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Re: [PSUBS-MAILIST] Fishtail propulsion

Good idea.  I might put someone up front with a tiller which will look a little strange.  I wouldn't have a good method of steering from the rear.
-Jim
 
In a message dated 12/2/2010 10:11:06 P.M. Central Standard Time, alanjames@xtra.co.nz writes:
I guess you'd need a large keel or rudder at the front of the canoe to stop the aforementioned
side to side movement, wich would be more pronounced being on top of  the water.
Alan
 
----- Original Message -----
Sent: Friday, December 03, 2010 4:47 PM
Subject: Re: [PSUBS-MAILIST] Fishtail propulsion

Very true, Alan. 
 
It gets more complicated as you scale it up.  As you wag the tail faster, the forces on the mechanism and structure get pretty big.
 
In addition to the propulsion from the sculling action, a significant portion of a fish's propulsion results from the vortices generated from the tail motion which is why they can accelerate so rapidly.  It's similar to a whiplash action.
 
I may or may not be able to get the canoe to move more easily or conveniently than with a paddle.  Or I might just make the yuloh master laugh.
 
Jim
 
In a message dated 12/2/2010 9:17:26 P.M. Central Standard Time, alanjames@xtra.co.nz writes:
They're pretty good Jim,
I saw some others when I followed the link. One was hard to tell from the real thing.
Looking at their side to side head movement convinces me that it would be a bad
form of propulsion for a sub as you'd get sick quickly.
Alan
----- Original Message -----
Sent: Friday, December 03, 2010 3:41 PM
Subject: [PSUBS-MAILIST] Fishtail propulsion

Frank,
 
Here are a few videos I found of mechanical fish such as we were discussing.
 
 
 
 
At some point just for fun, I might build a rig to try out on my canoe or a Jon boat.  From a top view:
B= body of the canoe
P= the powered section moved left and right
F= fin
x= hinges
 
BBBBBBBBBBBBBBBBBBBBBBxPPPPPPxFFFFFFFF
 
When power is applied to P to swing it left and right, F will swing in the opposite direction (by the force of the water) to provide propulsion from the sculling motion.  P will move through fewer degrees of arc than F.  The range of motion for P is determined by the configuration of the push/pull rods which power it.  The range of motion for F is determined by stops on the hinges.
 
I have several other projects with higher priority, but maybe one of these days...
 
Jim