Well - if you understand that the still air and moving ground is exactly same as wind and still ground from the point of reference of the cart then you understand that essentially the propeller blade is in 'constant tack'.
@axelerat3d I understand that it is also true from point of reference of the groud. If you stood still on the treadmill you would feel the wind. However, the treadmill slows down when it runs out of coal because it is electric; eventually the wind gets used up.
Isn't any propeller in the universe also in constant tack? Can't you essentially take the blade off grandma's oscillating fan and use that to run the machine?
@axelerat3d I see the connection between a powered fan shaft, a keel, push props, etc. but it is confusticating the main point, and unecessary baggage. You don't need to relate aeronautical terminology in order to know how a fan works and that is all you need to know. How a floor unit works is common everyday knowledge.
@axelerat3d Let me triple clarify and stick a nail through it and weld it to the floor. I never misunderstood the frame of reference. Not a wind is stirring, not even a mouse. There are no gusts, no gails, nothing but a propeller which is making the air to blow. Yes yes the high pressure causes lift, whatever.
This does not mean I understand tick about tack.
Think about the treadmill. You get to that point in two very different ways. The manned vehicle uses wind, the toy uses friction.
@axelerat3d A hand push does not equal wind. No problem though, like I said, I get it. All you need to prove the cart gets to the speed of the wind, it does, and you get into this frame.
The moment the cart is released is the one moment you prove the toy works and thus the larger contraption works.
To simulate real wind stoppage, then the wind is blowing the same speed as the treadmill, all you have to do is turn the treadmill off, or you can turn a fan on facing the toy.
@axelerat3d The volume of "wind" has energy, unlike the treadmill, which uses electric.
The (wind mass)*(change of wind velocity) = (cart mass)*(change in cart velocity).
This is a rudimentary description, not trickery.
What is the final velocity of the wind?
You have initial wind velocity that is positve and from the treadmill example you see that all the wind providing energy is given negative velocity by the propeller.
So now I wonder when a boat tacks wind does the wind ever get -velocity?
@axelerat3d We are looking at an image of a boat on "Points of sail" in Wikipedia. We are sailing broad reach.
If wind initially has a positive velocity and the boat initially has 0 velocity. Assuming the boat final state has a downwind component faster than the initial wind velocity; the keel the length of the boat. Does the air being tacked ever acquire negative velocity?
Should be a simple problem for anyone to see if the "tack" description makes sense then the answer should be yes.
@axelerat3d The "tack description" is the description you gave as the as 'constant tack' OR "air being tacked".
I mean, when a boat is tacking in the wind, the wind is tacked.
The keel is in a normal position, along the the length of the boat. Sorry, bad grammar, short sentences.
Negative velocity, this means the whatever the wind speed is initially, that at final, once the boat is travelling faster than wind in the direction of the wind, the sail has forced the wind to change direction.
@planetofthescums by constant tack I meant condition similar to a boat being for example in starboard tack. Basically traveling at an angle in relation to the wind Boat does it by changing tacks (zig zagging) propeller blade does this by nature as it has the similar effect as the sideways movement coming from the spinning.
Air doesn't need to reverse just slow down (of course from some point of reference this might look like reversing) .
@axelerat3d The only reason a boat zigzags is to get to an exact destination, this couldn't possible improve speed in any way, turning parallel to the wind where it has negative relative wind speed..
@axelerat3d If you are on a cart DDWFTTW when wind appears to stop around you, then the air behind the prop appears to move back with velocity opposite the acceleration of the cart.
When you sail you do not force the wind to move in an opposing direction, Sitting on the boat the relative wind hits the sail from the side and appears to blow backwards as well.
You said the aerodynamics don't change so the prop is, from perspective sitting in the cart, at any speed is pushing air backwards.
Even minimal change in wind speed can accelerate the boat as long as enough air is affected. Affect big mass of air just by tiny bit and it ads up to a lot if the system can use the leverage.
Treadmill is analogous to the sailcart. Sure there is power source in the t-mill but we can ignore that just like we ignore the fact that earth is spinning - ground travels quite a bit but from my point of reference its irrelevant. What is relevant is difference of speed between air and perceived ground.
@axelerat3d I know, the change in velocity could be any amount if you are given enough wind. Why bring leverage into it. That seems kind of counter-intuitive; just another name-drop?
Ok I will finally stop for good. I am not name dropping or confusing on purpose. You seem to constantly complain and suggest that somehow my way of communicating is wrong. Yet fail to see that ypu are the one doing the insulting.
And guess what the rolling friction + air/ground speed difference on the DDW cart is exactly the same thing as the cart on treadmill.
@axelerat3d I am constantly looking for ways to help you explain this to people. I don't know how far I plan on taking on this mission, but I will take the time to re-read your comments, resources, and make sure I am not in error before I take up your time again.
@axelerat3d No we can't simply ignore the fact this is a treadmill, things which could theoretically stop the wind would not stop a treadmill. This treadmill experiment was designed to prove a point and it was made. Rolling friction causes forward propulsion.
you might want to read a little more about that...
from wikipedia page 'Sailing faster than the wind': "The velocity made good downwind is often over twice as fast compared to the same land yacht sailing directly downwind"
This is really very common knowledge. Also could check the latest wired mag - Rick and his buddy made a land vehicle that "sailed" 2.8 times wind speed directly downwind.
@axelerat3d I wouldn't call this very common knowledge. I'm sure most people I ask would say this was impossible. This is pretty fascinating and counter intuitive. Is there a theoretical upper limit to vehicle speed from wind speed?
@axelerat3d I have found many websites that describe the basic physics of how the vectors can lead to greater down wind velocities, but I could not find one that actually discusses in detail how the velocity are generated beyond trivial explanations of basic aerodynamics. A true answer would provide detailed equations of the fluid dynamics. Despite this, there seems to be enough physics related websites that state that it is possible, so it seems reasonable that I retract my statement. Cheers
"The slowest point of sail for a landyacht is dead down wind when it sails a little slower than the wind speed. By sailing at 45 degrees off directly down wind the yacht can sail much faster than the wind. The 'velocity made good' down wind is often over twice as fast as sailing directly down wind. In moderate wind, the fastest point of sail is a little below a beam reach."
"On July 2, 2010 on El Mirage Dry Lake, Blackbird sailed directly down wind at a speed of 27.7 mph in a 10 mph wind to set a first record for the ratio of Boat Speed to true wind speed of 2.8"
just google "physics of sailing" or "sailing faster than the wind". Beating wind speed in certain points (angel to the wind) it is common to beat the wind speed with huge multitudes. Downwind tacks its not as easy and not all boats can do it.
check nalsa org. they have news of the propeller cart that travels directly downwind 2.5x or so faster than the wind.
me having a degree or not is irrelevant this is not that advanced physics. Its a brain teaser but high school physics will do
#1 The best way is to understand that the frame of reference is relative. Whether we extract the energy from the water or air is relative. We harness it from the speed difference of these two.
On actual down wind cart (like on fasterthanwind dot-org) the mechanics are more obvious. Basically on that wheels are geared so that they force the prop to spin (similar situation as the end of my anim.)
Power=Force*Speed
So with more speed same power creates smaller force and vice versa.
As the water keel (or ground wheel on the cart) speed difference is 9m/s 100N force slowing down the boat would have power of 900w (9m/s*100N)
As sail has only 1 m/s speed in its medium 900W would be enough to create 900N force. Plenty of room for losses.
That explains where the "energy" comes from - basically its slowing down the air. At this point its just a mechanics problem. Obviously sailboat down headwind will create not force (thrust) as there is no airflow
So wing has to move also "sideways" to the wind to keep airflow.
One thing that also helps visualize the forces is:
Think the forces and velocities of a boat traveling SouthWest in Northern wind (from north) at the very point when its downwind component matches the wind speed.
Obviously the apparent wind on the boat has no north south component at this exact condition. Yet the boat experiences strong Western wind that it can use for lift. It is matter of leverage.
Boat is not "creating the wind". It is suing leverage to create faster movement (as its going at an angle). Tish faster movement makes the sail "harvest" bigger mass of air. And yes it works a lot like airplane wing not like a bluff body or parachute.
Check faster than wind d.t org. - their cart goes 2.8 times the wind speed directly downwind. Debates over that cart is what made me do the animation in the 1st place. It is counter intuitive but the math does add up.
sorry for bad typing. Also I needed to add - that in the very slow speeds going downwind or traditional boat going directly downwind (running) sails indeed act liek chutes. Just adding drag. But at an angle as the boat gets going the apparent wind starts swinging around and starts flowing over the sail like an airplane wing.
Why is 400 ton airplane possible to get off the ground with relatively small engines. If same engines were blasting down the jumbo jet wouldn't nudge. It is because the drag that the engines need to beat is much smaller than the lift created by the resulting movement. get my point?
Same way in my example -north wind is the powering source. Without it there would be no movement towards west. Its not perpetual motion at all. Because the sail is in westward movement it creates lift
this animation is misleading. the windward component of the sailboat velocity never exceeds the actual wind velocity, so you can't get anything out of a propellor
Nope - iceboats, sailboats, sailcarts all can beat the wind downwind (just not directly). Their downwind speed component can be significantly faster than then the wind. This is generally accepted as a fact and proven over and over again.
just to be clear= A boat can beat a floating balloon to the downwind marker.
chrismasterith: "the windward component of the sailboat velocity never exceeds the actual wind velocity"
This is a common misconception. This animation shows how the air can push a boat forward, which already has a windward velocity component greater that wind-speed:
You can claim anything you want on the internet, even if it doesn't correspond to reality or physics in anyway. Your comments here are one example.
Search wikipedia for "Sailing faster than the wind". Tons of references there, about yachts & iceboats achieving a dead-downwind velocity component greater than true windspeed. You will find also vector diagrams and math there, showing that this animation is absolutely correct.
You are right - I could animate the boat to go as fast as I wanted. However I think this animation helps us to understand how sail and prop are acting very similarly.
Because the sail travels at an angle to the wind even when the downwind component reaches the wind speed the airfoil (wing, sail) experiences apparent wind keeps generating lift. You do not experience any kind of "barrier" or abrupt change at the point when the boat brakes the wind speed
Not misunderstood by physics by the longest stretch of the imagination. Misunderstood by naive short-tempered you-tube compatriots, possibly.
Perhaps how it is being presented was wrong?
Now, someone showed me a vector drawing of a boat tacking the wind, it had vectors to "prove it" but it didn't the vectors from the keel.
That can't possibly be mathematically correct because tacking won't work without a keel.
It may work in the real world, but the theory was not accepted because it was wrong.
planetofthescums 2 months ago
Not only does a ceiling fan work, but it works the same way as a boat that is tacking the wind.
planetofthescums 2 months ago
You have proven your point and I am convinced a ceiling fan works.
planetofthescums 2 months ago
Also, what does this have to do with a propeller powered by a treadmill?
planetofthescums 3 months ago
@planetofthescums
Well - if you understand that the still air and moving ground is exactly same as wind and still ground from the point of reference of the cart then you understand that essentially the propeller blade is in 'constant tack'.
In short - it has everything to do with it.
axelerat3d 3 months ago
@axelerat3d I understand that it is also true from point of reference of the groud. If you stood still on the treadmill you would feel the wind. However, the treadmill slows down when it runs out of coal because it is electric; eventually the wind gets used up.
Isn't any propeller in the universe also in constant tack? Can't you essentially take the blade off grandma's oscillating fan and use that to run the machine?
planetofthescums 2 months ago
@axelerat3d I see the connection between a powered fan shaft, a keel, push props, etc. but it is confusticating the main point, and unecessary baggage. You don't need to relate aeronautical terminology in order to know how a fan works and that is all you need to know. How a floor unit works is common everyday knowledge.
planetofthescums 2 months ago
@axelerat3d Let me triple clarify and stick a nail through it and weld it to the floor. I never misunderstood the frame of reference. Not a wind is stirring, not even a mouse. There are no gusts, no gails, nothing but a propeller which is making the air to blow. Yes yes the high pressure causes lift, whatever.
This does not mean I understand tick about tack.
Think about the treadmill. You get to that point in two very different ways. The manned vehicle uses wind, the toy uses friction.
planetofthescums 2 months ago
@axelerat3d A hand push does not equal wind. No problem though, like I said, I get it. All you need to prove the cart gets to the speed of the wind, it does, and you get into this frame.
The moment the cart is released is the one moment you prove the toy works and thus the larger contraption works.
To simulate real wind stoppage, then the wind is blowing the same speed as the treadmill, all you have to do is turn the treadmill off, or you can turn a fan on facing the toy.
planetofthescums 2 months ago
@axelerat3d The volume of "wind" has energy, unlike the treadmill, which uses electric.
The (wind mass)*(change of wind velocity) = (cart mass)*(change in cart velocity).
This is a rudimentary description, not trickery.
What is the final velocity of the wind?
You have initial wind velocity that is positve and from the treadmill example you see that all the wind providing energy is given negative velocity by the propeller.
So now I wonder when a boat tacks wind does the wind ever get -velocity?
planetofthescums 2 months ago
@axelerat3d We are looking at an image of a boat on "Points of sail" in Wikipedia. We are sailing broad reach.
If wind initially has a positive velocity and the boat initially has 0 velocity. Assuming the boat final state has a downwind component faster than the initial wind velocity; the keel the length of the boat. Does the air being tacked ever acquire negative velocity?
Should be a simple problem for anyone to see if the "tack" description makes sense then the answer should be yes.
planetofthescums 2 months ago
@planetofthescums
I don't know what you mean by:
"the keel length of the boat"
"air being tacked"
"negative velocity"
"tack description"
axelerat3d 2 months ago
@axelerat3d The "tack description" is the description you gave as the as 'constant tack' OR "air being tacked".
I mean, when a boat is tacking in the wind, the wind is tacked.
The keel is in a normal position, along the the length of the boat. Sorry, bad grammar, short sentences.
Negative velocity, this means the whatever the wind speed is initially, that at final, once the boat is travelling faster than wind in the direction of the wind, the sail has forced the wind to change direction.
planetofthescums 2 months ago
@planetofthescums by constant tack I meant condition similar to a boat being for example in starboard tack. Basically traveling at an angle in relation to the wind Boat does it by changing tacks (zig zagging) propeller blade does this by nature as it has the similar effect as the sideways movement coming from the spinning.
Air doesn't need to reverse just slow down (of course from some point of reference this might look like reversing) .
axelerat3d 2 months ago
@axelerat3d The only reason a boat zigzags is to get to an exact destination, this couldn't possible improve speed in any way, turning parallel to the wind where it has negative relative wind speed..
planetofthescums 2 months ago
@axelerat3d If you are on a cart DDWFTTW when wind appears to stop around you, then the air behind the prop appears to move back with velocity opposite the acceleration of the cart.
When you sail you do not force the wind to move in an opposing direction, Sitting on the boat the relative wind hits the sail from the side and appears to blow backwards as well.
You said the aerodynamics don't change so the prop is, from perspective sitting in the cart, at any speed is pushing air backwards.
planetofthescums 2 months ago
Even minimal change in wind speed can accelerate the boat as long as enough air is affected. Affect big mass of air just by tiny bit and it ads up to a lot if the system can use the leverage.
Treadmill is analogous to the sailcart. Sure there is power source in the t-mill but we can ignore that just like we ignore the fact that earth is spinning - ground travels quite a bit but from my point of reference its irrelevant. What is relevant is difference of speed between air and perceived ground.
axelerat3d 2 months ago
@axelerat3d I know, the change in velocity could be any amount if you are given enough wind. Why bring leverage into it. That seems kind of counter-intuitive; just another name-drop?
planetofthescums 2 months ago
@planetofthescums
Ok I will finally stop for good. I am not name dropping or confusing on purpose. You seem to constantly complain and suggest that somehow my way of communicating is wrong. Yet fail to see that ypu are the one doing the insulting.
And guess what the rolling friction + air/ground speed difference on the DDW cart is exactly the same thing as the cart on treadmill.
axelerat3d 2 months ago
@axelerat3d I don't know what leverage even means buddy. I am just getting started on the discussion.
You seem to be speaking on many points which we agree and I am starting to see this from your perspective.
But if you want to bow out I won't hesitate to say good luck and thanks for the discussion, it won't hurt me to leave this as it is.
planetofthescums 2 months ago
@axelerat3d I am constantly looking for ways to help you explain this to people. I don't know how far I plan on taking on this mission, but I will take the time to re-read your comments, resources, and make sure I am not in error before I take up your time again.
planetofthescums 2 months ago
@axelerat3d No we can't simply ignore the fact this is a treadmill, things which could theoretically stop the wind would not stop a treadmill. This treadmill experiment was designed to prove a point and it was made. Rolling friction causes forward propulsion.
planetofthescums 2 months ago
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planetofthescums 3 months ago
@planetofthescums
It is not obvious that the boat is faster than the balloon - however it is. I should have made that more clear.
The part where you just decide "not possible" is wrong. Why do you say its not possible? Sail carts beat this speed frequently.
Boat is not blocking any wind - wind is in direction of the cylinder's axis.
axelerat3d 3 months ago
Comment removed
planetofthescums 2 months ago
@planetofthescums
I don't have to win you over. I don't think tacking is outrageous at all. cheers. I am done here.
axelerat3d 2 months ago
@axelerat3d Still haven't answered my quesiton. Isn't this how ALL propellers work, sir?
planetofthescums 2 months ago
@planetofthescums
yes. hardly the point here.
axelerat3d 2 months ago
@axelerat3d So it is just a propeller.
planetofthescums 2 months ago
Sorry physics ruins this idea. Boats don't sail faster than wind.
Nice try though.
chodaboy51500 1 year ago
@chodaboy51500
you might want to read a little more about that...
from wikipedia page 'Sailing faster than the wind': "The velocity made good downwind is often over twice as fast compared to the same land yacht sailing directly downwind"
This is really very common knowledge. Also could check the latest wired mag - Rick and his buddy made a land vehicle that "sailed" 2.8 times wind speed directly downwind.
axelerat3d 1 year ago
@axelerat3d I wouldn't call this very common knowledge. I'm sure most people I ask would say this was impossible. This is pretty fascinating and counter intuitive. Is there a theoretical upper limit to vehicle speed from wind speed?
chodaboy51500 11 months ago
@axelerat3d I have found many websites that describe the basic physics of how the vectors can lead to greater down wind velocities, but I could not find one that actually discusses in detail how the velocity are generated beyond trivial explanations of basic aerodynamics. A true answer would provide detailed equations of the fluid dynamics. Despite this, there seems to be enough physics related websites that state that it is possible, so it seems reasonable that I retract my statement. Cheers
jongagne1 1 year ago
from ladnsailing -dot net :
"The slowest point of sail for a landyacht is dead down wind when it sails a little slower than the wind speed. By sailing at 45 degrees off directly down wind the yacht can sail much faster than the wind. The 'velocity made good' down wind is often over twice as fast as sailing directly down wind. In moderate wind, the fastest point of sail is a little below a beam reach."
axelerat3d 1 year ago
"On July 2, 2010 on El Mirage Dry Lake, Blackbird sailed directly down wind at a speed of 27.7 mph in a 10 mph wind to set a first record for the ratio of Boat Speed to true wind speed of 2.8"
google nalsa dot org
axelerat3d 1 year ago
Comment removed
jongagne1 1 year ago
@jongagne1
just google "physics of sailing" or "sailing faster than the wind". Beating wind speed in certain points (angel to the wind) it is common to beat the wind speed with huge multitudes. Downwind tacks its not as easy and not all boats can do it.
check nalsa org. they have news of the propeller cart that travels directly downwind 2.5x or so faster than the wind.
me having a degree or not is irrelevant this is not that advanced physics. Its a brain teaser but high school physics will do
axelerat3d 1 year ago
Comment removed
jongagne1 1 year ago
@jongagne1
#1 The best way is to understand that the frame of reference is relative. Whether we extract the energy from the water or air is relative. We harness it from the speed difference of these two.
On actual down wind cart (like on fasterthanwind dot-org) the mechanics are more obvious. Basically on that wheels are geared so that they force the prop to spin (similar situation as the end of my anim.)
Power=Force*Speed
So with more speed same power creates smaller force and vice versa.
axelerat3d 1 year ago
@axelerat3d
#2
As the water keel (or ground wheel on the cart) speed difference is 9m/s 100N force slowing down the boat would have power of 900w (9m/s*100N)
As sail has only 1 m/s speed in its medium 900W would be enough to create 900N force. Plenty of room for losses.
That explains where the "energy" comes from - basically its slowing down the air. At this point its just a mechanics problem. Obviously sailboat down headwind will create not force (thrust) as there is no airflow
axelerat3d 1 year ago
@axelerat3d
So wing has to move also "sideways" to the wind to keep airflow.
One thing that also helps visualize the forces is:
Think the forces and velocities of a boat traveling SouthWest in Northern wind (from north) at the very point when its downwind component matches the wind speed.
Obviously the apparent wind on the boat has no north south component at this exact condition. Yet the boat experiences strong Western wind that it can use for lift. It is matter of leverage.
axelerat3d 1 year ago
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jongagne1 1 year ago
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jongagne1 1 year ago
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jongagne1 1 year ago
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jongagne1 1 year ago
@jongagne1
Boat is not "creating the wind". It is suing leverage to create faster movement (as its going at an angle). Tish faster movement makes the sail "harvest" bigger mass of air. And yes it works a lot like airplane wing not like a bluff body or parachute.
Check faster than wind d.t org. - their cart goes 2.8 times the wind speed directly downwind. Debates over that cart is what made me do the animation in the 1st place. It is counter intuitive but the math does add up.
axelerat3d 1 year ago
@axelerat3d
sorry for bad typing. Also I needed to add - that in the very slow speeds going downwind or traditional boat going directly downwind (running) sails indeed act liek chutes. Just adding drag. But at an angle as the boat gets going the apparent wind starts swinging around and starts flowing over the sail like an airplane wing.
axelerat3d 1 year ago
@jongagne1
Why is 400 ton airplane possible to get off the ground with relatively small engines. If same engines were blasting down the jumbo jet wouldn't nudge. It is because the drag that the engines need to beat is much smaller than the lift created by the resulting movement. get my point?
Same way in my example -north wind is the powering source. Without it there would be no movement towards west. Its not perpetual motion at all. Because the sail is in westward movement it creates lift
axelerat3d 1 year ago
Comment removed
jongagne1 1 year ago
Nicely done.
davidglover 1 year ago
this animation is misleading. the windward component of the sailboat velocity never exceeds the actual wind velocity, so you can't get anything out of a propellor
chrismasterith 1 year ago
@chrismasterith
Nope - iceboats, sailboats, sailcarts all can beat the wind downwind (just not directly). Their downwind speed component can be significantly faster than then the wind. This is generally accepted as a fact and proven over and over again.
just to be clear= A boat can beat a floating balloon to the downwind marker.
axelerat3d 1 year ago 4
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jongagne1 1 year ago
chrismasterith: "the windward component of the sailboat velocity never exceeds the actual wind velocity"
This is a common misconception. This animation shows how the air can push a boat forward, which already has a windward velocity component greater that wind-speed:
watch?v=63hvQABLOaE
The same for the prop-blade:
watch?v=vVMqa7Mft0k
eyytee 1 year ago
@eyytee you can make anything you want in an animation, even if it doesn't correspond to reality or physics in anyway. this cartoon is one example
chrismasterith 1 year ago
This has been flagged as spam show
@chrismasterith
You can claim anything you want on the internet, even if it doesn't correspond to reality or physics in anyway. Your comments here are one example.
Search wikipedia for "Sailing faster than the wind". Tons of references there, about yachts & iceboats achieving a dead-downwind velocity component greater than true windspeed. You will find also vector diagrams and math there, showing that this animation is absolutely correct.
eyytee 1 year ago
@chrismasterith
You are right - I could animate the boat to go as fast as I wanted. However I think this animation helps us to understand how sail and prop are acting very similarly.
Because the sail travels at an angle to the wind even when the downwind component reaches the wind speed the airfoil (wing, sail) experiences apparent wind keeps generating lift. You do not experience any kind of "barrier" or abrupt change at the point when the boat brakes the wind speed
axelerat3d 1 year ago
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TraderTurok 1 year ago