Balsa is also used by the military, in ships, boats, and of course windmills. BUT there are some good news. Eventually they will use bigger blades (you get power from lower speed winds), and there the balsa does not shine anymore. So, as price goes up, it makes itself less atractive, and new techniques allow the use of other materials that are better suited for the windmills. But power boat manufacturers and also sail boat manufacturers are still using a lot. Even transport vessels, pretty much if they have fiberglass construction, they use balsa. Again, there are choices, and cost will drive the use. The current blades are huge, I saw them being manufactured in Fairless Hills PA, but the newer ones are gigantic.

Gerry

TYCOR W combines glass fibres with closed-cell, low density foam in an engineered architecture and has been used in the wind industry for two years. One blade manufacturer using the core material in place of balsa experienced an immediate weight savings of 325 lbs per blade on a 45 m blade. Blade manufacturers are also finding the composite core offers other advantages not normally associated with core material such as:

design optimisation;
yield optimisation achieved with kitting partners;
improved infusion;
better fit of fewer, larger core pieces; and
improved uniformity due to fewer core gaps.