Squid

The Hobie Mirage flappers are oscillating foils. Their twist, to set the angle of attack, is load dependent because they flex. They are conformable foils very similar to the flippers on penguin or wings on birds.

Rick W

 

none...

there is only one reason, why nature utilizes flapping und human technique is utilizing props:

human build engines/motors are transforming energy into rotary motion -> prop
nature muscles transform energy only into contract-expand motion and via a skeleton it could effectively only be transfomed into flapping (either up/down or side/side) -> flapping propulsion

nature knows no rotary motion - in fact that we are able to twist our lower arms/legs to a certain extent is fascinating in itself and requires a complicated design plan with several muscles involved and very a sophisticated joints/bones configuration... not to mention the exact points of attack for all the muscels involved.
on the other hand, if we try to put rotary motion from our engines into an heave/flapping motion.... a lot of additional techniques and structures/drives/levers are needed - hence reducing effectiveness.

mankind does not have any motor which might do the trick of a muscle - energy -> longitudinal (contracting) motion

 

this kind of drive is very complex and inefficient, nature only uses it on low speed fish and only for maneuvering, not generally because it is optimum. Nature has other environmental constraints, and as noted above, there are no large scale biological structures in nature that rotate on an axis.

The only reason to build one is to study the motion for its own sake, or just for the novelty of it.

The best way to make a maneuverable floating maintenance platform in my professional opinion would be to use several slow rotating electric props on a pivoting assemblies on each end of the platform. This way you can rotate the thrust around at any angle at each end of the platform allowing you full trust control is all directions. And you can buy such assemblies relatively cheap.

If I was going to build a novelty sightseeing submarine I would build it to look like a giant sting ray with large flapping wings and a plexiglass "belly". It would not be as efficient as a regular prop, but it would sure look cool and "high tech".

Good luck

 

Premairly Squid design

Dear All,

Find attached Premairly Squid design for ur comments

 

I didn't read the entire thread as this seems like the OP sounds like a Kid but here goes my 2 cents.

There was (maybe still is?) an unsinkable kayak with a foot pedal powered propultion system in it. It was not very efficient, more of a gimmick really. All I know about it is that it had 2 "fins" stuck on the bottom of the boat that would "flap" back an forth but opposite of each other. Power for this was a foot pedal.
Might the OP be thinking of some thing kind of like this? As for the water bag they blow out there little tubes (the so called "water jet") those are called jet skis or wave runners in polite talk. those of us who drive big boats have other names but they can not be said on a family friendly site. Mostly these come from the tendancy of "wave runner" drivers to get really close to bigger ships and run off there wake. they make hi speed, seemingly kamakazi runs, on us and are one of the most hated of boats.

 

on the "nature knows no rotary motion" part you are incorrect sir. there are Microscopic bacteria who's scillia can spin an spin an spin. upon closer examination researchers found the base to have no linkage to it at all. it truly can spin for eternity. it even has some structures which act like ball bearings in it.
Creationist like to point it out as evidence of a "Intelligent Designer" in there ID debates. That is where I first heard of it.

 

Here's how I would (try to ) do it:



A motor drives an eccentric (crankshaft) attached to a connecting link, the other end of which is attached to a flexible diaphragm which is spanning an opening in the side of the tube. When the motor spins, it flexes the diaphragm in and out, causing a change in the tube's volume as pulses of negative and positive pressure within the volume trapped between the one-way valves. The one-way valves respond to the pulses by opening the intake valve when the pressure pulse is negative (volume increasing) and opening the discharge valve when the pressure pulse is positive (volume decreasing) resulting in a net flow of fluid under pressure from one side of the tube to the other side.

Jimbo