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Old 7th June 2016, 04:13 AM   #201
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reply to mac doc.

Even Franky himself in an interview said there was a lag time with power compared to say propellors.

And that this was overcome as the power was not so much controlled but the pitch of each jet outlet.

If he was being honest about this algorithm controlling the direction of thejet outlet rather than the power as say in a drone, then how do you explain that the overall power response required for doing manouvers (without decending ) would be possible?

SOmething is not right with the story.

As someone said in this thread though - such inconsistencies and conflicts with the explanation he gives could be him hiding his technology so that others do not copy it.
But it seems a bit far fetched.
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Old 7th June 2016, 04:17 AM   #202
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Good post mart cookie and that TJ40-G1 specs fits the model very well. They are designed around 5 minutes at maximum thrust which also fits the demo.

There are other manufacturers in this class of miniature jet engine as well and they could craft their own.

Last edited by macdoc; 7th June 2016 at 04:19 AM.
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Old 7th June 2016, 04:18 AM   #203
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Originally Posted by smartcooky View Post
They throttle, just like big jet engines



Nonetheless, jet engines work just fine for hovering

https://www.youtube.com/watch?v=ecpCPdUGnWk



No, it would not. Read on


ps. the harrier jet is also not dynamically flying around and banking much at all. it is hovering in place more or less, or just going forward while also climbing. It would be more difficult to be moving around alot as the thrust would have to be alterted constantly to maintain the same altitude.


NOTE the divergent angle of the thrust vectors. The Harrier/AV-8B sits on a cone of thrust as I described earlier.

https://dl.dropboxusercontent.com/u/...EF/Harrier.png

This is why I suspect that the engines are not not parallel, but diverged outwards slightly at the base to create a cone of thrust. When the flyer leans in a direction (we'll call that "forward" for convenience) there will still be some component of the downward thrust in a forwards direction, but the rear thrust vector will be more angled pushing him forward

Perhaps these quickly mocked up drawings will help you to understand.

https://dl.dropboxusercontent.com/u/...t%20column.png https://dl.dropboxusercontent.com/u/...ust%20cone.png

To turn would be the same thing, lean in the direction you want to go, tipping the platform slightly and the vectored thrust will make the turn for you, then trim the platform around using the ducted fans.

Thanks for that picture.

Yes it makes more sense now. Thank you for taking the time in making it.

One thing though - the harrier has a smaller nose jet port as well. So it is kind of like a tripod in a way - and also the centre of gravity is quite low compared to the flyboard whihc has a very very high C or G.

But i agree - the divergent jet idea you put forth should increase stability. I had not considered it or really understood your point until i saw the diagram you made.

Last edited by esspee; 7th June 2016 at 04:20 AM.
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Old 7th June 2016, 04:21 AM   #204
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Dudes, the vectors don't matter. It could make a difference close to ground, but that's it. In the air, all the forces sum and you can replace them with one vector. Wide cone or parallel jets would both sum into same vector, only the wide cone would produce slightly less thrust.
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Old 7th June 2016, 04:22 AM   #205
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Um diverged thrust for stability was discussed much earlier.

Electric propellers throttle up very quickly as max torque is at zero.

The challenges I see is keeping weight down but structure sound and fuel flow control to the individual engines needs to be very precise,
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Old 7th June 2016, 04:26 AM   #206
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also note the harrier is hovering stationary and sluggishly. No big maneovers are made. To do so would require constant and rapid changes of thrust, even with divergent thrust.

the flyboard however zooms about the place doing banking turns maintaining same altitude. this would require responsive thrust adjustments not seen with the harrir

Last edited by esspee; 7th June 2016 at 04:29 AM.
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Old 7th June 2016, 04:29 AM   #207
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Originally Posted by Dr.Sid View Post
Dudes, the vectors don't matter. It could make a difference close to ground, but that's it. In the air, all the forces sum and you can replace them with one vector. Wide cone or parallel jets would both sum into same vector, only the wide cone would produce slightly less thrust.
I remember from physics in school before i got expelled reducing the sum of forces to one vector.

You have a good point.

maybe the divergent do not help much. But then why does teh harrier clearly have them?

My opinion? to lower the apparent C of G in realtion to the thrust.

But like i said - i never finished school so what do I know right lol
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Old 7th June 2016, 04:31 AM   #208
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Quote:
In the air, all the forces sum and you can replace them with one vector. Wide cone or parallel jets would both sum into same vector, only the wide cone would produce slightly less thrust.
not entirely. on point - you are concentrating on thrust not stability ..slightly angled jets give you more ability to make the platform stable by letting the engines work slightly against each other - as soon as the platform tips the controller puts more thrust into that corner that is tilted down - that tilt also puts the thrust on the affected engine closer to 90 degrees when it does.

As much as possible you want self correcting.

This from Wiki on multiple engine rockets,

Quote:
Multiple engines (often canted at slight angles) are deployed but throttled to give the overall vector that is required, giving only a very small penalty.
https://en.wikipedia.org/wiki/Rocket_engine

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Old 7th June 2016, 04:32 AM   #209
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The very high Center of Gravity of the Flyboard air is a big stumbling block for me.

It does not apply to the Flyboard water because that has a much lower c of g due to dragging a long tail full of heavy water below it.

If this Flyboard Air was real , it would make more sense to double or tripple the output with bigger engines, and have a counter-weight the samee weight or more than the pilot to increase stability by maginitudes.

C of G is EVERYTHING when it comes to stability in aviation.

p.s a counterweight hanging on a pole below the rider would make it pretty hard for landing though!

Last edited by esspee; 7th June 2016 at 04:54 AM.
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Old 7th June 2016, 04:38 AM   #210
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Originally Posted by macdoc View Post
not entirely. on point - you are concentrating on thrust not stability ..slightly angled jets give you more ability to make the platform stable by letting the engines work slightly against each other - as soon as the platform tips the controller puts more thrust into that corner that is tilted down - that tilt also puts the thrust on the affected engine closer to 90 degrees when it does.

As much as possible you want self correcting.
This increase would have to be done automatically by computer. Not only would it have to react quickly, and the jets react quickly, but it would have to calculate how much to increase thrust by and when to cut it down.

I say a computer would have to do it, because Franky is holding a single throttle controller in his hand. Its basically like a motorbike throttle, or like you get with scaletric cars - more power or less power only.

Its the same model throttle he uses for his Flyboard Water.

He has stated in interviews that drone algorithms are used to control the craft. but rely on changing the direction of the jet nozzles not the power.

This makes more sense than him claiming it changes the power ( which we can see he controls using throttle)
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Old 7th June 2016, 04:53 AM   #211
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Regarding divergent thrust.

What do you make of the photo here?
http://techxplore.com/news/2016-04-f...overboard.html

Also with divergent thrust one engine goes and you are out of control i would think. All balance is lost. Not so if all thrusts are in line. You would just lose altitude pretty damn fast is all unless you could increase power to the remaining 3 engines very quickly.

However in this article as with MANY it is stated "With the current design, Frank says that he can take off and land on three turbines. However, if one turbine experiences an unplanned power loss in mid-flight, he notes that landing becomes rather tricky"

So divergent or not?

Judging by the photo and the claim of not losing stability entirely if one engine cooks itself - it would seem they are likely not divergent.

( or even that the whole thing is a hoax lol)
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Old 7th June 2016, 06:24 AM   #212
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Originally Posted by esspee View Post
The very high Center of Gravity of the Flyboard air is a big stumbling block for me.

It does not apply to the Flyboard water because that has a much lower c of g due to dragging a long tail full of heavy water below it.

If this Flyboard Air was real , it would make more sense to double or tripple the output with bigger engines, and have a counter-weight the samee weight or more than the pilot to increase stability by maginitudes.

C of G is EVERYTHING when it comes to stability in aviation.

p.s a counterweight hanging on a pole below the rider would make it pretty hard for landing though!
Center of Gravity is important for winged craft but not so much for hovering vehicles.

When Robert Goddard designed and made the first liquid fuelled rocket he thought it would be more stable to have the thrust nozzle up at the top with the liquid tanks and other parts hanging beneath "for stability" - even though this meant that the tanks needed a heat shield to protect them from the rocket exhaust.





Later it was realized that it's only the vector (line) along which the thrust operates that matters - so all modern rockets have the exhaust nozzles at the back / bottom - and they're no more likely to 'fall over' than Goddard's original liquid rocket was.

Last edited by ceptimus; 7th June 2016 at 06:26 AM.
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Old 7th June 2016, 06:35 AM   #213
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Originally Posted by ceptimus View Post
Center of Gravity is important for winged craft but not so much for hovering vehicles.

When Robert Goddard designed and made the first liquid fuelled rocket he thought it would be more stable to have the thrust nozzle up at the top with the liquid tanks and other parts hanging beneath "for stability" - even though this meant that the tanks needed a heat shield to protect them from the rocket exhaust.

https://www.uwgb.edu/dutchs/Graphics...ft/goddard.gif

http://www.phy6.org/stargaze/Sfigs/SGoddard.jpg

Later it was realized that it's only the vector (line) along which the thrust operates that matters - so all modern rockets have the exhaust nozzles at the back / bottom - and they're no more likely to 'fall over' than Goddard's original liquid rocket was.
Yes good point. And i have seen lots of rockets take off so i hve to admit you are right.

THe only difference here I can think of is the flyboard is not accelerating rapidly through the unstable phase past 9.81m/s/s, but hanging right at it.

A rocket quickly surpasses this hovering stage, I would imagine it is always way past it infact from the second it takes off.
and after that the gravity part of the equation diminishes in comparison to its acceleration, so c of g might not be an issue.
Aerodynamics also come into play regarding stability as they get faster too I would imagine.
Also rockets are not hovering around and steering about the place at the same altitude like the Flyboard or like we see with toy drones.

It should also be mentioned that a rocket is a solid object.

You can balance it so that the thrust is directly in line with its center of mass. A rocket is symetrical.

The flyboard unit has a man on it. He is moving around, so the centre of mass is not going to be in the same place all the time, he is made of meat not steel.

Quite the balancing act.
Anyone who has been on a Slack-line will understand

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Old 7th June 2016, 06:52 AM   #214
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Originally Posted by esspee View Post
The very high Center of Gravity of the Flyboard air is a big stumbling block for me.

It does not apply to the Flyboard water because that has a much lower c of g due to dragging a long tail full of heavy water below it.

If this Flyboard Air was real , it would make more sense to double or tripple the output with bigger engines, and have a counter-weight the samee weight or more than the pilot to increase stability by maginitudes.

C of G is EVERYTHING when it comes to stability in aviation.

p.s a counterweight hanging on a pole below the rider would make it pretty hard for landing though!
CG is significant but not "everything." Zapata started the project by driving stock RC turbines with a stock quadcopter, but needed to change both hardware and software for his application. Drones don't care about CG - they power their way through the equation with brute force application of power, switched rapidly in response to the sensor data and controller inputs.

A Segway has terrible CG problems it overcomes with sensors, software and torque.
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Old 7th June 2016, 06:57 AM   #215
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Quote:
So how do you tame four microturbines putting out a total 160 kg of thrust?
That's TG40 -G1 thrust exactly. 4 x 88 ft lb

http://techxplore.com/news/2016-04-f...overboard.html
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Old 7th June 2016, 06:58 AM   #216
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Originally Posted by Jrrarglblarg View Post
CG is significant but not "everything." Zapata started the project by driving stock RC turbines with a stock quadcopter, but needed to change both hardware and software for his application. Drones don't care about CG - they power their way through the equation with brute force application of power, switched rapidly in response to the sensor data and controller inputs.

A Segway has terrible CG problems it overcomes with sensors, software and torque.
I will admit - the Segway argument is good.

Particularly as the modern 'hoverboard' ones do not even have handlebars. They too have a meat rider who moves around too.

I don't have a comeback to be honest.....yet.

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Old 7th June 2016, 07:01 AM   #217
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Originally Posted by esspee View Post
Yes good point. And i have seen lots of rockets take off so i hve to admit you are right.

THe only difference here I can think of is the flyboard is not accelerating rapidly through the unstable phase past 9.81m/s/s, but hanging right at it.

A rocket quickly surpasses this hovering stage, I would imagine it is always way past it infact from the second it takes off.
and after that the gravity part of the equation diminishes in comparison to its acceleration, so c of g might not be an issue.
Aerodynamics also come into play regarding stability as they get faster too I would imagine.
Also rockets are not hovering around and steering about the place at the same altitude like the Flyboard or like we see with toy drones.

It should also be mentioned that a rocket is a solid object.

You can balance it so that the thrust is directly in line with its center of mass. A rocket is symetrical.

The flyboard unit has a man on it. He is moving around, so the centre of mass is not going to be in the same place all the time, he is made of meat not steel.

Quite the balancing act.
Anyone who has been on a Slack-line will understand
Center of gravity and center of thrust on solid fuel hobby rockets is a careful balance of nose weight, body length and fin area, with CG about one rocket diameter ahead of CT. Liquid fuel rockets are not hollow tubes but a cylinder crammed with fluids and metal and CG changes rapidly as liquid fuel and oxygen are burned off. Actual working rockets are computer controlled dynamically with vectored thrust, no fins, and a CG that changes continuously and radically as fuel burns and stages are spent.

The flyboard is not a rocket, not a helicopter, but a quadcopter with footrests: a flying Segway.

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Old 7th June 2016, 07:24 AM   #218
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The main differnce i can think about with a segway or the segway style hoverboards, is that they work by moving themselves front and back to remain 'under' the passenger.

Kind of like how a circus performer balances on a ball.

The Flyboard however does not move itself forward and back or in all directions horizontally like the circus ball to stay under the weight ( Cof G) of the passenger. If it is real, all it can really do is change pitch using thrust changes vertically. So not the same thing.



It is more akin to a rocket in that respect than a segway.

( it does not move itself directly horizontally)
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Old 7th June 2016, 07:27 AM   #219
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good point about c of G changing in rockets.

This is true.

I would imagine it would mostly change vertically as fuel is used, and not horizontally much, as i am assuming baffles etc are used inside the fuel tank to stop fuel sloshing around on the horizontal plane in liquid rockets.

And i am assuming solid fuel (whatever that is) is solid and packed to burn evenly on the horizontal plane - ie you do not get lots burnng away on one side only.


Also - the c of MASS will always remain within the rocket fuesalage itself.

When franky waves himself around and leans about on the board ( as we can see in some vids) his c of g or c of mass will be moving around considerably and likely falling outside of the imaginary cylinder of a rocket body if you chose to imagine one above the flyboard the same diamater as the board

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Old 7th June 2016, 07:42 AM   #220
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Originally Posted by ceptimus View Post

Later it was realized that it's only the vector (line) along which the thrust operates that matters - so all modern rockets have the exhaust nozzles at the back / bottom - and they're no more likely to 'fall over' than Goddard's original liquid rocket was.
I missused my brain a bit upthread, making kids' lunch and breakfast as I post.

In model rockets it's CG and Center of Pressure one separates by a caliber. CP can be roughly figured by tracing a silhouette of the rocket with fins and finding the CG of that shape, math is more tedious but only uses basic algebra.

When CG is too far forward of CP the rocket will "weathercock," tilting into the wind and continuing forward motion with significant yaw. When CG is aft of CP, the rocket will get off the launch rod and start spiraling around as the ass tries to get ahead of the nose. When CG is about 1 caliber ahead of CP the rocket resists wind yaw (it involves leverage) and doesn't waste thrust sideways, while traveling forward in the intended direction for a maximum distance.

Badly balanced rockets get high enough before spiraling that everyone can see your mistake, as the effect is aerodynamic and thus speed related.
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Old 7th June 2016, 07:47 AM   #221
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Originally Posted by esspee View Post
The main differnce i can think about with a segway or the segway style hoverboards, is that they work by moving themselves front and back to remain 'under' the passenger.

Kind of like how a circus performer balances on a ball.

The Flyboard however does not move itself forward and back or in all directions horizontally like the circus ball to stay under the weight ( Cof G) of the passenger. If it is real, all it can really do is change pitch using thrust changes vertically. So not the same thing.



It is more akin to a rocket in that respect than a segway.

( it does not move itself directly horizontally)
Yes, the axes of motion are orthogonal to one another in the two examples, and thus the math underlying the two devices will differ. Zapata has stated that they had to write their own code after starting with quadcopter algorithms.
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Old 7th June 2016, 07:58 AM   #222
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Originally Posted by Jrrarglblarg View Post
I missused my brain a bit upthread, making kids' lunch and breakfast as I post.

In model rockets it's CG and Center of Pressure one separates by a caliber. CP can be roughly figured by tracing a silhouette of the rocket with fins and finding the CG of that shape, math is more tedious but only uses basic algebra.

When CG is too far forward of CP the rocket will "weathercock," tilting into the wind and continuing forward motion with significant yaw. When CG is aft of CP, the rocket will get off the launch rod and start spiraling around as the ass tries to get ahead of the nose. When CG is about 1 caliber ahead of CP the rocket resists wind yaw (it involves leverage) and doesn't waste thrust sideways, while traveling forward in the intended direction for a maximum distance.

Badly balanced rockets get high enough before spiraling that everyone can see your mistake, as the effect is aerodynamic and thus speed related.
Are you a hobby rocket guy?

You seem knowedgable
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Old 7th June 2016, 08:01 AM   #223
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I fly hobby rockets I design and build from scratch.
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Old 7th June 2016, 08:28 AM   #224
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Originally Posted by Jrrarglblarg View Post
I fly hobby rockets I design and build from scratch.
Thats awesome man. And glad someone with knowledge like yours is on the thread.

"hobby rockets I design and build from scratch"

...and you think this Flyboard is real?

Or are you just exploring and specualting about the possible working of it out of interest?

If you do not mind me asking, what is your position on it being a hoax ( btw feel free not to take a position, i am not requesting you to, just asking if you already have one)


My position is i think it is a hoax or deception of some kind AND i ma really interested in how it COULD work, or rather what are the kind of things involved in making something like this for real
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Old 7th June 2016, 08:36 AM   #225
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I agree that centre of gravity should remain in front of centre of pressure for a stable flight - but this is related to the rocket behaving like a (long, very thin) wing when moving through the air fast.

Most rockets don't hover though some of the new full size rocket stages that land back on the ground may do so very briefly before touch down.

My point was that when hovering (or when operating in a vacuum where the centre of pressure has no meaning) then it doesn't make any difference how far the centre of gravity is above (or below) the rocket exhaust nozzle, the only thing that matters is that the rocket's thrust line passes through the centre of gravity.

The stability of the rocket in this hovering or vacuum state is governed by its moment of inertia around its pitch/roll axes - so a long thin rocket tends to stay straighter than a short squat one, for example.

For any balancing system the control system has to be able to react faster than the system falls: with a bit of practice, it's easy to balance a broom vertically on your hand, but you can't balance a pencil vertically on your hand/finger as it falls faster than your human reaction speed - and you couldn't even think of balancing a shorter object such as a needle. A computer vision system linked to a control system with high speed servos is quite capable of balancing a pencil however, and a super-fast one might be able to balance a pin too.

The sorts of control systems we use on model quadcopters use their gyros to measure any rotation - and they do this many tens, or even hundreds of times per second. The speed controllers that work the motors driving the propellers are updated fifty times per second or more - and the motors themselves then change speed sufficiently quickly to give smooth control.

If a human were trying to control a small quadcopter without such a control system and had to vary the speeds of the four motors by manually adjusting them, then that human would be hopelessly too slow. Maybe if you built a quadcopter twenty feet across then it would have a big enough moment of inertia that direct human control of the motors to give stability would become a possibility.

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Old 7th June 2016, 08:39 AM   #226
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Esspee: You might consider reading the thread from the beginning. Most forums benefit from knowing what conversation has happened upththread and ISF is no exception.

The Zapata Racing Flyboard Air is not a hoax, scam, spoof or fake. Every piece of the device is built on preexisting equipment and ideas. Nothing in it is outside the realms of basic physics. You and I can order up most of the parts on Amazon to build our own from scratch.

Not one part of the Flyboard is incompatible with outside knowledge or preexisting equipment.

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Old 7th June 2016, 08:41 AM   #227
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Originally Posted by esspee View Post
As someone said in this thread though - such inconsistencies and conflicts with the explanation he gives could be him hiding his technology so that others do not copy it.
It could also be a translation issue, it could also be the reporter not understanding/transcribing correctly.
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Old 7th June 2016, 08:53 AM   #228
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Originally Posted by ceptimus View Post
I agree that centre of gravity should remain in front of centre of pressure for a stable flight - but this is related to the rocket behaving like a (long, very thin) wing when moving through the air fast.

Most rockets don't hover though some of the new full size rocket stages that land back on the ground may do so very briefly before touch down.

My point was that when hovering (or when operating in a vacuum where the centre of pressure has no meaning) then it doesn't make any difference how far the centre of gravity is above (or below) the rocket exhaust nozzle, the only thing that matters is that the rocket's thrust line passes through the centre of gravity.

The stability of the rocket in this hovering or vacuum state is governed by its moment of inertia around its pitch/roll axes - so a long thin rocket tends to stay straighter than a short squat one, for example.

For any balancing system the control system has to be able to react faster than the system falls: with a bit of practice, it's easy to balance a broom vertically on your hand, but you can't balance a pencil vertically on your hand/finger as it falls faster than your human reaction speed - and you couldn't even think of balancing a shorter object such as a needle. A computer vision system linked to a control system with high speed servos is quite capable of balancing a pencil however, and a super-fast one might be able to balance a pin too.

The sorts of control systems we use on model quadcopters use their gyros to measure any rotation - and they do this many tens, or even hundreds of times per second. The speed controllers that work the motors driving the propellers are updated fifty times per second or more - and the motors themselves then change speed sufficiently quickly to give smooth control.

If a human were trying to control a small quadcopter without such a control system and had to vary the speeds of the four motors by manually adjusting them, then that human would be hopelessly too slow. Maybe if you built a quadcopter twenty feet across then it would have a big enough moment of inertia that direct human control of the motors to give stability would become a possibility.
We have some more talent in the thread!

Regarding the text i highlighted in bold.

Do you think jet engines, or rather the direction of the nozzles or output could react fast enough?

I always thought of them as being laggy.

I have sat in turbine aircraft for many hours. Small planes mostly.

I know its not the same sort of thing as a small jet, but the engine is the same basic thing just much bigger and driving a prop.

Being around these things and hearing them, they do not seem ultra fast responding, and i can not imagine them changing output accuratley in fractions of a second, like with electric fans on drones etc.

What do you think?
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Old 7th June 2016, 08:56 AM   #229
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The Flyboard however does not move itself forward and back or in all directions horizontally like the circus ball to stay under the weight ( Cof G) of the passenger. If it is real, all it can really do is change pitch using thrust changes vertically. So not the same thing.
Of course it does....that's what the human is for. Riders keep bicycles balanced with small back and forth motions of their body...so do the water board and AirBoard riders. He is not being "flown" by it...he is flying it....big difference.

He is well locked into the FlyBoard and is an integral part of the flight system.

The biggest risk given the fairly large forces involved is PIO or something inherent in the design leading to undamped instability ....you can see the potential for it when he lands and takes off and small directional shifts can cause sudden shifts given the power of the jets against the ground.

That's also a reason they use a mesh to land on ...to reduce that potential
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Old 7th June 2016, 08:58 AM   #230
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Originally Posted by Jrrarglblarg View Post
Esspee: You might consider reading the thread from the beginning. Most forums benefit from knowing what conversation has happened upththread and ISF is no exception.

The Zapata Racing Flyboard Air is not a hoax, scam, spoof or fake. Every piece of the device is built on preexisting equipment and ideas. Nothing in it is outside the realms of basic physics. You and I can order up most of the parts on Amazon to build our own from scratch.

Not one part of the Flyboard is incompatible with outside knowledge or preexisting equipment.
My thread was merged with this one.

It was not my choice.
Yes I have read the first few pages though.

I still think a lot is up for discussion regarding this 'device'.

We will have to agree to disagree.
BTW i have found your input very good and thought provoking for what it is worth.
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Old 7th June 2016, 08:59 AM   #231
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Originally Posted by CynicalSkeptic View Post
It could also be a translation issue, it could also be the reporter not understanding/transcribing correctly.
fair point
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Old 7th June 2016, 09:02 AM   #232
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What do you think?
I think you are asking questions from a perspective of incredulous doubt rather than educatable curiosity. Skepticism doesn't mean kneejerk doubting of anything and everything just because you personally are unfamiliar with it. Skepticism is examining claims in comparison to known facts elsewhere.

Tiny liquid fuel turbines would have some of the same compressor lag as larger turbines, but far far smaller magnitude. The mass of turbine and air that needs to accelerate or decelerate on power adjustments are so small the computer might not even notice, but the logic underlying the dynamic stability has some amount of PID control so it can predict and correct for lag time, hysteresis and overshoot. That's how quadcopters stay off the ground. The control software is smarter than you think.
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Old 7th June 2016, 09:11 AM   #233
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Originally Posted by esspee View Post
the flyboard however zooms about the place doing banking turns maintaining same altitude. this would require responsive thrust adjustments not seen with the harrir
I recently got my first quadcopter and yes when I adjust pitch to go forward/backward or roll to bank left/right it does lose significant altitude. I suspect with practice I will become better and adjusting the throttle up to compensate.
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Old 7th June 2016, 09:12 AM   #234
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Originally Posted by Jrrarglblarg View Post
I think you are asking questions from a perspective of incredulous doubt rather than educatable curiosity. Skepticism doesn't mean kneejerk doubting of anything and everything just because you personally are unfamiliar with it. Skepticism is examining claims in comparison to known facts elsewhere.

Tiny liquid fuel turbines would have some of the same compressor lag as larger turbines, but far far smaller magnitude. The mass of turbine and air that needs to accelerate or decelerate on power adjustments are so small the computer might not even notice, but the logic underlying the dynamic stability has some amount of PID control so it can predict and correct for lag time, hysteresis and overshoot. That's how quadcopters stay off the ground. The control software is smarter than you think.
This is a fair point.
But it a mixture of both incredulity and the curiosity IMO. I think something like this device is possible, in the future. I like anything that flys.

But yes - it was incredulity over the flyboard that led me to this forum in the first place
This was the only place i found with descent doubting discussion about it.

I think you can see from the interest in this thread ( look at viewcount) that it is something a lot of people are very interested in thinking about and discussing.
So this thread (the one I started but got merged) belongs here at Int Skep - even if i do not meet the definition of a skeptic in some posters eyes.
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Old 7th June 2016, 09:15 AM   #235
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Originally Posted by CynicalSkeptic View Post
I recently got my first quadcopter and yes when I adjust pitch to go forward/backward or roll to bank left/right it does lose significant altitude. I suspect with practice I will become better and adjusting the throttle up to compensate.
As i said, Frankies throttle controller must very sensitive, and he must be very accurate and smooth in increasing power prior to maneovers.

Not impossible though. People can do amazing things when they practice.

Last edited by esspee; 7th June 2016 at 09:17 AM.
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Old 7th June 2016, 09:18 AM   #236
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Modern model jet turbines react pretty quickly to the 'throttle' - they're a little slow to spool up from idling, but once they get above about 30% thrust then they can change in the range from 30% to 90% in a second or less.

They might not react fast enough for normal model quadcopter control techniques - but maybe in the flyboard air setting with the pilot standing on top and steering by weight shift they may not need to react as quickly.

If you needed to alter the thrust more quickly than the turbine can spool up and down, you could always add some sort of 'spoiler' gates on the turbine outputs that would redirect/waste some of the thrust as fast as necessary.

On lots of full-size passenger jets, there are reverse thrust gates that deploy like this, to slow the plane down after touchdown.

I think such gates scaled down to model turbine size and driven by fast servos would give a reaction time of a tenth of a second or so.

But like I say, we don't know yet exactly what's needed in a weight-shift system. If the flyboard air isn't a fake then I expect that the technical details of how it's controlled will be released or will leak out once they manufacture a few more of them and try to commercialize the project. If it's not a fake then secrecy is their friend right now to stop competitors beating them to the market by copying their ideas.

I still think that small gas turbines are a hopelessly inefficient way of powering a hovering platform - to gain efficiency when hovering you want to get the same thrust by accelerating a larger volume of air to a lower speed.

So turbo fans would be more efficient than turbo jets, propellers would be better yet, and a large rotor best of all. This is why a ten-ton harrier jump jet uses about 10,000 HP from its engine when hovering, while a helicopter of the same weight can hover using about a tenth of the power.

I think the main problems with these 'flyboards' will be very short endurance because of the heavy fuel consumption, and the danger of crashing in the event of a motor or control system failure. I suppose that is why (assuming it's not a fake) that all the flying is carried out at relatively low altitude and over water so that the pilot stands some chance of surviving in the event of a failure.

I'm sure (assuming they're not fake) that reliability will improve and daredevils will fly them high over land. They'll wear parachutes to save them if the things fail high up, but there will be a 'death zone' from the height where falling will kill you up to the height you need to successfully deploy a parachute.

Last edited by ceptimus; 7th June 2016 at 09:20 AM.
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Old 7th June 2016, 09:22 AM   #237
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ESpee
There is no "decent doubting discussion" ...only people pointing out the errors in your knowledge.
Skepticism is not based on ignorance but on sound knowledge. You are loaded with the former and lacking in the latter.

Neils Bohr could be skeptical of Einstein...because he had the sound underlying knowledge.

You on the other hand need to do more listening and asking about what you do not understand instead of throwing up "speculations" about what you clearly do not comprehend.

Better to be congratulating the inventor on a wonderful toy and asking how it works instead of insulting him by doubting it's existence.

•••

Actually I think jet turbines are a very good method as their power to weight and their efficiency is very high. What else is there other than rockets. Full thrust limits are 5 minutes.

It would be interesting to marry a jet wing with an AirBoard for landing One part of Iron Man starts to take shape.

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Old 7th June 2016, 09:31 AM   #238
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Originally Posted by macdoc View Post
ESpee
There is no "decent doubting discussion" ...only people pointing out the errors in your knowledge.
Skepticism is not based on ignorance but on sound knowledge. You are loaded with the former and lacking in the latter.

Neils Bohr could be skeptical of Einstein...because he had the sound underlying knowledge.

You on the other hand need to do more listening and asking about what you clearly do not understand instead of throwing up "speculations" about what you clearly do not understand.

Better to be congratulating the inventor on a wonderful toy and asking how it works instead of insulting him by doubting it's existence.



Actually I think jet turbines are a very good method as their power to weight and their efficiency is very high. Full thrust limits are 5 minutes.

It would be interesting to marry a jet wing with an AirBoard for landing
If i had invented something amazing, and tiny minority of people doubted it and accused me of being a fraud I would be over the moon, not insulted.

As it would prove i had truly made something fantastic.
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Old 7th June 2016, 09:38 AM   #239
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Originally Posted by ceptimus View Post
Modern model jet turbines react pretty quickly to the 'throttle' - they're a little slow to spool up from idling, but once they get above about 30% thrust then they can change in the range from 30% to 90% in a second or less.

They might not react fast enough for normal model quadcopter control techniques - but maybe in the flyboard air setting with the pilot standing on top and steering by weight shift they may not need to react as quickly.

If you needed to alter the thrust more quickly than the turbine can spool up and down, you could always add some sort of 'spoiler' gates on the turbine outputs that would redirect/waste some of the thrust as fast as necessary.

On lots of full-size passenger jets, there are reverse thrust gates that deploy like this, to slow the plane down after touchdown.

I think such gates scaled down to model turbine size and driven by fast servos would give a reaction time of a tenth of a second or so.

But like I say, we don't know yet exactly what's needed in a weight-shift system. If the flyboard air isn't a fake then I expect that the technical details of how it's controlled will be released or will leak out once they manufacture a few more of them and try to commercialize the project. If it's not a fake then secrecy is their friend right now to stop competitors beating them to the market by copying their ideas.

I still think that small gas turbines are a hopelessly inefficient way of powering a hovering platform - to gain efficiency when hovering you want to get the same thrust by accelerating a larger volume of air to a lower speed.

So turbo fans would be more efficient than turbo jets, propellers would be better yet, and a large rotor best of all. This is why a ten-ton harrier jump jet uses about 10,000 HP from its engine when hovering, while a helicopter of the same weight can hover using about a tenth of the power.

I think the main problems with these 'flyboards' will be very short endurance because of the heavy fuel consumption, and the danger of crashing in the event of a motor or control system failure. I suppose that is why (assuming it's not a fake) that all the flying is carried out at relatively low altitude and over water so that the pilot stands some chance of surviving in the event of a failure.

I'm sure (assuming they're not fake) that reliability will improve and daredevils will fly them high over land. They'll wear parachutes to save them if the things fail high up, but there will be a 'death zone' from the height where falling will kill you up to the height you need to successfully deploy a parachute.
If i had a flyboard like Franky, this would be my method of demonstrating it.

- i would spend as little time as possible in the danger zone and i would get to parachute altitude as fast as possible.
- i would then fly my record distance, and land as quickly as possible.

I would have a balistic launched round parachute available at all times.

Take off and landing would be from a boat, i would go nowhere near any hazards such as people or boats or coastline.
I would not land next to concrete, or on a platform situated on concrete next to people who could be hurt or burned if something went wrong.





What we see with his demonstrations is flying close to crowds, at low altitude, and flying near boats with tall masts. All potentially fatal hazards should control be lost (assuming its real).

The safety at these events is crazy negligent and reckless (if real)



off topic- i truly believe in the future we will have proximaty wingsuiting like we see now, only done so in level flight - i am also PRAYING that the Jetman team led by Rossy do some flying in valleys. That will be great.

Last edited by esspee; 7th June 2016 at 09:41 AM.
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Old 7th June 2016, 10:05 AM   #240
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This is called an "if I ran the zoo" argument. It's a form of fallacy.

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