Build A Power Boat , Powered By Wind

What you are describing is a situation where the apparent wind velocity increases, which is analogous to a stationary wind turbine subject to an increasing true wind speed. In both cases the Betz limit does apply and tells you the maximum percentage of wind energy you can theoretically harvest for each istantaneous wind speed.

 

This doesn't hold true, unfortunately, even though the maximum theoretical amount of energy that can be extracted from the relative wind remains at the Betz limit. The key is to look at both sides of the energy equation and spot the way that the apparent extra energy from the increased velocity is matched by the additional energy expended to maintain that velocity. The two terms cancel, so the effective power that can be extracted remains the same. If this were not so then the machine would be in violation of the laws of conservation of energy - in effect it would be heading towards a "free energy" machine.

Seems like a good approach, trading drag for energy extraction efficiency. There has to be a "sweet spot" in the power extraction efficiency/drag compromise for any particular vehicle power requirement and speed and finding this will be key to getting their vehicle to go as fast as possible. My guess is that they may well have to do a few experiments to find this "sweet spot" as it will be damned hard to model aerodynamically. The drag of propellers/turbines is pretty complex to analyse in this application, where turbulence, ground induced wind shear etc are all going to be significant players in overall performance.

Jeremy

 

What I actually meant there was just the power harvested by the moving turbine itself, which is unlimited regardless of the Betz limit. I wasn't considering the energy expended to move it at that point.

 

The Betz limit does still apply though, the wind turbine can only ever get a theoretical 59.3% of the energy out of the relative wind speed (i.e. the apparent speed of the wind relative to the wind turbine).

The energy equation remains balanced at any speed, as it must to remain consistent with the law of conservation of energy.

Apart from drag increasing with the square of speed, and power increasing with the cube of speed, there is a slight efficiency gain with higher inflow velocities to a turbine, up to the point where compressibility effects begin to create additional losses. This means that the turbine for the upwind machine should be slightly easier to design than the prop for the downwind machine, as it doesn't need the relatively high static drag that the downwind machine needs to get going.

The downwind machine prop was a bigger compromise, because it actually needed relatively high prop drag in order to function, and this drag had to be high enough to overcome initial rolling resistance with the prop only turning very slowly (prop drag increases as prop rpm increases).

Jeremy

 

without calculation a 11m long handmade boat was built


This is a boat built by one of the aborigine of Taiwan. It is 11m long 1.75m wide. They have several hundreds years of built such boat. they do not have to calculate. just follow their ancestors memeries , the boat was built.
Just look at the hull shape, you will understand how to build a boat with low
resistance.

 

No complicated engineering and no investment money there. A lot of muscle and sweat. But a lot of boats failed and a lot of people died at sea in that era too.

 

What I want to say is, in the boat building. You don't have to calculate or complicated engineering . Just refer to similar esisting design (a well-known brand yacht maker). You
can build a safe boat. Despite poor soa and bad outward appearance.

 

You could build a boat by eye like they did hundreds of years ago or cobble together a bad knock-off of an existing, yes. But what's the point of building something less-than-optimal? The cost of proper engineering and design is not great in the overall cost of having the boat.

 

Did they ask for other investors money? Did they claim to have designed a boat and have no clue of what that "design" would be?
Did they sell the idea that it is a new kind of boat?

Your arguments are getting weak - 1st wright brothers and now this. Which one is it?

Of course there are lots of classic designs that were not calculated. They cam about through evolution over loooong period of time. Bad boats woudl be forgotten and good ones copied with small changes slowly improving the design.

Are you planning on building thousands of wind boats and always improving on the successful ones slowly reaching a working design?

How old are you btw. I can make you much more marketable illustrations for you project. 10k USD would probably get you something.

 

Wind,

Tell you what as soon as you have a couple of hundred years of boat building experience, building the same boat then it is a fair comparison.

What you are trying to sell is a brand new never before been done idea. So in this age of knowledge, where we know how to do calculations not doing them makes you look like either a fraud, or not very serious about the project. And since just a few simple calculations show your idea to be junk you need to show a lot more to be taken seriously.

 

You know it's pretty darn annoying to have people lie and viciously attack you as Boston is doing now. And it was just as annoying when he lied and attacked us the first time around. I just have to be glad that he chooses to lie about us now on the very same forum that still has the record in black and white for all to see. I can only imagine the attacks then (and now) came from the fact that this little brain-teaser challenged his intuition.

Nothing would make me happier than for anyone with questions on the issue to read the original thread for themselves.

My first post on that thread can be found on this page: http://www.boatdesign.net/forums/boat-design/wind-powered-sail-less-boat-24669-20.html
Boston's first response to me can be found on that same page.

 

Boy, the more I look back at that original thread, the more mad I get. I strongly encourage anyone here who's read Boston's consistently vicious lies to read it starting from my first post linked above. His lies and attacks are just wall to wall. And his lies in this thread are just as bad - nearly every word he's posted on the topic.

 

Have you worked out the power that is being delivered by the rowers in that rowing boat?

Each rower can deliver around a sustained 100 to 120W, so the 17 rowers in that boat are delivering around 1.7 to 2kW of power to the oars. Oars are around 50% efficient, so the effective propulsive power will be around 1kW or less.

How do you think this compares to your wild guess that you need 100kW for your boat?

Jeremy

 

For a boat that is non-critical in terms of performance you are right.

BUT, you want to build a boat that needs to be very carefully optimised in order to work at all, let alone have good performance.

Sorry, but you just can't guess at things like power requirements, battery size, wind generator size and hope to get close to something that will work well, if at all.

Jeremy

 

They did do it. But wern't the first. I think that's what Boston means.
Despite not being the first, they were very eager to take the credit when some of the media (not knowing the history of the subject) started to accord them the title of "inventors" and therefore they sought to gain the glory. Only belatedly did they acknowledge their idea was not original. In fact, Spork can be quoted from another forum (Merlin Rocket) that he "conceived the idea" and writes an article of how he evolved it without even mentioning other researchers. In fact the matter had been discussed in the relevant circles for many years.
However, the record shows that a working model made by Jack Goodman(which was later demonstrated on Youtube) was described in AYRS "Catalyst" in January 2006, but that the matter was not suggested by Spork on an r/c forum (or similar) until April of that year.