Wind powered vehicle speeds much faster than wind; downwind! - Page 2 - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > General Interest > General Discussion (sailing related)
 Not a Member? 


Reply
 
LinkBack Thread Tools
  #11  
Old 10-22-2010
JohnRPollard's Avatar
Moderator
 
Join Date: Mar 2007
Location: Chesapeake
Posts: 5,680
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 10
JohnRPollard is a jewel in the rough JohnRPollard is a jewel in the rough JohnRPollard is a jewel in the rough
Quote:
Originally Posted by johnnyandjebus View Post
...
He did say stupidier than the internet, he doesn't include sailnet in that statement, does he?...
Obviously not. He never showed up here with his "novel" ideas. Had he read Could a Fan in Front of a Sailboat Improve Sailing? , he could have saved a lot of time, effort, and money.

This is a clear infringement of our patented SailFan (TM) technology. Time to lawyer up.


__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Pacific Seacraft Crealock 31 #62

NEVER CALLS CRUISINGDAD BACK....CAN"T TAKE THE ACCENT
Reply With Quote Share with Facebook
  #12  
Old 10-22-2010
JohnRPollard's Avatar
Moderator
 
Join Date: Mar 2007
Location: Chesapeake
Posts: 5,680
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 10
JohnRPollard is a jewel in the rough JohnRPollard is a jewel in the rough JohnRPollard is a jewel in the rough
Quote:
Originally Posted by Dirtboy View Post
Yep, it's a wind driven vehicle. However, before you saw the video I think you would swear any wind driven vehicle would never be able to achieve twice or three times wind speed going straight downwind. Am I right or wrong? I don't recall anyone calling it a "sail powered" vehicle. The only thing it has in common with a sailboat is the power source: wind. That, however, puts it in an exclusive group that also includes our beloved sailboats.



It did have telltails, streaming forward at first the rearward as the machine exceeded wind speed.

I know it's not a sailboat and may not be appropriate for this forum, I'm just a sucker for cleaver ideas and the people who see them through.

Will it ever have any use on a boat? Who know's? The future is full of surprises and someday we may find out that everything we know is wrong.

DB

On a serious note, this is definitely fascinating stuff. I'm still trying to wrap my head around it. Not to take anything away from these guys, reading further along in the article it turns out this concept was previously proposed in the 1940's by a student at U Mich.

Also, did anyone notice that the author of the article is the same guy that the article is about? Kind of odd to write about himself like that.

But, like others, I don't consider it sailing, even if it is wind powered. We could have a wind-powered generator driving an electric motor. Would that count too?

I'd prefer to see efforts made toward improving windward performance. Even garbage scows will sail well dead downwind.
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Pacific Seacraft Crealock 31 #62

NEVER CALLS CRUISINGDAD BACK....CAN"T TAKE THE ACCENT
Reply With Quote Share with Facebook
  #13  
Old 10-23-2010
Junior Member
 
Join Date: Oct 2010
Posts: 16
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 0
eyytee is on a distinguished road
Quote:
Originally Posted by JohnRPollard View Post
This is a clear infringement of our patented SailFan (TM) technology.
Invalid due to prior art:

youtube.com/watch?v=0CrXvOKPymk

Quote:
Originally Posted by JohnRPollard View Post
But, like others, I don't consider it sailing, even if it is wind powered.
Well, some fundamentalists don't even accept the BMW-Oracle with the wing sail as a "sail boat". To me (and the North American Land Sailing Accociation seems to agree here) this rotor-yacht is still sailing, just with sails that move relative to the vechicle

Quote:
Originally Posted by JohnRPollard View Post
We could have a wind-powered generator driving an electric motor. Would that count too?
No, if you convert kinetic energy into electrical energy and potentially even store it, NALSA would not accept this. But this vehicle uses wind energy directly to propel itself, just like any sail boat does. Comparison of a sail boat on a broad reach to this propeller:

youtube.com/watch?v=UGRFb8yNtBo

Quote:
Originally Posted by JohnRPollard View Post
I'd prefer to see efforts made toward improving windward performance.
If you change the gearing (e.g. wheel size or blade angle) this vehicle will go directly up wind. Potentially faster than the true wind. Both directions (down & up wind) are visualized here:

youtube.com/watch?v=FqJOVHHf6mQ

Last edited by eyytee; 10-25-2010 at 01:49 AM.
Reply With Quote Share with Facebook
  #14  
Old 10-24-2010
tomaz_423's Avatar
Senior Member
 
Join Date: Feb 2006
Location: Slovenia
Posts: 410
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 9
tomaz_423 will become famous soon enough
I try to have open mind about it.

Few centuries ago people believed the earth is flat and a sailboat can sail any wind angle from DDW to reaching (close to 90%), but not higher.

I understand that the wind force is not linear with wind speed but squared and here apparent wind helps to create some healthy forces.
The sailboat can sail faster then true wind, but I understand not faster then apparent wind.

I have problems understanding this part:

Let us say the vehicle is traveling DDW.
Slower then the wind. It accelerates.
It reaches the speed of the wind.
What apparent wind does it have at that point? 0. Nada. Zero.
So, what the hell is turning the prop at that moment?
If there is no force from the wind it must come from somewhere else or we could make wind turbines to generate electricity in no wind.
I must take a closer look at this. At first glance it seems not possible.
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Beneteau Oceanis 473

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

full time cruising
Reply With Quote Share with Facebook
  #15  
Old 10-24-2010
JomsViking's Avatar
Splashed
 
Join Date: Apr 2007
Posts: 554
Thanks: 28
Thanked 4 Times in 4 Posts
Rep Power: 8
JomsViking is on a distinguished road
The propeller is NOT driving the wheels, it is the wheels driving the prop, hence it is changing the apparent wind - due to loss and friction, they can only go "somewhat" faster than the wind, hence they aim for 3 times.

Pls. note that BMW Oracle moved from A to B faster than an object that could have moved directly downwind with the speed of the true wind, hence it did the same as the vehicle discussed here (albeit by tacking instead of using a propeller).


Quote:
Originally Posted by tomaz_423 View Post
I try to have open mind about it.

Few centuries ago people believed the earth is flat and a sailboat can sail any wind angle from DDW to reaching (close to 90%), but not higher.

I understand that the wind force is not linear with wind speed but squared and here apparent wind helps to create some healthy forces.
The sailboat can sail faster then true wind, but I understand not faster then apparent wind.

I have problems understanding this part:

Let us say the vehicle is traveling DDW.
Slower then the wind. It accelerates.
It reaches the speed of the wind.
What apparent wind does it have at that point? 0. Nada. Zero.
So, what the hell is turning the prop at that moment?
If there is no force from the wind it must come from somewhere else or we could make wind turbines to generate electricity in no wind.
I must take a closer look at this. At first glance it seems not possible.
__________________
Watch great footage about the story of one manís slow odyssey around the UK:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #16  
Old 10-24-2010
Junior Member
 
Join Date: Sep 2006
Posts: 21
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 0
otaga05 is on a distinguished road
Quote:
Originally Posted by tomaz_423 View Post

I have problems understanding this part:

Let us say the vehicle is traveling DDW.
Slower then the wind. It accelerates.
It reaches the speed of the wind.
What apparent wind does it have at that point? 0. Nada. Zero.
So, what the hell is turning the prop at that moment?
If there is no force from the wind it must come from somewhere else or we could make wind turbines to generate electricity in no wind.
I must take a closer look at this. At first glance it seems not possible.
The wheels are pushing the prop. It is the thrust from the prop that is pushing the whole thing forward, not the wind as such.

Consider the example they give of the device operating on a treadmill with no wind. The treadmill turns the wheels, the wheels in turn operate the prop and the prop pushes the device forwards against the direction of the treadmill. In order for this device to work the forwards thrust from the prop has to be larger than the backwards force of static friction on the wheels. (If there is a hoax here, whether or not that is possible is at the crux of it.) The increased kinetic energy of the device as it accelerates forward comes from the treadmill motor.

Imagine that you are sitting in the device and it is moving downwind at wind speed. You sense no apparent wind, just like on the treadmill and the ground is running backwards underneath you just like the treadmill belt. The prop takes air that is at rest in front of you and gives it a backwards velocity from your perspective and the air gains kinetic energy. Where does the energy to do this come from? The Earth. When your wheels are pushed backwards by friction, you exert a forward force of friction on the earth slowing it down a tiny bit and reducing its kinetic energy. (Remember that the earth is moving backwards in a frame of reference where there is no apparent wind.) You don't notice any significant change in the motion of the earth because it is so massive.

From the point of view of a person on the ground the air that was moving faster in front of you has now been slowed down behind you by the prop. (Think of what an oar does to the water in a river as you row downstream.) The air has lost kinetic energy, and this kinetic energy loss is where the increased kinetic energy of the device comes from, and the ability to offset the energy loss due to drag. Where the energy appears to come from depends on your frame of reference.

Another way to visualize how this works is to take a spool of thread and set it up so that the thread unwinds from the bottom. Pull on the string and you will find that the larger force of friction on the edge of the spool (the thrust of the prop) causes the spool to move forward against your pull on the thread (the friction with the ground.)
Reply With Quote Share with Facebook
  #17  
Old 10-25-2010
JohnRPollard's Avatar
Moderator
 
Join Date: Mar 2007
Location: Chesapeake
Posts: 5,680
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 10
JohnRPollard is a jewel in the rough JohnRPollard is a jewel in the rough JohnRPollard is a jewel in the rough
Quote:
Originally Posted by eyytee View Post
Invalid due to prior art...
I get the impression you did not take the time to read the thread to which I linked above. Here it is again. Read carefully from cover to cover -- all the answers are there:

Could a Fan in Front of a Sailboat Improve Sailing?

P.S. Welcome to Sailnet!
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Pacific Seacraft Crealock 31 #62

NEVER CALLS CRUISINGDAD BACK....CAN"T TAKE THE ACCENT
Reply With Quote Share with Facebook
  #18  
Old 11-04-2010
JohnRPollard's Avatar
Moderator
 
Join Date: Mar 2007
Location: Chesapeake
Posts: 5,680
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 10
JohnRPollard is a jewel in the rough JohnRPollard is a jewel in the rough JohnRPollard is a jewel in the rough
Quote:
Originally Posted by Dirtboy View Post
... The fact that it creates apparent wind and then uses that aparent wind to increase speed ......... if you carry that thought through, it could potentially continue to accelerate to amazing top speed....
I just wanted to elaborate on what some others have already commented about, i.e. the prop blades are not acting as sails to propel the vehicle. In other words, there are no sails that use the apparent wind or benefit from its effect, as DB's post above seems to suggest (if I understand him correctly -- apologies DB if I misunderstood what you meant).

This is how I understand it:

The vehicle initially gets moving simply by wind pushing on the surface area of the entire vehicle from astern. This causes the wheels to spin, albeit very slowly at first. The wheels are connected to the propeller via a drivetrain that has a geared advantage. So, the propeller spins in turn.

The initial forward motion is VERY slow because the vehicle gets almost no benefit from the turning propeller at slow speeds. In fact, the thrust from the propeller only gradually improves as the apparent wind approaches zero. That is because the breeze is blowing downwind faster than the propeller is thrusting air aft.

Once apparent windspeed drops to zero, the vehicle begins to accelerate much more quickly. This is because the propeller, driven by the wheels via the drivetrain, is now creating more thrust relative to the eliminated tailwind.

With a sailboat sailing dead-downwind, driven by pressure from the wind on the sails, apparent wind drops to zero when (if) the boat reaches true windspeed. At this point the sailboat is at a disadvantage, because apparent windspeed is zero and since the vessel is sail-driven, there's no more wind power to tap.

Just the opposite with this vehicle. In this particular type of windpowered vehicle, it is actually advantageous to have apparent windspeed drop to zero (this is why you see small scale versions do so well on the treadmill with no fan running). Because, this is the point where the tail wind is no longer subtracted from the propeller's thrust. From that point forward, the propeller is moving "with the current" as it were, so speed over ground increases dramatically. The new apparent wind (now a headwind) and the prop thrust begin to work together to complement eachother.

From what I can gather, the controversy surrounding this vehicle and what it demonstrated has less to do with the concepts and more to do with how poorly they were expressed/explained. Unfortunately, proponents consistently employed oddly chosen terminology, and made the mistake at the outset of implying that there was a connection between this vehicle and the sport we know as sailing. There is not. Yes, it is windpowered, but the similarity ends there.

This vehicle would be more analogous to a wind-powered "motorboat". On the water, you'd build it with a pointy bow and a lot of surface area at the stern, and paddle side wheels. The paddle wheels would be connected to an underwater propeller via a geared transmission. As the boat began to move downwind, the paddles would spin due to resistance in the water and they would in turn drive the propeller and produce thrust. The whole effect would be much less efficient than on land due to the greater resistance of the fluid environment as well as lack of "traction" for the paddles -- and of course a displacement hull would be constrained by its hull speed -- but it would be the same concept.

Anyway, that's the way I see. Neat concept, nicely demonstrated. But I'm confident it poses no threat to SailFan(TM) technology, which is actually applicale to sailboats and has a proven trackrecord.
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Pacific Seacraft Crealock 31 #62

NEVER CALLS CRUISINGDAD BACK....CAN"T TAKE THE ACCENT

Last edited by JohnRPollard; 11-04-2010 at 04:47 PM.
Reply With Quote Share with Facebook
  #19  
Old 11-04-2010
bljones's Avatar
Senior Member
 
Join Date: Oct 2008
Location: South Coast Ontario
Posts: 8,129
Thanks: 32
Thanked 70 Times in 63 Posts
Rep Power: 7
bljones has a spectacular aura about bljones has a spectacular aura about
Of course, to be truly awestruck by it's speed, we are all assuming that the surface is level, and that the vehicle is not actually hurtling down a 20% grade.
Reply With Quote Share with Facebook
  #20  
Old 11-04-2010
Junior Member
 
Join Date: Oct 2010
Posts: 16
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 0
eyytee is on a distinguished road
Quote:
Originally Posted by JohnRPollard View Post
the prop blades are not acting as sails to propel the vehicle.
What do you mean by "acting as sails" in physical terms? In terms of aerodynamics they are acting excatly just like sails on a broad reach with a downwind VMG > wind speed. This animation shows this very nicely:
youtube.com/watch?v=UGRFb8yNtBo

Quote:
Originally Posted by JohnRPollard View Post
In other words, there are no sails that use the apparent wind or benefit from its effect,
What do you mean by "use the apparent wind or benefit from its effect" in physical terms? Every airfoil (sail or propeller blade) can create an aerodynmaic force if it experiences relative air movement (apparent wind).

Quote:
Originally Posted by JohnRPollard View Post
Just the opposite with this vehicle. In this particular type of windpowered vehicle, it is actually advantageous to have apparent windspeed drop to zero
Note that the apparent wind at the rotating airfoils never drops to zero

Quote:
Originally Posted by JohnRPollard View Post
The new apparent wind (now a headwind) and the prop thrust begin to work together to complement eachother.
What you mean by "work together to complement eachother" in physical terms? Thrust is a force while apparent wind a velocity so you don't make much sense here.

Quote:
Originally Posted by JohnRPollard View Post
From what I can gather, the controversy surrounding this vehicle and what it demonstrated has less to do with the concepts and more to do with how poorly they were expressed/explained. Unfortunately, proponents consistently employed oddly chosen terminology,
Actually I find your terminology very odd and unclear.

Quote:
Originally Posted by JohnRPollard View Post
and made the mistake at the outset of implying that there was a connection between this vehicle and the sport we know as sailing. There is not.
The analogy to sailing is only useful to those who actually understand the physics of sailing.

Quote:
Originally Posted by JohnRPollard View Post
This vehicle would be more analogous to a wind-powered "motorboat". On the water, you'd build it with a pointy bow and a lot of surface area at the stern, and paddle side wheels. The paddle wheels would be connected to an underwater propeller via a geared transmission. As the boat began to move downwind, the paddles would spin due to resistance in the water and they would in turn drive the propeller and produce thrust.
So you want to harvest power from the water(via paddle wheels) and transmit it back to the water(via underwater propeller), and hope to create forward thrust by this? Good luck with that!

Sorry, this is not how this vehicle (and sailing in general) works. Just like any sail boat this vehicle takes energy from the velocity difference between two different media.
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
What makes a boat sail faster in less wind? kldzx9r General Discussion (sailing related) 10 10-07-2007 03:27 AM
how much is too much wind jimspafford Seamanship & Navigation 27 08-24-2007 07:22 PM
wind point / wind speed bkw Learning to Sail 4 09-11-2006 03:01 PM
Faster than the Wind Dan Dickison Seamanship Articles 0 10-20-2000 08:00 PM


All times are GMT -4. The time now is 11:42 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.