New 6M HT boat porpoising

Discussion in 'Powerboats' started by Atomix 600HT, Feb 28, 2016.

  1. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    I have fitted wedges to boats with some success, but they are not as effective as tabs. I look at your pics and notice the substantial flat along the centreline, which I assume develops and widens from the forefoot back, like a long triangle. I wonder whether that is contributing to the issues.
     
  2. Atomix 600HT
    Joined: Feb 2016
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    Location: New Zealand

    Atomix 600HT Junior Member

    You are absolutely correct.... That is exactly how the bottom is.
     
  3. kfly
    Joined: Jul 2009
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    kfly Junior Member

    Maybe next time don't buy a Chinese boat. Especially considering you live in a country full of great boat builders. I think you would find a NZ brand far more willing to stand behind their product.
     
  4. Atomix 600HT
    Joined: Feb 2016
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    Location: New Zealand

    Atomix 600HT Junior Member

    Okay.... After trying a few props I used an american brand "Rupture" with good size rake and cup and improved dramatically but got even better once I installing her with bennett trim tabs. Finaly she is going great. No thanks to Atomix NZ. I ended up taking the advice of a prop designer/manufacturer and it paid off thank goodness.
    Thank you all for your help
     
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  5. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    I wonder if the the trims rabs helped, or the props. I had a problem like that before and the trim tabs fixed my problem.
     
  6. Atomix 600HT
    Joined: Feb 2016
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    Location: New Zealand

    Atomix 600HT Junior Member

    Would you believe The prop did make a huge difference ... Incredible, I would have never thought that a prop plays such a big part. What I believe my final prop did was, it gave my boat a a good grip on the rear with abit of transom lift. I tried approx 8 different props 3 blades and 4 blades....before I got the performance. What I also learnt was that your prop might be running within the recommended rev range (wot) but doest mean will give good performance. Pitch....Cup and Rake makes all the difference.
     
  7. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    HOw did the new best prop effect speed and rpms?
     
  8. Atomix 600HT
    Joined: Feb 2016
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    Location: New Zealand

    Atomix 600HT Junior Member

    Revs were well within the range and speed wasn't bad ...... But trim tabs made the speed even better..... by approx 6klms.
     
  9. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    Sounds like there was a design flaw in boat hull/engine placement. I had a very fast boat, 70+knots. Past 60 it would porposie, not a fun thing. Tabs and wings on the drives fixed it. One thing I didnt figure at the time was the life being generated by the motors. It ran faster becuase the engines stayed in the water.
    Here in Florida the really fast boats are using K-planes now to put some leverage on the downforce.
     

  10. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Choice bro. :D
     
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