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A wind-powered vehicle that can travel twice as fast as the wind itself

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Re: A wind-powered vehicle that can travel twice as fast as the wind itself

#241

Post by cblconfederate »

aaron695 wrote: post #238
cblconfederate wrote: post #235

Earlier quoted context omitted.

the sails on those sailboats act like a wing even downwind . That's only usable with racing boats which use light foils fly over water instead of heavy keels , but yes they can move faster than the wind . Curiously i can't find a good explanation of their design. The Blackbird cannot use a land sail to go faster because it needs something to act like the keel on a sailboat and provide a counterforce. The propeller is…

You are agreeing current sail boats can go DDWFTTW which is directly downwind not a degree either way, faster than the wind, for a indefinite period of time? Tacking is not allowed, since that's not directly downwind. This should also mean going directly upwind is practically possible, not a degree either way, directly upwind for a indefinite period of time with sails. Do you have a link for this? Here's a link to a…

I dont know much about sailboats but i think they mean this: https://en.wikipedia.org/wiki/Wingsail . when they are at a slight angle and in combination with lightweight foils pointing the other way it seems they are able to go faster than wind in any direction, without anything like a propeller. In any case i think talking mixing wings, sailboats and propellers makes it confusing to understand what the blackbird does

Re: A wind-powered vehicle that can travel twice as fast as the wind itself

#242

Post by [deleted] »

jasonwatkinspdx wrote: post #177
jfoutz wrote: post #119

Earlier quoted context omitted.

Sailboats are one I struggled with, especially sailing into the wind. I think my intuition there came from a boat going the same direction as the wind, say, north at 1 meter/sec. now the boat can't go faster than 1 m/sec, but if you turn 45 degrees to the east you can travel sqrt(2) m/sec, because you're still going north at 1/ms and the boat gets pushed along to the east as well. the closer you get to perpendicular…

A boat absolutely can sail downwind faster than the wind speed. The crazy cutting edge boats like you see in America's Cup or the giant trimarans that vie for various world records do this somewhat routinely. The key to understanding this is: sails are devices that work like wings, via lift, not via drag (exception, spinnakers and such). A sailboat has two wings: the sail, and the keel (or centerboard). The boat is e…

[deleted]

Re: A wind-powered vehicle that can travel twice as fast as the wind itself

#243

Post by rusk »

thehappypm wrote: post #240
tofof wrote: post #211

Earlier quoted context omitted.

Right. The people mover is analogous to the wind. You can get to move at the windspeed through drag alone, at which point you no longer move relative to the air. The air is being robbed of only the fraction of energy that you're losing to drag (rolling resistance, as there is no air resistance now). This is you riding along with the peoplemover on the skateboard. But then increase the rolling resistance - the generat…

To add on — the power you’re stealing from the ground is the power you can use for propulsion. So before you switch on the handrail skateboard, you have some power, P, available from the generator. You can use that P to power an air conditioner or a light bulb, or to crawl down the rail. The fact that you’ll then use that power for more propulsion is not relevant — Newton’s laws are linear so you can just add up the…

It’s gearing. Albeit elaborate.

Intuitively what’s difficult to get the head around is sailing directly into the wind.

However the penny dropped when somebody says it’s like sailing into the wind and that basically the propellers act like triangular sails that are continuously reorienting.

The only tricky part bow is the “faster than wind” bit. Presumably this “dynamic sail” is better at harnessing any divergent energy coherently. Kind of like how a LASER coaxes her photons out in phase to produce a coherent beam. The balancing coefficient is the (variable) pitch of the blades.

Re: A wind-powered vehicle that can travel twice as fast as the wind itself

#244

Post by aaron695 »

cblconfederate wrote: post #241
aaron695 wrote: post #238

Earlier quoted context omitted.

You are agreeing current sail boats can go DDWFTTW which is directly downwind not a degree either way, faster than the wind, for a indefinite period of time? Tacking is not allowed, since that's not directly downwind. This should also mean going directly upwind is practically possible, not a degree either way, directly upwind for a indefinite period of time with sails. Do you have a link for this? Here's a link to a…

I dont know much about sailboats but i think they mean this: https://en.wikipedia.org/wiki/Wingsail . when they are at a slight angle and in combination with lightweight foils pointing the other way it seems they are able to go faster than wind in any direction, without anything like a propeller. In any case i think talking mixing wings, sailboats and propellers makes it confusing to understand what the blackbird doe…

You can't go DDWFTTW with sails.

No one has gone DDWFTTW on water. It will take a propeller to do when it happens.

If you want to contradict this you need to post a link of someone agreeing with you, else you misunderstand DDWFTTW.

(The link on Wingsail leaves out 0 and 180 degrees for the Points of Sail which are the only two we care about, directly downwind and directly upwind, the wiki article makes no comment on DDWFTTW. This thread is just people saying random words like AC72 or broad reach. If your ideas correct someone else will sum it up for you and you can link it. )

Re: A wind-powered vehicle that can travel twice as fast as the wind itself

#245

Post by DarmokJalad1701 »

koonsolo wrote: post #239
twobitshifter wrote: post #136

Earlier quoted context omitted.

It’s really not that complicated - wind speed is not the same as energy. The propellor is a device that pushes against the air to move forward, it takes energy from the wind, produces a force, and the force produces momentum in the vehicle. We know that a stationary turbine can continually take power from the wind. When that wind energy is stored in a battery it can power your car much faster than the wind. This just…

This does not explain the most obvious issue (or at least my most obvious issue): when going as fast as the wind, there is no wind anymore. The answer: at that point, your wheels are turning, and so you can get energy from your turning wheels, but not directly from the wind. This is how I explain it in my head: 1. When going slower than the wind, the wind pushes you forward. Propeller at this point is useless. 2. Whe…

> 3. When going faster than the wind, all your energy will come from the turning wheels.

But why do the wheels keep turning in this scenario? Is there somehow a net-force on the back-side of the vehicle from the wind?

Re: A wind-powered vehicle that can travel twice as fast as the wind itself

#246

Post by jayd16 »

rusk wrote: post #167
ladberg wrote: post #166

Earlier quoted context omitted.

In this case they are actually "consuming" more wind. A normal sail "consumes" wind by taking moving wind and reducing its speed to 0. This "consumes" wind by taking moving wind and sending it back the other direction, so it creates more thrust per unit wind.

Sounds to me like it improves efficiency rather than consumes more

Same could be said for a turbocharger but we just happen to set the fuel mixture dynamically.

Re: A wind-powered vehicle that can travel twice as fast as the wind itself

#247

Post by jayd16 »

rusk wrote: post #161
jayd16 wrote: post #153

This is like putting a turbocharger on a sailboat. I love it.

A turbo charger increases fuel consumption though. You can’t just consume more wind.

Sure you can. Why not? Can't you extract varying amounts of energy from wind resulting in varying wind speed in your wake?

Re: A wind-powered vehicle that can travel twice as fast as the wind itself

#248

Post by DarmokJalad1701 »

tshaddox wrote: post #121
pkulak wrote: post #113

Earlier quoted context omitted.

The problem with this explanation, at least to me, is that it doesn't require any wind at all. Why not just give it a push in still air and have to take off into the distance forever? EDIT: I think it's clicking. It's because the air and the ground are moving relative to the craft at different speeds. So if the ground and air were still, there would be no speed difference to draw energy from.

Why would you consider those two scenarios analogous? In one scenario, the wind is “giving it a push” constantly, and in the other scenario, you’re giving it a push for only a brief moment.

When it is moving faster than the wind, is the wind still giving it a push?

Re: A wind-powered vehicle that can travel twice as fast as the wind itself

#249

Post by cblconfederate »

aaron695 wrote: post #244
cblconfederate wrote: post #241

Earlier quoted context omitted.

I dont know much about sailboats but i think they mean this: https://en.wikipedia.org/wiki/Wingsail . when they are at a slight angle and in combination with lightweight foils pointing the other way it seems they are able to go faster than wind in any direction, without anything like a propeller. In any case i think talking mixing wings, sailboats and propellers makes it confusing to understand what the blackbird doe…

You can't go DDWFTTW with sails. No one has gone DDWFTTW on water. It will take a propeller to do when it happens. If you want to contradict this you need to post a link of someone agreeing with you, else you misunderstand DDWFTTW. (The link on Wingsail leaves out 0 and 180 degrees for the Points of Sail which are the only two we care about, directly downwind and directly upwind, the wiki article makes no comment on…

There some speed graphs like this online: https://www.catsailingnews.com/2013/07/ac72-polars-penalties...

I think what you re saying is that you can't be at 0 degrees to the wind, which i guess is true

Re: A wind-powered vehicle that can travel twice as fast as the wind itself

#250

Post by rusk »

jayd16 wrote: post #247
rusk wrote: post #161

Earlier quoted context omitted.

A turbo charger increases fuel consumption though. You can’t just consume more wind.

Sure you can. Why not? Can't you extract varying amounts of energy from wind resulting in varying wind speed in your wake?

Not the same way as you do with turbo
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