Thought I'd go through the process I used, maybe someone will find it useful.
The
rudder post broke off during a sail and the
rudder was itself was
lost, so I didn't have a pattern to copy.
The
boat was of British construction, and I got the rough dimensions from a kindly soul on an owners' website. I also had pictures of the
hull and rudder
on the hard.
The rudder didn't have any compound curves. So was able to use a naca 0015 profile for a template. I printed it out at the appropriate size and transferred it to a quarter inch piece of plywood-- shaped it to use as a template.
I purchased grade 316 stainless for the rudder post and flat stock for the armature.
I asked the local yard if they could give a name of a local welder they could recommend, and he did a pretty good job, except he didn't switch back and forth on his welding that resulted in a bit of a hook into the post, but since it would be down in the rudder it wasn't critical.
Built a "coffin" sized slightly larger in dimension of width and length. Drilled a hole to fit the post through and used
wood blocks to center the post and armature in the coffin, as well as position fore and aft. Filled it with two part urethane 10# foam.
Used a pull saw to take off the worst overages, and then a
power plane and angle grinder with a flap disc for the rest. I used my template to maintain the shape.
Fiberglass consisted of one layer of knitted
fabric and three layers of 6oz. cloth, extra layers at leading and trailing edges and where the post enters the rudder, which on this
boat is normally above the
water line (a very good thing!)
Faired with West System fillers and System 3
epoxy. Sealed with two coats of
Interlux 2000 Barrier coat.