Rudder Revision

Before and after photos of Moonshine's rudder, showing the change from totally unbalanced, typical 1950s rudder design to a partially balanced layout which should be much lighter on the helm.

The ongoing lockdown due to coronavirus means I haven't been able to do any work on Moonshine over the past few weeks. Luckily I've got a few parts from the boat here at home which have been keeping me busy, one of which is the rudder. This job has been on my to-do list since I bought the boat because she has always been uncomfortably heavy to steer, especially in any kind of breeze. This is partially due to the age of the sails, rig setup and a couple of other factors, but since the boat was designed in the 1950s things have progressed a little and modern rudder designs are at least partially balanced. This means that some of the rudder's area is located forward of it's pivot point, balancing out the hydrodynamic forces acting on it and making the boat much easier to steer. So this is what I've done with Moonshine's rudder, removing some area from the trailing edge and adding area forward of the rudder shaft.

While I've been at it, I've also much improved the airfoil profile of the rudder, adding some thickness to the chord around the middle and thinning the trailing edge to a fine point. Basically making it look more like an airplane wing and less like a brick. This will reduce drag and make the boat go faster, but more importantly will reduce the amount that the tiller will need to be turned to produce a certain amount of lift, again reducing the effort needed to steer the boat.

I started by taking an angle grinder to the trailing edge of the rudder, cutting off the part that swept backwards and leaving a straight trailing edge. I thinned this out to a fine point, as close to a typical airfoil section as I could make it, and glued a block of laminated plywood to the leading edge with thickened resin.

After attaching the block of plywood I reinforced all of the edges and the glued joint with fiberglass tape, and then laminated the whole thing with a couple of layers of 300gm CSM. I used resin mixed with filler to smooth out any irregularities and fair the shape into a nice airfoil section, and then gelcoated. I'm pretty happy with how it turned out, but the real test will have to wait for a windy day when I've got Moonshine back on the water.

Finished!!