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  1. #1

    hum...............Think I found it......

    Think I found out how to stop the bucking.............

    Your ski might go little slower, but you woun't buck. Go with extended trim tabs

  2. #2

    Join Date
    Jan 2006
    Texas City, Texas
    I've been talking to a guy overseas about the "buck". He describes it as "choked flow", a condition where you can no longer process the amount of water the intake is bringing in, because you can no longer increase the outlet pressure. Remember, a fixed amount of water must be accellerated to get the boat to run faster. What if you can no longer increase the water accelleration, yet the intake literally brings in more water than your pump can accellerate? This excess water is entering your intake tunnel at speeds in excess of 70mph.

    As I am sure you are aware, at high speed water is driven into the intake rather than sucked in like at low speed. If the angle of the hull (angle of attack) changes as it moves through the water there is a potential for the pump intake angle to change as well, and with that change more water can be brought into the intake. If the boat porpoises or even bounces just a bit you may bring in more water than the pump system can pressure and accellerate out the back.

    It is possible that the extended trim tabs help to maintain a "set" hull angle of attack by keeping that bow planted, not allowing the intake to "change size" and bring in more water than it can process. It sure sounds like a good safety measure, and it certainly treats the symptom.

    Yeah, I believe that the "buck" is a symptom.

    The real PROBLEM is bringing in to much water into the intake. With fixed parts like the ones we have in the intake that allow X amount of water to flow at X speed, how do we vary the flow? I think that the answer is simple. The faster you go, the more the intake grate itself diverts a certain amount of water away from the intake tunnel rather than directs it into the intake tunnel.

    Easier said than designed......

  3. #3
    GoFastGuru's Avatar
    Join Date
    Jul 2010
    guntersville Ala
    every body remember franks not dealing with the hull we are accustom to well explained salty

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