Carbon rudder posts

[SeaJay]

Does anyone know if a carbon rudder stock can be used directly against an UHMWPE bearing, or should a stainless sleeve be attached to the stock? I thought I read somewhere that the SS needed to be used as a wearing surface, but that may have been in conjunction with roller bearings. The SS seems somewhat problematic as I suspect there may be some electrolysis occuring between it and the carbon. Thoughts?

[apex1]

Does anyone know if a carbon rudder stock can be used directly against an UHMWPE bearing, or should a stainless sleeve be attached to the stock? I thought I read somewhere that the SS needed to be used as a wearing surface, but that may have been in conjunction with roller bearings. The SS seems somewhat problematic as I suspect there may be some electrolysis occuring between it and the carbon. Thoughts?

One thought was : use more acro´s and get more replies!!! Naturally YWNUWIM?
at the end..............

[nero]

You will need a sleeve for a wearing surface. Or you can machine the bearing on to the stock and use a bearing surface in the rudder tube.

Or maybe someone can say if UHMW-PE can rub against UHMW-PE and survive.

[mark775]

And no, UHMW cannot ride well against UHMW.

[SeaJay]

Mark, Nero, Thanks.

Apex,

Ultra High Molecular Weight Polyetheylene

[Eric Sponberg]

In my carbon fiber rudder designs, I always specify stainless steel sleeves. This is because, in a composite laminate, the determining factor, really, is the resin, and epoxy resins wear down really fast. You have to have a hard wearing surface. I have had on occasion specified other plastice bearing surfaces to be bonded to the carbon fiber part--the point is, you need a bearing surface on the stock to take the bearing pressure and wear. Do not let the bearing ride directly against the carbon fiber stock.

Eric

[apex1]

SeaJay
thanks, I know that as "High modulus PE"

Richard

[SeaJay]

Thanks Eric,

Actually, I thought it was one of your articles that had mentioned the SS surface but I couldn't find it again (or was too lazy to continue my search!). What is the best method to attach the SS to the carbon stock? Set screws don't seem like a good idea, but does epoxy or similar (EasiChock http://www.tigerpropellers.com/orca_grease.htm ) provide enough adhearance between the SS and carbon? I saw a couple of rudders where it looked like this was the method used so I guess this is the way it is done.

Regards,

Doug

[Eric Sponberg]

SeaJay,

Yes, epoxy is fine for bonding. Sand the mating surfaces first to a good roughness with coarse grit sandpaper before gluing.

The article you probably saw was "Keels and Rudders: Engineering and Construction" in Professional Boatbuilder #96, Aug/Sep 2005, page72. Here is a link to the on-line digital version: http://www.proboat-digital.com/proboat/200508/

Eric

[SeaJay]

Thanks Eric. I was looking in that particular article but missed the notation in the drawings. That was exactly what I was looking for. SS it is!

Doug