One of the few complaints you hear about earlier Com-Pac sailboats is the tendency to exhibit excess weather helm. A number of Com-Pac owners have purchased the aftermarket IdaSailor foil rudder and reported extremely positive results. Improved slow speed tacking, greatly reduced weather helm, a feeling of having "power steering", and some reports of improved pointing seems to justify the relatively high initial cost of this rudder system.
As a contributing member on the Com-Pac Yacht Owners Association forum (CPYOA) I read a post about making an inexpensive foiled rudder out of the existing flat aluminum blade. I love building/repairing things, so this project went right to the top of my to-do list. I contacted the CPYOA member (Doug in Delavan, WI) with a request for a print out of the NACA foil outline which he quickly printed off and mailed out. Time to hit the shop!
Some folks have laminated layers of wood onto the aluminum blade stock to build up enough thickness for the final shape. I chose to use pink foam with just a leading edge made of a hardwood. Both methods have worked well, so the choice of materials is just a matter of preference. The process was quick and fairly easy to accomplish, although I don't believe I'll ever be a fan of working with fiberglass.
The finished product looked darn good for a first attempt, but the proof was in the initial sailing test. WOW! What a difference in the feel of the tiller. Instead of a tight grip on the tiller with a constant pull, we could just lay a hand across the top and gently make corrections. We used to switch off the helm every half hour or so due to arm/hand fatigue. Now we needed to ask the each other to give up the stick. Slow speed tacks were so much easier as the blade no longer acted as a big flat brake. The term "power steering" came to be used to describe the new feeling in the foiled rudder boats.
Man I love it when a plan comes together and works better than expected or even hoped for.
Check out our Projects page if you are interested in more photos of the process along with some building tips.Here is a link to the original forum discussion of foiled rudders on CPYOA: