I decided I needed a new rudder. The one currently on the vehicle is too sloppily made and the pivot axis is not placed correctly for minimum actuation force (it should be at 25% of the chord). So I'm making a mold for a new rudder. Which means I first have to make the plug. No CNC router or 3D CAD for me, just a free 2D CAD program (Solid Edge, actually pretty good) and some hand tools. I drew up the rudder, cut out a template, and glued it to a piece of balsa:
Cut the balsa out and hand-sanded to an airfoil shape. I'm a BIG believer that if you just take your time, you can create a near-perfect shape by just free-handing it with a sanding block. Your eye is amazing tool for getting the right shape. Here's the rudder after sanding:
I glued in the rudder post and put heat-shrink tubing over it to protect it for the time being. Then I vacuum bagged on a few layers of light fiberglass:
Now in parallel I'm building new struts/keel (not sure what to call them). The current vehicle has a single one but I'm going to two tandem struts for various reasons. Now for an airfoil section this long, I have no desire to sand it by hand. At least not when there are airfoil sections readily available in the form of R/C helicopter rotor blades. So I take a wood rotor blade of the appropriate size and glue two blocks on the end. The rectangular blocks will create ends that are easy to interface with the rest of the boat. Keep in mind that I'm creating a plug here, not the real part. Just as with the rudder, the real part will be composite. Here's how the plug for the struts starts out:
And here's the rudder and strut plugs after filling all the nooks and crannies with filler. Next comes waxing and then pulling fiberglass molds off of them: