A progressive Archemedic screw is submerged horizontally in the water. Upon pedalling the gear assembly causes the screw to rotate, drawing in water at the fat end, compressing it, and releasing it at the thin end causing a jet to form and propulsion to ensue.

Hydrofoils could be fitted to the front of the pedalo in order for it to rise above the water of the leisure-lake and given enough speed, to skip along with reduced drag.
-- zen_tom, Mar 10 2010

Halfbakery: pump boat/pedal jet pump boat_2fpedal jet
Prior art - not sure if the Archimedic Screw pump method is sufficiently different for coexistence. [zen_tom, Mar 10 2010]

Screw Compressors http://en.wikipedia...ki/Screw_compressor
Prior Art [8th of 7, Mar 10 2010]

I like it - the jet pedalo. The hydrofoil pedalo is a good idea too, but I'm not sure you'd ever get enough speed to properly hydrofoil.
-- hippo, Mar 10 2010


The thing I'm wondering is - how compressible is water? Could a "progressive Archemedian screw" actually work? Or would the casing tend to break under the pressure?
-- zen_tom, Mar 10 2010


Water is almost completely incompressible.
-- hippo, Mar 10 2010


Hmm, that's what I was wondering - so, in a screw where one end has a wider mouth than the other, the water, refusing to be compressed, comes out the other side that much faster, right?
-- zen_tom, Mar 10 2010


If you have an infinite amount of force to push the water in, then yes.
-- hippo, Mar 10 2010


Your link is broken [zen tom].

If you've not seen them yet, search for Pumpabike to see just how easily hydrofoils will skim across the water.
-- 2 fries shy of a happy meal, Mar 10 2010


Thanks 2 fries - I think it was because the original idea has an "ambiguous" character in it - I've edited it a bit now, so it should work.

[hippo] I don't think it needs to be infinite, after all, when you turn on a tap, it's the water being "compressed" that pushes it out of the tap - it doesn't take up any less volume, but it is under pressure, and an enclosed screw should work just the same (nodding encouragingly) at least I'm hoping that's how it would work.
-- zen_tom, Mar 10 2010


//progressive Archemidic screw//
1 shot Ouzo
1/2 shot grapefruit juice
1/4 shot absinthe
-- FlyingToaster, Mar 10 2010


We'll drink to that.

How about a slug of Grenadine to lift it a bit ?

It doesn't need to be progressive. It can be linear, with a small nozzle on the end.

<link>

A "Roots blower" pump would probably be cheaper and simpler. Or a diaphragm pump.

Or a lot of squid ...

Would it be possible to tow such a vessel by means of trained cephalopods ? Like a sort of very damp dog sled ? Cephalopods are pretty bright ... and you wouldn't need harnesses, because they could grip on to the boat with their tentacles.
-- 8th of 7, Mar 10 2010


//you wouldn't need harnesses// A good thing, too. Have you ever tried to harness a squid?
-- mouseposture, Mar 11 2010


<frenzied vigilante mob>"Pedalos! Lock 'em up and throw away the key!!!"</fvm>
-- hippo, Mar 11 2010


// Have you ever tried to harness a squid? //

Not yet.
-- 8th of 7, Mar 11 2010



random, halfbakery