Makers of rudder pintles/gudgeons and bearings

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Calico Jack

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I'm putting my ducks in a row in preparation for rudder repair on our Cobra 750, and may replace the lower pintle/gudgeon, (same as example in pic below). I will also replace the bearings/bushes.

Any experience of makers/manufacturers of these and bearings/bushes would be greatly appreciated
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You should be able to re-use the metal bits. Any decent machine shop can machine Delrin bushes for the bearings if they need replacing. Originally these would have been made by a subcontractor to the designers drawings or maybe in house if the builder had a fabrication and machine shop.
 
NB the comment ' Delrin bushes '; in case unaware, nylon swells in water and makes rudders stiff to turn, I mention this as it's not something one would really expect if unaware and it catches a lot of people out.

If you're in the Chichester area I can recommend a few good stainless fabricators.
 
Seajet said:
NB the comment ' Delrin bushes '; in case unaware, nylon swells in water and makes rudders stiff to turn, I mention this as it's not something one would really expect if unaware and it catches a lot of people out.

If you're in the Chichester area I can recommend a few good stainless fabricators.
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Thanks for the tip. It does seem to be widely used for replacement bearings and bushes??
What should be best to make these. I plan to have two at the bottom pintle, one seated on the pintle and on the rudder, much like the photo of another example shown in my original post above. There will be on the top of the rudder and at this stage I don't even know what sits in the aperture where the rudder stock enters the hull. No idea.
 
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Use an Acetal - Delrin is a brand name and is readily available in bar to be machined. It has very specific clearance requirements and a good machine shop will know this. You just need to give the dimensions and diameter of the shaft and housing. It can be used above the waterline for an upper bearing on a rudder stock or below the waterline. As seajet was trying to say, don't use nylon which absorbs water over time and swells whereas absorption in Delrin is almost nil. I have a Delrin lower bush that was installed in 1992 and is like new with no wear and no play.
 
Thanks for the useful info.

The worry I have with Delrin though in a cobra set up, is that I want to seat a bearing bush on the pintle and one on the rudder bottom, as per example below found online, however it would seem through some reading that it is near impossible to get anything to stick to it, so I may have to abandon that idea or use tufnel if i do choose to seat them.
I'll use Delrin for the upper bearing for sure i think.
I have a mini lathe and mill here so I can make the parts


WP_20150725_002 (1).jpg
 
Not sure why you would want to do that. I assume the pintle is the bottom of the rudder stock, in which case you just need a top hat bush in the fitting on the bottom of the skeg. If, however, the pintle is in the fitting on the skeg then a top hat bush recessed in an interference recess in the bottom of the rudder, perhaps with a bit of Sika when you push it in. The flange of the top hat in each case will provide a bearing surface.
 
Just made a similar set up for my current build. But I am puzzled by the idea of two bushes? I have a pin on the bracket bolted to the skeg and a Delrin bush ( from stock from directplasticsonline.co.uk ) in the rudder stock, a SS tube.
Maybe you need to remake the skeg fitting with a resized pin?

Edit: Crossed with Tranona, but not much different.
 
Tranona said:
Not sure why you would want to do that. I assume the pintle is the bottom of the rudder stock, in which case you just need a top hat bush in the fitting on the bottom of the skeg. If, however, the pintle is in the fitting on the skeg then a top hat bush recessed in an interference recess in the bottom of the rudder, perhaps with a bit of Sika when you push it in. The flange of the top hat in each case will provide a bearing surface.
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Good points. At this stage I believe the pintle is part of the fitting on the skeg, however I don't know if it goes into a hole in the bottom of the rudder stock, or if there is a tophat type bush there.

Downwest, how did you adhere the delrin into the rudder or is it a loose bush between the skeg pintle and the rudder?
 
Calico Jack said:
Good points. At this stage I believe the pintle is part of the fitting on the skeg, however I don't know if it goes into a hole in the bottom of the rudder stock, or if there is a tophat type bush there.

Downwest, how did you adhere the delrin into the rudder or is it a loose bush between the skeg pintle and the rudder?
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In my case, the rudder stock is a 50mm ss tube which the Delrin bush is a push fit. But even if it was not, it would be located by the stock not being able to rise and jump the pin in the skeg fitting.
Don't think Delrin glues very well...if you need to keep it in? Couple of side screws?
 
DownWest said:
In my case, the rudder stock is a 50mm ss tube which the Delrin bush is a push fit. But even if it was not, it would be located by the stock not being able to rise and jump the pin in the skeg fitting.
Don't think Delrin glues very well...if you need to keep it in? Couple of side screws?
Click to expand...

If my stock is hollow and can take a delrin bush, that'd be good.
But if it needs a top hat bush sunk into the bottom of the rudder, I'll not try and seal delrin for that to make the rudder watertight, simply won't work I think.

hard to believe with about 500 hundred Cobra 750s made, that there are no examples online of someone repairing the rudder, given they are known to need restoration work.
 
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Polyacetal (Delrin) is not Nylon and has quite low moisture absorption.

Tufnol is a phenolic resin composite, not really optimised as a bearing material.

Delrin works pretty well for many small yacht bearings but it has some moisture absorption and some thermal expansion that have to be catered for in sizing. It is also a material that softens with heat (friction) and can creep or deform under pressure.

Maritex which I import is a phenolic composite with low moisture absorption and low thermal expansion whilst also having two lubricants within the fibre and resin matrix. It is stiffer than delrin and doesn't creep. Wear rates for Lloyds rudder tests showed no wear dry for 1000hrs at up to 20Mpa on bearing or shaft. Maritex bonds easily with epoxy which is how we hold shaft bearings in place.
 
Neil_Y said:
Polyacetal (Delrin) is not Nylon and has quite low moisture absorption.

Tufnol is a phenolic resin composite, not really optimised as a bearing material.

Delrin works pretty well for many small yacht bearings but it has some moisture absorption and some thermal expansion that have to be catered for in sizing. It is also a material that softens with heat (friction) and can creep or deform under pressure.

Maritex which I import is a phenolic composite with low moisture absorption and low thermal expansion whilst also having two lubricants within the fibre and resin matrix. It is stiffer than delrin and doesn't creep. Wear rates for Lloyds rudder tests showed no wear dry for 1000hrs at up to 20Mpa on bearing or shaft. Maritex bonds easily with epoxy which is how we hold shaft bearings in place.
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Sounds like an interesting material Neil. Is it expensive in rod stock?
 
Yes it is expensive, and Delrin works pretty well for most small yacht rudder systems, just make sure you have enough clearance, if Delrin gets tight it will expand with heat from friction far more than water absorption. My own boat had Delrin, and as it was quite a big diameter pressure wasn't high enough to need anything better.

As a guide a finished Maritex tube 50 x 70 x 100 long is £107 Ex vat
Shaft 50.00 SS Carrier 70.00 bronze
We don't make solid as the cost is in the material, so make tubes as close as possible to finished size = less waste/cost
For a bearing as above min clearance would be 0.22mm, finished ID would be 50.22~50.32 OD would be just under 70.00, 69.90~69.95 for bedding on epoxy.
 
Neil_Y said:
Yes it is expensive, and Delrin works pretty well for most small yacht rudder systems, just make sure you have enough clearance, if Delrin gets tight it will expand with heat from friction far more than water absorption. My own boat had Delrin, and as it was quite a big diameter pressure wasn't high enough to need anything better.

As a guide a finished Maritex tube 50 x 70 x 100 long is £107 Ex vat
Shaft 50.00 SS Carrier 70.00 bronze
We don't make solid as the cost is in the material, so make tubes as close as possible to finished size = less waste/cost
For a bearing as above min clearance would be 0.22mm, finished ID would be 50.22~50.32 OD would be just under 70.00, 69.90~69.95 for bedding on epoxy.
Click to expand...

Thanks for the info Neil. I don't think I'll need to use such top draw materials for my boat, but interesting none the less.
 
I’m missing a pintle from my yacht (Halmatic 30) does anyone know what missing pintle would have been made of?
 

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Calico Jack said:
I'm putting my ducks in a row in preparation for rudder repair on our Cobra 750, and may replace the lower pintle/gudgeon, (same as example in pic below). I will also replace the bearings/bushes.

Any experience of makers/manufacturers of these and bearings/bushes would be greatly appreciated
View attachment 64926
Click to expand...
Like many people making enquiries on this forum ( so you are not alone in this) about supply of specialist parts you have not said where you are based.
It may help if you told us A) where you live & B) where your boat is.

May i also suggest ( although i cannot actually picture the part) that you might use Tuffnol Whale if wanting Tuffnol.
 
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