Design aluminium shallow water

Discussion in 'Jet Drives' started by Gian Milan, Jun 20, 2011.

  1. Gian Milan

    Gian Milan Previous Member

    Hi hoytedow,
    Our boats are identical.
    Mine, in meters, measuring 5.5 x 1.7 x 0.8.
    In High speed, the boat should slide out of the water.
    In low speed:
    - I needed to give shallow draft surface.
    - I needed to navigate the current of a long and narrow boat.
    Choice of a catamaran was required!
    You built that boat? How it was?
     
  2. Gian Milan

    Gian Milan Previous Member

    Hi thudpucker!

    The boat is 0.8 meters high and will navigate rivers absolutely without waves.
    Must navigate in extremely shallow water with a gravel surface.
    If my English was incomprehensible, please tell me the sentences incomprehensible. Thanks to all of Milan Gian
     
  3. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    There is a similar design I have seen in america ...BUT the guy has the ability to raise the outboard vertically ..so at low speed in shallow water the prop is in the tunnel and on the plane he drops it " to reach the water " BUT this is a jet boat so the design should incorperate a ride plate area like a jetski...Tunnels and jets dont seem to go together unless you have one for each pontoon. ? Has the poster considered the **** the jet will pull in in shallow water ? They recomend 600mm ??
     
  4. Gian Milan

    Gian Milan Previous Member

    Hi mohawk!
    I've seen your boat on you tube: BRAVO!
    But At low speed, a keel flat fish much less than a V-keel. In your opinion this is true or the difference between the V shaped keel and the flat is irrelevant for shallow water at low speed?

    Thanks for the valuable help! If I had to abandon the catamaran, can I have your keel plans?

    TU from Italy!
    Gian Milan
     
  5. Gian Milan

    Gian Milan Previous Member

    Hi Pistnbroke.
    What kind of propeller mounted outboard? The tunnel was filled with water even at low speeds?
    TU for your answer
     
  6. Gian Milan

    Gian Milan Previous Member

  7. mohawk
    Joined: Jun 2011
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    Location: New Zealand

    mohawk Junior Member

    Best I can advise is to
    Forget the tunnel , Go for a deadrise of 8-12 degrease to keep the unit in the water and reduce slideing.
    Defenately use a jetdrive
    Fit a strip of UHMWPE 600mm wide too the keel , it makes pushing easy if you get stuck.
    And look for an engine with abit more power and less weight
    Then look for rivers like this :D http://www.youtube.com/watch?v=5IqW6U0Nc7U&feature=mfu_in_order&list=UL
     
  8. hoytedow
    Joined: Sep 2009
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    Location: The Land of Lost Content

    hoytedow Fly on the Wall - Miss ddt yet?

    Prego. Ritorna presto. :)
     
  9. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Gian,
    I have to say I'm with Mohawk here. I don't understand why did you choose to go the catamaran/tunnel way. The way you have designed it, in particular, goes against the premises upon which this project was supposed to develop: shallow draft, low weight, maneuverability (as the possibilty of use by a governmental agency was mentioned) and optimized for a water-jet. Plus (since you were talking about a high-speed boat too), the plumb sidewalls you have there will introduce a dangerous possibility of fliping over during high speed turns.
    I believe it would have been much better if we had met in order to establish a correct SOR for this boat (as it was agreed during our phone talk). The way you're doing it now, wandering from one forum to another and learning along the way, you will end up with 20 different and conflicting opinions and advices for each problem you'll ask about. Good luck with your project, keep us informed about its progress.
    Slavi
     
  10. Gian Milan

    Gian Milan Previous Member

    Dear Slavi, I want to make that boat for fun.

    If it will be very well, it will be develop for market.
    Until then, it must be a game and I cannot engage a professional like you in a matter of no-profit.
    Also the time you have available is not sufficient for my goals.

    The choice of the catamaran ?I have no other options available.

    But on Sunday, catamaran or another, I will go in the damned Ticino river with my boat.

    Three of my workers are ready to start work Wednesday morning.
    To everyone a moment of madness has to be guaranteed: this is my moment!

    Because the boat must have a double bottom, we should apply a different keel.

    I'll let you know.

    Gian
     
  11. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    A monohull? Just to name one... ;)
    And if you really want a tunnel hull, at least make sure it is designed properly before spilling your money on the shop floor...

    No, Gian! First make sure you have a valid set of plans, or even hand-sketched drawings, with AT LEAST the hydrostatics calculated properly!
    There are some really low-cost stock plans out there which, though might not be perfectly corresponding to your (erratic - allow me to say ;) ) wishlist, can be used as a base for eventual modifications.

    Just few examples I came across in few minutes ofinternet search (mainly monos, but some tunnels too):
    http://www.metalboatkits.com/16_foot_skiff/16footskiff.htm
    http://www.bateau.com/proddetail.php?prod=XF20
    http://www.bateau.com/proddetail.php?prod=OB19
    http://glen-l.com/designs/hankinson/jetsetter.html
    http://www.boatdesigns.com/20-Jet-Setter---whitewater-sled/products/834/
    https://www.boatdesigns.com/20-Snake-Shooter-v-bottom-whitewater-sled/products/878/
    http://www.boatdesigns.com/Scrambler/products/759/

    Cheers
     
  12. hoytedow
    Joined: Sep 2009
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    Location: The Land of Lost Content

    hoytedow Fly on the Wall - Miss ddt yet?

    I once built a small catamaran with 2 boxy hulls that were each 2 feet wide and separated by a 2 foot gap which I ran with a 5 hp motor. It was only 8 feet long. It worked well for my purposes, just as this one will when I finally get it built. I will not start it until next year. Overall length is to be only 10 feet(about 3.05 meters). Bow of boat will face front of teardrop trailer box while in truck, with a few cm clearance at all times on road. The overhanging(cantilevered) catwalk deck will help with keeping water out and adds buoyancy.
     
  13. Gian Milan

    Gian Milan Previous Member

    tunnel is full or empty at low speed?
     
  14. hoytedow
    Joined: Sep 2009
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    Location: The Land of Lost Content

    hoytedow Fly on the Wall - Miss ddt yet?

    The tunnel would only be full if the boat were heavily loaded. The less the weight, the higher the freeboard. Do some displacement calculations. Back then with the little catamaran I only weighed 142(65kg) lbs. Now I weigh 245(111kg) lbs. The boat would definitely sit lower in the water.

    It only had 5 horsepower so it never went more than 10 miles per hour.
     

  15. Gian Milan

    Gian Milan Previous Member

    Look at this:
    http://www.flatscat.com/performance1.htm
    I am perplexed too in believe this demo, but:
    - water is sure forced in entering tunnel
    - youtube pictures of those boats can not lie.
    What about?
     
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