Rudder = Speed Loss? Is it worth removing?
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Rudder = Speed Loss? Is it worth removing?

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    Senior Member PonyFiveO's Avatar
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    Default Rudder = Speed Loss? Is it worth removing?

    Howdy,

    Has it been officially documented anywhere, or have been scientifically tested, or non scientifically tested with a GPS, or even seat of the pants tested whether a factory or small Place Diverter rudder creates such a substantial drag in the water that it will cause a loss of speed? And IF there is, is the trade off of removing it worth losing low speed maneuverability?

    IF it does create a substantial amount of drag, would grinding the cutting edge of the rudder to a knife edge and grinding in steps on the sides for aeration make a difference?

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    Senior Member Delemorte's Avatar
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    I cant answer the question but i will say that having it on my boat does not seem to help much.. If i am not putting RPMs to the jet i can turn the wheel all day and it wont turn for shit...


    saying that, i have left mine on and dont plan to remove it on the off chance i am massivly mistaken.

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    you will get all kinds of opinions here is mine. could never accurately tell a difference with a stalker radar gun , very little if any. personally would not trade off the low speed handeling for the difference. have seen more broke off on the driveways than anything else. i use one on my blown boat .

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    I don't feel tardy Hallett Dave's Avatar
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    Quote Originally Posted by PonyFiveO View Post
    Howdy,

    Has it been officially documented anywhere, or have been scientifically tested, or non scientifically tested with a GPS, or even seat of the pants tested whether a factory or small Place Diverter rudder creates such a substantial drag in the water that it will cause a loss of speed? And IF there is, is the trade off of removing it worth losing low speed maneuverability?

    IF it does create a substantial amount of drag, would grinding the cutting edge of the rudder to a knife edge and grinding in steps on the sides for aeration make a difference?
    I took mine off a few years ago because it was bent and caused the boat to steer hard to the left.
    I never noticed an increase in speed.
    I could not tell a difference in low speed manuevering.
    I still run the boat minus a steering rudder.
    I would not waste my time sharpening the leading edge nor would I try to modify it in any way. $.02
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    Senior Member bp298's Avatar
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    Quote Originally Posted by PonyFiveO View Post
    Has it been officially documented anywhere, or have been scientifically tested, or non scientifically tested with a GPS, or even seat of the pants tested whether a factory or small Place Diverter rudder creates such a substantial drag in the water that it will cause a loss of speed? And IF there is, is the trade off of removing it worth losing low speed maneuverability? IF it does create a substantial amount of drag, would grinding the cutting edge of the rudder to a knife edge and grinding in steps on the sides for aeration make a difference?
    don't know what you would define as scientifically tested. i haven't done anything with a gps or radar gun, all of my testing has been done on a track with a timing system. i cannot tell you how many times i have increased or decreased depth of something that drags in the water stream, from one pass to the next with no other changes, to know the difference - well over 100 passes. and i'm not talking about things even remotely close to the depth/width of a rudder. with respect to what i do or have done, i'm not going to be any more specific than that on a forum.

    what i will say is that yes, anything below the boat that is dragging in the water stream will slow the boat to some extent. sharpening the edge isn't going to make much of a difference, because the drag associated with it is based on the total area presented to the water stream (total depth and total width in the stream, like how wide is it at it's widest point?). i have had (significant to me) reductions in et and speed with much less total area than the rudder presents, and when making a large change (maybe 1/2 in2), yes i could feel it.

    but really, how you use your boat and how i use mine are most likely very different. you have to decide whether or not if you're after every last 0.10, or 1-2 mph you can get out of it, or if you feel the rudder provides you better controlability regardless of performance.

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    Senior Member 2savage4you's Avatar
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    They are too small for the boat to begin with and not deep enough to get a bite.

    Use it or lose it, your boat won't know the difference..

    Yes, i did stay at a Holiday in last night

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    Senior Member Fonz69's Avatar
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    Not sure on the speed thing but I have helped fix some jet boats in my area after they hit somthing in the water with that fin From the damage I have seen I would take that thing off asap. From busted nozzles to even the bowl getting damaged to the point they needed a new one

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    Senior Member Fonz69's Avatar
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    Quote Originally Posted by Delemorte View Post
    I cant answer the question but i will say that having it on my boat does not seem to help much.. If i am not putting RPMs to the jet i can turn the wheel all day and it wont turn for shit...


    saying that, i have left mine on and dont plan to remove it on the off chance i am massivly mistaken.


    Did you do some cutting on your bowl?

  11. #9
    Resident Ford Nut Sleeper CP's Avatar
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    Quote Originally Posted by PonyFiveO View Post

    IF it does create a substantial amount of drag, would grinding the cutting edge of the rudder to a knife edge and grinding in steps on the sides for aeration make a difference?[/FONT][/COLOR]
    I don't recall reading what type of boat and at what speeds?

    Is this an 80 mph boat,a 55 mph boat or a 100 mph boat? Depending on the boat and hull type a long with speed it could or might not make a difference.
    The boat could run-up against other limitations before the drag of the fin would make any noticeable difference.

    I'm guessing this is a 50-60 mph boat ?

    G-Code

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    Senior Member PonyFiveO's Avatar
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    Quote Originally Posted by Sleeper CP View Post
    I don't recall reading what type of boat and at what speeds?

    Is this an 80 mph boat,a 55 mph boat or a 100 mph boat? Depending on the boat and hull type a long with speed it could or might not make a difference.
    The boat could run-up against other limitations before the drag of the fin would make any noticeable difference.

    I'm guessing this is a 50-60 mph boat ?

    G-Code
    Thank you all for the insight sofar. My example would be an Eliminator Bubble style hull, in fact out of Eliminator's actual mold as I understand from Greg, and would run approximately 70.

    Thanks!

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    Senior Member jetboatperformance's Avatar
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    Agreeably the ruddders have little to no effect on our boats after "plane" speed and they create some "drag" and resulting small loss of speed , they do provide some measure of steering control at low speeds as well as in a "lost power/thrust" situation , as Jet boats require thrust to both move and turn and in a "engine off" situation they tend to go where they were last "pointed" Tom

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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by jetboatperformance View Post
    Agreeably the ruddders have little to no effect on our boats after "plane" speed and they create some "drag" and resulting small loss of speed , they do provide some measure of steering control at low speeds as well as in a "lost power/thrust" situation , as Jet boats require thrust to both move and turn and in a "engine off" situation they tend to go where they were last "pointed" Tom
    X2 Tom....

    Having personally done some 80MPH shore inspections do to a non running river boat, I believe the rudder has some limited values...

    Adversly, the rudder can also cause some interferance in shallow situations, which in turn could break a tiller arm, causing the same thing as no engine no steering ...

    As far as affecting top speed, maybe in the 100MPH area you could tell, but the everyday boat with a calibrated Ass-O_Nometer, no difference...

    Talk about a catch 22

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    Red Blooded American The Doctor's Avatar
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    Do you like to have steering at high speeds when the engine fails? I would, despite the tiny loss of performance.
    The best things in life aren't things!

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    Quote Originally Posted by 2savage4you View Post
    They are too small for the boat to begin with and not deep enough to get a bite.

    Use it or lose it, your boat won't know the difference..

    Yes, i did stay at a Holiday in last night
    I think they do help somewhat with "wander" tracking straight at on-plane speeds, but, other than 30 years of driving my boat with one (and the new place diverter does not, but has not been driven yet), I cannot prove anything.

    Differences in tracking could wel be more related to my speed and hull attitude than the rudder, running a Berk "F" pump with factory diverter.
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