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Thread: Is my roost big enough?

  1. #1
    BarryMac
    Well what do ya think, is it big enough...
    gjb
    http://www.***boat.com/image_center/...28DSC01226.JPG

  2. #2
    Rampager
    Is it ever really big enough?
    Looks good to me, cheers

  3. #3
    Nubbs
    No, it needs to be bigger.

  4. #4
    Squirtin Thunder
    Now This Is How You Squirt Tail !!!!
    Jim

  5. #5
    FlatRat
    Do roosters make ya faster?

  6. #6
    cal***boat
    Originally posted by FlatRat
    Do roosters make ya faster?
    Maybe, Maybe not
    I'am confused. Do they make jet boats faster ??
    My 18Ft CP Comp Tunnel I had did'nt throw a rooster like that and it was pretty darn fast & quick, It only had a droop snoot and no diverter. The rooster tail was only about as high as the top of the engines air scoop but it sure did go back a long way.
    Thats what I get of being a v-drive guy, I'am Jet Stupid.

  7. #7
    LVjetboy
    "Thats what I get of being a v-drive guy, I'am Jet Stupid"
    That's for sure.
    jer

  8. #8
    cal***boat
    Originally posted by LVjetboy
    "Thats what I get of being a v-drive guy, I'am Jet Stupid"
    That's for sure.
    jer
    Geeze Jer at least I admited it.

  9. #9
    LVjetboy
    Ya but you already knew the answer and played dumb so I called your bluff. Besides that, you're a v-driver so I hassle you
    Why are high roosters bad? Place claims their diverter has 20 degrees up travel. Depending on your wedge (if you run one), and droop built-in angle (if you run one), and hull ride angle...all these add or subtract to your final thrust angle.
    Overall thrust and angle determine your axial and vertical components. Axial gives forward speed but vertical can either reduce or increase drag depending on hull characteristics like weight distribution, hull design and moment arm...lift. For a mild engine with (330 hp on the lake) axial thrust varies with angle like this...
    http://members.cox.net/lvjetboy/Axial.jpg
    Axial thrust is overall thrust times the cosine of the thrust angle. For a typical small jet, loss in speed from geometry alone is...
    http://members.cox.net/lvjetboy/Angle.jpg
    If you run less than 10 degrees, not much of a hit from geometry...maybe not even noticeable. But the loss accelerates with angle and a full 20 degrees up may affect speed from loss in axial thrust alone. Hull drag reduction from downforce moment offsets to a point. What is that point? Too many variables to know...just have to run and test.
    BTW, my server's down so those pics will show up a bit later.
    jer

  10. #10
    LVjetboy
    ...hull downforce, the other aspect of diverter geometry affect on performance varies as the sin of the thrust angle times overall thrust. For your typical mild jet this would look like...
    http://members.cox.net/lvjetboy/Vertical.jpg
    Somewhat more linear through 20 degrees. Also can be significant even at 10 degrees or less. Does this mean downforce is slowing you down? Not necessarily. That depends on the complex relationship between how a lifting moment reduces hull drag, how downforce alone can increase hull drag, and how speed affects those two. Hull design and speed are major players in that.
    jer

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