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post #11 of 22 Old 03-20-2019
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Re: How much wiggle is OK in a rudder

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Originally Posted by davidpm View Post
I'm not too concerned about slop in the system as cables can be tightened or replaced.

As hellosailor mentioned an internal failure of the rudder webbing is a big deal but that is not what I saw.

I saw what I assume is wear in the bearing. I don't know how big a job replacing the bearings are and how much wear is allowed and if the surveyor will make a fuss about it.
The primary cause of rudder bearing wear is failure to lock the helm when not in use. Every time the boat rocks in the slip there is force against the rudder. It is wise to check rudder bearing play annually. One may have up to +/- 1 mm play for ever and its not a problem. But if it jumped from +/- 1 mm to +/-1.5 mm in just one year, that's an issue.

RE&RE a rudder bearing is a job. There are all kinds of designs. The steering mechanism has to be removed. It may be equipped with a stuffing box arrangement that has to be released. There has to be some support mechanism to keep the rudder from falling out of the boat. Then there is digging the hole to allow clearance of the rudder stock out the bottom of the boat. Finally the bearing removal can be a trick.

To hire it out can easily be a $2K job.
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post #12 of 22 Old 03-20-2019
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Re: How much wiggle is OK in a rudder

Is the working of the rubber when not underway more wear than use of it for steering? For sure it wears from moving. More it moves the more it wears. Moving in a slip or anchor is usually quite a but less than driving the boat. However it should be noted that large turns (tacks and gybes) are not a large part of the movement time... it's mostly slight steering corrections.

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post #13 of 22 Old 03-20-2019
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Re: How much wiggle is OK in a rudder

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Originally Posted by davidpm View Post
It is definitely rudder bearing. My question is how much if any is normal or acceptable.
Depending on the depth of the rudder and the design and type of bearing system, 1/8" lateral movement measured on the bottom is not a problem. In your case, 3/8" may or may not be an issue, but sounds like a lot to me. Would be nice to see what a sister ship has.

The degree of work in fixing this completely depends on how it is implemented, as well as access to the steering gear and bearing area. Is there a rudder tube or just stuffing box? You will need to have the boat lifted temporarily to drop the rudder (few yards allow one to dig holes in them), but reinstallation can wait until the boat is ready to go back in the water.

Just for an example, if the quadrant separates easily, and there is a rudder tube with top and bottom HDPE bushings, then replacement is easy - remove the quadrant, drop the rudder, pull out the bushings and install new, and put back together. I've done this type of system several times, and it doesn't take long at all.

However, there are much worse combinations that could have you working on it a week - particularly if the quadrant is seized on, and you don't have much room.

FWIW, loose bearings are rarely a dangerous thing - just something that needs to be addressed at some point.

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Re: How much wiggle is OK in a rudder

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Originally Posted by boatsurgeon View Post
The primary cause of rudder bearing wear is failure to lock the helm when not in use. Every time the boat rocks in the slip there is force against the rudder.
I don't understand this reasoning. When the boat is rocking, there is the same amount of lateral force on the rudder of a locked helm as there is on an unlocked helm. Rotational force shouldn't be a significant component of bearing wear, which is all a locked helm can prevent.

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post #15 of 22 Old 03-20-2019
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Re: How much wiggle is OK in a rudder

I've never contemplated rudder bearing wear at anchor before. I've always locked the rudder, but more in an effort to align the ship and not see massive swings that could push the helm from stop to stop, which is intuitively bad.

I'm imagining, at anchor, a rudder could receive more side load, as the boat swings in the current or wind, with a locked rudder. It almost seems counter-intuitive that a locked rudder would take less force that one which was trying to turn into the slip stream. Interesting.


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post #16 of 22 Old 03-20-2019
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Re: How much wiggle is OK in a rudder

A rudder is designed to take the side force, no? Typically, though, it would be a consistent or relatively smooth controlled motion. Left to freewheel in an anchorage or dock where there could be wakes, chop etc the motion would be jerky and possibly swing it rapidly from stop to stop, then as a wake subsides in increasingly shorter abrupt movements, until the next wake comes along. That can't be good for the bearings, or the steering mechanisms like quadrants, cables, chains etc.
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Re: How much wiggle is OK in a rudder

Makes more intuitive sense to me that the linkage would take excess stress, from an unlocked helm.


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post #18 of 22 Old 03-20-2019
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The greatest loads ive felt on my rudder are aft quartering seas.
They can take 20 degrees off my course....and im careful about getting it back. Yes you can anticipate but conditions change. I dont fight it.

I dont see an advantage gained in locking my rudder at anchor. Ill snug the brake to lessen noise from steering but if a current wants to take it...i say fine...
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post #19 of 22 Old 03-20-2019
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Re: How much wiggle is OK in a rudder

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Originally Posted by Minnewaska View Post
Makes more intuitive sense to me that the linkage would take excess stress, from an unlocked helm.
Well, here are my thoughts on this, and it's just my opinion, based on inspecting / repairing a fair number of rudders over the years.

The steering linkage will absorb some energy either way, but bearings tend to wear due to movement (which increases with load and torque), rather than deformation due to stress.

The rudder will rotate, even with the wheel locked, but only to the extent of the steering mechanism backlash.

If the wheel never moves when unlocked, it will be the same difference with it locked.

However, some move rather violently when the boat is rocked by waves or wake.

It is more pronounced in lighter boats, however, these are likely lighter built as well, than their passage-making counterparts that tend to be much more stiff.

Also, it depends on how well the rudder is balanced hydrodynamically and the inherent resistance in the steering.

Remember that most vessels are not underway 95-99% of their lives, and even then, sailed quite conservatively.

Because rudder bearings on these infrequently and lightly used vessels do wear out, I conclude it is not due only to underway movement, as if that were the case, a sistership would wear out the rudder bearing in just one ocean crossing, and they generally don't.
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post #20 of 22 Old 03-20-2019 Thread Starter
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Re: How much wiggle is OK in a rudder

As a point of reference, the lowest end of the rudder on the last C&C 34/36+ had no lateral movement at all.

It was also rebuilt in the last few years.

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