The Wind Powered Sail-less Boat

Rick: Slide 4. As you stated, thrust balances drag, so velocity is constant. There is no need to buffer the power, so you can remove the battery.

 

Guillermo
You should never be afraid NOT to be embarrassed.

I note spork has responded on the ice boat points you have put.

I have designed a boat that will achieve DDWFTTW. There is a rendering and performance data in post #668. I can give you all the variables for this boat for the range of wind conditions noted.

Rick W

 

OK. So I guess you have no problem with the possibility of DDWFTTW. Is that correct?

Are there any other suggestions you have to improve the series of slides? I am thinking I might include a picture of the turbine propelled vehicle I showed earlier and a reference to that bike site with a screen dump of the data. The drag figures are just about right for a manned trike.

What I would like to be able to do is to present the slides and challenge people to find an error in what I have offered.

Rick W

 

A propos of Guillermo's misunderstanding of what happens when an aerofoil derives a force from a moving air mass, it would be interesting to find a link to a diagram showing the vortex trail left by a moving aerofoil relative to the air mass, rather than the usual wind tunnel diagram showing airflow relative to the aerofoil.

That might help underline how localised the changes to the air mass are, and eliminate the tendency to feel that they extend an infinite distance downwind of the aerofoil.

 

Rick: Correct. I am convinced that a device can be made to run at the interface between two media, where at least one of those media is a fluid, at a velocity greater than the relative velocity between them, if the velocity between the media is non-zero.

I wonder if I've covered all cases. It's a very long time since I wrote a patent application, and I don't think anything in your arguments precludes a device running along the sea-bed in a tidal stream.

It isn't necessary in a scientific discussion, but most people are more likely to understand and believe if they can see real numbers and evidence, so adding the bike info and the videos will help them to believe, even if they don't understand why or how.

 

Actually, that history isn't quite right. I had conceived of the DDWFTTW cart before I'd known anything of Bauer or Goodman. I convinced myself it was entirely workable by working up the basic vector analysis. In fact I was the furthest thing from a sceptic. I've been offering $100K bet on this thing since long before I ever built it.

The reason we did finally build one was simply that so few people were satisfied with either our analyses, analogies, or even the videos we later learned about that Goodman had already made. We were naive enough to think we could more or less lay this to rest by demonstrating it under controlled conditions (i.e. treadmill, indoors, perfectly level, constant speed, etc.). In fact just the opposite ends up being the case. Rather than settling the silly thing, physical proof seems only to fan the flames of this holy war.

No need for either media to be a fluid even:

http://www.youtube.com/watch?v=E7vcQcIaWSQ

http://www.youtube.com/watch?v=k-trDF8Yldc

http://www.youtube.com/watch?v=9Yt4zxYuPzI

 

If I could con someone to put a bet of $100k on it I would demonstrate my boat. It would be about the only way of getting some value from the effort.

It is easy to talk about a 15m propeller but when you draw it on a slender 7.2m long hull you appreciate it is massive. The blades could be made out of 1m wide carbon fibre over thin foam core. I kept the chord below 0.5m so standard width would do the job in one layer.

I have not looked at how small the prop could actually be for a demonstration boat in ideal wind. The problem with the boat is the drag is increasing roughly with the square of speed and there is a wave drag hump to overcome at low speed with shorter hulls. So it is more demanding than the road vehicle.

By the way I was thinking about an open area test of a land vehicle and thought that a smoke maker on board might provide good visual evidence that it is exceeding windspeed.

Rick W

 

Yup. I always tried to convince people it was possible using some fairly straightforward analyses, as well as the various analogies. The bet was offered only to those that claimed to be absolutely positively certain that it's impossible - and were arrogant about it. It ends up no one was ever quite as certain as I was. One guy in Germany finally accepted the bet, started to raise the money from local "investors", but asked to be let out of the bet when he came to learn it does work. This guy had been astonishingly arrogant and insulting for something like 34 pages.

Agreed. That's what I've been promoting to JB for our full-scale vehicle. He also wants to do a streamer on the cart along with streamers all way along the course.

 

ROFLAO!! -- and you know this how?

We've presented plenty of physical evidence other than "some videos". Anyone who wants to see it in person is welcome to come around and quite a number have. Additionally we have made it very easy through parts lists and build videos for folks to build their own and quite a number have.

There's even a respectful skeptic over on Sailing Anarchy who I sent one of my very own carts to (I paid shipping) so he could test it on his own.

We've done independent peer review up the wazoo -- wanna be part of it or do you just want to spout of thing you don't understand?

JB

 

chabrenas
I have added the couple of extra slides and turned the thing around a little as a challenge. Hopefully this will engage people more.

Let me know what you think. Please feel free to use it elsewhere if you think it might get people thinking along the right lines.

I was trying to make it a plausible young engineer's dilemma thinking he has discovered perpetual motion. So it should be a challenge to would-be physicists

Rick W

 

Are you saying that a fleet of ice boats will not have a VMG>TWS? If there are several ice boats around you, those must have already "taken the energy" from the wind. So, according to your theory, a bigger fleet of ice boats is resticted to VMG<TWS, while a single ice boat can do VMG~3*TWS. Does that really make sense to you? I think you need to reconstruct your theory of a single ice boat having VMG>TWS.

Surely there is some "bad air" from the other ice boats and that "bad air" will slow you down. Also there is some "bad air" from one blade of the propeller to the other one, especially at slow apparent wind. That "bad air" slows a bit the ice boat, just likes it slows a bit any sailing vessel, and it makes the propeller less efficient. But why should it always drop the VMG below TWS?

Joakim

 

Because if it didn't that would suggest DDWFTTW might be possible.

These are getting too easy.

 

Rick: I like your challenge. One small typo on page 2 - "...after seeing the powered requred" s/be "power".

PS showing my age, and how long it is since I designed & built (free flight) model aircraft - the outrunner motor is a new concept to me. Neat.

 

Spork: My atrophied brain showing lack of imagination again - hadn't thought about leaving a gap between two solid surfaces <:=<

The last of the videos you linked to is an excellent demonstrator for frames of reference and relative motion.

PS I think this whole forum should be banned. I didn't get to bed until 01:15 this morning.

 

I saw the spello after I reread. I will correct.

The outrunner motors combined with Mosfet controllers and Lithium batteries are quite something. You can get 10kW motors that easily fit in the palm of your hand. They will not do this continuously but they are designed to have peak efficiency at power levels well above their continuous rating. The best of the lithium batteries will produce 10kW and still be carried in one hand.

The electrics are a fraction of the price of IC stuff and offer better power to weight. Could you imagine a $10 helicopter that actually flies with radio control 10 years ago.

Rick W