Abstract: A mainsail furling mast assembly utilizes a mast having a cross section providing a C-shaped outer wall and a transverse wall defining a rearwardly opening compartment in which is disposed a furling element about which the mainsail may be furled. The opening in the mast has a width equal to at least 50 percent of the maximum width of the mast to provide facile access to the compartment. The mast has a boom mounting bracket including a reinforcement portion with a section which extends within the compartment and flange sections which extend forwardly about the outer wall.