Oracle 45 footer foiling to windward

floater

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Yes - flying jibes were a big accomplishment for these boats. The video right above has a nice jibe right in front of the camera. Followed by some upwind foiling, which is something of a new phenomenon for these boats.

Because these videos were taken from the SF Cityfront, the breeze consistently blows left to right (from the Bridge, over Alcatraz, to Berkeley).

So, if the boat is heading right - it's downwind. Sort of.

The strange thing is that because they are moving downwind at about two times windspeed, a jibe includes "tacking" the sails.

There has been talk of eventually learning how to foil through tacks as well...

 
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jnavas

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...

The strange thing is that because they are moving downwind at about two times windspeed, a jibe includes "tacking" the sails.

There has been talk of eventually learning how to foil through tacks as well...
Foiling through tacks is unlikely, as I explain here.

 

jnavas

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Never say never, not that I disagree with your analysis, but I guess the notion originated with the designers.
I don't know of any actual designer with that notion.

All I've seen is optimistic (hopeful) speculation by enthusiasts.

I'd be willing to bet money we won't see foiling tacks in 35th AC.

 
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Doug Lord

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I wouldn't rule it out-the Moth tacks on foils even though the crew is a major drag. Every time anyone has categorically said something was impossible in the history of foiler development-it's been done.

 

jnavas

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I wouldn't rule it out-the Moth tacks on foils even though the crew is a major drag. Every time anyone has categorically said something was impossible in the history of foiler development-it's been done.
Totally different: Moth is single central foil:


 
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Doug Lord

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It's not totally different: one of the big foil design breakthroughs of 34 was the UptiP foil which is the first single main foil that can control altitude for the whole boat with no moving parts on the foil. So there are numerous pictures(many thanks to you) of the boats sailing on just two foils. Even with the two rudder foils immersed the drag, these days , may be able to be reduced by neutralizing the the weather rudder foil ,eliminating induced drag from that foil. I don't know if that's even legal but it's certainly possible.

AC 45 Oracle one.jpg

AC 45 2014 foils are future.jpg

 
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jnavas

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It's not totally different: one of the big foil design breakthrus of 34 was the UptiP foil which is the first single main foil that can control altitude for the whole boat.
Moth is a mono, not a cat. Apples and oranges.

 
tacking on a cat means each of the hulls have a different speed and therefore lift during the tack. You are turning the outer hull somehow around the inner hull. Hullspeed is close to zero in the turning point.

Is that true?

 

floater

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tacking on a cat means each of the hulls have a different speed and therefore lift during the tack. You are turning the outer hull somehow around the inner hull. Hullspeed is close to zero in the turning point.

Is that true?
The boat likes to keep some forward momentum through the turn.
If you watch the jibe sequences above, they keep enough forward momentum through the turn to be, at a certain instant, traveling DDWFTTW.

Dead downwind faster than the wind. Oh yeah, that's a great one to break the ice at cocktail parties.

Still, a similar notion would apply for staying on foils through a tack, the boat would need to keep enough forward momentum - head to wind - to sustain flow and lift over the foils sufficient to keep the boat in the air.

Moths do it. But so far, not foiling cats.

 

P Flados

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Foiling tacks are a challenge, but not an impossibility.

The big technical item that could potentially enable foiling tacks is how fast they can turn.

With both daggers down, the boat foiling but low low and held flat, it can turn very very fast without much loss of speed.

The biggest challenge would probably be amount of control required.

A significant concern could end up being how to keep the crew on the boat as it does the High G turn.

 
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jnavas

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Foiling tacks are a challenge, but not an impossibility.

The big technical item that could potentially enable foiling tacks is how fast they can turn.

With both daggers down, the boat foiling but low low and held flat, it can turn very very fast without much loss of speed.

The biggest challenge would probably be amount of control required.

A significant concern could end up being how to keep the crew on the boat as it does the High G turn.
With respect, given the weight (momentum) of the boat, there's simply too much drag (wind on the nose, foils and rudders in the water) in such a large turn. And it's a pretty pointless debate, since time will tell. Just place your bet. ;)

 
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