Rudder post slop & "thunking" - SailNet Community
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post #1 of 5 Old 06-27-2003 Thread Starter
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Rudder post slop & "thunking"

I sail an S2 7.3 which has an inboard spade rudder. I have some play (maybe ~1/4") in my rudder post; it wiggles a bit fore & aft, port & starboard. This causes a "thunking" noise coming from the hull when the rudder post moves around with the play. When I look over the transom, I can see the top, aft corner of the rudder pivot up and down a bit. At best, this thunking noise is annoying. But I''m concerned that the integrity of the rudder post tube (which spans/connects the horizontal cockpit coaming through the aft compartment to the hull) might be compromised over time. If the tube that houses the rudder post were to crack or break near the waterline, water would enter the aft compartment in a following sea.

Here''s my question, since I really have no idea how inbiard rudders are installed. Is there a "packing gland" of some sort where the rudder post exits the hull that can be tightened to reduce the slop? Or is this problem likely to be caused by something else? Got a fix for it? Thanks in advance!

--Dave S.
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post #2 of 5 Old 06-27-2003
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Rudder post slop & "thunking"

If you were to wiggle the rudders of the boats in your yard this fall, my guess is that 9 out of 10 are loose and have excess play. Some boat manufacturer had the foresight to incorporate a bushing system into their design to correct the situation you''ve described when the rudder tube assembly has too much play. In the fall at haul out inspect your boat to determine if such a bushing system was originally installed. I don''t know where you''ll get them as the sailboat portion of the S2s business is no longer in production although the company still makes stinkpots.

Finding bushings for your boat may be more difficult than finding Weapons of Mass Destruction in Iraq. That said, Harken does offer a limited number.

There is a stuffing box on some inboard rudder designs, not all. If one does exist on your boat, tightening it will not make much difference.

I doubt if enough force during normal sailing could be generated to crack the rudder tube, it''s probably more annoying than structurally dangerous.

I replaced both upper and lower bushings in my boat a few years ago; it is the 1 out of 10 that is nice and tight :-) I was able to get the bushings from the boat manufacturer.
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post #3 of 5 Old 06-27-2003
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Rudder post slop & "thunking"

You may still be able to get some factory help. Start with the info at the following website:
If your rudder bearing is like many it is just fiberglass built up inside the tube. I think the West Systems manuals have a section on repairing this. But I agree, I would wait until the end of the season.
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post #4 of 5 Old 07-26-2003
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Rudder post slop & "thunking"

I have a tiller steered ''78 Catalina 30 that developed the same symptoms. I contacted Catalina and they responded with a data sheet showing how to make a repair.

There are no bearings; just a fiberglass tube glassed to the hull into which the rudder stock fits. Since the rudder is buoyant, there is no vertical load. After a number of years, the lateral and vertical motion of the rudder caused wear on the inside of the fiberglass tube.

The recommended "fix" was to remove the rudder head fitting and drop the rudder (had to dig a shallow hole), clean the rudder stock and coat it well with "mold release" wax (available at West Marine), clean out the "tube" using acetone with the aid of rags and a broomstick, re-install the rudder in the tube and replace the rudder head fitting to hold the rudder in place, use modeling clay to seal the lower end of the rudder stock and tube, and pour resin (mixed with hardener) into the space around the top end to fill the gap.

Keep a watch on the leftover resin. As soon as it "sets", move the rudder back and forth to ensure that a hard and fast seal doesn''t develop. The wax should prevent that, but I think it''s best to play it safe.

Believe me, it took a while for me to get up the guts to do it but it worked out just fine and the rudder action is the best it has ever been.

Catalina also warns against using any kind of lubricant after the job is completed. They say that lubricants attract and hold foreign material and in general gum up the works.

That''s how it works on a Catalina 30. I''m not familiar with the S2.
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post #5 of 5 Old 03-15-2006
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Oceanis 413 carbon fiber rudder stock"clunk"..
I buyed my Oceanis 413 from the Moorings Charter Co. in Tortola, BVI. When the surveyor check the boat he recommend fixing the rudder stock bearings.. This particular model has the carbon fiber stock. Now, two years and several months latter I’m listening to some sound, particularly when we are with a following sea, similar to the one I felt when surveying the boat.
I took the cockpit floor panel to check the quadrant while sailing and noticed that the quadrant is connected to the stock with a throughout a bolt (about 3/8 of an inch) and at the same time the quadrant hole is square that fit into the square topside of the rudder stock. Anyway, that connection of the quadrant with the stock has a movement that correspond with the sound. Now, does anyone can tell me that if I change the quadrant to eliminate the"play” will be the culprit. or the movement is an indication of something worst in the bearing of the rudder stock? Please any comment or recommendation will be super appreciated.
Marco Gil
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