveness.
They would still have lost because the boat was made of fine china and Barker realistically wasn't up to the job.
JALhazmat
Super Anarchist
Not up to the job? yet many cups later he is still employed.
how many other skippers are still going?
how many other skippers are still going?
Priscilla
Super Anarchist
- 4,654
- 3,494
Don't think Barker the Blubberer has got his hand on Ernies wheel for AC37 but James "Pitbull" Spithill is still going strong it must be the Red Bull.
jaysper
Super Anarchist
There's a WORLD of difference in being allowed to play the game and bringing something that makes you a match winner.
I like Barker, I really do and am on record here saying that ETNZ handled his "retirement" poorly, but he DID need to go.
Look at Ronaldo at the last cup vs the cup before.
In the last cup he rode the pines, in the cup before that he was a God.
Sailbydate
Super Anarchist
Unless you're particularly unlucky, old age catches up with everyone. Even, Larry Ellison.
