myiW Current Conditions and Forecasts Community Forums Buy and Sell Services
 
Hi guest · myAccount · Log in
 SearchSearch   ProfileProfile   Log in to check your private messagesLog in to check your private messages   RegisterRegister 
AC 72 Wipeout!!!
Goto page Previous  1, 2, 3
 
Post new topic   Reply to topic    iWindsurf Community Forum Index -> Southwest USA, Hawaii, Mexico
View previous topic :: View next topic  
Author Message
hemmy007



Joined: 10 May 2002
Posts: 101

PostPosted: Thu Oct 18, 2012 3:12 pm    Post subject: Reply with quote

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!






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 !
Back to top
View user's profile Send private message
LeeD



Joined: 12 Jun 2008
Posts: 1175

PostPosted: Thu Oct 18, 2012 3:36 pm    Post subject: Reply with quote

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.
Back to top
View user's profile Send private message
SwellRipper



Joined: 21 Apr 2009
Posts: 193
Location: Channel Marker 11

PostPosted: Thu Oct 18, 2012 5:06 pm    Post subject: pitch pole? Reply with quote

Is "pitch pole" of a catamaran similar to "catapult" on a windsurfer, or can someone explain it? Thanks.
_________________
Carve the face!
Back to top
View user's profile Send private message
dllee



Joined: 03 Jul 2009
Posts: 5328
Location: East Bay

PostPosted: Thu Oct 18, 2012 5:19 pm    Post subject: Reply with quote

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.
Back to top
View user's profile Send private message
BRIMAR



Joined: 03 May 2004
Posts: 115

PostPosted: Wed Oct 24, 2012 12:24 am    Post subject: Reply with quote

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
Back to top
View user's profile Send private message
jse



Joined: 17 Apr 1995
Posts: 1460
Location: Maui

PostPosted: Wed Oct 24, 2012 1:22 pm    Post subject: Reply with quote

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
Back to top
View user's profile Send private message
hilton08



Joined: 02 Apr 2000
Posts: 505

PostPosted: Sat Oct 27, 2012 8:39 pm    Post subject: Reply with quote

It looks like they need to build a bigger set of these for the boat.

http://www.murrays.com/mm5/merchant.mvc?Screen=PROD&Product_Code=01-3240&Category_Code=C-RI&Store_Code=MS
Back to top
View user's profile Send private message
dllee



Joined: 03 Jul 2009
Posts: 5328
Location: East Bay

PostPosted: Sun Oct 28, 2012 5:12 pm    Post subject: Reply with quote

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?
Back to top
View user's profile Send private message
DanWeiss



Joined: 24 Jun 2008
Posts: 2296
Location: Connecticut, USA

PostPosted: Mon Oct 29, 2012 4:23 am    Post subject: Reply with quote

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
Back to top
View user's profile Send private message
dllee



Joined: 03 Jul 2009
Posts: 5328
Location: East Bay

PostPosted: Mon Oct 29, 2012 11:58 am    Post subject: Reply with quote

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?
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    iWindsurf Community Forum Index -> Southwest USA, Hawaii, Mexico All times are GMT - 5 Hours
Goto page Previous  1, 2, 3
Page 3 of 3

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You can attach files in this forum
You can download files in this forum

myiW | Weather | Community | Membership | Support | Log in
like us on facebook
© Copyright 1999-2007 WeatherFlow, Inc Contact Us Ad Marketplace

Powered by phpBB © 2001, 2005 phpBB Group