Dufour Rudder Bearings

[Spirit of Glenans]

Recent posts have reminded me of a problem I need to sort out:
When I bought Spirit, a Dufour Classic 30, the surveyor had highlighted play in the lower rudder bearing. I ordered new upper and lower bearings and had them sent to be fitted by the boatyard where the boat was stored at the time. When I checked up on the rudder subsequently, there was similar play evident. I spoke to the yard manager who said that they had fitted the bearings as normal and gave me the old ones. He showed me similar play in another Dufour rudder and suggested that perhaps this was normal. On here I discovered that rudder bearings generally give the problem of seizing up due to swelling while immersed, rather than rattling about, so I decided to wait and see if it would take up after re-launch. Unfortunately, after a year there has been no change, it still annoyingly vibrates the tiller while sailing above 5kts, and always while motoring, and now the boat is many miles away from the yard where the work was done, so no come-back, really.
The (self-aligning) bearing in question resembles a ball with the top and bottom flattened, and a hole through the middle, and I understand it's fitted by pushing through a rectangular slot, then turning through 90 degrees
I would like to know if any forumites have experience or advice about dealing with this kind of problem.

 

[Mrnotming]

Recent posts have reminded me of a problem I need to sort out:
When I bought Spirit, a Dufour Classic 30, the surveyor had highlighted play in the lower rudder bearing. I ordered new upper and lower bearings and had them sent to be fitted by the boatyard where the boat was stored at the time. When I checked up on the rudder subsequently, there was similar play evident. I spoke to the yard manager who said that they had fitted the bearings as normal and gave me the old ones. He showed me similar play in another Dufour rudder and suggested that perhaps this was normal. On here I discovered that rudder bearings generally give the problem of seizing up due to swelling while immersed, rather than rattling about, so I decided to wait and see if it would take up after re-launch. Unfortunately, after a year there has been no change, it still annoyingly vibrates the tiller while sailing above 5kts, and always while motoring, and now the boat is many miles away from the yard where the work was done, so no come-back, really.
The (self-aligning) bearing in question resembles a ball with the top and bottom flattened, and a hole through the middle, and I understand it's fitted by pushing through a rectangular slot, then turning through 90 degrees
I would like to know if any forumites have experience or advice about dealing with this kind of problem.

A place to start:
http://www.jefa.com/products/general-info.htm

 

[dom]

First up - no it is not 'normal', not after a professional yard fix.

From your description I take it you have a set of self-aligning roller bearings (prob Jefa or JP3). You don't say if your rudder shaft is steel, carbon, or just possibly aluminium? I'm guessing steel. As a quick aside the delrin bearings won't absorb a significant amount of water.

As a matter of interest; when the rudder was dropped did the yard use an electronic calipers to check for shaft sphericality? This incidentally is standard practice. These bearing dimensions have to be machined to within +/- 1 or 2 hundredths of a millimeter to eliminate the backlash you describe and any lack of sphericality on your shaft and/or slight wear can lead to the symptoms you describe.

The fix is simple enough: an additional collar to be accurately machined and attached to the stock. This collar will then marry perfectly with and rotate smoothly within the bearings.

The solution here is basically to drop the rudder and check all of this before proceeding. The only real cost here is poss another crane lift, which the yard should hopefully do FoC as it is their work being checked here.

 

[Spirit of Glenans]

A place to start:
http://www.jefa.com/products/general-info.htm

Thanks, Mrnotming, an educational read. I know a bit more about rudder bearings now, and the purpose of self-aligning ones

 

[RichardS]

My problems with my delrin self-aligning bearings have been posted previously.

The bearings do not expand but what happens is the housing corrodes and squashes the bearing which then tightens. If the tightening is not sorted the bearing then wears excessively and, when the housing is cleaned up, the stock is too loose. Hopefully the bearing rather than the rudder stock will wear.

In this thread http://www.ybw.com/forums/showthrea...-for-a-nylon-bush-spacer-for-the-rudder-stock I gave the exact dimensions of the stock measured with a vernier to the chap who made the delrin spacers for me. If you can measure the stock and the other dimensions I'm sure he would turn you exactly the right size to take up any play and spin smoothly in the housing.

Ideally, you might be able to send him the old bearing with the revised dimensions.

Richard

 

[Spirit of Glenans]

First up - no it is not 'normal', not after a professional yard fix.

From your description I take it you have a set of self-aligning roller bearings (prob Jefa or JP3). You don't say if your rudder shaft is steel, carbon, or just possibly aluminium? I'm guessing steel. As a quick aside the delrin bearings won't absorb a significant amount of water.

As a matter of interest; when the rudder was dropped did the yard use an electronic calipers to check for shaft sphericality? This incidentally is standard practice. These bearing dimensions have to be machined to within +/- 1 or 2 hundredths of a millimeter to eliminate the backlash you describe and any lack of sphericality on your shaft and/or slight wear can lead to the symptoms you describe.

The fix is simple enough: an additional collar to be accurately machined and attached to the stock. This collar will then marry perfectly with and rotate smoothly within the bearings.

The solution here is basically to drop the rudder and check all of this before proceeding. The only real cost here is poss another crane lift, which the yard should hopefully do FoC as it is their work being checked here.

I must admit that I approached this problem with a certain level of naivete, in that the yard being 400km away from me, I was not present when the job was done. Having ordered a pair of bearings from the Dufour agents and having them shipped direct to the boatyard was , it now seems also ill-advised, in that it would have been better to have had them machined to custom dimensions, from the correct material, by the yard itself, or a local machine-shop. Anecdotal advise about water-absorption was a further ingredient in a bad recipe
The shaft is indeed steel, but the bearings are of the gliding type, the lower one as described above is like a ball with the top and bottom cut off, a plastic doughnut, if you like. My worry is that it is not the bearing itself that is the problem, but wear in the housing in which it sits.

 

[RichardS]

The shaft is indeed steel, but the bearings are of the gliding type, the lower one as described above is like a ball with the top and bottom cut off, a plastic doughnut, if you like. My worry is that it is not the bearing itself that is the problem, but wear in the housing in which it sits.

That's an interesting thought. When the yard did my seized port bearing in the slings (I was helping them) the doughtnut still fitted perfectly on the steel shaft once it was out as I caught the seizure as soon as it happened and sailed straight back to the marina. The problem was getting the doughnut out of its housing as the corrosion was jamming it in. When the yard guy eventually got it out with an lot of easing oil and an old rudder stock to use as a lever, he used a wire brush on the inside of the housing to remove the corrosion but didn't use anything too severe as he didn't want to enlarge it. The doughnut looked perfect and when the whole thing was slathered in waterproof grease and put back together it ran smoothly with no discernable play at all.

I did the starboard side myself in exactly the same way earlier this year. It had not seized but there were a couple of patches of corrosion on the inside of the housing so it was only a matter of time as any grease that was once there had virtually washed away.

If the housing has been cleaned up too vigorously, an oversize doughnut would be the simplest and cheapest solution.

Dropping the stock and re-greasing the doughnut is such a simple job that I will do it every couple of years or so from now on. The top doughnut is well above the water level and these were still both well greased from when the boat was built in 2008.

Richard

 

[dom]

Agree with what Richard says and it is indeed possible that a combination of pre-existing corrosion and over enthusiastic cleaning of the bearing-housing has created excess play in the system. The potential trouble here is that the housing may no longer be perfectly spherical if this is what happened. It is also possible that the bearing housing is itself moving inside the hull, which would need to be sorted.

I'd give the rudder a good wobble when the boat comes out of the water and you can see hopefully see what's what. The good news is since these are fairly basic glide bearings, as opposed to the much more complex roller ones - the costs should not get silly; which they seriously can with the fancier systems!!

 

[yotter]

I do not have a solution, but as a Dufour owner, I can recommend another couple of forums:

http://www.boefamily.dk/dufour/

http://www.dufour.org.uk/

These are both very useful recourses for Dufour owners.

Regards
Angus

 

[Spirit of Glenans]

Thanks to all. I will take the route suggested by Dom and RichardS, and arrange to have the boat held in the slings during the next lift-out, so that I can investigate further. I will actually have to drop the rudder to do this, as there is a spacer disc between the rudder and the hull which obscures direct sight of the bearing/housing.
For the moment I will be a hopeless optimist and assume that it can be solved by cleaning and greasing
Thanks also to yotter. I will be keeping an eye on the sites to which he has provided links.