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Rudder Tuning

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jameski View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jameski Quote  Post ReplyReply Direct Link To This Post Topic: Rudder Tuning
    Posted: March-27-2007 at 10:13am
I have recently started using my new (to me) '94 Sport and I notice a huge difference in handling compared to my '78. Mainly, the pull to the left when underway and significant effort to steer right while underway. I've heard that the rudder can be tuned by grinding the trailing edge, but I don't know which edge to grind nor how much to grind. Can anyone advise? I've also heard a couple of other possibilities including shortening the shaft, and changing props.

BTW, it's a 351W with 1.23:1 PCM transmission (RH 14X16 Federal prop)
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94 Sport Nautique
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78 Martinique
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The Lake View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote The Lake Quote  Post ReplyReply Direct Link To This Post Posted: March-27-2007 at 9:12pm
Jameski,

I get a lot more pull to the left with the 540 prop that i put on last year. I asked this question then, and I got some good answers. Now, if I could only remember them.

I think if you file down the starboard trailing edge the rudder it will help, or is it the other way?

Some help I am,

Chuck
Walk on Water
www.coldwater.me


69 Ski Nautique
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David F View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote David F Quote  Post ReplyReply Direct Link To This Post Posted: March-28-2007 at 10:41am
Just throw the rudder in the can and go buy a tunable rudder from the dealer I did and it is the way to go. I can dial in neutral steering or a slight pull to either side.

I believe the cost was just south of $400. The rudder is made by Z-Marine, but good luck chasing down that rabbit.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote quinner Quote  Post ReplyReply Direct Link To This Post Posted: March-28-2007 at 11:36am
The tunables are really awesome, our 206 is set up pretty much neutral and it will run straight without touching the wheel, like the old days "look mom, no hands"!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 87BFN owner Quote  Post ReplyReply Direct Link To This Post Posted: March-28-2007 at 4:22pm
Had a tunable rudder on the 01 sport, never had to mess with it. Drove straight right from the factory.
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jameski View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jameski Quote  Post ReplyReply Direct Link To This Post Posted: March-31-2007 at 8:21am
Thanks for the help. It sounds like the consensus is that I CAN fix the problem by tuning the rudder. My existing rudder is in perfect condition, so I hate to trash it when I only need to tune it. Now, if I were only sure which side to grind. The Lake, are you sure I need to grind the starboard trailing edge?
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78 Martinique
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Post Options Post Options   Thanks (0) Thanks(0)   Quote The Lake Quote  Post ReplyReply Direct Link To This Post Posted: March-31-2007 at 8:36am
Jameski, here was my original post:

http://www.correctcraftfan.com/forum/forum_posts.asp?TID=2618&KW=rudder

Here is an article I found on the subject (http://www.waterskimag.com/article.jsp?ID=12220):

Rudder torque is a measure of the amount of directional steering system pressure generated by the rudder as it travels through the water. When operating a boat with significant rudder torque, the driver must apply greater steering pressure to counteract the directional "pull" of the steering system.
Generally, the amount of rudder torque varies among powerboats and can usually be adjusted to suit specific applications or driver preferences. While excessive rudder torque is unsafe and tiring to the driver, the positive pressure and "heavier" steering feel created from a "loaded" rudder are preferred in some skiing applications.
Tournament ski boats used for relatively short, straight runs through a slalom course generally benefit from more rudder torque. This pressure on the steering system provides the slalom driver with a frame of reference, helping him to lock into a straight course through the buoys and counteract the strong opposite lateral pull of the skier. This solid frame of reference becomes even more critical in world-class slalom skiing with shorter line lengths and tighter course tolerances.
For recreational skiing, boarding or cruising, though, this constant pressure on the steering wheel can become annoying and just plain tiring on the driver. In this case, a more neutral rudder, one that creates less torque and steering system pressure, tends to be more comfortable, more forgiving, and safer.
The hydrodynamic force of the water passing around the vertical hydrofoil that is the rudder creates torque. In most cases, rudder torque can be reduced or exaggerated by manipulating the surface and shape of the hydrofoil to change its hydrodynamics.
Flattening the right side of a rudder, for example, will increase a boat's tendency to pull to the right, while flattening the left side of the same rudder will reduce the right-hand pull.
In addition, all inboards have a natural tendency to pull left or right based on the direction of prop rotation. This is known as prop torque. Grinding a rudder to pull in the opposite direction of prop torque
is not recommended, as it generally has an adverse effect on both steering performance and wake characteristics.
Since rudder tuning is not an exact science, it should be performed by a trained professional and through a gradual process of trial and error. The rudder shape is carefully altered by grinding; then the steering is tested on-water to see if additional adjustment is needed.
"Most high-quality rudders are manufactured with a precise, symmetrical hydrofoil shape," says Charlie Pigeon, president of Tigi Boats. "But just like propellers, we lake-test every one to make sure, and sometimes we find one that needs some tuning." Because Tigi boats are designed for versatility, Pigeon says, they have relatively neutral steering. "A loaded rudder can create some tired arms at the end of a day on the lake, so we go with the two-finger steering approach."
Pigeon adds that customer preference, however, comes first, so if rudder torque is requested, Tigi will make the necessary modifications.
"It's really a matter of taste and how you use your boat. If you're in the slalom course all day pulling a serious skier competing at a world-class level, a boat with a heavier rudder is definitely beneficial. More neutral steering would be a handicap in this case. But if you're cruising, towing boarders or most skiers, you probably don't want to be fighting the steering wheel all day. The important thing is that rudder torque can be easily modified to fit your needs, but it should only be done by someone who knows what they are doing."
Walk on Water
www.coldwater.me


69 Ski Nautique
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jameski View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jameski Quote  Post ReplyReply Direct Link To This Post Posted: March-31-2007 at 7:37pm
Thanks Chuck. That's exactly the info I was looking for. Did you tune yours?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote The Lake Quote  Post ReplyReply Direct Link To This Post Posted: March-31-2007 at 8:21pm
No,

I'm a chicken. Although it pulls left, when we run the slalom course having that pull actually helps keep the boat from drifting. I guess I've kind of gotten used to it. Most of the time when we are out on the boat we're skiing or boarding. I suppose if we used it more for cruising I'd think about it more.

Now, if you get brave and try, let me know!

Chuck
Walk on Water
www.coldwater.me


69 Ski Nautique
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Carl View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Carl Quote  Post ReplyReply Direct Link To This Post Posted: April-03-2007 at 8:13am
Jameski,

I tuned the rudder on my 94 SNOB to add rudder torque. It was easy. I used a dremel tool to grind with. Ground a little off tried it out and then ground a little more.

It's perfect now. You really don't have to remove much material to feel an effect so don't worry about that.

Carl
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Darrel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Darrel Quote  Post ReplyReply Direct Link To This Post Posted: April-03-2007 at 12:19pm
I've started with a small Makita grinder then finished with hand file.
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jameski View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jameski Quote  Post ReplyReply Direct Link To This Post Posted: April-03-2007 at 1:44pm
I think I'll give it a try. I don't ski the course much, and my arms are gitting tired of fighting the torque. One thing I really loved about the '78 was the EASY steering at any speed.

I notice the recommendation is to only have it done by a professional. I don't know what it takes to become a professional rudder-grinder, but I think I might qualify. I'll let you know how it goes.
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94 Sport Nautique
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