Can i use TUFNOL as a rudder tube, brass is ok but we sail in salt water and the brass will react with the stainless in the end. 

Tufnol is a composite material so I would say yes you can. There are many different types of Tufnol.

Whale, Carp, Kite, 6F/45 etc. They all have their own applications.

Any of the above would be suitable for something as simple as a rudder tube.

I would use Delrin. It can de machined and will take a course thread. Try EBAY. That is we’re I get mine. 

As Martin says; delrin may be a better bet. Nothing wrong with Tufnol as a bearing material though. I vaseline the rudder stock before fitting, which will do a lot to help in many ways.

Interestingly brass will de-zincify quite happily on its own.

Richard

If I have got it right 'Delrin' is a thermoplastic.

Also if I have understood the IOM rules thermoplastic is allowed which may be moulded, containing only permitted materials.

Where do I find the permitted materials?

Also is the rudder tube part of the hull as it keeps the water out or is it a fitting?

Thanks in anticipation of answers to these stupid thoughts/questions

Eric

12 hours ago, Eric Finley said:

If I have got it right 'Delrin' is a thermoplastic.

Also if I have understood the IOM rules thermoplastic is allowed which may be moulded, containing only permitted materials.

Where do I find the permitted materials?

As I believe your referring to hull materials as defined in IOM CR D.2.1 (a) (8), the class rules work by design in only allowing the specified material and excluding those by omission (if not listed they cannot be used) so therefore the definition of "permitted material" would seem to be defined by those materials listed in the same IOM CR D.2.1 (a) in sub-clauses (1) - (8) inclusive.

So for Delrin, you can use it as it is a thermoplastic as defined in IOM CR D.2.1 (a) (8) as long as it is not moulded with a material not listed such as carbon fibre as an example.

Edited February 3, 20224 yr by womble66
Typo

to my mind the rudder tube would be part of the hull as it is moulded in not a fitting, but if you are worried about corrosion what is wrong with stainless steel it is a little bit heavier but on the majority of IOMs I measure it will just mean less corrector weights, Keep It Simple (KIS)

Hi Mike. I have had3 IOM’s. On all the rudder tube was stuck in after the hull had moulded and not part of the basic lay up. It is not part of the hull basic structure so don’t think it is affected by this area of the rules. I would still use delrin for the reasons I stated I my first post. On my current boat a V9 it has a gland at the top with an o ring to stop water working up and into the hull. I just put a thin wipe of silicone grease on the rudder shaft to lube it and aid water resection. 

womble66, How are you going to find out what the make up of Delrin is as I don't expect the manufacturer is going to tell you? Therefore how can you guarantee that there are only listed materials in its make up?

Like Mike I think this would be part of the hull as without it the boat would not be watertight.

Delrin is a Dupont Trademarked engineering thermoplastic (it is a form of Acetal) used in precision parts requiring high stiffness, low friction, and excellent dimensional stability. I don't believe it contains any additional (IOM non-compliant) compounds to provide its strength and wear resistance. see https://www.dupont.com/brands/delrin.html

10 hours ago, Eric Finley said:

womble66, How are you going to find out what the make up of Delrin is as I don't expect the manufacturer is going to tell you? Therefore how can you guarantee that there are only listed materials in its make up?

Like Mike I think this would be part of the hull as without it the boat would not be watertight.

Thanks Eric but I don't have to as I am not the one suggesting to use Delrin but I do agree once it is formed and fitted it would be part of the hull and therefore would need to comply with the CRs.

The onus is on the boat owner/builder to comply with CRs and the measurer to endorse the hull to those CRs, not me, but thanks and I think Peter has addressed your "how" questions well.

EDIT: As a builder you could take Delrin in resin form and include an additive that is non-compliant and mould/cast a part such as a rudder post tube which was my point. So the onus is on the builder not do do so therefore it's not just about the Delrin but rather how it is used but in its natural form I believe it would comply under the "thermoplastic" definition.

Edited February 8, 20224 yr by womble66
Added a point of clarification