America’s Cup - ETNZ launches 1st AC75 (new)

[CassidyNZ]

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.

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.

[barnakiel]

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.

[Tillsbury]

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.

[a64pilot]

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?

[CassidyNZ]

Originally Posted by barnakiel

Really?


I thought I had seen a NYYC AC 75 on youtube like 3 weeks ago or something.

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.

[Factor]

Great to see they bought traditional monos back

[CassidyNZ]

Originally Posted by Factor

Great to see they bought traditional monos back

Traditional??

[a64pilot]

I believe he was being sarcastic

[IslandHopper]

Originally Posted by Factor

Great to see they bought traditional monos back

Nah they didn't buy them they built them.....

[barnakiel]

Originally Posted by Factor

Great to see they bought traditional monos back

Traditional is the key word here


b.

[barnakiel]

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.

[barnakiel]

At least one source shows they are self-righting too.


???


b.

[Tillsbury]

Yes the can be righted by the correct use of the wings.

[jmh2002]

Yes the foils are ballasted and when in the 'both down' position act somewhat like a traditional keel.

[jmh2002]

Originally Posted by jmh2002

Yes the foils are ballasted and when in the 'both down' position act somewhat like a traditional keel.

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:

https://www.youtube.com/watch?v=_bNO0t2s02I

The AC75 is the next step on from the IMOCA60 which introduced foils but still had a canting keel:

https://www.youtube.com/watch?v=leZEIf3fKB4

https://www.youtube.com/watch?v=ufpGh_c-fOU