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Rudder Bushes on Boat

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Daniel15/05/2019 06:19:49
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220 forum posts
39 photos

Hi everyone,

I need to make two rudder bushes for a sailing boat.

The old ones look like nylon, but I'm assured it isn't.

Apparently nylon isn't suitable for marine use.

Does anyone know what material it would be.

Many thanks for any help.

Daniel

Frank Gorse15/05/2019 06:44:06
25 forum posts

Delrin,or acetal which is similar but not the same,has far less water absorption/swelling problems than nylon and has long been used for such things. Or try UHMWPE,even less absorbent and the frictional properties of teflon but slightly more trouble to machine than delrin.

Direct Plastics’ website has lots of info and they give a good service-usual disclaimer.

Sam Longley 115/05/2019 07:22:11
718 forum posts
26 photos

Before beginning to make rudder bearings it may be worth looking on this site. Jefa make roller bearings for a wide range of craft & by the time one has invested in the material one could have bought a ready made bearing

**LINK**

But in any event do NOT use nylon. I use tufnol in my rope cutter bearings, but in rod form, can be very expensive-- depending on diameter, of course

 

Edited By Sam Longley 1 on 15/05/2019 07:25:32

Paul Kemp15/05/2019 12:09:38
285 forum posts
9 photos

Thorplas from Thorndon plastics is an established marine bearing material, the blue grade will be fine, it's available in cored rod form so not too much waste. Quite expensive though if I recollect correctly. As already said nylon is no good as it absorbs water and will swell, which will mean your rudder stock will be well and truly stuck!

Paul.

Clive Hartland15/05/2019 14:39:49
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2456 forum posts
40 photos

Boil the Nylon and let cool and it will not absorb any more water.

Philip Rowe15/05/2019 16:34:58
170 forum posts
14 photos
Posted by Clive Hartland on 15/05/2019 14:39:49:

Boil the Nylon and let cool and it will not absorb any more water.

First time I've ever heard that. I've always understood nylon is hygroscopic, end of story. But no doubt someone will be along soon to prove/disprove.

Phil

vintage engineer15/05/2019 16:52:10
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142 forum posts

Why not use PTFE?

Neil Wyatt15/05/2019 18:27:31
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16257 forum posts
679 photos
74 articles
Posted by Philip Rowe on 15/05/2019 16:34:58:
Posted by Clive Hartland on 15/05/2019 14:39:49:

Boil the Nylon and let cool and it will not absorb any more water.

First time I've ever heard that. I've always understood nylon is hygroscopic, end of story. But no doubt someone will be along soon to prove/disprove.

Phil

I think Clive's approach fills it up with water, so if you machine it before it dries it might go loose but it won't swell up.

Clive Hartland15/05/2019 19:30:44
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2456 forum posts
40 photos

OK, the supply of surveying staves was from Australia. We sold them on and then the complaints came in that they were sticking as the stave guides were Nylon. Complaint to Surmac in Aussie. set them off to find a cure.

The cure was to boil the Nylon. They then sent us boxes of sliders that had been treated and we replaced them as soon as they came in, If I recall we never had another complaint.

Clive Hartland15/05/2019 19:31:54
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2456 forum posts
40 photos

Neill, no, the item was hot formed in a press and then boiled.

Craig Smith 317/05/2019 07:15:13
7 forum posts

Hi Daniel,

Can you tell me what size is your sailing boat? Dinghy, Trailer Sailer or bigger?

I am a boatbuilder by trade and rigging boats ready to go sailing was my business for many years. I think most of the materials the other guys suggested will do the job and yes Nylon tends to cause issues. Might be able to minimise the issues using Clive’s suggestion, I don't know, but with other stuff readily available and easier to machine, I would go for something else.

Frank is correct, rudder bearings are quite often made from Acetal or Delrin, which is the trade name of one of the common forms of Acetal. It is easy to machine and is hard enough that it can be polished up if required.

Depending on the size required, it might just be faster and easier to by some off the shelf as suggested.

Craig.

Circlip17/05/2019 10:01:01
961 forum posts

Some nylons are hygroscopic and yes, boiling in hot water does work. Was given this tip when freshly molded nylon components were found to be brittle. Water absorbed made them flexible.

Material was Nylon 6. Nylon 66 was designed to be less absorbent.

+1 for Delrin or Acetal.

Regards Ian.

Ian S C17/05/2019 13:42:38
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7427 forum posts
230 photos

I think I used Delrin for the bushes on the rudders of my brother in law's 16 m/ 12 tonne catamaran. Built to Safe Ship Management survey standards, steering is hydraulic. Folie a Deux is a twin 150hp Volvo powered ocean cruising boat now based in Australia. The rudders did have a problem on the voyage from NZ to Fiji, over use of the steering caused the hydraulic fluid to over heat, so the sensitivity of the steering (electronically controlled with a Navman G pilot 3100 autopilot), I don't think it was tight bushes that put a load on the steering as the manual steering was quite free.

Ian S Cimg_20170510_0001 (640x426).jpg

Daniel18/05/2019 10:06:53
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220 forum posts
39 photos

Thank's to everyone for the input. Looks like Delrin is the favoured option.

Craig - It's a Westerly something. I'll see if I can find a photo.

I agree that it probably would be easier to simply buy them. But, it's my father's boat, and

he's decided that I can make them for him. crook

Her's a photo of the old ones ...

20190515_203239.jpg

20190515_203305.jpg

Thank's again, everyone, for the interest.

ATB, Daniel

Frank Gorse18/05/2019 11:35:06
25 forum posts

Do have a look at Ultra High Molecular Weight Polyethylene. I used it for a job on our ‘Westerly Something’. It’s even less affected by moisture than delrin,has similar frictional properties to ptfe and is very hard wearing. It’s also quite cheap.

Craig Smith 319/05/2019 05:08:04
7 forum posts

Hi Daniele,

Like always, a picture says it all. I wondered if you were talking about small bearing inserts like in a dinghy rudder gudgeon or as your picture shows, larger bushing for the rudder shaft. You did say bushes, but best to check.

Hard to be certain, but the way the break has happened it looks like a form of Acetal. Delrin/Acetal tends to be quite hard and boney , if that is even a word (like bone), so it breaks cleaner than a lot of other plastics, which stretch and deform before they and break.

Frank has mentioned it a couple of times and I think he is spot on. UHMWPE (you can see why they use the acronym) is a great alternative. Doesn’t machine as cleanly as Delrin, but it machines well enough. It’s has good dimensional stability in moisture and great resistance to abrasion. And like Frank says, CHEAPER, especially as you have to buy some quite large diameter solid rod.

I used it a bit in the past and I remember one time in particular I used it as end plugs in a spinnaker pole. I made them a neat fit and even after five years in and out of water and UV, the plugs never swelled and always slid in and out without issue.

Hope it goes well.

Craig

Daniel19/05/2019 08:57:34
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220 forum posts
39 photos

Thank's Frank & Craig, for the suggestion.

I'd already been off to the stockists. They were short on Delrin, so I bought a length of HDPE.

I hope that will work.

For clarity, the physical damage to the old bushes (all of it), was the result of my father's efforts in extracting them. He has since told me that the top bush had no play at all; and the bottom one had about 1/4" (6mm), side to side.

disgustdont know !!!

For those who may be interested; here are a couple of pics, of said boat.

36640247_3409143082434969_3992237599883264000_n.jpg

33784278_3340759692606642_7218018258362826752_n.jpg

Thank's again for your interest and help.

ATB, Daniel

Craig Smith 319/05/2019 09:31:07
7 forum posts

Hi Daniel

Okay, you are into it. I'm sure the PE will do the job. Seeing the boat moored like that takes me back to my youth. No sailing anymore, but now I spend a lot less money as well.

You mentioned about the top and bottom bearing/bushing of the rudder stock. Just keep in mind that the bottom one is the fulcrum and takes most of the load, so any slop down there is not good. If either is to be an interference fit, it should be that bottom one. The top one can handle a small amount of tolerance if needed to ease things up.

Once made, let us know how it went. Just as a matter of interest, where is the boat moored in that photo?

Craig.

Circlip19/05/2019 09:50:57
961 forum posts

Forgot the obvious one, Lignum Vitae.

Regards Ian.

Daniel19/05/2019 10:43:18
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220 forum posts
39 photos
Posted by Circlip on 19/05/2019 09:50:57:

Forgot the obvious one, Lignum Vitae.

Regards Ian.

wink 2 .... I even briefly considered bronze

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