Rudder bearings

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mhouse

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I am just about to replace the rudder bearing with new Nylon bushes. I have contacted Dehler and they have informed me I will have to distroy the bottom bearing to remove it from the alloy tube into which it is stuck.Is it normal to use epoxy or a mastic type sealer to hold in the new bearing.
Many thanks fro the posters for previous rudder posts as RS components as recommended before delivered the goods in 2 days.
 
you'd probably be safest with a sikaflex type adhesive as it will cope better with thermal expansion. not much will stick to nylon though. have you been advised to use nylon - it is inclined to absorb water and swell so Delrin is a more common choice.
 
I was also under the impression that if nylon were used it would hold grit and quickly abrade the surface it was bearing.
 
Be very wary about using Nylon for rudder bearings. Some common grades absorb moisture and consequently swell. The result can be a completely jammed rudder! Tufnol is a far better bet.
 
The existing is nylon, and has lasted 15 years, I intended to soak the blank for a month before getting it turned up.
 
[ QUOTE ]
The existing is nylon, and has lasted 15 years, I intended to soak the blank for a month before getting it turned up.

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Don't do that as it is a waste of time.
Contact your local Tufnol depot and tell them what you want. They will advise on best material but will machine out of anything you want. They know the expansion ratios etc of their materials and make allowances accordingly.
BTW Tufnol do not only supply Phenolic resin materials, they also supply most engineering plastics as well.
 
I would suggest not using nylon.

In addition to the other suggestions that have been made it is worth considering Thordon. It is a widely used material for shaft and rudder bearings (a google on Thordon will take you straight to it together with typical applications) - it is probably the best of the alternatives.

The supplier can probably recommend how the bearing should be located, but assuming the aluminium log is solid enough and there is no axial load, I would have thought a press fit would be adequate for a material such as Thordon.

John
 
Thordon might be difficult to obtain without considerable expense? Interestingly, Thordon claim superiority over nylon & UHMWPE (being sniffy, they class polyamides separate to nylons) but omit any claim of superiority over polyacetals eg delrin. Quite surprising in a way.

Delrin can of course be bought in rods and easily machined (if you can put up with the smell of cat's piss .... )

I presume that the part was made originally from Nylon 66 or one of its near ilk. The structural strength of delrin and (saturated) Nylon 66 are similar. I think if it was my boat I'd be inclined to stick with what has worked and that is partly because I don't understand this particular application ...
 
Not sure of the price of Thordon, but no one has ever complained when specified (possibly because only small quantities are required) and is widely used and easy enough to obtain here in NZ (although I think Thordon is a UK product).

In addition to your comments, the material the stock is made from may or may not influence the bearing choice. I am assuming the stock is stainless steel or aluminium.

John
 
HI i dont know what it is called but i made a bush for bottom of rudder last year out of that stuff engineers use for heavy duty bearings on machines looks like nylon but isnt, black in colour but maybe you can get it in other colours you can shape it on a lathe easily and it works a treat sits in skeg nicely.. Have a happy new year all
 
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