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Old 18-06-2016, 21:53   #31
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Re: Lubricant for rudder bearings

warm to hot fresh water with a small squirt of dishwashing soap poured over the rudder hinges / bearings while moving the helm cleans out the gunk and dissolves crystals / not sure about soap on carbon fibre / soap is a good lubricant


out of interest our boat was built in 1893 / as far as we know has original top phosphor bronze rudder hinge and the bottom pin replaced after breaking the rudder at babel island in '03 / replaced with 316 stainless pin not as light as carbon fibre but then again we very seldom do 20kts
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Old 18-06-2016, 22:24   #32
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Re: Lubricant for rudder bearings

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Originally Posted by Schooner Chandlery View Post
Don't know anything about your boat but the reason I say 10K nm is sort of short is because you can't make it very far in 10K nm. I previously wouldn't have thought this but we just managed to rack up 4.5K nm in one fairly lazy summer of coastal cruising here on the US West coast.

The Jefa bearings are available online in a number of sizes and configurations and they do custom work. It seems a phone call between your boat designer/naval architect and you to get the drawings so you can send them over to Jefa will do it.

Is there a reason your designer is not already supporting you on this? Usually they're very helpful even if you're not the original purchaser of the vessel.

Best of luck.
Brenda, thanks.

The boat was not designed for us, and is well past any kind of warranty coverage. The designer does lend us some very friendly advice, but he is also the designer of the rudders and hydrofoils for the US America's cup catamarans, so his plate is really pretty full these days. I try not to ask for too much of his time-I don't want to wear out my welcome!

I have the good fortune to have a couple of sets of bearings, so I can simply send one to Jefa and have them make me one to the same dimensions, but with rollers, rather than the current setup.

My point about the 10k offshore miles we've sailed the boat, plus her numerous ocean crossings prior to my ownership (with the same setup) was simply to make the point that there isn't some major defect here. I don't think that I would call 10,000 miles 'nothing', however, when it comes to getting to know a boat's systems. That sum of miles would get you from the E. coast USA to Australia, after all. It's enough distance to know the boat and the issue intimately.

Thanks to the forum for the tips. We'll probably do a mclube/marelube cocktail, and hopefully it'll make things a bit slicker down there. No big deal if it doesn't work.

TJ
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Old 20-06-2016, 05:56   #33
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Re: Lubricant for rudder bearings

I'd try synthetic grease thinned with whatever you can ( Try alcohol if worried about petroleum based thinner ). Have found Mobil synthetic grease to last ages on outboard clamp screws but cant remember the exact type & I've run out. Or any salt water grease. Just thin it to consistenscy required to get it in. Some should sit in there after solvent boils off
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Old 20-06-2016, 07:37   #34
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Re: Lubricant for rudder bearings

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Originally Posted by TJ D View Post
Hello, nobody knows who made the bearing.

I'd like to state again, I'm 100% sure that there is no deflection, and even if there was, the way the bearing is constructed, some misalignment or deflection will not have any impact on the operation of the bearing. I would say that the rudder shaft could bend up to 10 degrees of arc before bearing performance was compromised.

Carbon fiber does not bend like that. It would fail long before it reached anywhere near the deflection needed to compromise bearing function.

I wish I had a picture, then we wouldn't have to keep having the 'deflection/misalignment' conversation. The rudders are massively overbuilt carbon structures, designed to survive a heavy impact due to their location on the boat. These things simply are not down there flexing. The bearings are fairly new in their installations, as well. Wear is not a factor.

Also, note that 1/2 of this equation is stainless steel. The other half is carbon fiber. Does that make it a non-metallic bearing? I don't know.

I'm really, really, absolutely, positively sure that this is simply an issue of the stainless inner race pressing hard enough on the carbon outer race that it is creating friction during the heaviest part of the load cycle in a very limited set of sailing conditions. Hence the plan to replace these with roller bearings at the next haul. In the meantime, I wish to lubricate them with something to help out with this small issue.

So, I guess that my question is, considering the materials involved, am I actually going to destroy carbon fiber with any type of lubricant?

Thanks, I don't mean to be snippy, but this same thing keeps coming up, and it's just not happening that way.

Insight into lubricants destroying carbon would be appreciated, however.

TJ
Carbon fibre bends like any other material. It aint magic. It just has high specific stiffness and fails catastrophically at low strain rates compared to other boat building materials.

Bending stiffness is a function of area moment of inertia and distance of the outermost particles from the x section centroid. Material properties are a second order effect.

If you feel the rudder getting stiff under load compared to no load then you have deflection in the region of the bearings.

Sliding or slipper type bearings are very sensitive to clearance. (Very few thousands of an inch or less) The slightest deflection leading to an out of round condition will cause binding. The deflection could be local to the bearing. Very hard to measure in situ. Possibly visible as wear marks, high spots, etc when dissassembled.

Lubricants for composite or plastic bearings. Simple. None with the exception of water for cooling.

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Old 21-06-2016, 07:26   #35
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Re: Lubricant for rudder bearings

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Originally Posted by leftbrainstuff View Post

If you feel the rudder getting stiff under load compared to no load then you have deflection in the region of the bearings.

Sliding or slipper type bearings are very sensitive to clearance. (Very few thousands of an inch or less) The slightest deflection leading to an out of round condition will cause binding. The deflection could be local to the bearing. Very hard to measure in situ. Possibly visible as wear marks, high spots, etc when dissassembled.

Yep. This deflection is the reason the OP needs to work with the designer or another NA or engineer to make sure the NEW bearing is designed for the expected loads and weaknesses of the entire rudder system.


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Old 15-04-2017, 18:19   #36
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Re: Lubricant for rudder bearings

Try ship 2 Shore industrial, here is a customer that replaced the failing bearing grease in her Lewmar winches.
https://youtu.be/himeS3oL9uI
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Old 15-04-2017, 20:44   #37
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Re: Lubricant for rudder bearings

Just going through this on another boat. We decided to use tefgel. I thought it was a little viscous for the application, but the pro's swear by it. and it simply doesn't break down in salt water.
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