Building a "Aquascooter"

Discussion in 'Boat Design' started by logic88, Jul 24, 2013.

  1. logic88
    Joined: Jul 2013
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    Location: Germany

    logic88 New Member

    Hello friends of "boatdesign.net",

    i am from germany and i have a very exotic hobby.

    Three years ago, i bought me an "Aquascooter" (link: http://images02.olx.co.za/ui/18/42/63/1329055137_314593963_1-Pictures-of--Aquascooter.jpg).

    Its a machine where you can hold your hands on it and it will turn you through the water when you push the throttle (of the carburetor of the two stroke engine). It has a fuel tank (circa 1 litre) and a air tank, that it can swim on the water surface.
    A capped propeller is used to power the machine and the person.

    A long time later, i tinkered with the idea of doing a selfmade aquascooter with more power.
    I used a lawnmower engine with 6 hp and "developed" a own aqua jet with pvc tubes (escape pipes).
    A pump impeller should suck the water from the underground and push it out on the rear hole of the pump case.
    You can show a lot of pictures of the project in the following link:

    http://www.boote-forum.de/showthread.php?t=90512&page=6


    I used a bodyboard as "body" of the whole aquascooter and two stabilizer to compensate the high balance point of the lawnmower engine.

    After 4 month developing and handicraft work, i tested the scooter on a lake.
    And the result was: too less power :mad: :(

    The problem was the pump impeller i think...it didnt transport water with the required pressure.


    Now i am ready to build a new Aquascooter. The Aquascooter "version 2" with a (hopefully) better efficiency/power on water.


    So i really need your help....
    I thought about very different drives....a model aquajet is too small.
    A jetski jet is too big.
    A lower unit of a outboard engine is to difficult to mounting it (rough surface: rabbets...)
    A propeller shaft is too long and now i have a idea.

    I wanna use a propeller of an outboard engine (5 hp) and put it in a metal case (like the picture of the link: http://www.boatdesign.net/forums/at...ngine-conversion-outboard-rangajamman-009.jpg).

    this is (from my view) the best engine solution, if the shaft of the lawnmower engine goes vertical through the board.

    In the attached picture you will see a small sketch of my idea.
    The name of this kind of power unit is named "Veth-Jet".

    [​IMG]
    Now my question:
    What dou you think about my idea and what can you give me as "idea of improvement"?


    Thank you very much!

    Greets from Germany,
    Johannes
     
  2. portacruise
    Joined: Jun 2009
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    portacruise Senior Member

    Too much water friction everywhere is what I see, you may have reached the speed limit? Dragging a semi submerged human body through water has a lot of friction, so doubling power may only increase speed by 10%? Outboard motor props will be very inefficient (water turbulence within the cage) compared to the inside impeller of a jet drive in the drawing. Maybe try a design like that used by scuba divers in their electric scooters?

    Porta
     
  3. Petros
    Joined: Oct 2007
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    Petros Senior Member

    use the impeller off a large truck engine water pump, cheap and more efficient than a propeller for this application. a regular prop is actually more efficient, but in this application would be a very large hazard to the user and everyone around him.
     
  4. logic88
    Joined: Jul 2013
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    logic88 New Member

    Hello,

    The problem is to clogging up the electric engine (like a diving scooter).
    The other problem is, that i wanna drive how long i want.
    And charging batteries is very annoying... :(
    ..and of course, i love gas engines!


    Can you give me a example picture of the truck water pump impeller?
    I searched and it gives a lot of different designs of the impeller.

    The question is: What is the difference between my pump impeller in the link of my first aquascooter and a truck water pump impeller? :confused:

    Here is another link frommercury from a jet device on a outboard lower unit:
    http://www.mercurymarine.com/_media/images/engines/jetdrives/jet_drive_illustration.gif

    thanks
     
  5. capt vimes
    Joined: Apr 2009
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    capt vimes Senior Member

    others name these "Pump Jet"... ;)
    http://www.schottel.de/marine-propulsion/spj-pump-jet/
    has been done and is already there for years... look at the function principle and you get an idea of how the casing should look like...
    you need to press the water in and accelerate it via a sort of jet nozzle like thingy (for no better word)...

    edit:
    so petros suggestion to use a pump impeller is spot on because these apparatus are way closer to a pump than anything else...
    why not trying to find one fluid pump the right size and modifying it?
     
  6. portacruise
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    portacruise Senior Member

    Comments Below:

    Hope this helps.

    Porta

     
  7. CDK
    Joined: Aug 2007
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    CDK retired engineer

    There are plenty of pumps you can use for that particular purpose, but most are sold with a 5 hp (or more) engine attached to it. They are used to fill, clean and empty swimming pools, supply water to large gardens or fire fighting.

    Just an impeller , a well designed cover and a bottom plate. Attach a piece of pipe to the radial output port and you're in business.
    Such pumps you may find wherever they service small agricultural machines. Not in the shop but probably in the yard behind it, waiting for the "Sperrmüll" collector.
     
  8. Petros
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    Petros Senior Member

    here is a rebuild kit for a truck water pump. the impeller is on the left. You can find a junk one and use the parts, when the seal goes on the pump assembly they usually throw out the pump. As CDK notes, there are lots of pumps that use a similar impeller, I just thought a used water pump out of large truck engine would be cheap, about the right size, and easy to find almost anywhere there are trucks. it sucks in the center and the high pressure end is the perimeter of the vanes. a simple housing will work, or you can use the truck water pump housing. all you need is a coarse screen over the inlet to prevent fouling.

    [​IMG]
     
  9. tom kane
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    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Hamilton Water jet started out with the same idea and it did actually work well
    even though the pump was not designed for the purpose it was used for. For a more efficient propulsion effect it was found that the intake water needed to be discharged into the lower pressure of the atmosphere, similar to the effect of surface propulsion which a water jet is.
    The only requirement to push a boat forward is to move as much water rearward from the boat at the highest velocity possible.
     

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  10. bluesketcher
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    bluesketcher Junior Member

    Doesn't the intake direction contribute?
     
  11. yipster
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    yipster designer

    Exactly my idea too Tom Kane. Outlet water jet above the water line. Than again i learn a jet is a jet, in water, air or space action gives reaction. Thought it had to do with slamming what Hamilton jets found. Imagined pulse slamming but was told a jet is a jet, one of Newtons laws. do have to read up on that. Doenst seem to rhime:confused:
     

  12. tom kane
    Joined: Nov 2003
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    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Building an "Aquascooter"

    Everything you can do to improve the design to work better contributes.
    Such improvements as screens to keep out debris will lower efficiency and help block the intake flow and finally all flow. The speed of the boat moving forward defines where the water flow will come from but generally from all directions.
     
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