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Thread: hey POPS1 have you disappeared

  1. #1
    fullwood
    You still haven't explained why you said that 95% of forward motion is caused by the biting edge of the impellor drawing the boat forward.

  2. #2
    wsuwrhr
    The action of an impeller is the same as a propeller. The impeller is just enclosed in a housing.
    Both drive forward as a result of the design of the "paddle" of the blade.
    Not that I proclaim myself to be an expert by any means.
    Brian

  3. #3
    toad polumsky
    Hey wsuwrhr, what about the jet stream coming out of the nozzle? What does that do. If the impeller pulls the boat through the water then it seems you could waste the jet stream in any direction and go just as fast. As I see it a propeller just moves water from the front to the back, and an impeller makes pressure. The forward motion of the boat does load the pump but the forward motion is a result of the thrust of the jet stream and not the blades of impeller pulling through the water.

  4. #4
    Jungle Boy
    Here we go again. We need a scientist type guy to settle this once and for all. Anyone know one.

  5. #5
    Jet Hydro
    I wish someone would figure it out...lol...
    I too thought it was the stream that pushed the boat forward but I was told "NO"
    I said "pick up a fire hose and point it at a wall and see if it pushes you back". Then I was told to pick it up and point it at a wall not so close and see if it still pushed me back.
    Still cant figure it out...lol...
    If that was right then why do you slow down if you shoot your tail up?
    All I know is IF I smash the gas I go forward and some time`s real fast...lol... I leave that stuff up to my pump guy, I just make sure I`m on the rope come role call.

  6. #6
    fullwood
    i would like to hear the explaination from Dave himself, as he is the one that came up with this idea!!

  7. #7
    MikeF
    Take your garden hose and open the valve to the max.......not much movement out of the hose.
    Now put on a nozzle w/an outlet 1/8th the size of the hose i/d and open to the max again.....what happens.

  8. #8
    wsuwrhr
    I didn't say ALL of the forward motion comes from the impeller bite.
    How do you think the boat moves forward at a good clip with the diverter pointed skyhigh trying to spray water over a bridge?
    Brian

  9. #9
    MikeF
    So, If you have only the bowl expellng the water, you will be moving nearly as fast as a bowl w/ a nozzle on it?
    Que?!

  10. #10
    cruser
    So, how do you think the water in the bowl/nozzle decides to exit the nozzle? The impeller accelerates it into the bowl, creating pressure, causing thrust. It may help to think of it as the impeller pulling you along but, it is really the impeller supplying the eneragy to accelerate the water that makes you go.
    The pulling action of the impeller is localized to the area of the impeller. As the edge of the impeller blade slices off a chunk of water from the column of water presented to it, the backside of the blade creates a low pressure area. This can start the water moving into the gap between the blades, helping to set up the next bite of water for the next blade. I don't believe that this is where 90% of the forward motion of the boat comes from but I do think this has some impact on the performance of the impeller.
    If the impeller is spun up slowly, this sucking action can help load the next blade with water, keeping the impeller coupled to the water. If, however, the motor is powerfull enough, and the impeller spins up high enough, quickly enough, this low pressure can grow strong enough to cause the water to change state to a gas. (The temperature at which water boils relates directly to the atmospheric pressure around the water.) This is where the cavitation we see in high powered jets comes from. If the jet is in good repair, it can not "suck air" when launching.
    As the water in the intake starts moving toward the impeller, either becuase it must fill the void left by the water shot into the bowl or because boat has gained speed, more water is forced into the impeller. This starts to supply more water than the impeller can use and even though the low pressure zone still exists, more water is forced in between the blades than the low can suck, reducing or eliminating the chance of cavitation.
    This is enough for now. Gotta go to work in the morning.
    cruzer

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