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Old 8th June 2016, 11:55 AM   #321
Jrrarglblarg
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Originally Posted by CynicalSkeptic View Post
Not sure if you need to register to read it.

http://www.bullshido.net/forums/show...ght=hoverboard
Just glancing around that forum, it looks like another cesspit of ignorance and rampant emotionalism, but with looser moderation.

I won't be it joining soon, that's fershur.
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Old 8th June 2016, 12:00 PM   #322
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Originally Posted by CynicalSkeptic View Post
Not sure if you need to register to read it.

http://www.bullshido.net/forums/show...ght=hoverboard
thankyou!

(p.s thats me tied up for the next 2 - 3 hours, potentially turning into 5 hours given google searches getting out of hand , video watching, and smoke breaks...so- see you guys later!.....keep the thread moving)

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Old 8th June 2016, 12:10 PM   #323
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Originally Posted by foophil View Post
If it weren't for Guinness having witnessed and confirmed it, along with the folks in this thread who are knowledgeable in the general fields related to the Flyboard saying it could be feasible with off the shelf parts, I'd still be skeptical of it all. I know I certainly was before all that happened.

Now I happily accept that it is likely and quite possible because I don't buy into the conspiracy theory that Guinness would be behind covering up all this. It would ruin their reputation. Your quip earlier about 'any press is good press' is simply not true. It is an over-used phrase that doesn't possibly cover every circumstance. If Guinness were caught in outright fraud, they'd never be able to recover their image. They gain nothing by lying to their customers in this circumstance.
Regarding the text in bold.

If you can move past that - things become much more fluid and mushy.
The walls begin to move.

It is not pleasant.

Here is an excellent video- maybe you should watch- or maybe not.

This flyboard situation is the weirdest thing i have ever come across online.
Hoax or real, that is irrelevant.
It is still the weirdest thing and weirdest rabit hole online i have ever had the misfortune to stumble across.

One of the the entrances to the rabbit hole lol - https://www.youtube.com/watch?v=B5LVFhFTbWE
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Old 8th June 2016, 12:34 PM   #324
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Originally Posted by esspee View Post
Regarding the text in bold.

If you can move past that - things become much more fluid and mushy.
The walls begin to move.

It is not pleasant.

Why would I move past it? You've presented absolutely zero solid evidence they are behind a conspiracy. Quit hand-waving that away. If it weren't for Guinness stating this did happen as claimed, I'd still be skeptical of it all (though not claiming it is impossible) as would most here most likely. If it were instead some unknown tabloid making the claim, I'd be skeptical. But that isn't the case here.

Until you can show solid evidence that Guinness is now no longer to be trusted and an outright fraudulent source of information, I'm sticking to the side with evidence. YouTube videos, website screenshots, and hunches are not solid evidence.
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Old 8th June 2016, 12:38 PM   #325
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He spends the first two minutes complaining about editing then this:

2:13 "I know how marketing campaigns work, and this is not beyond the scope of a marketing campaign."

For what? Flyboard? By claiming to invent something that doesn't exist? What marketing campaign has ever used that? What company has ever used that kind of marketing?

Still just arguments from ignorance and incredulity.
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Old 8th June 2016, 12:40 PM   #326
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Originally Posted by foophil View Post
Why would I move past it? You've presented absolutely zero solid evidence they are behind a conspiracy. Quit hand-waving that away. If it weren't for Guinness stating this did happen as claimed, I'd still be skeptical of it all (though not claiming it is impossible) as would most here most likely. If it were instead some unknown tabloid making the claim, I'd be skeptical. But that isn't the case here.

Until you can show solid evidence that Guinness is now no longer to be trusted and an outright fraudulent source of information, I'm sticking to the side with evidence. YouTube videos, website screenshots, and hunches are not solid evidence.
You don't have to watch the video - but if you don't watch it ( in full) you will not understand where i am coming from or why marketing could be a big thing in this discussion. Or why Guinness, alone, is not as relevant as you and 99.9% of people think it is to this discussion.


its up to you...

i have no dog in the race. I am just here for the "kudos" when the world realises they were conned ( perhaps)

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Old 8th June 2016, 12:44 PM   #327
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Originally Posted by Jrrarglblarg View Post
He spends the first two minutes complaining about editing then this:

2:13 "I know how marketing campaigns work, and this is not beyond the scope of a marketing campaign."

For what? Flyboard? By claiming to invent something that doesn't exist? What marketing campaign has ever used that? What company has ever used that kind of marketing?

Still just arguments from ignorance and incredulity.
clearly did not watch the full video.
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Old 8th June 2016, 01:19 PM   #328
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Originally Posted by Ernie M View Post
I don't know the math well enough to know the change. But I'll guess the answer would be that head pressure is insignificant.

But for me, the issue at hand is that for safety and performance issues, it would be best to store the fuel in the Flyboard and not on the operator. Fuel pump(s) should take care of the delivery, gravity should not be relied upon in this situation.
Understanding the dynamics of the fuel might help you to understand why it is not a safety concern .

Jet Turbine engines use a fuel called Jet-A (or something similar) with a 5% mixture of synthetic turbine oil (such as Aeroshell 500) for lubrication so that there is no need for a complex oil system and pumps with their attendant weight penalty (this is similar to the concept of having oil added to the fuel for two-stroke engines that are used in chainsaws and lawn mowers).

The thing about this type of Jet fuel is that it is nowhere near as flammable as petrol. Its very similar to Kerosene, it will burn but it will not explode unless "misted" (Kerosene heaters can be used in the home). You can safely light a pool of kerosene, something that would be very dangerous to do with petrol. Carrying this type of fuel on your person is less dangerous than carrying a cigarette lighter.

Additionally, carrying fuel on the pilot is more sound from an engineering standpoint. Putting a fuel tank in the platform itself leads to couple of serious engineering concerns.

1. Fuel in a solid tank will slosh around, altering the weight distribution and therefore the balance of the platform. Such a fuel tank will have to be baffled to minimise the sloshing. Fuel on his body can be carried in something similar to a cyclists drink pack (a Camelbak for example). The big advantage of this is that, as fuel is sucked out of the the backpack's bladder, the bladder shrinks, leaving no air in the bag, therefore no sloshing of unburned fuel in the Camelbak. This would be very difficult to engineer into the platform.

2. Fuel in the platform will add weight to it. If my earlier calculations are correct, a two minute flight will need about 3kg of fuel, this is a significant amount of additional weight on a platform that only weighs about 15kg...and is additional weight that the flyer will need to displace when he is leaning to tilt the platform and steer it. If he carries that fuel on himself, the additional weight is only a very small proportion of his weight (so the penalty in raised CofG is minimal) and in fact this would assist rather than hinder his ability to steer.

Originally Posted by Jrrarglblarg View Post
I see no problems this solves. It limits fuel capacity, requires adding a separate system of sensor and indicator for the operator to monitor fuel status,
This is not necessary. The fuel flow rate of these RC engines is known to a high order of accuracy, down to a few millilitres per second. He can calculate exactly how much fuel he needs for given flight, and add a reserve. All that is then needed simple cellphone App (into which he inputs his fuel quantity on board) and it uses the known fuel flow rate against time elapsed to give the pilot an accurate readout of his remaining fuel/time, without ever actually measuring fuel itself.
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Old 8th June 2016, 01:30 PM   #329
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Originally Posted by esspee View Post
You don't have to watch the video - but if you don't watch it ( in full) you will not understand where i am coming from or why marketing could be a big thing in this discussion. Or why Guinness, alone, is not as relevant as you and 99.9% of people think it is to this discussion.


its up to you...

i have no dog in the race. I am just here for the "kudos" when the world realises they were conned ( perhaps)

I don't think you understand how this works. You are on a skeptics forum claiming to be a skeptic yourself. You made a claim. A pretty huge one. Now present the evidence. Show me actual evidence that Guinness is committing fraud and/or flat out lying to the world. JAQ'ing (Just Asking Questions for those who are new and unfamiliar with the term) and linking to YouTube videos talking about "what if" scenarios is not evidence.

Until you do that, I doubt you'll change anyone's minds here. In fact, this is beginning to seem like it should be moved into the proper sub-forum with the other conspiracy theories. A place where I could easily claim that aliens are in control of Guinness and mind controlling everyone involved. I 'd have the same amount of evidence you've presented so far. You couldn't prove me wrong, so maybe I'm right!
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Old 8th June 2016, 01:59 PM   #330
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Quote:
Quote:
I see no problems this solves. It limits fuel capacity, requires adding a separate system of sensor and indicator for the operator to monitor fuel status,
This is not necessary. The fuel flow rate of these RC engines is known to a high order of accuracy, down to a few millilitres per second. He can calculate exactly how much fuel he needs for given flight, and add a reserve. All that is then needed simple cellphone App (into which he inputs his fuel quantity on board) and it uses the known fuel flow rate against time elapsed to give the pilot an accurate readout of his remaining fuel/time, without ever actually measuring fuel itself
I don't like the idea of the operator of this vehicle using a cellphone while in flight. At all.

I don't like the idea of using dead reckoning to monitor fuel use above 2 meters from the ground, without other information available to cross-check.

A fuel bladder on your back provides eye-free monitoring of fuel status, by sense of touch and weight.

For an onboard tank, rather than baffles I would use foam sponge like race cars have inside their tanks. But I think the backpack fuel bladder is a far more elegant solution than anything that could be cludged into the tiny form-factor of the device itself.
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Old 8th June 2016, 02:47 PM   #331
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Originally Posted by Jrrarglblarg View Post
I don't like the idea of the operator of this vehicle using a cellphone while in flight. At all.

I don't like the idea of using dead reckoning to monitor fuel use above 2 meters from the ground, without other information available to cross-check.

A fuel bladder on your back provides eye-free monitoring of fuel status, by sense of touch and weight.

For an onboard tank, rather than baffles I would use foam sponge like race cars have inside their tanks. But I think the backpack fuel bladder is a far more elegant solution than anything that could be cludged into the tiny form-factor of the device itself.
Having it as a bladder rather than a rigid fuel tank would make it better for flow, as you don't need to fight a partial vacuum.

ETA: I don't know if you could use something to squeeze it as an assist, and whether that would be controllable
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Old 8th June 2016, 03:30 PM   #332
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Originally Posted by Jrrarglblarg View Post
I don't like the idea of the operator of this vehicle using a cellphone while in flight. At all.
He would not be using a smartphone as such, it is simply a way of monitoring what is happening, in the same way that flight instruments do. This is no different from a pilot used his flight instrument panel, except he might no even have to look at it. The App used could give him an audible warning when he has entered the fuel reserve.

I wouldn't mind betting his platform automatic stability control is done using a smartphone.


Originally Posted by Jrrarglblarg View Post
I don't like the idea of using dead reckoning to monitor fuel use above 2 meters from the ground, without other information available to cross-check.
This is SOP with a lot of microlights, for example, the Manair Blade, which has no fuel gauge fitted. The fuel tank contents are only visible through the translucent plastic wall of the tank against a calibrated scale, but this is not readily visible to the pilot.

Originally Posted by Jrrarglblarg View Post
A fuel bladder on your back provides eye-free monitoring of fuel status, by sense of touch and weight.
You are advocating a very inaccurate method of fuel measurement. Fuel flow monitoring is very accurate, it will predict engine cutoff with only a few seconds uncertainty.

Originally Posted by Jrrarglblarg View Post
For an onboard tank, rather than baffles I would use foam sponge like race cars have inside their tanks. But I think the backpack fuel bladder is a far more elegant solution than anything that could be cludged into the tiny form-factor of the device itself.
A agree. Its a simpler and more effective solution, with no safety issues at all.

ETA
I just remembered something from my days working on Bell Huey choppers. They can extend their flying time/range by fitting extra 150 USGal fuel bladders (called "Aux Bags") into the rear cabin in place of the side seating on each side of the main rotor gearbox housing. They were secured to the rear bulkhead using tie down straps.

Most importantly, they contained no direct fuel quantity monitoring. Fuel remaining was determined by calculating fuel flow using the on board fuel computer.
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Old 8th June 2016, 03:39 PM   #333
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Originally Posted by esspee View Post
i have no dog in the race. I am just here for the "kudos" when the world realises they were conned ( perhaps)
You're just here to look silly.
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Old 8th June 2016, 03:42 PM   #334
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Good comments about micro/ultralight aircraft, thanks. That would be a fine example of an opinion colored by wrong information. An now an example of how to respond to corrections:

If this thread were a whiteboard in the planning room for us building the thing, I'd happily erase those suggestions based on the comparison with existing applications. Then I'd schedule lab time to see what of several options works best with the actual hardware.

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Old 8th June 2016, 04:07 PM   #335
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You're just here to look silly.
and doing a superb job on that.....

•••

I concur - this is smart phone controlled - I would not be surprised if there was failsafe that the power is reduced slowly after a certain fuel flow so the pilot immediately knows he is down to reserves as his height starts to reduce.

I would actually think the power is controlled by the phone down to the landing and the pilot guides it in instead of having to worry about throttle control

seems both his arms were grabbed as he landed.
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Old 8th June 2016, 04:19 PM   #336
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Zapata's board uses a red industrial control pickle that appears to be hard wired to the board. That suggests to me he's using micro controllers of some flavor, which seems to me a more robust, quick acting, flexible to prototype and reliable solution.

I don't know enough about the computational capacity of smartphones, but my understanding is they aren't mathematically powerful, and PID controls need that. And I'd expect PID in there somewhere, if for nothing else than just the fuel delivery PMW.
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Old 8th June 2016, 04:35 PM   #337
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Originally Posted by esspee View Post
Not true, i think some of the people must be real as in 'in on it'. And some of the footage must have been shot of him in the air - but maybe from a crane or a helicopter or a huge drone.
You have fallen for the hoax. None of the people in those videos are real - not Franky, his helpers, spectators, nobody! And no cranes, helicopters or drones were used because the entire thing was computer-generated! Also Monaco doesn't exist.

In fact, nothing in those videos is real. Guinness World Records, You Tube, this forum, even the Internet itself are all part of the hoax. Truth is that you are actually in the Matrix, and everything you think you see, hear, touch or smell is actually being implanted directly into your brain by an alien supercomputer.

OK, that's not quite true. Actually you don't have a brain, because you don't exist!
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Old 8th June 2016, 04:55 PM   #338
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Originally Posted by Jrrarglblarg View Post
I don't know enough about the computational capacity of smartphones, but my understanding is they aren't mathematically powerful, and PID controls need that. And I'd expect PID in there somewhere, if for nothing else than just the fuel delivery PMW.
Actually smartphones are 'mathematically powerful', but they run an OS which is not optimized for real-time control. A microcontroller board may be less powerful, but can dedicate itself to running the PID (Proportional Integral Differential) algorithms required to stabilize the platform.
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Old 8th June 2016, 05:55 PM   #339
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Originally Posted by Dr.Sid View Post
You're just here to look silly.

It clearly really scares you that this might be hoax.




.....it is
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Old 8th June 2016, 06:03 PM   #340
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Originally Posted by Jrrarglblarg View Post
Zapata's board uses a red industrial control pickle that appears to be hard wired to the board. That suggests to me he's using micro controllers of some flavor, which seems to me a more robust, quick acting, flexible to prototype and reliable solution.

I don't know enough about the computational capacity of smartphones, but my understanding is they aren't mathematically powerful, and PID controls need that. And I'd expect PID in there somewhere, if for nothing else than just the fuel delivery PMW.
I've build PID controllers completely from a handful of analog component parts (resistor, inductor, capacitor, op-amp). No need for any digital computation.
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Old 8th June 2016, 06:12 PM   #341
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.



A step forward as significant as the Wright Bros first motorised flight...

...or an advert for a car.?



You decide.

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


(you either get it, or you don't)
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Old 8th June 2016, 06:17 PM   #342
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Originally Posted by jimbob View Post
Having it as a bladder rather than a rigid fuel tank would make it better for flow, as you don't need to fight a partial vacuum.

ETA: I don't know if you could use something to squeeze it as an assist, and whether that would be controllable
you use a "Hopper Tank" in the body--that is, a small tank fed by the main fuel tank. It always stays full, and can be arranged to be constant pressure, regardless of main tank placement
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Old 8th June 2016, 08:14 PM   #343
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Originally Posted by Jrrarglblarg View Post
Just glancing around that forum, it looks like another cesspit of ignorance and rampant emotionalism, but with looser moderation.

I won't be it joining soon, that's fershur.
Good for you. Nobody asked you to join.
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Old 8th June 2016, 08:32 PM   #344
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Originally Posted by Ernie M View Post
I don't know the math well enough to know the change. But I'll guess the answer would be that head pressure is insignificant.
If I’m remembering my numbers correctly, and assuming that the jet fuel runs about 80% the weight of water, then you get about 1 psi for every 35” of elevation. So if the backpack is 18” high you get a loss of about .5 psi from full to empty.
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Old 8th June 2016, 08:42 PM   #345
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Originally Posted by JimOfAllTrades View Post
If I’m remembering my numbers correctly, and assuming that the jet fuel runs about 80% the weight of water, then you get about 1 psi for every 35” of elevation. So if the backpack is 18” high you get a loss of about .5 psi from full to empty.

Yep. SG of Jet-A runs from about 0.78 to about 0.84 depending on temperature, although if these are RC turbines, then the fuel with have 5% synthetic oil mixed in, which might change the SG a little.
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Old 8th June 2016, 09:00 PM   #346
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Originally Posted by smartcooky View Post
Yep. SG of Jet-A runs from about 0.78 to about 0.84 depending on temperature, although if these are RC turbines, then the fuel with have 5% synthetic oil mixed in, which might change the SG a little.
Cool, I was close then, thank you. I was going by memory that 28" of water gives you 1 psi, and guessing on the 80% weight of water for the fuel.
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Old 8th June 2016, 09:02 PM   #347
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Originally Posted by JimOfAllTrades View Post
If I’m remembering my numbers correctly, and assuming that the jet fuel runs about 80% the weight of water, then you get about 1 psi for every 35” of elevation. So if the backpack is 18” high you get a loss of about .5 psi from full to empty.
Thank you, JimOfAllTrades.

I'm still trying to find which make and model rc jet engine Franky Zapata used. But it definitely looks like using the stock, manufacturer-supplied fuel pump should be enough to properly deliver the fuel and gravity feed pressure from backpack wouldn't matter?

If there was fuel in that backpack I'd like to know how Franky delivered it to four jet engines. And the jet engines were supposed to be modified, so hard to tell how much fuel they would use.

Looks like the jet engines used have a silver body with a light gray color top. Picture of jet engine here

Doesn't look like Flyboard Air uses either a JetCat 200P or a PBS Velka Bites TJ 40-G1 as other have speculated.
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Old 8th June 2016, 10:23 PM   #348
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Originally Posted by Ernie M View Post
Thank you, JimOfAllTrades.

I'm still trying to find which make and model rc jet engine Franky Zapata used. But it definitely looks like using the stock, manufacturer-supplied fuel pump should be enough to properly deliver the fuel and gravity feed pressure from backpack wouldn't matter?

If there was fuel in that backpack I'd like to know how Franky delivered it to four jet engines. And the jet engines were supposed to be modified, so hard to tell how much fuel they would use.

Looks like the jet engines used have a silver body with a light gray color top. Picture of jet engine here

Doesn't look like Flyboard Air uses either a JetCat 200P or a PBS Velka Bites TJ 40-G1 as other have speculated.
In the picture you linked: see the white plastic tips above the boot on the right side? Those look to be hose quick-connectors connected to the black flexible running across the top of the turbines. One of the earlier pictures from their website showed both the tubing and connectors in a different position, which makes sense if it's flexible. Run that up a pant leg and clip in to the backpack. It looks to be a dual hose, so it could even be simultaneously providing repressurization.
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Old 8th June 2016, 11:31 PM   #349
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Originally Posted by Ernie M View Post
Looks like the jet engines used have a silver body with a light gray color top. Picture of jet engine here

Doesn't look like Flyboard Air uses either a JetCat 200P or a PBS Velka Bites TJ 40-G1 as other have speculated.
Oh FFS, it doesn't matter what colour the induction fan cone or the engine nacelle is, because they come in different colours from some manufacturers so that you can match the colouring of your RC plane.

I have seen Jet Cats with red. blue and yellow fan cones and nacelles.

It is quite obvious you are trying to keep up in a subject you know nothing about

ETA

This should answer all your questions

Quote:
JetCat P-200 turbine comes complete with heavy duty starter and includes:

Jet-tronic ECU (fuel control electronics)
GSU (Display and Programmer)
LED I/O board · Miniature fuel pump
Electronic starting gas valve
Electronic Fuel valve
Fuel tubing, tubing connector set, filters, and cable set

2 cell, 3800mA LiPoly battery pack
Starting gas tank
Turbine mounting clamp
Detailed instruction manual
Thrust: 52 lbs @ 112,000 RPM

Weight: 5 LB

Diameter: 5.12 inches

RPM Range: 32,000 - 110,000 RPM
Exhaust gas temp.: 580°C-720°C

Fuel consumption: 24 oz per/min at full power

Fuel: Jet A1, 1-K kerosene

Lubrication: approximately 5% synthetic turbine oil in the fuel

Maintenance interval: 25 hours

ETA2: FWIW Those engines look like TG40-2s to me
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Old 9th June 2016, 01:27 AM   #350
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Originally Posted by esspee View Post
Regarding the text in bold.

If you can move past that - things become much more fluid and mushy.
The walls begin to move.
I suppose it comes down to "extraordinary claims require extraordinary evidence". The Guinness Book of World Records people have a business which is largely based on public confidence in them being impartial, reliable and accurate.

If they went out on a limb like this, authenticated a fake, and then were found out, then that image would be destroyed. There may be reasons for taking such a risk but in this case I cannot see what's in it for The Guinness Book of World Records people. I mean if a group of them were investors in this product and stood to make £££££££s in an IPO based on this evidence (even if it subsequently destroyed both companies) then there may be a motivation but I do not see it here.
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Old 9th June 2016, 01:36 AM   #351
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Originally Posted by esspee View Post
.



A step forward as significant as the Wright Bros first motorised flight...

...or an advert for a car.?



You decide.

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


(you either get it, or you don't)
False dichotomy and strawman.

Strawman:

I don't think anyone is arguing that it's A step forward as significant as the Wright Bros first motorised flight, after all it seems that most of the components are off the shelf, most of the principles are well established and there isn't scope for societal change that aeroplanes in both their civil and military roles. IMO it's as "revolutionary" to flight as the jetski is to water transport.

False Dichotomy:

Why can it not be a (modest) advancement in flight which is used in a car advert ?
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Old 9th June 2016, 02:19 AM   #352
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Originally Posted by macdoc View Post
Jets are very efficient and throttle up instantly as it's entirely fuel feed.

I'm a little skeptical of this. I believe it's certainly not instant. I would guess that smaller jets spool up faster than larger ones?
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Old 9th June 2016, 03:35 AM   #353
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Originally Posted by The Don View Post
I don't think anyone is arguing that it's A step forward as significant as the Wright Bros first motorised flight, after all it seems that most of the components are off the shelf, most of the principles are well established and there isn't scope for societal change that aeroplanes in both their civil and military roles. IMO it's as "revolutionary" to flight as the jetski is to water transport.
Another thing to consider here is that with the advent of modern digital processing, ultra-fast processing speeds and super miniaturisation technology, feats of aviation design & engineering have become possible that quite simply were impossible previously. A case in point...

NOTE: Don't click the spoiler before you read this, and see if you can guess which aircraft I am talking about...

This aircraft is completely unstable from an aerodynamics perspective in all three flight axes; roll, pitch and yaw. It needs continual flight control corrections from a flight control system (FCS) computer to maintain flight. Turn off the FCS, and this aircraft has all the glide characteristics of a set of car keys.

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Old 9th June 2016, 03:45 AM   #354
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Originally Posted by 3point14 View Post
I'm a little skeptical of this. I believe it's certainly not instant. I would guess that smaller jets spool up faster than larger ones?
Yes, but while jets are notoriously sluggish in the lower revolution range, once they are at higher revolutions, they respond to throttle settings more quickly. However, even if there is some lag, its not a show stopper.

The examples we have surmised here, the Jet Cat200 and the TG40 operate in the range 32,000 to 117,000 rpm.

To put that in some perspective, the lower end of that range is about six to eight times the red line rpm for your average family car!


Frank Zapata is a pretty skilled Flyboard rider (he did invent the thing after all) and I have no doubt that he would have no problem keeping balanced on four jet engines. I am pretty certain he will have an Engine Control Computer to keep the four engines synchronized. The little red ducted fans (for yaw control) on the sides of the platform are running all the time, and only shut down when he lands.

However, one of the things that makes landing and taking off using jet thrust really difficult is ground effect. It could destabilize the platform and the jet engines could flame out of they end up ingesting their own exhaust gases

Zapata's solution to this problem appears to be that he never gets close to the ground. He uses that launch platform for take off and landing,. I haven't see it up close, but I'm guessing the floor of that launch rig is hard wire mesh or something like it, which would allow the exhaust gases to pass through.... very clever.
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Old 9th June 2016, 04:21 AM   #355
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This image...



.. seems to support macdocs and my suggestions that the four engines are angled slightly outwards from vertical
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Old 9th June 2016, 04:28 AM   #356
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Originally Posted by smartcooky View Post
Yes, but while jets are notoriously sluggish in the lower revolution range, once they are at higher revolutions, they respond to throttle settings more quickly. However, even if there is some lag, its not a show stopper.

The examples we have surmised here, the Jet Cat200 and the TG40 operate in the range 32,000 to 117,000 rpm.

To put that in some perspective, the lower end of that range is about six to eight times the red line rpm for your average family car!


Frank Zapata is a pretty skilled Flyboard rider (he did invent the thing after all) and I have no doubt that he would have no problem keeping balanced on four jet engines. I am pretty certain he will have an Engine Control Computer to keep the four engines synchronized. The little red ducted fans (for yaw control) on the sides of the platform are running all the time, and only shut down when he lands.

However, one of the things that makes landing and taking off using jet thrust really difficult is ground effect. It could destabilize the platform and the jet engines could flame out of they end up ingesting their own exhaust gases

Zapata's solution to this problem appears to be that he never gets close to the ground. He uses that launch platform for take off and landing,. I haven't see it up close, but I'm guessing the floor of that launch rig is hard wire mesh or something like it, which would allow the exhaust gases to pass through.... very clever.
So is the video real? We think so. This is an amazing achievement for [Frank Zapata]. Is it practical or safe? Heck no! Nor is it cheap – those engines cost €8,845.00 each. That said, we’d love a chance to ride the Flyboard Air – after a few hours of training on the original Flyboard of course.
Yeah - that price sounds about right.

Tell me - what would happen to one of those jets if, while it was still reaally hot got dropped it in water?

Lets imagine for a moment that it is not still spinning when you kill the fuel ( because if it was i believe the water destroy the blades instantly)

What would happen if you shock cooled one of these hot engines by putting it in water? WOuld the temperature shock not warp the jet blades, throwing the whole unit out of baclance so that it became useless forever more?


According to Franky - dropping the unit hot in the water did no damage to the jets - only the electronics.



Quote:
What happens if you do wind up in the water?

Nothing really serious, there’s no danger for me, because I fell in the water honestly three days ago. [Laughs] Three days ago I crashed in the water because we tried to — you know we’re going to do the hoverboard farthest trip. The last one was 275 meters, and we will break it by 10 times longer. We will do about 2 miles. We will cross 2 miles with the Flyboard Air at about 60 to 80 kilometers per hour. And we were training for that, and the last time trained we trained with 80 kilometer per hour wind. And we didn’t realize that when we have wind we go through more battery for the stabilization system. So just five seconds before I landed on the platform, I go out of battery. And the machine starts to turn like a torpedo, like if you lost the small rotor on a helicopter. I started to turn like [Franky makes a noise, “Shooooh!”], and I had no choice but to kill the engine just before I landed in the water. I broke all the electronics on the board, so it will cost me money, but the rest of it is fine.
http://www.h2romagazine.com/zapata-racing/flyboard-air



p.s "the last time trained we trained with 80 kilometer per hour wind" lol
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Old 9th June 2016, 07:27 AM   #357
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Originally Posted by 3point14 View Post
I'm a little skeptical of this. I believe it's certainly not instant. I would guess that smaller jets spool up faster than larger ones?
Turbo and turbine lag is a result of the feedback loop of more fuel first demands and then delivers more air, so there's a delay. A tiny turbine has lower mass to accelerate than a big turbine, and lower air volume to pump. A PID controller helps a closed-loop control system overcome hysteresis and other consistent delays in the equipment.
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Old 9th June 2016, 07:31 AM   #358
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Originally Posted by GodMark2 View Post
I've build PID controllers completely from a handful of analog component parts (resistor, inductor, capacitor, op-amp). No need for any digital computation.
It's good to be reminded that uncomputerized solutions like this exist. Thanks.
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Old 9th June 2016, 07:53 AM   #359
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Quote:
What would happen if you shock cooled one of these hot engines by putting it in water? WOuld the temperature shock not warp the jet blades, throwing the whole unit out of baclance so that it became useless forever more?

How do you think jets fly through hail and rain at huge temperature gradients.
The material in jet turbine blade is VERY tough.
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Old 9th June 2016, 09:16 AM   #360
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Originally Posted by macdoc View Post

How do you think jets fly through hail and rain at huge temperature gradients.
The material in jet turbine blade is VERY tough.
I wouldn't discount this question out of hand. I can't speak for the materials in a R/C gas turbine, but many of the military engines I work with cannot even be shut down from military power without a cool down period at idle speed. There's a big difference between ingesting rain during flight while the combustor is still lit versus immersing the turbine in water.
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