Rudder Bearing - how snug?

[Tim Good]

Hi.

I dropped my rudder the other day, not because it needed it, but out of course since it hasn’t been done in the boats life and we’re circumnavigating this year.

Everything seems in good condition. However the main delrin or plastic bearing where the shaft enters the hull is something I’m unsure of.

I’ve spoken to various “experts” and many have different views. How snug should it be? To the shaft. It slides up and down easily at the moment without any signs of specific wear.

Also if it is in good condition after 27 years what material is it likely to be? Delrin in the mid 90s?

 

[vyv_cox]

Is there a shoe and another bearing at the foot of the skeg? My boat (Sadler34) is like this, three bearings, top, middle and foot of the rudder. I replaced the lower bearing with acetal (Delrin is the trade name of this plastic), which removed all the play. Full story here https://coxeng.co.uk/stern-gear/sadler-34-rudder-bearings/

Your bearing does not look excessively worn but it is difficult to be certain based on one photo. A common rule of thumb for clearance is 0.001" per inch of shaft diameter. For a slow moving shaft such as a rudder I am guessing that you could go up from this figure quite a lot.

 

[Tim Good]

Is there a shoe and another bearing at the foot of the skeg? My boat (Sadler34) is like this, three bearings, top, middle and foot of the rudder. I replaced the lower bearing with acetal (Delrin is the trade name of this plastic), which removed all the play. Full story here https://coxeng.co.uk/stern-gear/sadler-34-rudder-bearings/

Your bearing does not look excessively worn but it is difficult to be certain based on one photo. A common rule of thumb for clearance is 0.001" per inch of shaft diameter. For a slow moving shaft such as a rudder I am guessing that you could go up from this figure quite a lot.

Thanks. I’ve added you as a friend on Facebook so I can send you a video. I can’t attached videos on here.

But yes there is a shoe at the bottom which doesn’t look overly worn. Then right at the top is a roller bearing, again in good condition.

See pics.

 

[Tim Good]

Is there a shoe and another bearing at the foot of the skeg? My boat (Sadler34) is like this, three bearings, top, middle and foot of the rudder. I replaced the lower bearing with acetal (Delrin is the trade name of this plastic), which removed all the play. Full story here https://coxeng.co.uk/stern-gear/sadler-34-rudder-bearings/

Your bearing does not look excessively worn but it is difficult to be certain based on one photo. A common rule of thumb for clearance is 0.001" per inch of shaft diameter. For a slow moving shaft such as a rudder I am guessing that you could go up from this figure quite a lot.

The one thing I’m unsure about is the plate where the rudder comes into the boat. It’s like a large bronze plate and It has grooves in it where the shaft comes through. Perhaps it had some kind of fibre seal or o rings?

In one photo you can see the plate with just the end of shaft stick up (square end as it’s the top of the rudder shaft.

 

[DinghyMan]

Like you say the grooves are probably for O rings to act as seals to prevent water rising up the rudder shaft

The bearing / bush in the shoe looks to have some wear but the advantage of the shoe is that the rudder is better supported so bush wear is less

Best way to check for wear is to rock the bush side to side on the shaft, you should feel some movement but not much

 

[Tim Good]

Like you say the grooves are probably for O rings to act as seals to prevent water rising up the rudder shaft

The bearing / bush in the shoe looks to have some wear but the advantage of the shoe is that the rudder is better supported so bush wear is less

Best way to check for wear is to rock the bush side to side on the shaft, you should feel some movement but not much

Thanks. Before we dropped it there was no play at all.

 

[vyv_cox]

Your video does not show a great deal of wear. When I began to feel fluttering in my tiller when sailing the play in the bronze shoe was maybe 2 mm, mostly in one direction.

 

[Tim Good]

Your video does not show a great deal of wear. When I began to feel fluttering in my tiller when sailing the play in the bronze shoe was maybe 2 mm, mostly in one direction.

Thanks. Given then there isn’t much play could I assume they used the best possible material at the time. Delrin perhaps? Some have suggested Vesconite is superior to everything else?

If I had another made do you think a new one wants to have roughly the same amount of play? Just so it doesn’t swell and then bind?

 

[Tranona]

Delrin is very stable and does not swell which is why it is used in this application. With a well supported rudder like yours it should last "indefinitely". A new one will be machined with the appropriate clearance. Explanation here eagle-plastics.com/2023/05/achievable-tolerances-in-plastic-materials/