Tufnol

[Mike S (Guest)]

I've been advised this is the stuff to use to help solve my recurring problem of the centreboard pin wearing through the aluminium "hatchet" of my board. I just need a small scrap a few inches in dimension. Anyone got a bit lying around?
Also any advice on the best way to bond it to the aluminium hatchet? Epoxy?
Mike
N3491
 
 

[TERRY COOKE (Guest)]

Hi Mike
 
We have some, about 6 mm sheet give me a call if you still require it, the numbers in the book.
Epoxy bonds well to Tufnel the alloy will be the hard part, we use Plexus put it only comes in big expensive tubes
 
Terry 
 
 

[Tim Gatti]

Alternatively, try and get some 2mm wall thickness stainless tubing that your cb bolt will just pass through.  Cut a short length - about 2mm longer than the thickness of your aluminium centre plate.
Drill out the existing bolt hole in the plate (if it's not too distorted) to the O.D. of the tubing, roughen all the mating surfaces with a course file or emery and epoxy the collar in place in the plate.
The bolt will now bear on the stainless steel collar or liner, and not on the aluminium.
I did this fix on N341's alloy plate in 2006 and it's still holding up fine. Cheers. Tim

[Mike S (Guest)]

Terry - I think 6mm will be too thick. I can't think how I can make that work. I think I need 3mm thick max so I can sandwich the alloy hatchet between 2 pieces of tufnol and still get it into the centreboard case which is only 10mm wide around the pivot.
Tim - Yours seems a neat solution. My centreboard bolt is 6mm diameter, so if anyone has a stainless tube of that internal diameter or a little wider, I only need a 1cm long piece.

[Tim Gatti]

Hi Mike - part of the problem may be the small dia centre board bolt you are using - a lot of load concentrated over a small area will certainly cause excess wear in the pivot hole over time.
You might consider fitting a bigger diameter bolt - maybe 10 or 12mm, as well as fitting the collar. That way the pivot loads will be spread over a much wider area. Or are you on a mission to reduce all-up weight?
'Fraid I can't offer any tubing though - the bit I used was already in place on the c.board bolt of N341, which had its original heavy, slotted galvanised steel plate when I got it. Given that it was put together in 1938, I was amazed to find it fitted with a stainless steel pivot collar.  Inside the case, I also discovered that a large stainless steel washer was placed at each end of the collar so that, as well as supporting the plate, it also acted as a spacer, preventing the sides of the case from being distorted inwards when the bolt was tightened.  Very neat. Good luck. Tim

[Mike S (Guest)]

I'm thinking I might get away with stainless penny washers to sandwich the hatchet and provide a wider bearing surface. Fingers crossed....
Mike

[Derek]

I would strongly sugggest that you avoid putting stainless in direct contact with Al in an envirnomnet where there is rubbing. That would create a perfect receipe for galvanic corrosion and the material will be lost from the Al = the hatchet.
I cannot visualise the problem, but if a plastic will work, try the Tufnol. It is a very early composite dating from the '50s or '60s and is simply cloth layers in eurea-formaldehye resin. It is tough enough to resist abrasion well but easily worked and homogeneous i.e. doesn't have the grain characteristics of wood. You could easily sand it down to the required thickness and then seal the worked surface with a coat of epoxy.
Good luck
Derek