Just to add another example of wooden rudders:
My boat a C&C25 has a solid wood laminate rudder. I say laminate because it is nothing like the plywood we might commonly think of. I have no idea how old this rudder is or who made it originally but it is made from a very hard deep red wood, perhaps Cyprus or Redwood. At the top (tiller end) it is 2.5" thick and tapers as it meets the water line. The leading edge is tapered as is the trailing edge. The trailing edge has a much wider taper than the leading edge to make it more of an airfoil. The layers of laminate wood are of varying thickness; (see photo). Where the laminates are tapered there is extra layers of glass cloth buildup as well as on the leading edge and bottom foot of the rudder. The whole rudder is encapsulated in a thick coat of epoxy resin.
I recently sanded it down to bare glass and re-coated it while I was replacing the gudgeons and pintels. I had to trim a small area of the rudder with a saw and was able to see the laminates very good in the cross section.
The rudder is very heavy for its size (about 5' tall) weighs 50lbs. I'm hanging it on a new set of Shcaffer transom mounted gudgeons and the pintels are 1/2 inch heavy duty custom stainless steel.
Just thought you guys may be interested.