Fish-like propulsion

[Senyorita]

Guys, any ideas on alternative (say fish-like) propulsion for a small personal submarine?

[Fanie]

A fish has very strong muscles it uses to curve the body so that foreward propulsion takes place. This may not be so easy to duplicate to the level where it reaches similar efficiency. The other thing is the speed with which it takes place.

Maybe get the crew big flippers and they can hang in the water and just kick... or advertise...

Vacancy for four kickers, warm water environment, 50% kick duty cycle with TV to help pass the time. But that's not all, if you apply right now a comfy resting chair for in betweens a throwed in as a bonus.

[TeddyDiver]

Fins and scuba gear
JetFins for frog like propulsion, Split fins for sealy and regular for fishy

[Petros]

biological mechanisms are generally way too complex to make practical in a man made device. It can be done, it is just not easy to duplicate.

Also the wheel or axle is almost non-existent in nature, so you have no examples of naturally occurring propellers. But the so far the most efficient way to convert mechanical power in to fluid propulsion is the propeller, which turns on a shaft.

It was actually this realization, after many centuries of failed attempts, to build a practical man carrying aircraft. To separate thrust from lift, and then develpe differant way of providing them. To many centuries of trying imitate birds resulted in a lot of wasted effort.

It might be a fun experiment, and others have done this, but I am not sure it is practical.

[Fanie]

biological mechanisms are generally way too complex to make practical in a man made device. It can be done, it is just not easy to duplicate

I agree, seems the only thing we can get to duplicate is the amuba (that wich some of us think with), slurp spiders and polution. That should cover about everything

Amazingly man claims near life creation with his DNA replication (can we get a perfect woman here please ) but could not come up with a more efficient form of transportation than telling someone to go to hell

Sigh. It seems man has a bit of way to go yet.

If man was as clever as we think we are then -
why aren't we all rich
and why don't we develop all future technologies today

[robherc]

Originally Posted by Fanie

A fish has very strong muscles it uses to curve the body so that foreward propulsion takes place. This may not be so easy to duplicate to the level where it reaches similar efficiency. The other thing is the speed with which it takes place.

Hmmm, if a sub were moving itself into the positions a fish does, and at the same (or even similar) speeds, the contents of the sub would quickly turn from A. Human beings, to B. Red, bloody mush.


...just my $0.02

[Guest625101138]

Originally Posted by Senyorita

Guys, any ideas on alternative (say fish-like) propulsion for a small personal submarine?

A propeller wins out. If anything in the animal world could duplicate a shaft and bearing that animal would use a propeller and would be the fastest and best swimmer of them all.

The wheel and the technology that goes to make it work - the axle and bearing is not duplicated anywhere in nature (at least as far as I know). That is why it is such a significant invention. It is one of the rare instances where nature has not found a better solution.

Imagine if you held the perpetual intellectual property for the shaft and axle and its associated spin-offs such as the wheel.

Rick W

[ancient kayaker]

A fish's tail and a boat's propeller do exactly the same thing in exactly the same way, by producing a longitudinal force from a lateral motion, just like a screw thread. In fact ship's propellers are properly called screws. The prop uses a continuous rotary motion, the tail an oscillating one. Experience and theory have both established that continuous motion is more efficient that oscillation. Although a fish tail is remarkably efficient, it has taken millions of years to get that way. The propeller was optimized in far less time.

Having got that off my chest, maybe you're not so much concerned with efficiency as innovation, you asked for ideas after all! There's jet propulsion as used by squids, gas propulsion as used in toy pop-pop boats, flapping wings per the manta ray, and related to that perhaps flexing the sub's sides in a wave motion may generate some thrust.

[robherc]

Maybe some form of belt drive with semi-flexible "flippers" attached? You could run the belt down the side of the sub like a conveyor belt (one on each side...or better use 3-4 of them for 3 dimensional maneuvering) and have the belt enter a narrow slot that folds the "flippers against the belt for the forward-travel portion of its revolution.

[Fanie]

Hmmm, if a sub were moving itself into the positions a fish does, and at the same (or even similar) speeds, the contents of the sub would quickly turn from A. Human beings, to B. Red, bloody mush.

I wasn't suggesting !

A fish has the fastest pull away of all animals. It bends it's body and when it goes streight it is on speed. It would probably knock your eyes right to the back of your head Unless you are looking aft that is... then you would be looking for them

[Fanie]

See Petros's post. Copying animal propultions has never been done except running on land, but in the air we cannot flap wings and in the water we cannot swim with fins on our boats.

[robherc]

Actually, the hobie mirage drive is close to using fins...but it's more like a fish using its pectoral fins to move (they tend to do this when "bored" or "loafing" mainly), NOT like using the tail...but that's about the closest I know of for boat propulsion.

[alan white]

One fishtail design I tried (in model form) was a flexible (conveyor belting) rudder-like "flag" that was affixed vertically to the end of the boat.
What made it go was at it's aft end and not the leading end.
A rod bent to 90 degrees was affixed to the vertical aft edge of the tail as follows: The horizontal part of the same rod was above water and swung an arc from a pivot above the leading edge of the tail (corresponding with the customary pivot axis of a rudder). The rod ran horizontally back to the bend. Now vertical, it entered the water and the aft end of the tail attached to it.
Here's the trick: The horizontal length of the rod was less than the horizontal length of the tail. Therefore, there was always a sideways "sag" in the conveyor belt tail. This sag could be adjusted while underway as well, but there was always a sag.
The back and forth (like rudder pumping) application of power to the bent rod caused the tail to propel the boat forward, exactly like a fish tail.
This same action can be made to derive power from water or from wind (using sailcloth).

[ancient kayaker]

Originally Posted by Fanie

I wasn't suggesting !

A fish has the fastest pull away of all animals. It bends it's body and when it goes streight it is on speed. It would probably knock your eyes right to the back of your head Unless you are looking aft that is... then you would be looking for them

They're pretty quick it's true, but for sheer acceleration over a short distance the squid is tops. Hard to beat jet propulsion.

[sigurd]

Senyorita,

Do search for ornithopter, MAV (micro air vehicle), flapping wing propulsion.
I think one of the most efficient ways to do it in a sub would be to have two foils, configured like a biplane, flapping up and down, 180' out of phase. This way there is something similar happening as the surface effect - induced drag is reduced if I am not mistaken.
Triangular motion would be more efficient than sinusoidal, I think.
You could use simple NACA0012 foils and you should have an adjustable angle of attack, which reverses for each half stroke. Good luck.