Rudder shaft seized

eyehavit

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You do not state how old the assembly is nor if it is a dry, or water or grease lubricated system .
As it is not (yet) seized, try patiently working the rudder back and forth for about an hour.
 

Csail

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It has a nylon bush or similar at the foot (replaced recently and moves fine) then a grease lubricated through hull fitting then connected to hydraulic steering (ram is ok) but rudder still stiff. Must admit after a long passage it is slightly better but still hard work.
 

VicS

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[ QUOTE ]
It has a nylon bush or similar at the foot (replaced recently and moves fine

[/ QUOTE ] When you say moves fine do you mean it moved fine when replaced or still moves fine? If the former has it absorbed water (maybe the wrong grade of nylon) and swollen.
 

Robin

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Plastic bearings underwater will absorb moisture and will swell. Nylon is one of the worst materials to use for an underwater bearing, others like Delrin are better but in all cases plastic will swell, just by differing amounts for different plastics. It is possible to calculate the amount of predicted absorbtion and to take this into account when machining the bearing and allowing additional clearances. Much better is to use a more suitable plastic and then have it machined by someone who knows what is required. Bottom line is if you have recently replaced a bearing the probability is that this is the cause of your problem now it has been submerged.
 

VicS

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Fair enough its not that then. Obviously not the only one thinking along those lines!
 

rogerthebodger

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You say "Mild steel" rudder shaft.

Mild steel will rust in sea water and the steel expands by a factor of 11.

If you realy mean mild steel you have a big problem.

Most rudder shafts are stainless or aluminium.

Nylon should never be used below or near the water line if the bottom one is OK check the top one.

The only plastic bearing material to use fro rudder or prop shafts IMHO is vesconite.
 

Cliveshep

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The rudder shaft on my old Dutch Steel seized up, it was a 28mm stainless bar, bottom bearing in a keel bar, top seal in the tube was stuffing/grease, top bearing under the stern deck normal grease nipple type. The problem was in the tube, the grease had thickened up and the shaft just pretty much froze in the tube. I drilled/tapped an extra nipple into the tube but the grease just wouldn't go in,. In desperation I substituted diesel for grease, got a little in, worked it back and forward, still not free, finally applied massive amounts of heat to the tube to melt the old grease, added a little more diesel and then as it freed off was able to add loads of grease into the hot tube via the nipple. When it all cooled down the rudder stayed free so the mucky grease had clearly been melted/thinned by the diesel plus heat and displaced with the fresh grease. Thereafter I kept greasing it regularly (i.e. for about a day until I forgot) but it remained light to use over the following 2 years up 'till I sold the boat. A bit drastic but it did work and it was done boat afloat.
 

boatmike

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Mild steel is not a very good material to make a rudder stock from........ /forums/images/graemlins/confused.gif
 
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