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11-09-2019, 13:30
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#16
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Registered User
Join Date: Jun 2019
Location: Bay of Islands New Zealand
Boat: Morgan 44 CC
Posts: 1,136
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Re: America’s Cup - ETNZ launches 1st AC75
Quote:
Originally Posted by a64pilot
Has to be yes to both your questions, but I’d assume the foils and strut are quite heavy.
There has to be ballast, hull stability can only go so far.
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One would think that nothing on this boat is “heavy”.
75 feet of boat weighs around 6 tons which is nearly twice the size of mine and half the weight but the pressure on the sail is in no way diminished and it’s sail area is easily 3 times mine.
I remain puzzled.
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11-09-2019, 14:07
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#17
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Registered User
Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,437
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Re: America’s Cup - ETNZ launches 1st AC75
Really?
I thought I had seen a NYYC AC 75 on youtube like 3 weeks ago or something.
Both boats look amazing and I am looking forward to the races.
b.
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11-09-2019, 14:30
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#18
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Registered User
Join Date: Mar 2018
Location: New Zealand
Boat: 50’ Bavaria
Posts: 1,809
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Re: America’s Cup - ETNZ launches 1st AC75
Both foils are effectively the only ballast there is, and when they're both down it's relatively stable. They have substantial wings on the bottom of each, remember. The windward one goes up to provide righting moment a good distance from the centre of the boat.
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11-09-2019, 14:35
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#19
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: America’s Cup - ETNZ launches 1st AC75
I think a lot of it is form stability, from the hull. But those foils have to be ballast too.
What’s the beam on one?
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11-09-2019, 16:05
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#20
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Registered User
Join Date: Jun 2019
Location: Bay of Islands New Zealand
Boat: Morgan 44 CC
Posts: 1,136
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Re: America’s Cup - ETNZ launches 1st AC75
Quote:
Originally Posted by barnakiel
Really?
I thought I had seen a NYYC AC 75 on youtube like 3 weeks ago or something.
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Don’t think so. This clipped from a media release:
“Emirates Team New Zealand have launched their first AC75 monohull at their team base in Auckland.
The reigning America’s Cup champions are the first of the five challengers to launch the new generation of AC75 foiling monohulls that will be used in the 36th America’s Cup.”
Having said that, the report may be inaccurate as the journo reporting seemingly doesn’t know the difference between the defender and the challengers so inaccuracy is entirely possible.
NYYC were the first to foil an AC75 under sail, something ETNZ have yet to do.
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11-09-2019, 16:09
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#21
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Marine Service Provider
Join Date: Dec 2006
Location: Brisbane Australia
Boat: Multihulls - cats and Tris
Posts: 4,859
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Re: America’s Cup - ETNZ launches 1st AC75
Great to see they bought traditional monos back
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11-09-2019, 16:12
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#22
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Registered User
Join Date: Jun 2019
Location: Bay of Islands New Zealand
Boat: Morgan 44 CC
Posts: 1,136
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Re: America’s Cup - ETNZ launches 1st AC75
Quote:
Originally Posted by Factor
Great to see they bought traditional monos back
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Traditional??
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11-09-2019, 16:23
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#23
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: America’s Cup - ETNZ launches 1st AC75
I believe he was being sarcastic
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11-09-2019, 16:48
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#24
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Registered User
Join Date: Dec 2009
Location: Bundaberg, Qld.
Posts: 2,192
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Re: America’s Cup - ETNZ launches 1st AC75
Quote:
Originally Posted by Factor
Great to see they bought traditional monos back
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Nah they didn't buy them they built them.....
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11-09-2019, 18:42
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#25
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Registered User
Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,437
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Re: America’s Cup - ETNZ launches 1st AC75
Quote:
Originally Posted by Factor
Great to see they bought traditional monos back
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Traditional is the key word here
b.
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11-09-2019, 18:51
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#26
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Registered User
Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,437
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Re: America’s Cup - ETNZ launches 1st AC75
I listened to one of the designers for the UK team explaining the foils need to be heavy and light at once (easy, eh?). At times it would be best for the foils to have positive displacement, at other times it would be better to have heavy foils.
The same applies to the foils area - at times minimum would be best at other moment max area is what they want.
These boats are far more compromises than our cruising tubs.
b.
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11-09-2019, 18:53
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#27
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Registered User
Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,437
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Re: America’s Cup - ETNZ launches 1st AC75
At least one source shows they are self-righting too.
???
b.
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11-09-2019, 18:55
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#28
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Registered User
Join Date: Mar 2018
Location: New Zealand
Boat: 50’ Bavaria
Posts: 1,809
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Re: America’s Cup - ETNZ launches 1st AC75
Yes the can be righted by the correct use of the wings.
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11-09-2019, 20:38
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#29
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Registered User
Join Date: Jul 2018
Location: NZL - Currently Run Aground Ashore..
Boat: Sail & Power for over 35 years, experience cruising the Eastern Caribbean, Western Med, and more
Posts: 2,129
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Re: America’s Cup - ETNZ launches 1st AC75
Yes the foils are ballasted and when in the 'both down' position act somewhat like a traditional keel.
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11-09-2019, 21:58
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#30
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Registered User
Join Date: Jul 2018
Location: NZL - Currently Run Aground Ashore..
Boat: Sail & Power for over 35 years, experience cruising the Eastern Caribbean, Western Med, and more
Posts: 2,129
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Re: America’s Cup - ETNZ launches 1st AC75
Quote:
Originally Posted by jmh2002
Yes the foils are ballasted and when in the 'both down' position act somewhat like a traditional keel.
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Here is some basic info for those not familiar with the concept.
Approximate dimensions:
Length: 75ft / 22.8m
Beam: 17.7ft / 5.4m
Beam incl Foils 49ft / 15m
Draft, Foils down: 16.5ft / 5m
Foil Weight: 1.2-1.5 tons each
How the new AC75 will fly:
The AC75 is the next step on from the IMOCA60 which introduced foils but still had a canting keel:
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