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post #1 of 7 Old 11-13-2015 Thread Starter
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Skeg-hung Rudder Question

I have a full skeg-hung rudder and recently I noticed a problem that dates back to 1982 when the boat was built. I pulled the rudder in 2008 and completely rebuilt it when I noticed a bit of water had penetrated where the fiberglass attaches to the rudder stock. I did the removal and reinstall myself but this problem never showed itself.

It seems that the threads on the rudder stock for the two top retaining nuts and the threads on the nuts themselves are different threads. There are two nuts at the top that are tightened on each other and then a set screw goes through the top nut and wedges against the bottom nut to lock them in place. The static arrangement rides on delrin bearings atop a large bronze bearing/sleeve. Two feet below that is the stuffing box assembly, and then a large bronze gudgeon at the bottom of the skeg.

The problem came to light on my way from Cocos Keeling to Rodrigues when I heard a loud thud from the compartment where the nuts are exposed and you would install the emergency tiller. When I looked in, I noticed the nuts were loose. It was a bit alarming but I tightened them back down only to have the same problem a couple days later. When I arrived at Rodrigues, I pulled both nuts of and, just out of curiosity, got out my thread gauges. To my surprise, they are different threads than the male threads on the rudder stock! After 33 years, almost 100,000nm, and once dropping the rudder, this finally came to light. After a little tinkering, I found that if the threads are aligned just right, they will grab well and stay put. However, just a fraction of a turn in either direction causes them to jump up one thread. I must have set it just right on the reinstall in 2008. The thunk I heard was this jumping threads.

Now Iím in Madagascar but heading for South Africa where I will have the proper nuts machinedóitís 3.5Ē solid stainless stock so Iím guessing I will have to have some fabricated. My question is: just how much of the weight of the rudder should be resting on the gudgeon and how much taken by the nuts/top bearing? 100%, 90%, 75%Ö? Right now, it is secure and wonít fall out of the boat but most, if not all, the weight is on the gudgeon and Iím worrying about wearing the glass out down there as the rudder turns back and forth.

I have not had a very reliable internet connection, so have not been able to research this very thoroughly but I thought I would put it out here and see what advice or opinion is out there. Any input is much appreciated. Thanks.

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post #2 of 7 Old 11-15-2015
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Re: Skeg-hung Rudder Question

I would think that the nuts/top bearing would be there to keep the rudder from jumping up out of the bottom bearing. There would therefore be no "weight" on them whatsoever in normal usage. The fact that you had a "clunk" only after a substantial voyage lends credence to this idea. If they bore weight you'd have had issues like noises and binding earlier on. If the nuts are only there to keep the rudder from jumping out of the lower bearing, all of the rudder's weight would therefore bear on the lower bearing. How much does the rudder assembly weigh? Perhaps 75 kg or less for a boat your size? The bearing on the skeg should be able to handle that, and be inspected easily enough to see if there are any issues that need attention before they become problems.
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post #3 of 7 Old 11-15-2015
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Re: Skeg-hung Rudder Question

Many rudders float. The upper nut, or whatever retains it, is there only for the occasional airborne maneuver or haulout. In that case there is no weight, only an upward force on the shaft bearing, or whatever is there.

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post #4 of 7 Old 11-16-2015
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Re: Skeg-hung Rudder Question

I would PM Bob Perry. He's usually willing to help.

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post #5 of 7 Old 11-16-2015
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Re: Skeg-hung Rudder Question

If there's enough room between the stuffing gland and the what ever supports the end, Could you make a clamp out of two bits of channel iron. Blow semi circles to fit shaft and 4 bolts to clamp them tight on the shaft position.so it can't jump or fall. Ugly is OK . Richards bay is a long wys.

Last edited by Capt Len; 11-16-2015 at 05:48 PM.
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post #6 of 7 Old 11-16-2015
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Re: Skeg-hung Rudder Question

I'd be happy to help. I like to see the weight of the rudder supported at the top. I'd need to see a drawing of what is going on here. A collar above the upper bearing should do it. I like a "doughnut" bearing on the stock above the heel fitting.

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Last edited by bobperry; 11-16-2015 at 06:07 PM.
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post #7 of 7 Old 11-18-2015 Thread Starter
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Re: Skeg-hung Rudder Question

Thanks for the replies guys. I have gotten the nuts to stick well on the threads without jumping and decided to take the weight on that upper bearing because I don't like the idea of that fiberglass grinding so much on the bronze at the gudgeon. Will have some new nuts machined in SA. I will update with some pics when the job is done.

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