Rudder bushing material? Delrin, PTFE, UHWM, VHF, CIA.. - SailNet Community
 
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Rudder bushing material? Delrin, PTFE, UHWM, VHF, CIA..

I recently pulled down my rudder and noticed the bushing (not the regular rudder bearings) that sits between the top of the rudder and the bottom of the hull has been worn down to just about nothing.

I plan on buying some bushing material and cutting it myself with an adjustable hole saw (prices seem reasonable, less than $20 for a 1/8" sheet 1 foot by 1 foot online) but I don't know what material is best - there are so many to choose from: Delrin, PTFE, UHWM are what

Does anyone have any experience or advice? TIA!

Photos below:




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post #2 of 7 Old 12-26-2013
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Re: Rudder bushing material? Delrin, PTFE, UHWM, VHF, CIA..

I'd call that a washer rather than a bushing.. and it's kind of unusual to see one there in our experience. Probably doesn't matter what you use, though I do know some nylons expand when immersed in water - used it for a bottom bushing once, had to ream it out because it became a tiller lock in a month or so!! But that was a real bushing/bearing, not just a washer like what I see in the picture.

Ron

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".. there is much you could do at sea with common sense.. and very little you could do without it.."
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post #3 of 7 Old 12-26-2013
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Re: Rudder bushing material? Delrin, PTFE, UHWM, VHF, CIA..

What youre probably referring to is a thrust washer and its probably delrin which was commonly used for such marine bearing and thrust washer applications.

Delrin, alone, is relatively poor choice for such applications as its wear (abrasion) characteristics are dependent on the smoothness/roughness of the surfaces that it interfaces with. Delrin applied against macroscopically 'rough' surfaces will quickly abrade away by 'transferring' itself to the roughened surface. Delrin in such 'plain bearing service' usually must 'ride' on mirror polished surfaces - similar visually to the 'bright' surface of your exposed rudder shaft.
UHMWPE or 'teflonic' degradation via abrasion will be similar to delrin.
The answer here is to provide a smooth mirror polished surface, etc. for whatever the polymer bearing material you choose to 'ride' on.

Usually this type configuration was found on boats with tillers and usually there was such a thrust washer under the tiller head - directly connected to the rudder shaft. The thrust bearing was to alleviate friction between the tiller head and the FRG tube which contained/constrained the rudder shaft ... and the delrin thrust bearing usually only lasted a season or two, then 'fell out' due to extreme abrasion wear. Some bearing designs for this configuration had the thrust bearing portion as a part of the rudder bearing .... the bearing looked like a hollow 'top hat'.

You might find other solutions to this situation by doing an intensive internet search for "Pearson + 26 + rudder bearings" as this delrin problem with boats and rudder bearings has been quite constant over the years. The Pearson 26 owners group had published several successful 'work arounds' over the years --- but I dont know if this info is still available on the net.

:-)

Last edited by RichH; 12-26-2013 at 07:29 PM.
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Re: Rudder bushing material? Delrin, PTFE, UHWM, VHF, CIA..

Very helpful, I will look into the Pearson 26 issue. I certainly don't intend to change this every year! Right now, the rudder top is wearing away (as is the bottom of the hull) from rudder movement.
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post #5 of 7 Old 12-27-2013
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Re: Rudder bushing material? Delrin, PTFE, UHWM, VHF, CIA..

Here's a iisting and solutions offered by the P26 folks as regards this common (delrin) rudder bushing issue, etc. Such may be helpful to you on your non-Pearson 26/30 boat that has this rudder bushing configuration.

Rudder Bushing Repair Details - Pearson 26
Rudder Bushing Consderations - Pearson 26
Rudder Bushing Repair Alternative - Pearson 26

take note in the Rudder Repair Alternative posting the usage of DIY made bushings using filled epoxy + carbon powder ... I can attest that such a choice of materials will outlast most 'store bought' materials in such applications, especially if you add very finely chopped up Gore-Tex fibers to the 'mix' - I preferred GoreTex dental floss as the top layer of my 'epoxy filler'. Again, the secret here is a smooth and polished surface to 'run' against.

Last edited by RichH; 12-27-2013 at 11:40 AM.
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Re: Rudder bushing material? Delrin, PTFE, UHWM, VHF, CIA..

Those were very interesting - in the end it seems most folks are using the delrin - either the stock ones from D&R marine or fabricating their own.

I liked the third link alot, it explains a good way to fill the tube with epoxy and graphite to from a long continuous rudder bearing. That's on my list of things to do this spring..

I have a sort of whacky idea for my thrust washer, thoughts would be appreciated:

On the top rudder post mating surface (underside of hull at shaft opening): I will rebuild the rough surface with an epoxy & graphite mix. This way the upper surface will be smooth and fairly low friction thanks to the graphite.

Now for the lower surface (top of rudder where the shaft exits the rudder): I could have a shop make a stainless steel washer (316 stainless), but it would have a slightly enlarged inner diameter, say 1/4" too wide. I would then epoxy that washer in place centered on top of the rudder. This way the washer would not corrode or cause corrosion with the shaft (since I don't know what grade steel it is) because it would be offset from the shaft by a 1/8" gap filled with epoxy.

In my mind, this seems like a great solution - the compression washer won't scrape away in a year or two and no shaft corrosion. So I'm sure I'm missing something - what is it?

Do the plastic (delrin) washers act like shock absorbers - meaning the steel would just be too hard to use in this situation?

As always, anyone's thoughts, insights, or experience would be greatly appreciated!
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post #7 of 7 Old 12-27-2013
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Re: Rudder bushing material? Delrin, PTFE, UHWM, VHF, CIA..

I agree with your recent thoughts ... except that filling the entire length of the rudder shaft tube is not really necessary as all you need is a top and bottom bearing/bushing. Too long of a single bushing will be hard to control especially if you have any 'bend' or 'out of round' at all in the rudder shaft.
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