Pivot joint at rudder base failure

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November 4, 2016 at 14:28 #25977
Suala
Suala
Participant

The pivot joint at the bottom of the rudder comprises a male peg seated onto the footplate and a female cap that is seated up into the rudder base. Mine was remade and fitted two years back. The female cap has again worn loose out of the rudder stock. It rides up and down on the peg below. I suspect the rotation now occurs between the cap and the rudder not the cap and the peg as it should. The cap was made from brass by the local mechanic. I see it is not smooth and possibly the friction has caused the failure. what do you other Nic owners have here? Should it be a chrome joint both peg and cap? Anyone use a silastic washer to improve gliding? Or are the forces under load too heavy? Does anyone know of a joint off the shelf that could be purchased, and where I could get it?

Any advice would be welcome.
Many thanks, Brian

November 6, 2016 at 02:03 #25981
Van
Van
Participant

Hi Brian,

I rebuilt our rudder a few years ago on Rainshadow, described on our own blogĀ here.

When we removed the rudder, it was clear the bronze cap had become free (unglued), but it was still in place. It was very worn (no longer circular) and there was a lot of play between the pin and the cap. The cap is supposed to be glued into the rudder – there is a plastic part that is in the rudder that the cap fits into. The bearing surface of the cap is flat.

I had the cap remade out of bronze (not sure what type of bronze, but the shop that made it – Port Townsend Foundry – probably used a high quality silicon bronze alloy.Brass is not a good choice because it corrodes quickly, and it is contact with the metal of the shoe (as I call it in the link, your footplate) which is a bronze from C&N. I glued it in with sikaflex.

The pin, built into the shoe, has a conical top surface that comes to a point, that I believe is intended to be the bearing surface. The 40 year old pin on Rainshadow did not seem to be too badly worn, and the shoe itself seemed fine after scraping off surface corrosion. So we did not replace it.

AFAIK, you do not need anything between the pin and the cap to reduce friction. I found nothing there. The small point on the pin makes a small area of contact with the cap, and also you can apply a lot of torque with the steering.

The fit with the new cap was close but not tight, and left no play in the rudder. It is still like that after 3 years – have not hauled out, but diving on the rudder it seemed fine. Before we fixed this, at fast sailing speeds we had a lot of vibration in the steering that you could feel at the wheel. This is gone now.

Van

November 6, 2016 at 08:22 #25983
Suala
Suala
Participant

Thanks Van,
I understand how it works now. Your rebuild article was especially interesting! I was advised to put in a Delrin thrust washer between the cup and the base of the pin, but I now see that this is unnecessary if the bearing surface is at the conical point. I think the problem arose when the cap in Suala’s rudder was dislodged. I will inspect the plastic seating for the cup to check it’s integrity. If it is destroyed I will have to seat the cap with epoxy as I would not be able to find a plastic part to refit into the base. If still functional I will glue the cap in with Sikaflex as you did. Much obliged!
Brian

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