Navier 27 (from the FP)

McGyver

Anarchist
816
54
San Diego
Last week was the Eco Clipper without a rudder.  Now we have a foiling motorboat without propellers or jets.  Will wonders never cease?

 

sailman

Super Anarchist
8,295
423
Portsmouth, RI
It's been done before (USS Pegasus)

a-starboard-bow-view-of-the-patrol-combatant-missile-hydrofoil-uss-pegasus-3c2476-1600.jpg


 

Left Shift

Super Anarchist
10,532
3,267
Seattle
I would trust Paul to figure out the means of propulsion.  Spinny things at the end of the two aft pods seem likely suspects, although the drawings are very nicely obscure about that.  Maybe propellers are hard to draw in CADD ;)

In summary:  I want one.

 
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Cheap Beer

Anarchist
551
17
Anacortes, WA
Nevertheless, water jets are too inefficient for electric propulsion in this case. I'm assuming they're meant to be pod motors w props at the bottom of the aft foils. Details TBD. Don't hit anything. Don't run at night in the PNW.

 

Left Shift

Super Anarchist
10,532
3,267
Seattle
Nevertheless, water jets are too inefficient for electric propulsion in this case. I'm assuming they're meant to be pod motors w props at the bottom of the aft foils. Details TBD. Don't hit anything. Don't run at night in the PNW.
Everybody knows that deadheads all go down to the bottom to take naps at night around here.  Nothing to worry about.  

(Actually there are remarkably fewer deadheads in the Salish compared to the pre-2000s.  Basically after McHouses replaced all the forests around Puget Sound.)

 
The problem with hydrofoils had not changed since the very first attempts over a hundred years ago: control in a seaway.

The first successful hydrofoils flew on lakes in very smooth conditions.

After a century of investment by the US Navy, there are exactly zero operational hydrofoils. The reason has always been the same: a very limited sea state can be handled, and then the vessel crashes with grave danger and often injuries to the crew.

All existing hydrofoils exhibit the same problem: once you exit the "safe zone" aka flight control envelope, things immediately go pear shaped, often with horrible results.

The challenge of control at high speed in close proximity to a formally chaotic surface (the surface of the water) is daunting, and is CERTAINLY not solved by any control theory currently being widely used in aerospace. While such control systems can work well within the flight control envelope, they don't work at all outside of that envelope: think jumping out of the water due to a big wave. Worse, waves that are too large to handle can be "rouge waves" that are random combinations of wave interference, which due to randomness cannot be predicted with sufficient reliability to ensure safety to the vessel and crew.

While some might say "foil borders jump all the time" one must also admit that they often crash. Even with a highly experienced, highly trained human brain, reliability is certainly not achieved.

It aint carbon, it aint foil shapes, it aint propulsion efficiency, it aint styling, it aint price. Its all about control.

Control in chaos is non-trivial and unreliable at this time. I do expect that something will be discovered, as chaotic mathematics have only been understood by very few people for a handful of decades. Quantum computing, that intrinsically allows computing the many concurrent possibilities presented by quantum computing, MIGHT be the necessary breakthrough. But a mathematical breakthrough is required, after which science will be required, and once that is proven out, then engineering can be done.

Until then, hydrofoils are a fun toy, but a dangerous application for human transport.

 

spankoka

Super Anarchist
I don't think the Macau-Hong Kong hydrofoils have killed anyone. If you go to the Bell Museum in Baddeck NS, they have the first hydrofoil there. Bell did all kinds of interesting things besides the invention he is best known for. 

 
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The JetFoils don't kill people wholesale because they fly very high, so the wave height they can tolerate before ventilation is high. Still, exceed the limit, and watch out, as with any hydrofoil. Also, many hydrofoil accidents are related to other aspects of control, including the very large turning circle at speed, and the general difficulty in changing velocity up or down.

Its not just wave height, but all 18 degrees of freedom (DOF): x, y, z, rotations around x, y, z, their derivatives, and their second derivatives. The linkages between each is non-trivial (non-linear, and stateful, therefore chaotic). Specifically, traditional control theory does not work unless all DOF are within limited ranges.

Chaotic functions generally have some ranges where things do work similarly to non-chaotic functions. This is the reason some people are fooled into thinking "it all works, there are just some surprises that we are working on to solve."

https://computing.dcu.ie/~humphrys/Notes/Neural/chaos.html

 

Left Shift

Super Anarchist
10,532
3,267
Seattle
The problem with hydrofoils had not changed since the very first attempts over a hundred years ago: control in a seaway.

The first successful hydrofoils flew on lakes in very smooth conditions.

After a century of investment by the US Navy, there are exactly zero operational hydrofoils. The reason has always been the same: a very limited sea state can be handled, and then the vessel crashes with grave danger and often injuries to the crew.

All existing hydrofoils exhibit the same problem: once you exit the "safe zone" aka flight control envelope, things immediately go pear shaped, often with horrible results.

The challenge of control at high speed in close proximity to a formally chaotic surface (the surface of the water) is daunting, and is CERTAINLY not solved by any control theory currently being widely used in aerospace. While such control systems can work well within the flight control envelope, they don't work at all outside of that envelope: think jumping out of the water due to a big wave. Worse, waves that are too large to handle can be "rouge waves" that are random combinations of wave interference, which due to randomness cannot be predicted with sufficient reliability to ensure safety to the vessel and crew.

While some might say "foil borders jump all the time" one must also admit that they often crash. Even with a highly experienced, highly trained human brain, reliability is certainly not achieved.

It aint carbon, it aint foil shapes, it aint propulsion efficiency, it aint styling, it aint price. Its all about control.

Control in chaos is non-trivial and unreliable at this time. I do expect that something will be discovered, as chaotic mathematics have only been understood by very few people for a handful of decades. Quantum computing, that intrinsically allows computing the many concurrent possibilities presented by quantum computing, MIGHT be the necessary breakthrough. But a mathematical breakthrough is required, after which science will be required, and once that is proven out, then engineering can be done.

Until then, hydrofoils are a fun toy, but a dangerous application for human transport.
As long as those "rouge waves" are colored a tasteful red, I don't see the problem of identifying and correcting for them tout suite.

The JetFoils don't kill people wholesale because they fly very high, so the wave height they can tolerate before ventilation is high. Still, exceed the limit, and watch out, as with any hydrofoil. Also, many hydrofoil accidents are related to other aspects of control, including the very large turning circle at speed, and the general difficulty in changing velocity up or down.

Its not just wave height, but all 18 degrees of freedom (DOF): x, y, z, rotations around x, y, z, their derivatives, and their second derivatives. The linkages between each is non-trivial (non-linear, and stateful, therefore chaotic). Specifically, traditional control theory does not work unless all DOF are within limited ranges.

Chaotic functions generally have some ranges where things do work similarly to non-chaotic functions. This is the reason some people are fooled into thinking "it all works, there are just some surprises that we are working on to solve."

https://computing.dcu.ie/~humphrys/Notes/Neural/chaos.html
When did smarty-pants people decide that "non-trivial" was the cool, scien-terrific way to say "difficult" or "complex"?

 

Spoonie

Anarchist
742
91
Sydney
When did smarty-pants people decide that "non-trivial" was the cool, scien-terrific way to say "difficult" or "complex"?
technically, a solution can still be trivial even if the problem is difficult or complex.  It is probably more correct to relate non-trivial to complicatedness.

just say'n...

 
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