I have finally got around to bulding a real rudder for the Saralee. The plank specified in the drawings has worked OK todate but now I want more out of the boat what with the new rig and all. The questions for our resident profesionals is this: Is there any advantage to making my new rudder ~ 48 inches vs. the 42" stock rudder? I am building a 14" NCAC 0012 that puts the extra 4" below and in in front of the pivot. Do I gain anything positive with the extra depth or just more drag. Thaks for the help.
A longer rudder blade is often the prescription to ease mild weather helm. The 0012 section will be fine on a stock length blade, increasing its efficiency. There are plenty of other areas to clean up around the hull, that will make larger improvements in reducing drag, then what a few extra inches on a foil shaped rudder, can muster. I'm not sure how Stevenson calculated rudder area, but I'm assuming at least 50% of it's area was taken into account, when balancing the sail plan on the hull. It seems effective enough, assuming the rig is tuned.
To directly answer you, a longer blade will increase it's aspect ratio and this is generally good. Choosing a good all around, low speed, foil shape will keep the blade "hooked up" over a wider range of incidence. The amount can be calculated, but will be difficult to feel through the typical wheel steering assembly. A tiller would instantly tell you something was different, if you're reasonably sensitive in the hands. Steering response may also improve a measurable amount, but could also go unnoticed at the helm. A lot of the steering characteristics on this boat, are keel and rudder box related, not a fault in the blade. I use foil shaped appendages always. They sail better, transmit information better and are easier on their gear.
