The Wind Powered Sail-less Boat

Rick: Slide 3 should perhaps say 'The extra power USED to run the generator' rather than 'REQUIRED'...

I like the inclusion of acceleration in Slides 1 and 2. Makes me feel a lot more comfortable.

 

Rick,
I'm afraid I'm not embarrassed at all. I'm just managing my times and my resources, as I have all the right to do. So don't be so self-satisfied yet.

I have to apologize for not being able to answer all and any directed to me posts, as you are too many for my scarce time and poor english. I'm sorry, but I'm not able to handle this that way. My M.O. is (and will be) the one I can manage, sorry.

I have thought about something interesting:

An ice boat is able to keep an steady greater than the wind downwind speed component, because it is continuously taking energy from a bigger amount of wind than it is available in a strict DDW course, by sailing to an angle with the wind. If it tacks there is no problem, as the wind acting in the new course has taken again energy from the surrounding wind because the ice boat moves in long tacks in a real world within real air.

But in a theoretical and simplified mental test as the one in the video at http://www.youtube.com/watch?v=IMEerIkOVZ0, where the cart is moving inside an ideal steady speed, laminar and non viscous fluid, when the boat tacks down to the other side of the frame, the wind the sail sees through its new way has not anymore the full original energy, because it has lost part of it speeding the cart downwind in the previous tack.

So, an apparatus composed by a wheeled (or skated) frame and one or two tacking sailboats within it, in fact would not be able to get enough energy to go DDWFTTW, except in the real world (if we could build a big enough frame without drag ), where the slowed mass of wind acting on the cart as a whole would be accelerated again by the surrounding and not steady viscous wind. But this would be a not valid example of DDWFTTW, as there would be additional energy brought into the system.

I'm afraid I was wrong about this, when I said it was possible.

Now your turn, amigos.

Cheers.

 

That sounds like the one I have in mind. It's here:
http://www.physicsforums.com/

I started using the ice-boat approach 3 years ago when I first posted this as a brain-teaser on an R/C heli forum. It seems essentially impossible to argue against it - but plenty did (and still do) - including professors of aero, physics, and mechanical engineering.

That's an appealing notion, but it takes away the vehicle's ability to slow the wind relative to the surface. This is where it gets its energy and momentum from.

 

Wrong.

Wrong.

Wrong.

Wrong.

I'd offer more detailed explanation of where you've gone wrong in each step, but as you say, your M.O. doesn't permit such an exchange.

Back to you.

 

Lets look the frame from behind standing still. So we are looking downwind.
Consider this : The iceboat on the right side is moving towards left.
It's sail produces a force component forward=downwind & towards right.
Let me repeat that the sideways force component from the sail is against movement in sideways direction related to the frame. If blade force is taken out from iceboat into frame, nothing is providing the force needed to continue the sideways movement. If the frame does this, it needs a powersource for it like electric winch & battery. That's the problem. Lateral aero forces of 2 iceboats do cansel out, but power does not, it adds up as it's scalar quantity, not a vector.

This is a mistake resulting from the different co-ordinate system oriented with true wind, when sailors normally use the one oriented with boat centerline, where sails do have forward component aligned with the movement.
In this case only the downwind component is forward and with the downwind movement, lateral movement is different.

No, that's not the problem with the reasoning based on forces. If you apply the electric winch, the air does slow down and craft can continue ddwfttw.

 

The ice boat can exceed wind speed by reaching. Old news and it's easy to demonstrate why by looking at the apparent wind and resulting lift vectors. However, if you split the ice boat's speed into two vectors, one pointing directly downwind and the other at a right angle to the wind, you'll find that the downwind vector is less than or equal the wind speed. You have to multiply the boat's indicated speed by the cosine of the boat's angle relative to the wind direction to get the true downwind speed.

You can get around this by reaching for a bit and building up speed, then turning downwind carrying the excess speed with you. But the excess speed will bleed off fairly quickly. Technically, this technique doesn't meet the required challenge of sailing DDW due to the reaching maneuver.

 

He didn't mention any electric winch in his setup. That's your addition. So you can't tell me his setup does work given your electric winch. His craft has no way of slowing the air relative to the surface. It cannot work on that basis.

We have clearly stated several times that this is wrong. The downwind velocity component can reach 3X to 4X the true wind speed. It's really annoying when people simply ignore the evidence given and simply make blanket incorrect statements like this with nothing to back them up.

Thanks for the lesson in basic trig. But you're still wrong.

That's right. Your contrived technique doesn't meet the challenge. But every approach we've proposed does.

 

This is exactly the level of rigor I've come to expect from so called sceptics... "conservation of energy and such". I guess that's an air-tight argument if ever there was one. Or is that just the topic, and it's up to us to form the actual proof that you can't quite get your head around?

 

Feel free to build your device. Post it on YouTube. If you can pull it off, you'll likely get featured in Scientific American. But my money is on conservation of energy.

 

Done. I've built a pile of them. We've posted a pile of videos on youtube - just search on spork33.

Hopefully the folks at Scientific American understand basic physics well enough that this doesn't seem like magic to them. I'm not expecting their call.

Mine too. But I understand conservation of energy.

We've posted the analyses that show how this works from an energy perspective. Whereas you feel simply invoking a term you don't understand somehow constitutes proof that it can't work. But let me ask you this - how do you reconcile your "proof" with our physical evidence?

 

You haven't presented any physical evidence other than some videos. Put your device up for independent peer review.

 

I have presented physical evidence. And you happen to have seen videos of that physical evidence. If you come to my house you can see it first hand. I've also built a number of these and mailed them to people that have requested them.

Perhaps you noticed the series of build videos I provided. Any "peer" that would like to can follow the detailed videos and reproduce our results. Why don't you do so? At least then you'll be asking us how it works rather than trying to prove it doesn't by throwing around terms you vaguely recall from high school physics.

 

The reason spork and JB built their device was to verify what Goodman had shown a couple of years earlier and Bauer contemplated many years before that. They were skeptics prepared to build something to test it rather than just put ill informed arguments that it cannot be done.

If this is not comprehensive peer review to prove that it works then I do not know what is.

If you care to go back through this thread you will find a mathematical proof that Mark Drela produced. If you want to shoot it down based on your understanding of conservation of energy that is a good place to start. When you have taken your best shot at that you might gain some respect here.

IntRoadkill you are digging that hole that I pointed out earlier without giving it proper thought. You raise points that show lack of insight here. You have taken a position that it cannot be done based on an opinion and now you are defending that ill informed opinion without any research at all. Just shooting off stupid comments.

Rick W

 

It seems you agree with Slide 2 and I will look at wording in Slide 3.

In Slide 4 we add the generator from the vehicle in Slide 3 to the electric powered propeller driven vehicle used in Slide 2. The questions here:
1. With the forces shown will the vehicle accelerate, slow down or continue at 4m/s.
2. If the electric motor and generator are connected directly can we remove the battery and get it to run - at what speed.


On the boat topic I have provided a rendering of a boat that will work. It shows the proportions required for a 1-man boat and why I have problems seeing any practical for use of the idea on water.

Rick W

 

Sailor2: Do-oh-oh. Thanks. I should have spotted that. So the iceboats still need their own skates.