New Propulsion system?

Discussion in 'Props' started by Ike, Sep 11, 2012.

  1. Ike
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    Ike Senior Member

  2. RayThackeray
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    RayThackeray Senior Member

    The contrapel website is totally unreadable. Their text is wider than my screen!! If they can't do a simple thing like build a web page that billions of others have done, it doesn't bode well for their engineering skills.
     
  3. WestVanHan
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    WestVanHan Not a Senior Member

    Works for me Ray-change/update your browsers?

    A contra rotating low speed jet/surface drive wrapped up in a steerable cort?
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

  5. latestarter
    Joined: Jul 2010
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    latestarter Senior Member

    I had the same problem, you can fix it by holding down the Ctrl button and tap the minus button until it is all visible. Use Ctrl and plus button to get back to normal on the next site.
     
  6. SheetWise
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    SheetWise All Beach -- No Water.

    I agree. It's amazing how many people who design with HTML haven't got a clue what Markup Language means.
     
  7. Ike
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    Ike Senior Member

    Works in Google Chrome, Mozilla and IE9 for me.
     
  8. kroberts
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    kroberts Senior Member

    I can't vouch for the propeller tech, but the site works fine for me. I have my browser window set up as exactly half of my screen width and the site wraps nicely. As well, firebug shows no errors on the page.

    I can't say I really like the layout, but it doesn't seem to have anything technically wrong with it.

    I'm almost afraid to ask what your screen resolution is, and what operating system and browser you use?
     
  9. Red Dwarf
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    Red Dwarf Senior Member

    Wow 14 minutes of my life wasted on that idiotic video.:mad: What a joke.
     
  10. baeckmo
    Joined: Jun 2009
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    Location: Sweden

    baeckmo Hydrodynamics

    No news! Amazing how the wheel is invented over and over again. The patent litterature is full of counter-rotating water jets; ring-shaped nozzles have been around for looong time and the optimizing of the s.c. "reaction factor" (the relation between static pressure and dynamic pressure in the impeller outlet) has been a concern for pump designers for ages! That goes for the power split proportion between the two rotors as well.

    There is only one relevant part of the design that is in line with current developments, and that is the claims they make on using a constant-pressure impeller of low reaction. In an industrial pumping application, the normal transport velocity in the pressure piping is about 5 m/s (an optimation between investment costs and energy costs). Thus the "surplus" dynamic energy at impeller outlet has to be converted to static pressure, which creates additional losses.

    What we need in a wj application, however, is all of the added energy in dynamic form, contained in the jet, without the intermediate steps to static pressure and then back to dynamic. In this respect, the waterjet industry has been slow to understand the underlying principles; most jet pumps beeing copied from industrial units. One of the big Swedish supplyers actually started with a standard pump impeller from a big sewage pump.

    Reading through the various pages of the site, there is not one single number of data available for comparison or proof of the pudding, and the text writer has got it all wrong about the Archimede's screw; it is in fact a displacement pump, with no correlation to a rotodynamic machine whatsoever.

    For those who want a check on evaluation of "non-standard" wj variants, see

    "Band, Lavis et al:
    Comprehensive assessment of advanced high-speed waterjet propulsors - Final Report"

    Available at: "www.ccdott.org/transfer/projresults/2001/task2.17_finalreport.pdf"

    With a slight travesty of Fanie's motto, I'd say "numbers, gimme numbers..."
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    I didn't go right through it, the jargon got too much, but if there is no performance comparisons of identical boats with this system compared to existing alternatives, that is not encouraging. If the thing was getting better mpg, you'd be screaming it at every opportunity.
     
  12. kroberts
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    kroberts Senior Member

    @baeckmo,

    DISCLAIMER: Not even sort of an engineer!

    OK so is this at all similar to what would happen in a high velocity air system?

    It seems that for air jets people think in terms of a compressor tank and a nozzle, when in fact they should try to keep the velocity pressure the entire way through the system as much as possible. Which as I understand it means smooth walls, short direct paths and much attention to directing air properly in any deflections that must occur, as well as attention to the cross section of the path at any point.

    I'm pretty sure jet engines on aircraft are good examples, but I don't know if the compressibility of the fluid makes any difference here?
     
  13. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Their website sucks, their idea is old. But proof is in Pudding. Get five identical boats, put standard shaft drive in one, Levi drive in one, Jet drive in other, Contrapel in other, and finally large outboards in the other.

    Same hull, same horsepower. I think they are going to be very similar. The shaft drive would have advantage in rough seas, the Levi in shallow water.

    We may never know.
     

  14. Ike
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    Ike Senior Member

    My boss in the 80's Lysle Gray, used to say about things like this, give it a year and it will go away.
     
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