Parallell coupled fish tail boat propulsion

[kjellhoegseth]

Hi!
Some years ago I was in a group who went through a week course in the Russian developed innovation technique of TRIZ, and in the "keelwater" after the course, I got the idea ; Why not use the same propulsion principles for boats like the fishes, an waving oscillating tail,or to get more pushing force, set more tails parallell to each other and drive them oscillating mirrorred along a center plane to avoid any swinging tendency of the hull . Should be possible to drive from a common engine shaft like a propeller. The benefit as long as none can prove the opposite, was taken from the idea : The nature (here the fishes)has over millions of years usually found the most energy efficiant way of moving around - and if you look at the acceleration ability of a Barracuda or a Marlin this idea of a swinging tail looks quite impressive. Does anyone have any experiences here ?? Or is this a forgotten good idea.
kjellhoegseth

[Bergalia]

Interesting. But possibly an unwelcome form of propulsion in a tightly packed marina (back-wash). A mechanical form of sculling.... :rolleyes:

[kjell]

Hi!
Some years ago I was in a group who went through a week course in the Russian developed innovation technique of TRIZ, and in the "keelwater" after the course, I got the idea ; Why not use the same propulsion principles for boats like the fishes, an waving oscillating tail,or to get more pushing force, set more tails parallell to each other and drive them oscillating mirrorred along a center plane to avoid any swinging tendency of the hull . Should be possible to drive from a common engine shaft like a propeller. The benefit as long as none can prove the opposite, was taken from the idea : The nature (here the fishes)has over millions of years usually found the most energy efficiant way of moving around - and if you look at the acceleration ability of a Barracuda or a Marlin this idea of a swinging tail looks quite impressive. Does anyone have any experiences here ?? Or is this a forgotten good idea.
kjellhoegseth

Hi
Is this something you are looking fore?
Viste my website for more information.
http://www.dahlberg-sa.com/kd/Tail.htm

TREK1
http://video.google.com/videoplay?do...40064555232864

TREK2
http://video.google.es/videoplay?doc...94079313250276

Cheers
KJELL

[Bergalia]

Interesting idea - sort of mechanical sculling as used in Japan, China etc

[jehardiman]

Kjellhoegseth;

While it is fairly easy to mimic the fin sculling motion of slow, but agile, fish; the large powerful fast fish swim with an entirely different mechanisum. Look at the MIT RoboTuna/RoboPike ( web.mit.edu/ahtechet/www/CMI/CMIpt2by2.pdf) or several of the Japanese Fisheries papers on the different swimming mechanics of fishes. Until we mate MPP sensor feedback to an effective mechanical muscle, high efficency propulsion like swimming fish is not really practical.

Check out this paper: https://ritdml.rit.edu/dspace/bitstream/1850/2630/1/AStreettThesis09-2006.pdf

[kjell]

I have now installed the Wiggle Tail Drive in an R/C model boat. The horizontal mounting works very well. As soon as I have made the navigation tests, I will show you a video with the test results.
Kjell

[Rick Willoughby]

Hi!
Some years ago I was in a group who went through a week course in the Russian developed innovation technique of TRIZ, and in the "keelwater" after the course, I got the idea ; Why not use the same propulsion principles for boats like the fishes, an waving oscillating tail,or to get more pushing force, set more tails parallell to each other and drive them oscillating mirrorred along a center plane to avoid any swinging tendency of the hull . Should be possible to drive from a common engine shaft like a propeller. The benefit as long as none can prove the opposite, was taken from the idea : The nature (here the fishes)has over millions of years usually found the most energy efficiant way of moving around - and if you look at the acceleration ability of a Barracuda or a Marlin this idea of a swinging tail looks quite impressive. Does anyone have any experiences here ?? Or is this a forgotten good idea.
kjellhoegseth

The best execution of oscillating foils I have seen are the Hobie flappers. Google Hobie Mirage. These get a peak efficiency around 50%

I played with a large foil. Lots of acceleration because of the swept area and very efficient up to about 9kph. Beyond that the boat starts to bounce and the efficiency drops off. I have attached a video of one of my test boats and photo of the foil used. I later went to a foil that was 1.1m wide and 120mm long. This was the most efficient I tested.

Things in nature are highly developed but there is no living organism, as far as I know, that has a rotating shaft with unlimited angular range. It is very difficult to make a flapping foil as efficient as a rotating, twisted foil. If flapping foils were really efficient we would see them frequently used on aircraft.

Rick W.

[Rick Willoughby]

I have now installed the Wiggle Tail Drive in an R/C model boat. The horizontal mounting works very well. As soon as I have made the navigation tests, I will show you a video with the test results.
Kjell

Kjell
One of things I eventually learnt about foils (wings) is that the efficiency goes up as the aspect ratio goes up. If you look at fast fish like tuna they have a short wide tail. Same thing with dolphins. They have a knuckle at the end of the tail that is controlled by tendons to allow the tail to flex so the angle of attack is not very high. This gets complex to engineer. I did it with a parallelagram linkage and a torsion spring inside the foil. This gives nice smooth angular control of the foil relative to the velocity over it.

There are some good videas of dolphins and penguins swinmming on the net that shows how their tails operate. There are also mechanically swimmers. Swimming in nature is a a whole body function with the animals having ability to use more than just their tail.

You would find a short, wide foil at the end of a swing arm would be more efficient. You might find it better to locate the foil under the CoG to reduce pitching if it is an issue. If the boat is pitching then the drive loses efficiency.

Rick W.

[kjell]

Tail Propulsion.
When talking about tail propulsion it is important to understand the two different types of movement of the tail.
1. Slow moving wide foil shape.
2. Fast fanning flexible fin shape.
They are producing the thrust in different ways.
Fast swimming is produced with the number 2 movement.
Kjell

[kjell]

I have now tested the Wiggle Tail Drive in an R/C model boat. The horizontal mounting works very well.
http://video.google.es/videoplay?docid=-1510234176741290787

Kjell