Centerboard

[rshowarth]

I am refinishing a cast iron centerboard. It is about 4 1/2 feet long, 18 inches wide and 1 - 1 1/2 inch thick (at the pivot point); 160 pounds.

It will be sandblasted this Friday and coated with epoxy as soon as possible.

It has developed an elongated hole where the pivot bolt (approximately 1 inch in diameter) goes through the centerboard. I want to tighten this up to prevent movement of the board.

I felt it should be re-bored and then a new larger bushing installed in the hole. I found bushings at McMaster-Carr. My questions are:

How do I go about making a new hole? Do I simply get a very large drill bit sized just large enough to make a larger, symetrical, hole through the cast iron board?

Can I do this with a hand held drill? Or is there too much risk of the hole not being formed at a 90 angle to the board?

Should the bushing and bolt be of the same metals? I was going to use a bronze bushing and steel bolt.

What kind of washers should I use on either side of the board once reinstalled to fascilitate easy swinging of the *swing keel*? Hopefully large enough to restrict sideways play in the board once lowered.

Thank you

[Tim]

I'd recommend a drill press, with the centerboard clamped tightly in place. Since there's already a hole in place, any drill bit is going to tend to want to wander when you start the hole, so if you can stack the deck as much in your favor as possible (by using the more accurate drill press and clamping the workpiece securely), you'll be better off. You want the bushing to fit as securely as possible--and also at 90? to the board, or you could run into problems with the board's operation later.

Can you find a stainless steel bushing? I'd go with that, and a stainless bolt, and avoid the bronze in this case. Bronze is kind of soft to use as a wear surface, as with a bushing. Similar metals is also wise wherever possible. Of what material was the original pivot bolt? You could just stick with that material, but I'd try to keep bushing and bolt of the same material regardless. I don't think galvanic corrosion is much of an issue in your case, and the pivot is probably located in a trunk above the waterline, but still, it helps to do what one can.

You might consider washers of some "slippery" material such as delrin or similar, which would not only tighten up the board, but would assist its operation (as long as things aren't too tight).

[George ( C&C 40 )]

Hello,

I went through the process of cleaning up the cast iron centerboard on my C&C 40 two years ago. I had it sandblasted, washed down with Ospho, and then painted with West System epoxy. Be very careful that you don't build up too much material on the surface of the centerboard or it might get stuck when you put it back. This happened to me and it was a real bear to extract the centerboard from the trunk. Cast iron boards are great in that they don't bend, however, they do get rust on them no matter what you do.

Good luck,

George