Aluminium

Extruded aluminium is an excellent material for making masts.
Loads generated by mainsheet, vang, outhaul and other controls are transferred onto the mast. Mainsails are normally designed according to the curvature of the mast, and if you have a stiff mast, this means you can reduce the luff curve to the mainsail, and add area to the roach of the sail, where it is more efficient. Forestay tension is also crucial to performance, and this is helped by a stiffer mast section.