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 Boat Design Forums Windmill or Wind Turbine- powered boats: how many are out there, and are they viable?

#406
09-22-2009, 03:08 AM
 Guest625101138 Previous Member Join Date: Jan 2007 Rep: 0 Posts: 0
Quote:
 Originally Posted by Windmaster "There is absolutely no correlation between the thrust and speed." - you said it! So therefore, if a jet is flying slowly, and the pilot opens the throttles to increase the engine thrust, you are saying it makes no difference to the speed. Well they certainly needn't bother with reheat then! Similarly, opening up a speedboat and increasing the propthrust does not make it go faster. Quite surprising, I never knew that! ...
The rated thrust will usually be the maximum the engine can deliver. It may be at take-off speed, a static thrust (usually stated) or some other speed. The rated speed means the peak speed it will get to in level flight - this implies movement of course.

Measuring the thrust under static conditions will give no indication of what thrust will be produced at the rated speed. This is something you need to comprehend.

When moving through water or air the relationship between speed and drag is typically close to a squared function providing wave drag is not significant for the case of a boat.

It is important that you appreciate there is no point in measuring static thrust as a means of forecasting the speed.

The analogy you have given with extra thrust producing extra speed has no relationship to what happens at static conditions.

You cannot measure the static thrust of a turbi-prop boat and use it to predict speed. The only way to determine speed is through complex analysis or to actually measure the speed. The simple way is to measure the speed.

So anything you do measuring force is a waste of time in terms of predicting what speed can be achieved.

If I wanted to produce the highest force with the turbi-prop I would have chosen a much larger prop and geared it down. As I said this could drag you through the water quite easily. Its terminal speed would be about 1kph. But we are not making tugboats. We are making craft to go somewhere at pace comparable to other small craft.

Rick W
#407
09-22-2009, 03:32 AM
 Guest625101138 Previous Member Join Date: Jan 2007 Rep: 0 Posts: 0
Quote:
 Originally Posted by Windmaster Let me help you, what you really mean to say is that thrust and speed don't necessarily correlate because there is another factor involved - load. A high thrust may not move a heavy load as fast as a low thrust with a light load. Simple isn't it!
No that is not the point.

The point is that the thrust will change with the speed. At some point there is a ballance between drag and thrust and the boat achieves a terminal speed. Both the thrust and drag are changing with speed. The thrust is not constant because the conditions at the turbine and prop are a function of speed.

You have a very low geared system that can pull strongly from rest. However it soon reaches terminal velocity that is disappointingly slow. You had a little more flexibility because the gearing could be varied in your original boat.

By contrast my system is higher geared and does not get into its straps until it winds up. I could have easily made something more like a tugboat but my object is to MOVE, make headway not PULL at zero speed. THis is very important. PULL does not mean MOVE.

You would not be able to trim the big straight blades to get the pitch I can achieve with my twisted blades. My thin blades whipping around at high velocity achieve much higher efficiency than you can with a large number of fat blades.

System efficiency is the factor that determines the boat speed relative to the windspeed.

Think about hooking an F1 racing car to a Mack truck and having a tug-of-war. Despite the F1 car having more power the Mack truck will easily win. Now line the Mack truck up on the grid beside the F1 and have a race around the track. This is actually MOVE. The F1 will finish before the truck gets into top gear.

If you measured the pull of the Mack truck and compared it with the pull of the F1, by your reckoning, you would predict the Mack truck would have the highest speed because it would pull a lot more. That would be wrong as static pull has no correlation to terminal speed. Static PULL does not equate to SPEED.

Rick W
#408
09-22-2009, 04:20 AM
 Windmaster Senior Member Join Date: Nov 2006 Rep: 56 Posts: 225 Location: Norwich UK
Well, ok.
We will have to differ on these points.
I would recommend however, that when I publish details of my simple model, that you build one, exactly as I recommend. Then you can satisfy yourself in your own mind that your system is better.
#409
09-22-2009, 05:17 AM
 Guest625101138 Previous Member Join Date: Jan 2007 Rep: 0 Posts: 0
Quote:
 Originally Posted by Windmaster Well, ok. We will have to differ on these points. I would recommend however, that when I publish details of my simple model, that you build one, exactly as I recommend. Then you can satisfy yourself in your own mind that your system is better.
Why would I take up your recommendation. I have a boat that I can sit on that does something like twice the speed of the boat you could sit on and you somehow think your system is better.

What I may do is take my existing boat out on a day of steadier/stronger winds to see what I can do closer to the power limit of drive system. I will take a camera on board so you can get a sense of what it means to move rather than just pull.

You should do yourself a favour and measure the terminal speed your model achieves. The fact that it will pull on a piece of string is not at all significant. If you could achieve something like the windspeed into the wind then that would have serious merit. Pulling on a piece of string means nothing.

Rick W
#410
09-22-2009, 12:41 PM
 Windmaster Senior Member Join Date: Nov 2006 Rep: 56 Posts: 225 Location: Norwich UK
[quote=Rick Willoughby;300930]Why would I take up your recommendation. I have a boat that I can sit on that does something like twice the speed of the boat you could sit on and you somehow think your system is better.

What I may do is take my existing boat out on a day of steadier/stronger winds to see what I can do closer to the power limit of drive system. I will take a camera on board so you can get a sense of what it means to move rather than just pull.

You should do yourself a favour and measure the terminal speed your model achieves. The fact that it will pull on a piece of string is not at all significant. If you could achieve something like the windspeed into the wind then that would have serious merit. Pulling on a piece of string means nothing.

Rick W[/QUOTE

Exactly the answer I predicted. I just hope other members of this forum are reading these posts and noting your attitude.
#411
09-22-2009, 12:55 PM
 backyardbil Junior Member Join Date: Jul 2009 Rep: 39 Posts: 61 Location: Scotland
Quote:
 Originally Posted by Rick Willoughby Why would I take up your recommendation. I have a boat that I can sit on that does something like twice the speed of the boat you could sit on and you somehow think your system is better. What I may do is take my existing boat out on a day of steadier/stronger winds to see what I can do closer to the power limit of drive system. I will take a camera on board so you can get a sense of what it means to move rather than just pull. You should do yourself a favour and measure the terminal speed your model achieves. The fact that it will pull on a piece of string is not at all significant. If you could achieve something like the windspeed into the wind then that would have serious merit. Pulling on a piece of string means nothing. Rick W
Rick
Don't you think you're being a little unfair on the guy. After all, his boat was before yours by 14 years. It's like the Concorde builders belittling the Wright brothers because they didn't go so fast.
By the way there does not seem much difference to me in the videos, espescially since his boat was rather fat and had a lot of wind resistance.
#412
09-22-2009, 07:14 PM
 Guest625101138 Previous Member Join Date: Jan 2007 Rep: 0 Posts: 0
Quote:
 Originally Posted by backyardbil Rick Don't you think you're being a little unfair on the guy. After all, his boat was before yours by 14 years. It's like the Concorde builders belittling the Wright brothers because they didn't go so fast. By the way there does not seem much difference to me in the videos, espescially since his boat was rather fat and had a lot of wind resistance.
bil
You have hit the nail on the head. Without any understanding of how things actually work and measurement of performance we would not have advanced from what the Wright brothers achieved to what we have now.

My very first turbi-prop model in 1983 used a typical windmill multi-bladed turbine and a typical boat propeller. It worked poorly ie it moved very slowly, aided by roughly made interconnecting pulley drive but principally because the turbine and propeller were low efficiency.

The lack of scientific enquiry in what Peter has done astounds me. He is bemused by the fact that it can work rather than actually doing any performance measurements. If you built something like this wouldn't you want to measure the speed achieved? Would you be satisfied with just moving? The idea has been around forever and it has not been exploited in any significant way. Doing any testing without measurement leads nowhere.

There is very little interest in this thread because anybody can see all that complexity to produce very ordinary performance when compared with a simple sail - why bother with the system.

As far as comparative performance I know what I have done and can show others in various ways. Peter has not bothered to measure the speed or provide any means of assessing it. He puts up video of a model gently pulling on a piece of string to show how well it works. This is meaningless. He needs to measure speed. He then needs to make adjustment, measure speed again, make more adjustments based on outcomes and continue the process until he understand what works best. Eventually he will realise that efficiency of turbine and propeller are the driving factors, as the Aeolus racers demonstrated, and then concluded high speed, high aspect twisted foils are the best for his blades.

I know these things because I understand how they work. I actually have a photograph playing with a cardboard VAWT in 1976 as the possibility intrigued me and there was no internet to easily search for what others had done. As the earlier part of this thread shows there have been useful boats built. Some have a reasonable idea of what they were doing and backed their ideas with big investments. The limit in any useful system is the power transfer requirements to get any decent speed into the wind. All that complexity is hard to justify when compared with a stick in the air supporting a piece of fabric.

Rick W
#413
09-23-2009, 11:48 PM
 backyardbil Junior Member Join Date: Jul 2009 Rep: 39 Posts: 61 Location: Scotland
50/50

Quote:
 Originally Posted by Windmaster 5. With tip speed on only 1, half the lift force is used to turn the turbine with only 50percent adverse thrust, therefore relieving the stress on the drive system. ....
Rick
Something interested me about what Windmaster said:

He says his is 50/50 (turning vs adverse) how different is that from your turbine? Maybe yours is nearer 30/70?
#414
09-24-2009, 12:39 AM
 Guest625101138 Previous Member Join Date: Jan 2007 Rep: 0 Posts: 0
Quote:
 Originally Posted by backyardbil Rick Something interested me about what Windmaster said: He says his is 50/50 (turning vs adverse) how different is that from your turbine? Maybe yours is nearer 30/70?
Peter's understanding of this is simplistic. The force is only half of the equation.

Near the tip my blades are at about 80 degrees to the wind direction. The rotating component of the lift force is about 16% of the drag component so in Peter's terminology the ratio is 16/84. Even worse than he estimated.

However the velocity of my blade near the tip is about 7 times the near field wind velocity. So my force ratio might be adverse but my velocity ratio is highly favourable. My high velocity single blade will be generating substantially more power than a slow moving blade for a given force to hold it against the airflow.

The actual power to push the turbine through the air will be the velocity of the boat through the water against the force on the turbine. Because I can generate considerably more power for the force on the blades I can get a higher terminal boat velocity.

The most effective part of my blades is within 80 to 90% of the tip as this is where a significant portion of the power is produced. The most efficient part is around the 50% point but the efficency does not vary that much across the blade.

Understanding the relationship between force, velocity and power are the keys to understanding why a turbi-prop boat works and also what will give the highest ratio of boat speed to wind speed.

Rick W
#415
09-24-2009, 04:31 AM
 Windmaster Senior Member Join Date: Nov 2006 Rep: 56 Posts: 225 Location: Norwich UK
Quote:
 Originally Posted by Rick Willoughby However the velocity of my blade near the tip is about 7 times the near field wind velocity. So my force ratio might be adverse but my velocity ratio is highly favourable. My high velocity single blade will be generating substantially more power than a slow moving blade for a given force to hold it against the airflow. Rick W
I know this, why do you think I have 8 blades (latest models) when you have only two? also my blades have much greater area (more lift) than yours. So your 7 times amplification may very well end up with less power.
.....
#416
09-24-2009, 04:39 AM
 Guest625101138 Previous Member Join Date: Jan 2007 Rep: 0 Posts: 0
Quote:
 Originally Posted by Windmaster I know this, why do you think I have 8 blades (latest models) when you have only two? also my blades have much greater area (more lift) than yours. So your 7 times amplification may very well end up with less power. .....
What you do not know is how the Re# alters the lift to drag. I have somewhat lower chord blades operating at much higher velocity with considerably better lift to drag ratio. I also have a greater swept area so I am not slowing the air down as much for the power I am extracting. Again this keeps my blades in a more favourable regime. You blades will be interfering with each other.

But then you do not bother to measure performance so this is not something that would interest you.

Rick W
#417
09-24-2009, 04:59 AM
 Windmaster Senior Member Join Date: Nov 2006 Rep: 56 Posts: 225 Location: Norwich UK
Quote:
 Originally Posted by Rick Willoughby What you do not know is how the Re# alters the lift to drag. I have somewhat lower chord blades operating at much higher velocity with considerably better lift to drag ratio. I also have a greater swept area so I am not slowing the air down as much for the power I am extracting. Again this keeps my blades in a more favourable regime. You blades will be interfering with each other. Rick W
Let me correct your errors here.
Your don't have greater swept area, mine is bigger.
At the angle of my blades, 45 degrees, they don't interfere with each other.
Of course, if I used your angles there is no doubt they would interfere with each other.
Your autogiro type lifting rotor is the one that is slowing the air down (and hence creating enormous backforce) my slow-speed rotor merely diverts the air, and behind the rotor will be a vortex. It makes more sense to let the air through and divert it somewhat rather than stopping it dead and creating huge pressures that you then need to overcome.
.....
#418
09-24-2009, 05:08 AM
 Guest625101138 Previous Member Join Date: Jan 2007 Rep: 0 Posts: 0
Quote:
 Originally Posted by Windmaster Let me correct your errors here. Your don't have greater swept area, mine is bigger. At the angle of my blades, 45 degrees, they don't interfere with each other. Of course, if I used your angles there is no doubt they would interfere with each other. Your autogiro type lifting rotor is the one that is slowing the air down (and hence creating enormous backforce) my slow-speed rotor merely diverts the air, and behind the rotor will be a vortex. It makes more sense to let the air through and divert it somewhat rather than stopping it dead and creating huge pressures that you then need to overcome. .....
Peter
If you start to do some actual speed measurements and understand what gives the best performance you will stop making silly statements. When you are getting 40 or 50% of windspeed into the wind then you might start to get some attention. However that will mean you will have to understand what is happening and design the system to take the maximum advantage of it.

Good luck with your unscientific fiddling.

Rick W
#419
09-24-2009, 05:21 AM
 Windmaster Senior Member Join Date: Nov 2006 Rep: 56 Posts: 225 Location: Norwich UK
Quote:
 Originally Posted by Rick Willoughby Peter If you start to do some actual speed measurements and understand what gives the best performance you will stop making silly statements. When you are getting 40 or 50% of windspeed into the wind then you might start to get some attention. However that will mean you will have to understand what is happening and design the system to take the maximum advantage of it. Good luck with your unscientific fiddling. Rick W
Thankyou. I'm getting quite near to the 40 or 50 percent you mention. Don't forget the basis of all science is experimentation, not theory alone.

Good luck to you too!
#420
09-24-2009, 08:30 PM
 Guest625101138 Previous Member Join Date: Jan 2007 Rep: 0 Posts: 0
Quote:
 Originally Posted by Windmaster Thankyou. I'm getting quite near to the 40 or 50 percent you mention. Don't forget the basis of all science is experimentation, not theory alone. Good luck to you too!
Experimenting without measurement is fiddling. How do you know you are within 40 or 50% of the windspeed - wet finger guess. You have not taken any measurement. You will never improve because you have no reference.

Rick W