Yet Another Silly Human Powered Propulsion Idea

In my never ending think of different ways to pedal a boat, I dreamt up what I'd call the Umbrella/Piston thingy idea. Thing is, would it work at all?

First of all, imagine that the boat has lever action, not circular pedalling motion. Now connect each via a system of cables and pulleys to a small umbrella like piston, contained in a submerged tube and to each other. As one lever moves forward the corresponding piston moves forward and the "umbrella" furls itself allowing water to pass and fill the tube. As it does so the other lever is moving back, and so the cables are pulling this "umbrella" down the tube. Of course it opens as it does so driving the water behind it along and out of the tube.

The question is, would it provide any workable thrust compared to a propeller? Would the tubes be better restricted so that the water was forced out of a small nozzle? And is it just a very stupid idea?

 

Not often particpating in these crazy pedaling threads, but--why do you need an umbrella piston , why not just a piston with an opening one way valve on it. Like big bicycle pump.
You would need very long strokes,-- I would have thought, that might be difficult to arrange into pedaling power.

I think I know why you moved out of Uk and went to france.

But then its a bit quiet and I have no one to talk to.

 

Well I only thought of something umbrella like as it would fold up thin, whereas a bike piston style has quite a large surface area even when it's letting air in. But yes, bike pump piston/umbrella/piston/valve/flap whatever.

 

I can imagine it working but I would think that 3 cylinders would keep the thrust equal and constant,--overlapping!! Perhaps you could alter the size of the orifices.---(jets), manualy whilst on the go.

 

Instead of an umbrella arrangement, what about a butterfly valve instead? Much less complex...