Rudder stock maintenance

[Anonymous]

My 321 has a skeg hung rudder as I think 331s do.

Just before launching for the season I found some small movement in the rudder stock.

The rudder stock passes through a tube glassed into the hull. The top of the tube inside
the boat is threaded on the outside and there is a large bronze nut that is screwed onto it.
It has a locking ring/nut as well. It is virtually the same as I have on the propshaft stern gland. 
Also on the tube is a grease nipple which I annually grease up.



My query is should I be looking to adjust the big nut because it is intended to take up any wear
 or movement in the rudder stock. If that is the case it is extremely difficult to do because of 
the very limited space available to get to what looks like a 50mm nut.

The owners manual gives no guidance.



Steve McCarthy

N321/119

[Anonymous]

Steve, you are right that the top of the rudder post has the same type of fitting that the prop shaft has, its doing the same job, ie keeping water out while letting the shaft move. The adjustment is to achieve the correct pressure on the packing to maintain a water seal while not restricting movement. The lower bearing, in the water I believe to be platic, not sure what the top bearing is made of, but tightening the gland will not have effect on the bearings. What amount movement have you? I can speak to Nauticat to find the normal tolerance if you like. Alan Warrell, Technical Secretary

[Anonymous]

Alan, thanks for the response.

The movement is pretty minimal and difficult to quantify, but I assumed largely lateral. I had not noticed anything previously. If you can get a response from Nauticat that would be good

Do we assume there is some packing material in the ‘gland’ that can wear?

Interestingly I renewed the stern gland packing this year. It was the first time it had been done since new, after 1050 engine hours. Over the years I had tightened up the big nut a few times when the water drip seemed to be excessive and I thought the packing must need replacing.
What surprised me was that there seemed to be virtually no wear on the packing. When undone the packing stuck out and when I tried to screw it back up without doing anything else it was quite difficult. I then extracted the first ring of packing which was basically all intact with a bit of wear on the front surface. I estimated there could only be one other ring of packing inside the nut and I decided not the disturb that. I then put in one new packing ring and re-assembled it all.
I was quite surprised about all this because I had researched extensively about doing the job and had expected to find minimal packing left and that the nut should have about 3 rings of packing.

Any comments gratefully received

[Anonymous]

Steve,

Not sure on the manufacturer of the Nauticat stuffing box, but on my NA35 1995, I had similiar experience, in that trying to get two rings in was hard, let alone the three which you would expect to do. I will talk to Nauticat about the tolerance on the rudder shaft and also ask about the prop stuffing box.

I have never had a look but I assume the rudder gland is a similiar arrangement as the prop.

Alan

[Anonymous]

Steve,

I followed up the rudder stock tolerance question  with
Nauticat and have the following information.

 

The normal amount of play is 0.5mm at build
time.

The bottom bearing is adjustable, as it comes in two
halves (not obvious at first sight as its gel coated over) and can be sanded to
achieve a good fit, the top bearing does not have any adjustments, other than
the packing in the top of the rudder stock.

 

Hope this helps

 

Alan

[Anonymous]

Alan

Many thanks.

They seem to have confirmed that the top bearing has packing as per the
prop shaft and I suppose gets very little wear in comparison. Presumably it
could be tightened up a bit, but only if it was possible in my case to get big
enough spanners in such a confined space.

I have never thought much about the bottom bearing, but I guess it is
obvious that it has to be in two halves because otherwise the rudder could not
be installed up into the hull.

I will have a look again next time the boat is lifted out.

Best regards

Steve

[Author]

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