It's funny, in many things I'm more than happy with "good enough," but in other things I'm a perfectionist. Well now I'm at a stage in the project where I start second-guessing some of my previous work and then redoing a lot of it. One thing I've decided to "fix" is the propeller. I've been using off-the-shelf model airplane propellers which are made out of fiber-reinforced nylon. It turns out that that doesn't do too well in water. I took one brand new propeller and dipped it in a cup of freshwater overnight and felt it in the morning. The portion of the propeller that had been submerged was now much less stiff. That explains why my propellers have been looking very bent after a few hours of running in water. So what do do? Make a carbon fiber/epoxy propeller, of course!
This actually is fairly easy if you're copying an existing propeller, like I am. In the picture above you can see an off-the-shelf propeller that I've placed on a bed of Bondo to form the plug. After sanding and waxing, I poured pure epoxy onto the plug. I've never done it this way before; normally you'd use fiberglass to make the mold. But using epoxy alone is nice because it makes the mold transparent, which then makes actually using the mold a lot easier, since you can see what the fibers and epoxy are doing inside the mold.
I would include a picture of the finished propeller but you really don't need to see it. It looks just like the propeller above except that it's black. Simple as that.