Wow...

[Davidasailor26]

I haven't followed this thread but because it is so long, I finally watched the video.

I don't know what the commentator is going on about, but he keeps saying, "no wind,....no wind,.. no wind", yet every video shows,...wind, on the water, when the tri is sailing.

Kind of reminds me of kids in sailboats that call you on the phone and say, "Dad, can you come out and give us a tow back in, there's no wind"

Then the Dad looks around the harbor,.." No wind,..? Then how come the trees are moving?"

When somebody starts sailing in no wind, wake me up.

I know you're jumping in here late Tom, but if you think about it, the ripples on the water make sense given their situation. The water is moving 10 knots, so there's a 10 knot differential between the water speed and the air speed. That difference in speed between the two fluids stacks up ripples, just as it would if it was the air moving instead of the water.

 

[Simon Sexton]

I don't think the actual video footage is of them sailing in the Amazon river. Doesn't look like the same water...

 

[dlochner]

I don't think the actual video footage is of them sailing in the Amazon river. Doesn't look like the same water...

Yep. Some of the video is animation. And note they don't say how far up the river they can sail before they run out of wind.

 

[Simon Sexton]

how far up the river

They literally said "to the source of the Amazon"... That's funny right there...

 

[TomY]

Yeah I know, but if he claims the sailing will be in no wind, stop showing us the boat sailing in wind, show me the boat sailing, say on this

 

[Scott T-Bird]

I don't think the actual video footage is of them sailing in the Amazon river. Doesn't look like the same water...

Bingo! They are not on the Amazon at all! They are simply showing a video clip of the boat doing what it does when there is actually wind! They are making a theoretical argument and attempting to pull the wool over our eyes! Does anybody actually think they would bring that boat to the Amazon? Did there just so happen to be a race at the mouth of the Amazon?

When you listen to the narrative at the beginning, the narrator says "Let's place Artemis in the Amazon River … " then they show a graphic. I wonder what the carbon footprint would be for such a ridiculous experiment?!?

 

[capta]

Yeah I know, but if he claims the sailing will be in no wind, stop showing us the boat sailing in wind, show me the boat sailing, say on this

Great pic, but I doubt there is much current there, and that IS the point of this particular video scenario.

 

[Scott T-Bird]

The really silly thing is that this little commercial is really just intended to convince us that this globe trotting billionaire really does care about the environment. Sure, Artemis isn't just a $500,000,000 ode to his ego. His ultra-efficient sailing machine can really teach us all a lesson about how energy efficiency is going to save the world! Artemis isn't just a hobby that is the focal point for hundreds of sailors and support personnel to globe trot and party and race around the world at ALL of the elite hotspots. They are serious warriors in the fight to save the climate! Hail TEAM ARTEMIS! Save the Planet!

 

[Meriachee]

That picture looks an awful lot like Moose Lake just outside of Jasper Alberta, and it is that calm a lot. Except when it's not.

 

[Davidasailor26]

Bingo! They are not on the Amazon at all! They are simply showing a video clip of the boat doing what it does when there is actually wind! They are making a theoretical argument and attempting to pull the wool over our eyes! Does anybody actually think they would bring that boat to the Amazon? Did there just so happen to be a race at the mouth of the Amazon?

When you listen to the narrative at the beginning, the narrator says "Let's place Artemis in the Amazon River … " then they show a graphic. I wonder what the carbon footprint would be for such a ridiculous experiment?!?

Yeah, don't get me wrong, I think the video and the premise of getting this magical electricity source is total nonsense. As far as I can tell, the Amazon doesn't even run at 10 knots (more like 4 per http://wwf.panda.org/knowledge_hub/where_we_work/amazon/about_the_amazon/ecosystems_amazon/rivers/). Even if it did, how does the boat make energy? It just sails along. Use wind or water turbines to generate energy from the moving wind or water; no sailboat needed. Still, I think the physics of sailing upstream works.

 

[Scott T-Bird]

Still, I think the physics of sailing upstream works.

Yes, but there has to be real wind. Lewis & Clark sailed their keel boat up stream against the Missouri River current when the wind was strong enough from the south. It beat towing it upstream from a tow path along the bank, where they could barely make 5 miles a day.

 

[dlochner]

Still, I think the physics of sailing upstream works.

Sometimes it is best to get some empirical evidence. Next spring on a day when there is no wind, try sailing against the tide. While I doubt your Beneteau will be as fast as a foiling tri, if it is possible you should be able to make some head way. Let us know how that turns out.

 

[dziedzicmj]

You're on your boat. It's got that big fancy wing sail and carbon foils all over your hull. You're out in the bay. There is no wind. At all. Zero. You run by motor power with your sail up trimmed as close as you can get it, and you get moving at a pretty decent speed with your motor. I don't know who in their right mind would think, "Oh, I feel wind on my face, I think I can probably sail now," and turns off their motor and magically is able to keep sailing with the air that they've been feeling on their face. Sorry, there's just no way. I don't care how many "wind vectors" and "variable forces" there are in the technical equation. When you're sailing, if no wind, no go. Doesn't matter how fancy or light or drag-resistant your rig is. Here's my equation:

sailboat + no wind + no motor = no moving. None. Especially with an opposing current.

Wrong assumption. If you turn the motor off, the wind dies. In the case of the Artemis, the water keeps moving. This is not a case of a "push start" and "momentum", but a sustained current.

 

[dziedzicmj]

Sometimes it is best to get some empirical evidence. Next spring on a day when there is no wind, try sailing against the tide. While I doubt your Beneteau will be as fast as a foiling tri, if it is possible you should be able to make some head way. Let us know how that turns out.

Not the best test, because any displacement boat would not be able to sail faster than wind. You need something like a foiler or an ice boat (both have very little drag over the surface).

 

[dlochner]

Not the best test, because any displacement boat would not be able to sail faster than wind. You need something like a foiler or an ice boat (both have very little drag over the surface).

It would not be definitive, it would be a proof of concept. Replicate the conditions, calm conditions sail against the current. If this is possible the sails will fill and the boat will move in the desired direction, i.e., directly upstream.

I would have no expectations that the boat could actually out sail the current in these conditions. Frankly, I don't think you could get the sails to fill.

 

[Simon Sexton]

This is not a case of a "push start" and "momentum", but a sustained current.

This specific video, no, you're correct. But there's also rumors going around that team Artemis is claiming that they can use an electric motor to get up to speed, and continue sailing on the wind generated by the forward speed produced by the motor.

 

[Davidasailor26]

Not the best test, because any displacement boat would not be able to sail faster than wind. You need something like a foiler or an ice boat (both have very little drag over the surface).

Exactly right.

The key here is that the AC boats can get a VMG above true wind speed. Here is a polar plot of the AC boats in 2013, showing their VMG vs wind angle. At the bottom right quadrant, see how the VMG is about 35? Here are the conditions that day - "Early forecast for winds 17-20 knots, replaced by morning forecast for winds 20-25, and an hour before start time the winds are verifying at the higher end of the range. Initial Wind limits are 24.7 knots for Race 17 (23-knot nominal limit plus 1.7-knot Flood Tide) and 24.1 knots for Race 18 (23-knots plus 1.1 knot)."

So the boats were going downwind faster than the wind was blowing.

By comparison, here is a polar of a displacement hull -

With the displacement hull, VMG never exceeds wind speed, so it will never go upstream, only down.

 

[Simon Sexton]

I just hope no one falls overboard during the tests. There's some crazy stuff in that river...

 

[capta]

I just hope no one falls overboard during the tests. There's some crazy stuff in that river...

Just for the fun of it;
On my voyages to the Amazon, our agent would occasionally invite me to join him and his family for a day at the 'beach', a nice sandy strip on the south side of the river, not too far from town.
On my first visit there, I was told that I should only go in the water between the red flags at either end of the beach. Apparently, the Piranhas will not cross these flags into the swimming area. I wonder who figured that out, and how? Or a really great negotiator?

 

[Simon Sexton]

who figured that out, and how?

It's actually a very little known fact that Piranhas prefer to school and hunt in deeper waters, usually at least 4-5 feet deep. They also tend to stick around areas that provide heavy cover, such as fallen trees, sunken boats, docks and slips, etc.. That beach was probably one of the safer places because of the sandy habitat and shallower water level. The thing to worry about in those areas are the stingrays.