Originally Posted by Walt
The main advantage of carbon fiber is that it's lightweight. That's why you see it used for masts on performance sailboats. But they don't use it for the keel, because you want the keel to be heavy for ballast.
I sailed 49ers (www.49er.org
- men's doublehanded Olympic skiff) for a couple of years and I have to say that my carbon top section was heavier than my aluminum bottom section. Weight is not the reason. Carbon is used in masts for its flex properties. By modifying the wall thickness, the masts can be either quite stiff or quite flexible while still being strong, whereas an aluminum mast with equivalently soft flex would be too thin-walled and thus too weak. A soft top mast is advantageous to responsively spill off the top of the sail when faced with gusts, making the boat much easier to sail due to a more constant heeling force (the force pushing the boat over sideways). The crew then have to worry less about responding with their actions to changes in wind force to keep the boat flat since the mast does some of it for them.
While the 49er uses a flexible carbon top mast and a stiff aluminum bottom mast, this design is no longer cutting-edge, originating in the early 1990s. Newer rigs have fully carbon masts with increased stiffness toward the bottom for a more consistent flex, eliminating the effect of the junction between metal and carbon.
Anyway, I'm not sure how that relates to the topic at hand but I thought I should share my knowledge.
I guess what would be good about carbon boots is that they could be custom moulded to a person's foot, and it would be easier to control flex in certain areas by modifying the thickness of the layup. The downside (read: MAJOR downside) is durability. Carbon fiber deteriorates significantly when faced with UV radiation, especially on areas where the top coat of resin is scratched. And modifying the boots after layup would be near impossible, since punching and grinding are not options.
Plastic seems to work...