Sorry, but when I look at the water in the video, I say there is some wind....
Dave in Tampa
Dave in Tampa
Wow...
- Thread starter Simon Sexton
- Start date
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.
The current-made wind is TRUE, the vessel and motion vector convert it to usable APPARENT wind.
my Ascow gets half way to the speeds of the AC vessels, ice boats go well over double of what AC boats do. the guy we bought our scow from at that time was the second fastest ice boater in the world, 143 mph average on two passes in opposite direction of the same course. this is not new stuff. sail power is fun. the facts of that video were all 'just supposed'.
i say it ain't going to work as he claims
i say it ain't going to work as he claims
fun to ponder this. steaks in the broiler, and i'm ready for the alberta clipper to slam in here in toledo.
as long as the electricity stays on. i have backup, but it takes work
as long as the electricity stays on. i have backup, but it takes work
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.
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.... Maybe they needed to go down stream first to get the speed to ride the foils... in order to reduce drag enough to then sail up against the current with the slight breeze they actually had. But maybe they did break the first law of thermodynamics. There have been a LOT of unexplainable things happening this year.
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.
The wind generated by the current flow is an apparent wind, not a true wind. That's the fault in the analysis.
Those of you having trouble conceptualizing what is happening, try looking at the situation from the boats perspective. The boat doesn't know if the water is moving with 0 knot true wind speed or if it is in a still current with a 10 knot wind from the downstream direction. If you were on the boat, without a GPS and couldn't see the shore could you tell the difference?
Yes, true wind is relative to the water, not to shore, which means the boat sees a 10 MPH true wind. These boats can turn that into almost 30 MPH boat speed off the wind.
When they first launched the AC72s they performed much better than predicted, mostly because the Velocity Prediction Programs were not set up to deal with this type of performance, probably because the designers and the people writing the software had no idea this kind of performance was possible. The AC72s were originally rigged with flying sails for down wind but by the time they got to the America's Cup races they didn't bother putting them on board because the wind was never more than about 30 degrees off the bow, even down wind!
When they first launched the AC72s they performed much better than predicted, mostly because the Velocity Prediction Programs were not set up to deal with this type of performance, probably because the designers and the people writing the software had no idea this kind of performance was possible. The AC72s were originally rigged with flying sails for down wind but by the time they got to the America's Cup races they didn't bother putting them on board because the wind was never more than about 30 degrees off the bow, even down wind!
The 10kt breeze on your trunk lid is the true wind, the 60kt breeze on your windshield is the apparent wind.
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.
I know the AC 72s could do 50 mph downwind with only 20 knots true wind and yes, that means 30 knots apparent wind coming from the front but that is still downwind and it’s still the wind providing the energy. 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.
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.
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.
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.
The problem when going upstream as the speed upstream approaches the current speed the wind speed decreases. When the boat is moving directly upstream at the same speed as the current, then the windspeed, true and apparent becomes 0. This happens because the apparent wind is not wind moving across the boat, it is the boat moving through still air.
The same thing happens when motoring dead down wind. Once the boat is moving at the same speed as the wind, the airflow across the boat is 0. Wind and boat are moving at the same speed and in the same direction. When sailing downwind as the boat speed approaches the windspeed, the spinnaker collapses.
I understand how it works, but can the America's Cup please get back to sailing, not this silly go-cart racing they are doing? The boat generates its own wind with no wind. The main is a foil that has sensors feeding a computer which trims it hydraulically. What happened to the days of Ted Turner and Dennis Conner when we actually sailed these things and need something called breeze?
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.
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.
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.
Simon, Ascows are the oldest one design racing class in north america. they sail twice the speed of the wind. speed is fun. what kind of wind toy should they race.
the America's cup race has always been about technology. the first race was about the ship's technology. it's all been a natural progression for that one race.
then there is the 'sydney 18' race that is a very old racing tradition. there is only one rule for the race. the boat can be no longer than 18'. fun stuff
the America's cup race has always been about technology. the first race was about the ship's technology. it's all been a natural progression for that one race.
then there is the 'sydney 18' race that is a very old racing tradition. there is only one rule for the race. the boat can be no longer than 18'. fun stuff