After much research and talking to people I realized I do not want to pay about $1000.00 for an improved kick-up model and I also do not want to pay $300.00 to $400.00 for a used one built the same as the one I broke nor a new equivalent replacement for about $600.00
Here's a picture of the broken one.
As you can see it has some plywood core and then most of it is some kind of filler; which is kind of heavy by the way.
Problem #1: Notice how the bolt closer to the edge goes through filler, not plywood. I think this is a flaw which I intend to correct on my design.
Problem #2: The place where the bolts go through have no sealer of any kind and allow water to penetrate to the core and make it prone to deterioration; by the way, as per my research and judging by the way this particular rudder broke, that is the weakest point on a rudder of this kind; therefore I intend to change that to make the two bolts go through plywood and also to remove the core around the hole and fill it with epoxy. I also plan on other changes that I will show later.
OK, to begin with, I started by making a template of the existing rudder (it was at this point when I realized it was not only a good idea to recover it, but it was also necessary).
My research on rudders seem to suggest that if the rudder extends forward of the pivoting axle it would be more balanced, making steering easier and more relaxed, specially on those moments where you have a lot of weather helm; so I decided to extend the rudder about one inch forward under the water line. I'm being conservative here as I do not want to end up with something that does not work, if the change has negative effects on steering and/or performance I expect it to be not that bad as to not having to build another one. I will just have to deal with it. If it proves beneficial, great...
Also notice at the top I extended it past the horizontal line (as the original) as I found that I mostly steer with the tiller slightly elevated, this change makes the hardware that holds the tiller to the rudder grab on solid rudder opposed to applying leverage on the hardware alone.
I proceeded to cut the main or center piece out of 1/2" marine plywood, then I added one more section of 1/2" marine plywood on each side but just over the water line. Used epoxy to glue the whole sandwich together.
Now, the hardest part (at least for me) is to shape the underwater section of the rudder with the foil shape and the chalenge of getting both sides the same as to not get any lift or pull from one side.
I thought about how to achieve this and after much consideration I came up with a plan.
I will copy the original shape of the rudder. Easier said than done considering that I made mine larger than the original. I decided that I would leave a portion flat which will account for the forward extension I added to my design. I cut a strip of 1/2" plywood, shaped it accordingly and tapered the edges, this will give me the highest point of the foil. Then, with filler epoxy I will contour the final shape of the foil.
Fist I traced the original rudder shape into what will end up being the shaping tool.
Since the one I'm building is wider I needed to split the "shaper".
Then I epoxied the center piece of plywood and applied the first coat of filler, this first coat is just to build up the shape so the shaping coat can be thinner and easier to work with.
The next step after that was to measure and secure a straight edge on which to run the shaping tool. I screwed a section of 1x3 to the center plywood piece, did one side, re-screwed the straight edge on the right position for the opposite edge side and did the same. The bottom part was shaped by hand. It would have been better to run front and back side, let dry and then do the bottom part but, with the drying time and mixture waste I decided to go for it, I still need to do a light sanding and a final skim coat anyways.
So far, this is what it looks like, I'm very pleased with they way it's coming out.
I will try to finish shaping both sides this weekend and next week I will wrap the whole thing in fiberglass mat, applying an additional layer on the mid section.
Originally I was planing on doing three layers of cloth but it's not necessary, I will do only one plus some reinforcement along the water line (the weakest part of the rudder).