Sine wave propulsion

[cyclops]

I will take 2.

[chandler]

Tesla, isn't that a band from Boston??

[chandler]

Wouldn't it be great if all the innovative technology that didn't profit big buisiness{sp} was actually developed?

That it isn't?

Being Developed - that is!

The proper queston tho is, "Who's developing it and to what use is it being put?".

Another pertinent question might be...

"Why release a new energy development, if you haven't already cornered the market on it?"..

So - just how do you corner the market on a global free enegery source?

If your a Fascist global oil oligarchy, how do you prevent everyone else from no longer needing, what you've spent a few generations creating? (A global oil oligarchy)?.

All good questions! - but 'the answer's could get us all into hot water - probably better not to go there!

Cheers!

[Guillermo]

A simplified propulsive model of bio-mimetic robot fish and its realization

[VladZenin]

Unfortunately this file is not available. [S0263574704000426a.pdf].

[Guillermo]

Go to: http://journals.cambridge.org/action/login
On the right side of the screen there is a search facility: Type there "robot fish" and you'll find the article as the first one in the list that appears.
Cheers.

[VladZenin]

The page you refers to is currently unavailable too. Could you send forward this article to vladimirz@iimetro.com.au please?

[sigurd]

Question from the uneducated peanut gallery: For boat propulsion, what would drive the preference toward either a (or two opposing) stiff high aspect wing, or a flexing unit like a diver's monofin? I was thinking that some of the efficiency gain from a monofin over two fins (used as a monofin) might be due to the longer span that it enables - so why has it not evolved to even higher AR (looks like the high performance models are approx square or atleast very low AR) - and would it be feasible to try and construct a diving fin with a rigid, high AR foil section like a NACA 0010 or whatever?

Kjell mentioned that humans can't kick fast enough to benefit from it - but I don't understand why. The slower crafts (planes, boats) usually benefits from a large span.

Another thing I don't quite get, is that the propulsive area of slow fish are usually bigger than on the very fast fish, in opposite to diving fins. As was mentioned, maybe acceleration and agility has something to do with slow fishes' preference for a large area, but acceleration is not a high priority in many of the watersports where large high speed fins are used.

I have read about the mirage drive that it is less exhausting to use at cruising speed than a kayak oar (it utilises bigger muscles so this isn't a surprise), but that the top speed is less. So why is that? Too large area? Too much flex? Is lack of torsional stiffness in the wings the only thing that sets the AoA in the mirage?

Is the turning point of fins a large loss source, so that amplitude is preferrable to frequency for efficiency? I have read something about insect flying, and there seems to be all sorts of odd, complicated things going on, one of them being the utilisation of vortices to increase lift if I remember correctly - especially the smallest insects I think. Is this relevant to any fish, or manmade oscillating propulsion?

[AleX`G]

Originally Posted by safewalrus

Apart from the inflated ego's of the main protagonists in this entertainment (got as far as page 4, and had to stop - exhausted!) the main problem I can see from a practical view point is the fact that if the whole boat is "snaking" through the water, you puts yer coffee cup down and bingo! you got coffee all over the the bloody table! Just a thought!

And Masrapido 'tis great to see that your OK buddy, there was some concern (see Open forums) that you might be swimming round the "Mexus/Texico Gulf" great to see that your not!

Surely if you made the contraption the size of a supertanker the snaking movement would be reduced to a steady sway which you may not notice. Due to the relativly small movements.
I might try some experiments of my own on this subject. Do you think the wave created my the boats in that experiment were cancelled out by destructive interference from the fin.
Sounds like an interesting idea.

[sigurd]

The lauder et al pdf linked in this thread speculates that the bluegill caudal fin benefits (makes more thrust) because of the vortex from the dorsal fin. Wonder what those little protrusions on the aft part of the mackerel are?

" Although the design of thunniform swimmers is optimised for high-speed swimming in calm waters, it is particularly inefficient for other actions such as slow swimming, turning manoeuvres and rapid acceleration from stationary, as well as for turbulent water."

How does the proximity of the surface affect the design of flapping boat propulsors? The flapping (aero) wing paper I once read stated that the opposing flapping wings acted like they were in "surface effect" IIRC. But, from the other side of the surface, in the water, the surface effect is detrimental to lift in all directions? Also would the turbulent surface water give points to the flexible fin over the high AR rigid wing as seen in the "pump-a-bike" or whatever it is called? On a tangent, is proximity to the sea bottom hydrodynamically beneficial for fish?

Specifically also, I am looking for a means to manually drive a singlehanded 20' by 3m cat.
I suppose a propeller would be too drafty if an efficient size is chosen.
Two rowing oars?
A single rowing oar, sitting on one hull with the blade between the hulls?
A pedal, or "mono-pedal" system for flapping a fin (or two opposing fins)up and down?
Somewhere some time I read that if you put a horizontal foil on the bow, wave action and pitch resonance of the vessel could drive the vessel forward against the sea and wind. Is this bollicks?

[sigurd]

sorry, not "pump-a-bike" - it's called a trampofoil

http://ourworld.compuserve.com/homep...dgen/tramp.htm