AC Boats

G

getakey

Well-known member
Member
Joined
Oct 11, 2010
RO Number
32379
Messages
2,237
So, the AC boats cannot use spinakers downwind because they go faster than the wind and a spinaker would not work. Still trying to figure out the physics of them going almost 50 mph downwind in 20 mph wind conditions.
They actually create their own apparent wind
 
The wing creates lift just like and airplane... They don't go straight down wind but have to jibe back and forth south wing is at a maximum angle to create a vacuum behind it.

But what do I know... I m still in the 19th century playing with gaffs! :)
 
Yeah, I get the wing part and the lift. Just seems crazy that they can go more than 2X wind speed.
 
quote:
Originally posted by getakey

Yeah, I get the wing part and the lift. Just seems crazy that they can go more than 2X wind speed.

Click to expand...


Well, straight down wind, they can't.
The fast speeds are achieved on a beam reach or broad reach.
 
I understand about straight downwind they can't. However, they are not at a big angle, I'd say maybe 20 degrees max. I think they have their tracks on the web site, I'll take a look

Edit: Reviewed the race tracks. Looks like they go at about a 30 degree angle downwind and more like a 45 degree angle upwind

here's a pic of them on the foils going downwind on Thursday. It was a "solo" race

9323065266_1c29f8ffbe_c.jpg
 
They have a great exhibit on the AC Pier that covers a lot of the physics.

Their highest speeds are at an angle to the wind.
 
They've built a wind-powered vehicle that can travel DIRECTLY downwind faster than the wind, and (with a different propeller) can also travel directly upwind. It will be interesting when the technology can be applied to boats.
 
quote:
Originally posted by getakey

Yeah, I get the wing part and the lift. Just seems crazy that they can go more than 2X wind speed.

Click to expand...


Magic. Each boat has it's own witch.
 
getakey, have the politics, etc settled down now? Are they getting on with the real races and therefore worth the trip to go watch? I'm not interested in seeing one boat race itself.....
 
I don't know if the politics ever subsides, but they are racing.
Starting Aug 6, all races are 2 boat races. That begins the semi finals for the Challengers. It will be Artemis vs Prada in a best of seven series. They will race Aug 6, 7, 10, and 11, Then Aug 12, 13, and 15 if needed.
They moved the start time from 12:15 to 1:15 for these semis. They have a wind limit, so I would bet some of the races might be pushed - they have reserve days for the make-up races.

The Challenger Finals start Aug 17 and there will be 2 races per day in the Finals. New Zealand is already in the finals and awaits the winner of Arteis and Prada.
Then the Full Americas Cup Finals begine Sept 7

Here's the schedule
http://www.americascup.com/en/schedules/races

From a viewing perspective, people onshore have as good if not better view than being out in a boat (except for the start)
Marina Green has a great view. Also the seawall at Aquatic Park, almost anywhere you can get to the water along that stretch.
Actually, the end of Pier 39 has a good view as well.

The only thing you can see at the Americas Cup Pavilion (Pier 27/29) is the finish line. However, they have big screens set up and you can watch the TV coverage which is quite good.
Replays here (scroll down and look for "replays")

http://www.youtube.com/user/AmericasCup
 
I should add that you cannot see the finish from any of the waterfront from Marina Green to Fisherman's wharf.
You can see the finish at the end of the pier at Pier 39 (and from Piers 27/29)
That said there has not been a race yet where they were close at the finish.
That final leg from the downwind mark to the finish line is very short
Map of course and area around
http://www.americascup.com/sanfrancisco/getting-here
 
Wow!!! Thank you so much for all of this info. I may be going to watch one day on a friend's boat.....

Thank you again.......
 
Tips from boat:
If you look on the map from the link above, you will see the light blue spectator boat areas. They allow VIP boats up front, so you cannot get as close as the VIPs :(
So far, the spectator area west of Alcatraz is only good for the start. They go closer to the marina green area on that portion of the course and then go up towards Alcatraz (at least for the downwind legs). So the area east of Alcatraz is better.
Of course that may change depending on tide currents.

However, in the last race we were able to loiter in the no loiter area on the south side of the course. Just had to keep moving slowly. Not sure if they will enforce differently whem more boatas are out.
We watched most of the race from there adn then motored east back around Pier 39 to Pier 27 and then "underneath" the finish line to view the finish from that southwest spectator area.
 
How long is the course? At those speeds, I would think the race would be about as long as the '62 Liston v. Patterson fight.
 
The race has 7 legs, but legs 1 and 7 are short. The main part of the course is legs 2 thru 6 where they go downwind 3 times and upwind twice. Race takes just over 45 minutes to complete. However, there is a 15 minute pre-race part where they jockey for position.
I will have to check the actual lenght of the course.
Edit: Checked as below

Stats from the last race on 7/28; ETNZ is New Zealand; LR is Lunna Rossa (Italy):

Today’s performance data
•Course: Seven legs
•Course length: 15.27 nautical miles
•Elapsed time: ETNZ – 45:05; LR – 48:26
•Total distance sailed: ETNZ – 18.29 NM; LR – 19.75 NM
•Average speed: ETNZ – 25.21 knots (29 mph); LR – 24.5 knots (28 mph)
•Top speed: ETNZ – 42.76 knots (49 mph); LR – 39.55 knots (45 mph)
•Wind speed: average 15.3 knots; peak gust 19.6 knots
 
So private boats can travel along the 'Transit Area' during the race???
The spectator areas seem a bit 'off in the distance'.
 
quote:
Originally posted by jtybt15

So private boats can travel along the 'Transit Area' during the race???
The spectator areas seem a bit 'off in the distance'.

Click to expand...


yes, private boats can go in transit area.
I also responde in tthe other thread. Aug 13th may not have a race because current match is best of 7 and the 13th would be the 6th race
 
get, good point. When would be a good weekday for a race in August? Any suggestions?
 
You must log in or register to reply here.
Back
Top