Tufnol water absorption question....

[dukes4monny]

I am making a new rudder for my JAG27. I am using a Tufnol bush at the top of the rudder which will bear against the bottom of the existing Tufnol lower rudder bearing (top hat).
Does anyone know how much Tufnol (Carp) will expand by when immersed in seawater for long periods?
I will make up Stainless packers to take out any up and down movement of the rudder, so I need to work out how much gap to leave to allow for possible expansion of the Tufnol bush.

Thanks for any pointers.

 

[VicS]

Have you tried the Tufnol website? http://www.tufnol.co.uk/

 

[dukes4monny]

Have you tried the Tufnol website? http://www.tufnol.co.uk/

Hi VicS, yes I have thanks.........I couldn't find anything specific on there..........unless I missed something?

 

[sarabande]

there are some pages hidden away. Typically, here is one for Grade 6F/45.

Perhaps the page on Tufnol bearing materials might help?

http://www.tufnol.com/tufnol/default.asp?id=24


also their advice on designing for use with water:

http://www.tufnol.com/tufnol/default.asp?id=97


these include details about expansion.

 

[Bilgediver]

I am making a new rudder for my JAG27. I am using a Tufnol bush at the top of the rudder which will bear against the bottom of the existing Tufnol lower rudder bearing (top hat).
Does anyone know how much Tufnol (Carp) will expand by when immersed in seawater for long periods?
I will make up Stainless packers to take out any up and down movement of the rudder, so I need to work out how much gap to leave to allow for possible expansion of the Tufnol bush.

Thanks for any pointers.

The latest Tufnol material seems to swell very little however one factor many forget to take into account is bore closure due to using an interference fit.

Tufnol have a data sheet for this material which shows how to calculate this if you know the wall thickness etc. Show this sheet to your machine shop and you should be fine.

Give us the actual dimensions and there will be a race for the first to give you the correct measurements to allow for closure etc.

http://www.tufnol.co.uk/tufnol/default.asp?id=119

 

[Crabman]

Do not use Tufnol it will expand over time ,use Nylatron and the correct grade.

 

[dukes4monny]

That's what I was looking for, thanks for all the replies.
It looks like I'll get about 0.375mm expansion (normal to laminates) with my 15mm thickness (2.5%). The bore is not critical and will be a sliding fit and epoxied in position........

 

[Neil_Y]

In reply to Crabman, so will nylatron, over 7.00%, I believe.

Lowest moisture related expansion and more importantly thermal expansion is available in a phenolic composite which looks very similar to tufnol but is quite different in its characteristics as a bearing.

Tufnol is OK as a bearing but not nice to machine.