Thoughts on a New Centerboard for Sanderling (Long post)
About 10 days ago there was a thread about using epoxy or urethane foam and glass microspheres to build a rudder. I followed this thread closely because I want to build a new centerboard to replace the pitted and corroded cast iron board now in Sanderling.
The cast iron not only rusts, but it swells inside the trunk and gets jammed. Plus there is galvanic action between the board and the stainless shackle on the trailing edge which attaches the pennant to the board. The hole gets thin and eventually the shackle tears out like a piece of paper in a loose leaf notebook, causing the board to drop into the mud.. Every other year or so I have to grind the old hole away and drill a new hole further inboard. I replaced the 1/8" SS wire pennant with one of the new high-tech synthetic lines ( I forget which). That works fine, but the shackle is still there.
The board, which weighs 168 pounds, does not count much in terms of ballast. It just provides lateral resistance to reduce leeway, take pressure off the tiller and balance the rig so she can sail herself. It has to be heavy enough to drop on its own when the pennant is eased. It is 5'7" long, has a chord of about 13" and is 7/8" thick at its widest point.
Foss Foam or Idasailor could possibly make me a new board just like their rudders. But that might cost one Boat Buck or more, which, being retired, I cannot now afford.
I considered several materials to build this new board: 1) Plate steel. I could make it out of 7/8" plate and coat it with epoxy tar and paint it. Or I could use 1/2" steel and wrap it in fiberglass and epoxy to the required thickness.
2) Starboard. But I decided that this material would flex too much under the considerable lateral loads on a reach or going to windward.
3) I could make a board using plywood wrapped in fiberglass and epoxy, maybe placing a 5/8" lead bar on the leading edge for weight and impact protection.
4) I could build it out of fiberglass using woven roving and bi-axial for strength and build-up. Alternatively, there's a form of fiberglass consisting of glass rods held together by a scrim. A couple layers of that would be very strong and heavy enough.
5) I saw an article about a cockpit hatch that was made of strong pre-made fiberglass sheeting (forgot the name of that stuff). But that material might be very expensive.
6) Bronze. That is my preferred material for a centerboard. But that might cost several Boat Bucks.
7) As a last resort, I could just glass over the clot and forget about using the board. Several people I know have done this. But it changes the handling characteristics of the boat, resulting in much more leeway. Charlie Morgan wasn't no dummy. I don't wanna do that.
There's another consideration. The board pivots on what I believe to be a 1 1/2" bronze pin embedded in the forward part of the keel. If I used steel, I'd have to somehow isolate the steel board from the bronze pin. If I used any other material, I'd have to provide some sort of bearing or bushing so that the pin does not wear away at the pivot hole.
This is my thought process on this issue.
What say you all? Have you any ideas, suggestions, comments concerning the foregoing?
I'd appreciate your input.
Sanderling, 1967 C-31 #77
- Many of you know that my daughter, Becky, is an avid sailboat racer.
Among other venues, she races out of Annapolis on Wednesday nights. This
last Wednesday, things got a little more exciting than usual. They blew
the carbon fiber mast on Wanda. You can see the results at about 2:25
into the video. Nobody got hurt but a new mast is somewhere north of
Capt'n Pauley (Paul Esterle)
Freelance Boating Writer