Wow...

[Will Gilmore]

I'm becoming a convert, but there is still something, I feel it's missing when sailing where no wind is actually blowing. Check out this very well presented article on sailing faster than the wind. https://ipfs.io/ipfs/QmXoypizjW3Wkn...Wo6uco/wiki/Sailing_faster_than_the_wind.html
It compares sailboats to iceboats and sand yachts. There are tables and graphs that cover nearly every question and it is up to date.

-Will (Dragonfly)

 

[Scott T-Bird]

Well, I have no problem with the concept of "sailing faster than the wind". For crying out loud, we even sail upwind! It's the mistaken notion that apparent wind is generated and then somehow becomes independent from true wind. If that were the case, we could start sailing in one direction on a flat pond with no current and a good stiff wind that generates an apparent wind vector, and then when the wind stops, the apparent wind would enable us to continue sailing. Of course that's absurd. The true wind stops and apparent wind stops soon after, as momentum declines to zero. You have to have true wind for apparent wind to be sustained. If the current causes true wind to exist in a no-wind condition, as soon as you turn the boat away from the "true wind" and start bucking the current, you turn off the true wind and the apparent wind then goes to 0 … end of forward motion against the current. The best you can do is sail back and forth across the current, always losing ground with the current.

The only thing that Artemis could hope to describe is that with efficiency and friction reduction, they could resist the loss of momentum for a longer period of time and a greater distance than a conventional boat could. There is no such thing as a magical boat that can sail up current without any real wind for a sustained period of time.

 

[Davidasailor26]

It's the mistaken notion that apparent wind is generated and then somehow becomes independent from true wind.

No, they're not independent. They add as vectors do.

we could start sailing in one direction on a flat pond with no current and a good stiff wind that generates an apparent wind vector, and then when the wind stops, the apparent wind would enable us to continue sailing

No, we can't do that, and that's not what's happening here. The water is always moving relative to the air, which is wind.

You have to have true wind for apparent wind to be sustained.

Absolutely. The motion of the water relative to the air is "true wind".

If the current causes true wind to exist in a no-wind condition, as soon as you turn the boat away from the "true wind" and start bucking the current, you turn off the true wind and the apparent wind then goes to 0

But it never goes all the way to 0. The upstream /downstream component shrinks, but there's always a cross stream component from your motion across the river.

Well, I have no problem with the concept of "sailing faster than the wind".

Ok, let's start there. You can sail faster than the wind. Specifically, you can sail downwind with a VMG greater than the true wind speed, right? That is exactly what is happening in the river model.

Say the river is flowing east. The "wind" (motion of air relative to water) is 10 kts from the East when you are stationary in the water. Per the above, that means you can make VMG of, say, 20 knots relative to the water, right? So relative to the water, you're going west at 20 knots (plus north or south at some speed since you're reaching). Since you're going west at 20 kts relative to the river, and the river is going 10 kts east relative to the land, you're going 10 kts west relative to the land.

 

[Davidasailor26]

How about this -
Put a fan and a pool on a stationary conveyor belt. Set fan at 10 kts. Boat in pool can sail away from the fan with a VMG of 20 knots. I think we can all agree on that based on the demonstrated performance in the AC. If the boat looks at the walls beyond the conveyor belt, it can tell it's going 20 kts.

Now, run the belt up to 10 kts, in the direction opposite the fan is blowing. The fan is still blowing air over the pool at 10 kts, because they're all moving together. The boat in the pool still sails away from the fan with a VMG of 20, as before, right? That 20 kts relative to the pool is now 10 kts relative to the walls. The air from the fan isn't moving at all relative to the walls.

Now in the above, replace "belt" with "current", and "walls" with "land".

 

[sailnoproblem]

I think I was just put to sleep.

 

[Brian D]

.Regardless, one cannot sail by creating their own wind. If that was the case, then the doldrums would be a thing of the past.

 

[Davidasailor26]

.Regardless, one cannot sail by creating their own wind. If that was the case, then the doldrums would be a thing of the past.

I agree. No making your own wind. Sailing in 10 knots of wind, however, is totally allowed. Since wind is the motion of air relative to the water under it, we're all good.

 

[heritage]

I find that trying to analyze this in terms of vmg, vectors, apparent, or true winds is confusing for me as a non-technical sailor.

I can easily see that a boat in a body of water that is moving at 10 kts will see a 10 kt wind.. exactly the same as one would experience in the middle of the ocean with a 10 kt wind created by thermal conditions. You couldn't tell the difference until you glanced at your gps.

If our boat is able to go almost directly downwind at twice the speed of our 10 kt wind, it will be going 20 kts through the water. On checking the gps, you see 10 kts,, ah ha,, there must be a 10 kt current. The speed to get to a destination directly downwind would be probably around 15-17 kts.

 

[Gene Neill]

I find that trying to analyze this in terms of vmg, vectors, apparent, or true winds is confusing for me as a non-technical sailor.

That's what the makers of the video were counting on. All you need to ask yourself is, can a sailboat sail in zero wind. Period. Everything else is a smokescreen.

I'm moving on to possible motives for the hoax. Since the video was not released on April 1st, it doesn't take a genius to figure out the motive is MONEY. Dollars to doughnuts, team Artemis is angling for some save-the-planet bucks from some gullible, deep-pocketed source(s). And, of course, virtue-signaling to anyone who's watching.

If they can fool people here, how much more can they fool the non-sailing, "useful idiots" who write checks for this sort of thing?

 

[Will Gilmore]

Regardless, one cannot sail by creating their own wind. If that was the case, then the doldrums would be a thing of the past.

The doldrums will always be waiting in the wings for anyone interested. Or, I should say, not interested.

If our boat is able to go almost directly downwind at twice the speed of our 10 kt wind, it will be going 20 kts through the water.

After some research into high performance sailing. The foiling cats, ice boats, sand yachts. The most efficient and fastest point of sail seems to be the broad reach, not the beam reach. This means that for boats that can exceed twice the wind speed, their downwind component of their velocity is actually faster than the wind.
I'm having a hard time with this, but if we are to believe that the land and ice sailing speed record are well in excess of 80 knots (in 25 - 35 knots of wind). They are outrunning the true wind off their stern quarter. They will cross a finish line perpendicular to the wind's direction before a balloon released at the same time they get up to speed from the same distance away. They won't be sailing the same course, but they will beat to balloon across that line. I believe the data, but I don't understand it. https://ipfs.io/ipfs/QmXoypizjW3Wkn...Wo6uco/wiki/Sailing_faster_than_the_wind.html
Read this page.

-Will (Dragonfly)

 

[Will Gilmore]

Remember Shoot the Moon?

-Will (Dragonfly)

 

[Davidasailor26]

Remember Shoot the Moon?

-Will (Dragonfly)

That last try was very dramatic.

 

[Scott T-Bird]

That's what the makers of the video were counting on. All you need to ask yourself is, can a sailboat sail in zero wind. Period. Everything else is a smokescreen.

I'm moving on to possible motives for the hoax. Since the video was not released on April 1st, it doesn't take a genius to figure out the motive is MONEY. Dollars to doughnuts, team Artemis is angling for some save-the-planet bucks from some gullible, deep-pocketed source(s). And, of course, virtue-signaling to anyone who's watching.

If they can fool people here, how much more can they fool the non-sailing, "useful idiots" who write checks for this sort of thing?

On a scale of 1 to 10 Likes, I'd give you 10 Likes! Alas, Phil only gives me one to give!

 

[Davidasailor26]

All you need to ask yourself is, can a sailboat sail in zero wind. Period.

Well, we agree that the answer is No.

Where we disagree is on the definition of "wind". You say wind is movement of air over land. I say that since the boat is sailing on water, not land, wind is defined as the movement of air relative to water. In their description there is movement of air relative to water thus "wind", thus, sailing.

I agree with the rest of your satements that it's a nonsensical way to make energy. To me their motive in that ruse is to build brand awareness and loyalty.

 

[Scott T-Bird]

If they can fool people here, how much more can they fool the non-sailing, "useful idiots" who write checks for this sort of thing?

Like a Congress filled with AOC types? Yikes! (Sorry, couldn't help it! )

 

[Captain Larry-DH]

The doldrums will always be waiting in the wings for anyone interested. Or, I should say, not interested.


After some research into high performance sailing. The foiling cats, ice boats, sand yachts. The most efficient and fastest point of sail seems to be the broad reach, not the beam reach. This means that for boats that can exceed twice the wind speed, their downwind component of their velocity is actually faster than the wind.
I'm having a hard time with this, but if we are to believe that the land and ice sailing speed record are well in excess of 80 knots (in 25 - 35 knots of wind). They are outrunning the true wind off their stern quarter. They will cross a finish line perpendicular to the wind's direction before a balloon released at the same time they get up to speed from the same distance away. They won't be sailing the same course, but they will beat to balloon across that line. I believe the data, but I don't understand it. https://ipfs.io/ipfs/QmXoypizjW3Wkn...Wo6uco/wiki/Sailing_faster_than_the_wind.html
Read this page.

-Will (Dragonfly)

Hi Will -
Boat speed exceeding true wind speed can be accomplished even in displacement boats (in light air). I haven't read the rest of this thread so forgive me if this is redundant.
First you need to think about true wind vs. apparent wind. As you sail on a beam reach the apparent wind moves forward, because the angle is a combination of true wind direction and boat direction. The lift of the (properly trimmed) sails is determined by pressure gradients, not by the wind "pushing" from the windward side. So as the boat goes faster the apparent wind also increases (and pressure gradient, or difference in air pressure between the windward and lee sides of the sail) . Boat speed can exceed true wind speed (not apparent wind) if the pressure gradient is greater than drag (primarily water resistance).

 

[Will Gilmore]

I agree with everything you just said, Larry.

-Will (Dragonfly)

 

[Gene Neill]

You say wind is movement of air over land.

No, I didn't. I don't think "wind" requires a definition here. We all know what wind is.

In their description there is movement of air relative to water thus "wind"

No again. At 0:37, the narrator begins with "Imagine. There's no wind at all." Then at 0:53, he repeats "Let's recap that again. We've absolutely no wind at all." Then he goes on to say Artemis can "fly" back upstream to the source of the Amazon ... in other words, indefinitely. Artemis can sail indefinitely, in "absolutely no wind at all", if she's just given a push to get started.

Utter nonsense.

 

[Scott T-Bird]

Well, we agree that the answer is No.

Where we disagree is on the definition of "wind". You say wind is movement of air over land. I say that since the boat is sailing on water, not land, wind is defined as the movement of air relative to water. In their description there is movement of air relative to water thus "wind", thus, sailing.

@Davidasailor26, I'm not sure I understand your argument correctly. I agree with you that it is possible to sail across the river current back and forth as long as the boat is always moving with the current. That would mean that True wind is whatever the current is. I agree that if you pointed the bow of the boat down current at a 45 degree angle, you would have 10 knot True Wind (in their case) and an apparent wind with vector that is a little bit more aft that would actually give you lift. It is an interesting question if you can actually "sail" downwind at higher SOG than the current when the actual wind is 0. I'm guessing that it may be possible, if the lift you get from apparent wind overcomes water friction and drag from true wind.

Where you go wrong is the notion that you can actually sail upstream because there is a vector of apparent wind that gives you lift. That's false for 2 reasons. #1: True wind goes to zero when your boat speed (in the water) equals the current (when SOG = 0). #2: You seem to be assuming that the vector of apparent wind stays the same relative to the sails. It doesn't. When you think about it logically, no matter which direction you are moving, when true wind goes to zero, apparent wind moves forward and aims directly at your bow. Apparent wind no longer gives you a lift, that you need for speed, apparent wind moves forward so that it is directly on your nose. It is nothing more than drag. So now you have current and wind drag moving against the boat. You come to a stop and have to drift with the current. Perhaps you turn down current and begin the cycle again, but you always, always lose ground with the current.

Think about what happens when you sail DDW, apparent wind goes to zero because you can't go faster downwind than True wind without putting apparent wind right on your nose, causing drag. Well, when True wind is 0 or right on your nose, where is apparent wind? It is right on your nose, making it impossible to sail.

 

[jon hansen]

TRUE WIND: the natural wind over the surface of the earth. (land or water)
there is no other definition