The Wind Powered Sail-less Boat

I stand corrected. I was thinking of another analysis that he's been hounding me for. He described the parameters of the analysis fairly specifically, they just didn't make much sense. What he asks for in #462 is more sensible.

No doubt for you or me (or anyone that understands the basic physical principles). But I suspect you may still see some doubt from G.

 

My dear friends,
Sorry for the delay, but I’ve to attend some social compromises and couldn’t attend the forums yesterday night. Now I have more time available and try to put my thoughts in written for you (painfully, as english is not my native language and I do not master it).

I’m afraid I’m going to delude some of you, but here my thinking:

- The Goodman’s cart open air experiment, never repeated or at least with results never made public again, was done in a not controlled environment, so it cannot be considered valid to prove the DDWFTTW theory. Real wind over such a long distance and so close to the floor cannot be steady and unidirectional, the transmitted power to the wheels was not measured, the effect of the perturbed air by the car running alongside was not taken into consideration, etc, etc, so we cannot take conclusions at all. Goodman itself stated it was not possible.

- The treadmill test is NOT an equivalent of the open air test, because of the lack of equivalency between them. At the treadmill ALL power is applied to the wheels, asuming this it is what happens at the open air test, which has not been proved at all. Also where the power is applied is vital to the experiment, as it is not interchangeable because of the not bidirectionality of loses (i.e. a propeller, other than the most simple, is not an inverted mill).

- An equivalent and better controlled test could be putting the Goodmasn’s cart over a NOT POWERED, very low friction and of an equivalent inertia (mass) to that of the cart treadmill, in a wind tunnel. I put here the challenge to anyone wanting to perform it.

- It is said, by the DDWFTTW proponents, that the cart can go from downwind to upwind because there’s energy coming from the wheels to the mill, making it a propeller and not a mill. Well, in my opinion, this totally untrue except, perhaps, at a speed very close to the mean wind speed in an open air test, where the cart (and also mill blades’) inertia can take its part through small wind speed/direction variations, which for a very efficient mechanism could produce a fluctuation over and under the mean (down) wind speed.

- The only available energy to move the cart is the one from the wind, which moves the blades of the mill, which moves the cart and the belt/wheels. The reaction force at the wheels is a consequence of the energy of the wind being transmitted to them and cannot exist without it.

- The total energy applied at the cart can never be greater than the one available from the wind acting on the mill and the structure of the cart. Putting apart the force due to drag, the cart takes most of its energy from the wind turning the mill, at ANY given moment. So, the closer we come to wind speed, the less energy we can take from it

- The trick with the wheels and belt thing is to increase the efficiency of the whole system, thus permitting the craft to come closer to the wind speed. The cart without the wheels and the belt transmitting mechanism would move at an speed noticeable less than wind speed.

- Of course the blades of the mill move in an apparent wind greater than the wind (like the sails of an iceboat), because of their spinning movement. That’s what allow them to use more energy from the wind that the one corresponding to just their projected area. When the cart approaches wind speed, the component of the real wind at the blades diminishes and the energy gotten from the wind diminishes. So the transmitted power to the wheels diminishes and eventually dissapears. Once there is not real wind component (V = W) or even before, when the profiles lose lift when the angle of attack is small, there is no more energy transmitted to the cart other than the one due to pure drag over its structure. Only inertia can counteract and allow for some forward movement for a while in the real world, allowing for the fluctuation mentioned above.

- If the cart could take enough energy from the wheels to make the mill become a propeller and ‘go upwind’, where does that energy come from?. Not to mention that we would need a device to invert the pitch of the rotor, of course.

- Another way to look at the thing is to think about an ice craft with a mill over it going DDW. The small friction of the ice would also allow the craft to come very close to wind speed, but NEVER overpass it, if I'm not wrong (except for the possible inertial fluctuations in the real world, as told before).


Well, it’s enough for today. My ‘real’ world, in the form of a family, is calling my dooor, asking for my attention. I will be happy to hear your comments, but I would be very gratefull if you try to avoid bad tempered ad hominem attacks that are useful for nothing, except to darken debate. Words as silly, krook, close minded and other disqualifications etc, should be always avoided. Just criticise the ideas not the people behind them.


All the best.


P.S. As I was writting, I have had not time to read Mark's and Rick's analysis, which I'll gladly do later today.

 

OK, I have [some] knowledge of [some] of the physics involved in this, but please bear with me, as I prefer (or, shall we say, my mind can better comprehend) to use the simplified model of a perfectly upright/level sailboat with sail & keel forces, as opposed to wind & water turbines.

In a sailboat that is going any direction at all, other than PERFECTLY upwind, or PERFECTLY downwind, it is possible for the sailboat to extract power from the difference in flow directions (relative to the boat) of water vs. wind.
Any wind flow acting laterally on the sail surface of the boat is countered by the boat's keel/rudder being acted on in an opposing direction by the water (thus the boat can maintain it's selected course, instead of "sliding" to whichever direction the wind is blowing).
By turning the sail to a direction that forces this lateral-movement of the air towards the stern of the boat, with the corresponding equal lateral force being applied to the boat itself by keel+rudder, the boat is able to create forward thrust for itself from wind that was not coming from directly behind it.

I'm sorry, but I have a great deal of trouble expressing in writing the physics properties that I consider visually & mentally, so I can't give a written energy analysis, but I can tell you that when there is any air movement (relative to the water) that is in a direction that is at all lateral to the boat, the boat can take advantage of this, and my conclusions are easily supported by observing, testing, or experimenting on any sailboat, or sail-powered iceboat/cart that is tacking or jybing...and VERY often, they will achieve surface speeds (water/ice/land) that are WELL above actual wind speeds relative to themselves, OR to the surface.

Now, as far as applying this knowledge to guiding a craft directly upwind, or downwind faster than wind speed (which becomes upwind), I can envision it being possible, but I can't prove that it is or isn't with the information I know...so I won't argue anyone on that point until I know more.

 

More to the ORIGINAL point of this thread, however:

Why are we arguing about maximum DUW/DDW speeds anywise, for the purposes of the project at hand, it has already been stated that speed is (nearly) meaningless, and that "tacking" and using stored mechanical energy are perfectly allowable.

Can we PLEASE cease this useless (for THIS project, at least) debate (that is quickly becoming more of an emotion-driven argument, than an information-driven debate) and get back to the (intended) subject of this thread?

If you want to further debate this possibility/plausibility, by all means do, but please start a mroe appropriate thread for it, instead of robbing the student who started this thread of any hope to extract useful information from the conversation.

Thanks

 

After reading your lengthy argument against the prop cart I conclude the following:

- You've admitted that an ice-boat can achieve and maintain a downwind velocity component greater than windspeed by tacking - and thus that DDWFTTW is possible by connecting two such ice-boats.

- You've simply dismissed nearly everything we've said about how the prop cart itself works, or how it's actually equivalent to the tacking ice-boat - and done so without any explanation as to what concerns you have with any of our explanations.

Therefore, I have to be satisfied that you accept DDWFTTW (which is my only real interest here), and that we won't likely convince you that it can be done by the prop-cart (despite the fact that we have inexpensive carts that easily and repeatably prove it - and build videos showing how you can easily make one of your own).


If you actually care to understand how the prop-cart can achieve and maintain DDWFTTW, there are several of us here that are more than happy to explain that to you. But that is a conversation. Simply demanding a very specific form of analysis that you think is appropriate, while ignoring everything any of us say, won't get us there.

 

Hope this clarifies your deeply mistaken view of what is going on.

I have attached an article Goodman wrote on his testing. I would like to see anything you have that shows he has contradicted this.

Rick W

 

The idea of extracting more power from the wind than is there seems to be like the Underwear Gnomes on South Park...

Stick to the premise, wind powered, not multiple HP treadmill power. Once you attain wind speed there is no more power available. You can't even attain wind speed because of friction/resistance. Trying to grab traction power from the inertia of rolling over the ground or water adds even more resistance.

 

Please check your work, SamSam. You're at about Stage 0.25, where "I have thought about it for 15 seconds"

 

Even after a minute, where I should be to Stage 1, my beliefs are still the same. How many Stages or levels of "thinking" does it take to make the impossible believable?

I have to edit and explain that I am talking about directly downwind, or DDWFTTW. It seems even RickW agrees with this, as posted in post #27.

 

Agreed. Extracting more power than is there is a silly notion.

You might want to crack open that high school physics book and look for "inertial frames" somewhere around chapter 1.

Strike 1

Strike 2

True enough. If only we had a source of power greater than that resistance. Oh - yeah the wind will provide plenty of power.

We'll just call it 2.5 strikes. So you want to slow down and keep your eye on the ball, maybe get a base hit? Or are you just going to come back and swing with your eyes closed again?

 

Hmm. I think this statement identifies one major misconception which causes so much confusion: The idea that "the wind" provides the power. It doesn't, at least not to all observers.
An observer in a hot-air balloon always feels zero wind, so to him the concept of "wind power" seems strange. To him, the DDW cart is clearly "ground powered", by the ground moving past the balloon.

It's better to say:
Sailboats, iceboats, DDW machines, Dynamic Soaring gliders, are all powered by the velocity difference between two media.
This works because a velocity difference is the same for any observer, regardless of his own motion.

Some examples of the two media, for specific machines:
DDW cart, land yacht: Airmass and ground
DDW boat, sailboat: Airmass and watermass
DS glider, albatross: Airmass above and airmass below a shear layer

 

This is correct. In fact the energy flow is always extracted from the surface and "spent" by the air propeller.

 

Well, SamSam, if you can't ever get to where you see that it works, that's not my problem.

It does work, it works fine. You can see endless videos of several different people doing it with several different carts. It's not cold fusion -- it's reproducible, and easily so. You can reproduce it as well, parts lists are available, and there's at least one group of people that will loan you a working cart.

That's Science for you.

The fact that you don't believe it doesn't really matter. I was just telling you that many people (most? almost all?) start out where you are, and then think it through more thoroughly, and eventually see not only that it can work, but that it does.

 

Let it go, LeeJerry, let it go.

It is no more "extracted from the ground" then the energy which drives your car is "extracted from the differential gears". In fact, the analogy is precise.

 

May I cheekily suggest that "doubters" would be well served and find enjoyment by visiting the "Drivel...." or "Global Politics....." threads for naught that anyone says will ever be believed by them?......

The energy used is derived from the differential (not that car thing), but differences in movement/force.... While there is a difference there is a potential source from which energy may be extracted... Wind is moving land is not (or in another relative velocity and direction)... There are differences in velocity and direction of wind at different altitudes.... and above/below wings otherwise aircraft would behave as bricks and nothing would work as we know....