There shall be a Planning Board of Appeals consisting of three
members and three associate members. Such board shall have the duties
and authority provided for it by law or given to it by vote of the
town. Associate members may be designated by the Chairman of the Board
to sit on the Board whenever, for any reason, fewer than three regular
members are available. The members and associate members of such board
shall be the members, respectively, of the Zoning Board of Appeals.