Sorry, but when I look at the water in the video, I say there is some wind....
Dave in Tampa
Dave in Tampa
There is wind and you don’t need much of it to sail when there is virtually no hull drag. What they have found with the AC72 is you only need to get the force of the true wind near the beam before the super efficient wing sail can convert it to lift, and bring the apparent wind to 20d off the bow with forward motion. They are wind force harvesters.No wind, no move. That defies the laws of physics (I think). A sailboat cannot generate it own wind to sail. Granted, the boat moving because of current will generate apparent wind, but not off the side of the boat. It will be head-on. Sorry, I call BS on this.
The current-made wind is TRUE, the vessel and motion vector convert it to usable APPARENT wind.however, if the vessel achieves a vmg upstream that is a positive number then the current made apparent wind is gone.
I can't wrap my head around that. I'm not buying the fact that they first sailed downstream, generated enough apparent wind to sail, and then turned around into the current and used their speed to generate wind in order to have speed to generate wind in order to have speed against the current. Sorry but not going to buy that.We saw this played out in San Francisco. Once the AC72 boats come up on their foils, their wing sails are generating so much power relative to hull drag that the boat will be able to convert downwind true wind to effective lift-effect apparent wind and sail trimmed close-winded. It took the crews some time to figure this out and early Louis Vuitton qualifiers did not get it figured out downwind. The boats eventually were ALWAYS in close-wind trim. Once it became clear how apparent wind force could be converted, boat speeds increased downwind and the challenge became keeping the boat on her feet in that 60mph control range.
But it isn’t really 30kts COG up river it is 30kt-10kts = 20kts SOG up river. - as long as the river current is imparting movement through the air. That may what some of you are not accounting for - the river current motion is a source of wind power.
In the video, the true wind is 0. Multiply anything by 0 and the answer is 0. It was the easiest multiplication table to learn back in grade school.their wing sails are generating so much power relative to hull drag that the boat will be able to convert downwind true wind to effective lift-effect apparent wind and sail trimmed close-winded
The 10kt breeze on your trunk lid is the true wind, the 60kt breeze on your windshield is the apparent wind.The wind generated by the current flow is an apparent wind, not a true wind. That's the fault in the analysis.
A sail doesn’t care how air is made to move across it. An AC72 is demonstrably better at conserving that energy than a displacement daysailer. Entropy.They are claiming that the river current is providing the energy for the boat to move up stream against the current. No way! There has to be some wind they are not accounting for....
AC, You got some 'splainin to do!If you have zero wind and get going with the motor until you have 8 knots apparent wind you can’t shut off the motor and sail the rest of the day.
This is more or less correct. It is like ferrying a kayak across a river current. Get the angle right and the paddling speed right and the kayak crosses the river without going downstream. Paddle a little harder and the kayak can gain a little on the stream bank.Out on a limb here...
The only way I believe this would work would be if the current pushing to boat is on the beam. The boat is perpendicular to the current flow. The sails can then be trimmed for a beam reach and maybe the boat would start to move in the direction it is facing. But once the boat starts to move, it will create a new wind flow over the bow thus cancelling the effects of the beam wind created by the boat flowing in the original direction of the current flow.
I totally agree. I'm getting tired of watching a mere few spaceships flying around on a race course for a few hours and watching one of them win and make a few million. It's the same way Formula 1 and NFL have gone; its all political now.can the America's Cup please get back to sailing
Nope. It is a pitch to inspire exploring the unconventional. The AC72 were a creation of pure sailing physics efficiencies, and they worked, like this example, in ways unanticipated. Many people don’t know how it works, maybe stabilizing climate change is like that.Actually, this was a commercial for sustainable energy, not sailing. They just used Artemis as an example of something creating energy out of nothing. Again, BS. And as mentioned before, fake news.