The Wind Powered Sail-less Boat

TUO
I essentially agree with what you say. I have concluded that most of the time the upwind set up would be used. For any practical purposes the difference between the upwind boat and the DDWFTTW boat would exclude their combination in a single system. It is somewhat like trying to make a spinnaker a good upwind sail or making a flat cut jib a good directly downwind sail.

As for getting the thing moving downwind I would expect the following to occur.

Think about the propeller blades and turbine blades connected on a common shaft with the propeller having a pitch of 1m and the turbine having a pitch of 3m. The propeller blades will present almost flat surface to the line of the hull. The turbine blades will have a much flatter angle to the line of the hull.

With everything at rest the wind past the blades will be trying to turn the propeller backwards but they are in a stall condition with AoA maybe 80 degrees. They might give a slight nudge backwards but this will be strongly resisted by the turbine blades churning in the water - effectively rotating paddles given their angle to the line of the hull.

The wind is exerting force on the propeller and the boat superstructure so it starts to move forward. Remember that a boat does not have static friction so the slightest force starts it moving. The windspeed past the propeller reduces so its tendency to turn backwards is reduced. Water is now moving past the turbine blades. The AoA of these blades is only around 40 degrees at rest so they will be generating maximum lift and high torque. This torque will overcome the counter torque from the propeller and begin to turn it forward.

So we now have both the turbine and the propeller spinning in the forward direction. The local slip steam at the propeller blades is going backwards relative to the boat although the far field apparent wind is still moving forward faster than the boat. So the propeller is now creating its own localised apparent wind due to its forward rotation.

The boat speed will continue to build until the power produced by the turbine balances the power absorbed by the propeller plus the drag on the hull and air drag on the boat when it exceeds the wind speed.

If you wanted to demonstrate a boat it is easy enough to do an unmanned model. I would use a long slender hull about 20ft long and maybe 6" beam with two small stabiliser. Make a propeller using carbon fibre 4m in diameter and pitch around 1m. Mount this near the bow. Make a steel turbine 0.6m in diameter with a pitch of 3m. Mount this at the stern. Connect turbine to propeller with a 1/4" spring steel shaft. The shaft would need three intermediate supports to prevent vibration.

You need a large prop to get any reasonable efficiency because the wind speed is so low. You need a long slender hull so the wave drag does not rise too quickly. The single curved shaft supported on bearings will have very low losses.

You then need to find a place where the wind is blowing steadily around 10 to 15kph. Set the boat at the start of a course that has small waves and let it go. You could video the exercise showing a ribbon being blown backwards and post here but the skeptics will remain skeptics and continue to look for the trick because they simply lack open minds and the ability to reason.

I would applaud the effort for curiosity sake. Windmaster might even claim you to be world famous.

Actually I am impressed that there are so many more people now building the DDWFTTW wheel vehicles to satisfy their curiosity. I expect it will only be a matter of time before someone tries a boat.

Rick W.

 

Tcubed
I have full VPP models for turbine/propeller boats that are modelled on actual blade profiles and foil polar data over the full range of Re# used in the analysis. I expect if you do the same you will conclude that you cannot find a workable solution that covers all bases irrespective of what you do with variable pitch and variable transmission .

In my view the best solution for a practical boat is using electric motors/generators in combination with batteries for storage and solar cells for a little extra energy input in calm weather. The only benefit in making the air turbine able to operate as a propeller is as a back-up to the water prop. Similarly it is unlikely that the water prop would ever be used as a turbine.

The ability for DDWFTTW is of such limited value that it is not worth while contemplating other than for curiosity value.

Rick W

 

I'm aware that you are a proponent of this system to be used in conjunction with energy storage systems and i agree that on the whole that is doubtless the most pragmatic setup, despite the energy losses.

I'm also aware that optimization across all scenarios is impossible without organically morphing foils, which are as yet beyond the wonders of high tech engineering.

However i admire the simplicity of the directly mechanical setup and am analyzing the mechanics of it in a simplistic way so far. I have solved the first part and would appreciate someone going over it to check i have not made a mistake and if the equations can be reduced further as they are quite complex. I don't feel like attemting to type the workings in here as i'll be at it for hours. I guess i'll fotograph the paper and post that (tommorow) .

I believe that gaining full understanding of this phenomenon is beneficial to better understanding some of the subtleties of regular sailing craft.

The data you have i would naturally be very interested to see.

 

please people, I know I am treating this a little harshly, but when I see this kind of blatant failure to comprehend the most basic tenants of physics
its just hard to not snicker a little

these numbers are laughable
folks must be talking fig newtons
cause the newtons we use in physics are dependent on mass and velocity
not just velocity

if you want math, try this ( its about as basic as it gets )

N=kgV/s2

this is some really basic stuff but apparently it needs to be explained
Ill give you a hint although all the hints Ive dropped so far have been ignored
N = newtons

energy
as measured in newtons is directly proportional to velocity and mass
not just velocity

if you need to ask questions
dont
this is pathetically obvious

I attempted to add mass to the equation early on
knowing that the system wouldn't survive the proof if I did
its max speed potential can only be its kinetic energy minus friction once distributed to all moving components of the system
something else I pointed out earlier

but it got ignored

anyone wonder why

why would the proponents of this system refuse to address an obvious proof of the system

keeping it simple the max energy of this system
if the plate and the cart both weigh the same ( say 2kg each )
and if the cart starts out at 0m/s and the plate at 2m/s
is 1kgm/s
doesn't mater what the gearing is
we will consider torque in a moment

I pointed the mass component out earlier
but because it screws up the results
and because there were obviously preconceived results
and because the lesson in perpetual motion insisted on ignoring mass entirely
the folks on the band wagon insisted on ignoring my comments

which is one of many reasons your model
your understanding of the most basic physics
and your conclusions
are laughable
in the real world
we have mass
I want a few of you folks to drop a large rock on your big toe a few times
till you learn about mass

also
this model
ignores delta T and
if you consider delta T then you find a system in perpetual acceleration
doesnt work without perpetual increasing the available energy
(is the word perpetual anathema around here, cause its what this thing represents)
its a simple fact that in any system
the faster you go
the more friction
the less energy you have available as positive velocity
so again
the system only provides diminishing returns in the real world
if it constantly wants to accelerate from the fixed energy source of the plate
( ok so now Im about to be told the wind takes the place of the plate and the top roller is the wind turbine )
( makes no difference, run that directly down wind and it'll still hit the same relative wind barrier Ive been pointing out from the go )
( run it across the wind like the ice racers do and all the moving crap makes you slower than they any day )

if you were to actually graph the results of the energy requirement of the system over time you would find they are required to increase exponential

why do you think I wouldnt play the game in the first place when I gave you the proof considering for mass

next problem
torque
your torque considerations are completely fictional since you ignored mass considerations
and
the energy of the rotational velocity of the wheels is directly subtracted from the forward motion of the vehicle
and no
Im not going to explain that one
its way to advanced for a class that's just learning that N is in some way related to mass and not just velocity
and not something just wrapped around a fig

( this model you suggest doesn't work )
( for the reasons previously specified )
( your welcome to use a fan all you want )

at this point I dont care how you can do it
as long as the vehicle is going directly down wind
you win the beer
Im actually hoping someone can come up with something
but so far

 

what I notice most when I watch this is how slow it is
( not very efficient what with all the friction in the system from all the gizmo's )
and that it looks to be decelerating when facing directly into the wind
so it seems it would end up going backwards on an extended upwind heading

Ild love to see some time trials evidence if anyone has it
but it sure doesnt look like its about to beet any speed records

 

Boston
Can you please explain what you mean by this equation. I accept the N means Newtons - a force.

what is the k, g, V and S???

Rick W

 

I have no idea why you would offer this video with regard to the current discussion. It shows an air turbine that is driving a water propeller. The DDWFTTW boat we are discussing has a water turbine driving an air propeller. Very significant difference in operation.

Rick W

 

Hi all,

I just had the patience to go all the way this looong thread (reading diagonally at times!). And I was feeling a bit depressed, so l was looking for something a little mind blogging!

I am ASTOUNDED!

This started with an interseting question: how to loose a war that has already been fought sort of thing. Effectively, nothing - by far - beats the speed obtainable by simple foils that a "sail" is, sitting on another foil that fights against leeway (and eventually provides lift), if no other power source than present wind is used,.

Accumulation is then a good answer to the question that was primarily asked, since it was not excluding "internal" power source.

But then this discussion about the capabilities of rotating foils (call them props, turbines, or else) or other means of using directly or undirectly wind energy by anything that could not be called a sail somehow diverted to this icredible discussion about Directly Down Wind Faster Than The Wind.

May I first say that any discussion that pretends to resolve a problem should be - basically - about the same problem for everyone? If one says Directly Downwind, that is not even at a fraction of an angle: that is directly Downwind. Period.

We all know that the ice sledges can go much faster than the wind. NOT Directly Downwind! We all know that diverse experiments have been conducted that show possible to go strictly directly upwind: the result is a desolation, and tacking is much faster altogether, but it works.

But then, an impressive number of numbers have been written down to demonstrate that what has NEVER worked does actually work! Show one! Do not say "it works, I demonstrate it, but that...hmmm...wait...we think it works..we are sure it does...but...hmmm...well: so long must admit it DOES not!"

Sorry guys: if, with the basic scientific attitude of following strictly the question as it is written down: DDFTTW: it does not work. Tacking downwind: it works. No matter how you will angle your "wind catching contraption": if the vehicle moves strictly down wind, it will never go faster than the wind. None can be shown. These little vehicles nicely rolling along the road have to be at an angle to the wind.

Write figures, go round in circles, even do these (sorry: ridiculous!) little sliding ceiling comparison (got to have totally misunderstood the problem to put that here!!!) : NOTHING has been demonstrated!

Care joining the team for a beer?

 

2 things.
1.
If taking downwind makes it possible to go faster down wind can I make a machine that is a broad frame in which a device takes back and forth (down wind) and pushes that cage directly downwind?
If it is acknowledged that there is no weird science or perpetual motion in traveling faster than the wind when tacking it is only reasonable to extrapolate that it is possible to break those components and go straight down wind without braking any laws of physics. Obviously normal wing can't do that as its loses the flow on its surface.

2. If you suggest that the small carts are working because they are actually traveling of the wind then how do you explain the treadmill experiment. After all the starting phase of a treadmill experiment is as if vehicle is rolling (directly) downwind exactly at the speed of the wind (no apparent wind).

Call diagrams ridiculous at least Rick is taking time trying to explain his point.

And about the practicality of all this. Fully agree traditional wing beats these contraptions clearly - its more of a mental exercise on a dilemma that is counter intuitive and thus gets slammed by people like you.

 

2c - besides, I am enjoying the discussion, learning something and having a beer... Keep the discussion going it is interesting....

 

MR 3dyachts

team beer is ready for some new members anytime

also
I notice the timbre of my threads has gotten a little sarcastic
for that I apologize
Im just frustrated that the basics of physics are being so flaunted
and that the perfectly valid questions I raised earlier in this discussion were so studiously ignored

Rick if you are working in newtons
and dont know what a newton is
how much validity can possibly be found in your equations
Idont mean that to sound harsh
but it's true

I just am not going to explain basic physics
its late
I had a crap day
and Im just about out of beer

I will however explain theoretical physics
what theoretical physics does is dream up equations about things that for the most part dont exist but maybe could
it doesnt necessarily propose a solution for those equations
but it does insist that the equations balance with proofs to show the validity of those equations
in doing so it requires that all common denominators be resolved and that a consistent and generally obvious question be answered by the proof
to also show the validity of that proof
one that must also be answered by the original equation
it would be something like the conservation of energy proof I proposed for that model you first posted

as an example

in relativity old uncle Albert found a flaw
everyone said he was nuts
and he went on to be considered over the hill
but he dreamed up the field equations to try and resolve the problem
( by the way folks thought he was nuts for doubting his own discovery )

the field equations are the example Im going to use here

they could not be resolved unless you provide an arbitrary number called the cosmological constant
the cosmological constant is an imaginary number that makes up for the flaw in relativity and allows the field equations to be resolved
and yet
everyone clung to relativity with a death grip
really pissed off All
now
about a million years later
folks are starting to notice that quantum mechanics and relativity dont jive
( ok they new that from the start but they've lately given up on waiting for a reason why they dont jive )
along comes a guy named Joao
old Jo dreams op variable light spead theory and resolves the field equations
way to go Jo
thing is now every one who staked there rep on relativity
( which is still good up to the plank limit by the way )
hates Jo
why
why would they hate a guy with a name like Joao
and not just admit they were wrong in the first place
they are scientists
shouldnt they be interested in truth

thing is we all put our ego's on the line with some of our beliefs
and some of those turn out to be wrong
its a grim admission

so when there is only one of me
and ten of you
it doesnt mean I must be nuts
it could just mean
that I know a little more than you are giving me credit for

might just be time to admit that model is seriously flawed
when you have insisted on a calculating units or measurement in the model that dont exist in the model

and Ill still buy you a pint
it was entertaining
I dont care who is right or wrong

 

oh #$%@
I just noticed I put v instead of m

it should read
N=kgm/s2

told you I had a crap day
way to put my head on the chopping block
its basically the same thing
but not
oops
B

just I didnt look it up and then I went back and read the question again
I realized I had mixed the American equation with the conversion equation


its E=mv2/2
and N=kgm/s2

I think
been a long time since I used any of this crap

 

hmmmmmm
its kg moving at m per sec
I think I still wrote that wrong
but it represents V no matter
and you should be able to recognise the error in a heartbeat
hell I think its what caused one of the mars landers to crash
oh well
its dam late
or at least that would be Nasa's excuse

 

Boston
I have already deduced that you believe simple maths is crap. People usually do not like what they do not understand.



Rick W

.

 

The attached clips are not going to make much difference in the debate but it might help those who grapple with the understanding.

This is a highly imperfect little vehicle, built in 5 minutes, that does work. The wheel slip and flexible belt drive adds a dimension of reality that might trigger understanding in those prepared to open their minds. The vehicle is inverted to achieve the different operations.

It does show that you can build a vehicle that will advance directly against the force that it causing its motion. It also shows that the vehicle can advance faster than the media that it pushing it. Both examples work through the wonders of gearing. No witchcraft, no strings and no perpetual motion; just gearing.

Rick W