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Thread: Rudders

  1. #1
    Snowboat
    Can anyone tell me a little bit about rudders. Are there only two styles, wedge and trailing? Are the only sizes available, the ones Rex has in his catalog? Wedge for runners and trailing for flats? Can they be UT'd without pulling it from the boat? And lastly, where do they break the most frequently? Nearly ready to start the braided lines after finishing the engine upgrade and neglected to spend much time down under.

  2. #2
    Lookin for Liquid
    Snow....We sell a 100% Chromemoly Rudder designed for the Flatbottom that we have been putting under our boats for quite some time. It is a smaller version of the wedge rudder and we have put them under River Boats up to 170mph Top Alcohol Flats. If you need any more info please E Mail and I will help you as best I can. Maybe some of the people on the boards that have purchased this rudder can tell you what they think.
    Thanks Dan
    Canyon Marine

  3. #3
    Fiat48
    I do know you don't want what is called a tapered trailing edge rudder. Lot of guys tried them and there may have been a slight speed increase, but the boat felt very wierd over 100 mph. These may not be made anymore as most guys took them off in the 80's and went back to a standard rudder as mentioned by Canyon Marine.

  4. #4
    Senior Member
    Join Date
    Jun 2009
    Posts
    10,871
    There are many shapes of rudder blades out there. The two in our catalog are the most common for most applications. Stick with the wedge style on most flats and runner bottoms. The trailing "generally" work better on the 21 footers and larger. (Nothing is written in stone in rudder design). Many guys run a shorter version on the wedge also on drag boats (don't need to turn much hopefully). Those are "general" guidelines. I'm sure many of the racers here have more precise specs they prefer for particular hulls and setups.
    As far as where they break, I've seen quite a few. Generally it is very close to where the shaft meets the blade, sometime up inside the stuffing box just a hair (normally it's the shaft that actually breaks). Over time from vibration the material fatigues. In ski racing, annual mag inspection is required. I'm sure other forms of racing have requirements in this regard as well. Actually I think x-ray tells you a little better story. There was a thread on this very subject not too long ago if you do a search in this forum you'll likely find it.
    If it's a fast boat that see's alot of hard running I'd inspect the rudder (and the prop) often. The results of broken propellers or rudders can be somewhat radical with overturned boats, ripped out struts and pretzeled shafts being a few of the possible outcomes.
    Safety first when going fast.

  5. #5
    Lookin for Liquid
    As far as rudder design goes the bigger the boat and the bottom design will generally dictate the shape and length of the rudder. V Bottom boats require more lateral push to make them turn so usually as a general rule they would require a longer or wider blade. Flat Bottom boats can get away with a blade lenght of approx 11 inches and turn sufficiently without overloading the shaft. Mike is 100% correct as far as where they usually tend to show fatigue first, the leading edge of the shaft right above the blade, due to the fact that this is the shear point of the rudder shaft that will see the most load from forward movement and harmonic vibration. The extremely unfortunate thing is that the potential crack is hidden in the stuffing box that should be inspected frequently. The tapered trailing edge design not only creates harmonics cutting the water in a forward motion but also adds to the problem letting the water push against the rear taper of the blade returning the water to the center point adding more harmonics.
    I hope that this has sparked some people to get their rudders magnafluxed for the summer.
    Dan
    Canyon Marine

  6. #6
    Dragboat Dad
    We had our rudder X-rayed because it is chrome plated. This is 1 of 4 shots, they have indicated very small imperfections. [img]http://www.***boat.com/image_center/data/500/110Rudder-0.jpg[/img]

  7. #7
    Snowboat
    With that information, I'd be stupid not to check my rudder for cracks. What kind of rudder do Biesemeyers, Revenges and Daytonas have. Anyone got any measurements? Thanks.

  8. #8
    CircleJerk
    Snow, I was hoping to see you at Banks this year. We require certification on rudders, props, and shafts once every two years and 10 percent of racers have found cracked rudders. The trailing edge style are seen often on circle boats since the design is supposed to keep the bow lower in the corners. However, the wedge type are most common and work quite well at our speeds! Some hulls like our Lavey turn better with the drag race wedge. I guess it all depends on the bottom design and set up. Dont forget to check that cable quadrant that clamps to the top of it. I found hairline cracks there last year under the chrome! JeRk smile_sp

  9. #9
    GofastRacer
    Snowboat:
    With that information, I'd be stupid not to check my rudder for cracks. What kind of rudder do Biesemeyers, Revenges and Daytonas have. Anyone got any measurements? Thanks. Hey Ken, don't you have one like this?..
    [img]http://www.***boat.com/image_center/data/500/12Rudder-med.jpg[/img]

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