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hemmy007
Joined: 10 May 2002 Posts: 101
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Posted: Thu Oct 18, 2012 3:12 pm Post subject: |
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us44eric wrote: | To each, his or her own, but man I think the America's Cup high speed Cats are amazing in the SF Bay.
Speaking of AC 45s fi
As for AC 72s --
Team USA did indeed make history -- they were the first to capsize an AC 72. And judging from reports, the iwindsurf graph, the ebb, and the video footage, it seems it was pretty windy and choppy at the time and location of the capsize, even for Bay standards. Of course, the AC 72 is unlike virtually all other 72 footers. And similar length boats that are anything similar to AC 72s (namely the previous gen AC multihulls) didn't sail in nearly as much wind and chop.
I think the devastating crash of USA's 1st AC 72 (reportedly only $8-10 million surprisingly) is a blow. I suppose it's better now than later. And not really for the same reasons, but I do agree that this is getting fun!
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As I was saying in August on the same subject, old AC thread:
PostPosted: 28 Aug 2012 20:42
Post subject: America'sCup
mac wrote:
John Craig (race director) argued that the 72 foot length of the hulls for next year would be long enough that the voodoo chop at Crissy would not affect them. But he also thought that the 45's would be long enough.
Looking forward to seeing the photos
soon that will refute this point.
Ouch, 72's on the pitch-pole-roll ! |
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LeeD
Joined: 12 Jun 2008 Posts: 1175
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Posted: Thu Oct 18, 2012 3:36 pm Post subject: |
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I would imagine any sailing vehicle that doesn't allow for sail twist, has a mast twice as long as the hull, has a narrow bow and no deflectors/spoiler's/trimtabs, would be suceptitble to pitch poles, wouldn't any of you?
Sometimes, the scientists/engineers can't see the truck right in front of their cars, so busy they are making calculations and exotic equations. |
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SwellRipper
Joined: 21 Apr 2009 Posts: 193 Location: Channel Marker 11
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Posted: Thu Oct 18, 2012 5:06 pm Post subject: pitch pole? |
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Is "pitch pole" of a catamaran similar to "catapult" on a windsurfer, or can someone explain it? Thanks. _________________ Carve the face! |
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dllee
Joined: 03 Jul 2009 Posts: 5329 Location: East Bay
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Posted: Thu Oct 18, 2012 5:19 pm Post subject: |
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YES....
For experts, it happens most often after an upwind beat, just after turning hard downwind, the sail loads up, the mast drives the nose of the board downwards, the rider (s), didn't get far enough back, the wind overpowers the ability of the sailor (s) to handle the loads, the nose digs down into the water, the boardspeed slows drastically, they go over the bars. |
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BRIMAR
Joined: 03 May 2004 Posts: 115
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Posted: Wed Oct 24, 2012 12:24 am Post subject: |
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Here's a Video from the 45 Capsize and the comments I wrote
(Brian Marshall)
with all the negative replies I felt like My good Friend LeeD
But like Demond I held my ground and was proven correct
http://www.youtube.com/watch?v=Bxs2Ra9mWGQ
Have a look at the comments!
Thanks,
BRIMAR |
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jse
Joined: 17 Apr 1995 Posts: 1460 Location: Maui
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Posted: Wed Oct 24, 2012 1:22 pm Post subject: |
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Before I windsurfed I raced Hobie 18's. My sail number was 862, meaning it was the 762nd production 18. (The first 100 were prototypes.) I was told it was not possible or at least very difficult to pitchpole the thing. I had pitchpoled 16's and Prindles before. The reason for the claim on the 18 was that the bows of that boat were very deep, and rose way above the water. It really cut through chop and swell nicely, much better than the 16's did. But I pitchpoled that thing numerous times. The reason was inattentive crews manning the jib. If I saw a pitchpole situation I would instinctively change my stance to prevent slipping on the rail (we were always out on the trapeze). My crew would lose their footing, get swung out over the bow as the boat decelerated rapidly, and literally pull the boat over on top of them. We had to be going seriously fast and we had to undergo serious deceleration. But it happens.
I don't see how those 72 footers can expect not to pitchpole with the low bows that look like they just want to dig in, the fixed sail (no twist and longer than the boat), and the fact that crew positioning will have little effect on the trim of that boat in a pitchpole situation. In other words, not much they can do to prevent it when it starts to happen.
Should be fun to watch. It was fun last Tuesday for all of us at Crissy.
Steve |
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hilton08
Joined: 02 Apr 2000 Posts: 506
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dllee
Joined: 03 Jul 2009 Posts: 5329 Location: East Bay
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Posted: Sun Oct 28, 2012 5:12 pm Post subject: |
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What really astounds me is that after 30 years of windsurfing sail twist ideas, these guys chose not to imcorporate twist into their wing masts.
Didn't we go thru this already? Shouldn't they learn from experience? Or are they all just engineers/weatherman who never look outside beyond their drawing board and computer screens? |
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DanWeiss
Joined: 24 Jun 2008 Posts: 2296 Location: Connecticut, USA
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Posted: Mon Oct 29, 2012 4:23 am Post subject: |
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WRT the pitch-poling of Oracle 17, there is a terrific and highly technical discussion of that subject on www.sailinganarchy.com 's forum.
Remember, the AC 72s are foiling and 17 tended to exhibit a great deal of twist across its hull structures. That twist appears to have contributed to plowing the windward hull and contributing greatly to the flip. TENZ appears better balanced and can foil for very long periods of time. Oracle 17 seemed to be far less balanced.
Consider the role bow volume plays. One one hand, a higher bow volume will prevent the bow stuffing and diving but will cause the bow to stop dead once buried.
Foiling aside, stuffing it is part of the game. It can be very appealing to back off when the bow goes under a bit, but that itself can cause a flip due to rig inertia. Sometimes you must just keep pressing through and hope things stay upright knowing sometimes it won't. _________________ Support Your Sport. Join US Windsurfing!
www.USWindsurfing.org |
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dllee
Joined: 03 Jul 2009 Posts: 5329 Location: East Bay
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Posted: Mon Oct 29, 2012 11:58 am Post subject: |
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Perhaps the inherent instability of the cat design?
Those big catamarans sailing from Spain to WestAfrica, averaging 33 knots, what were they really? Were they tri hulls? |
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