In the diagram, OAB is a sector of a circle with centre O and radius 8 cm. Angle BOA is \(\alpha\) radians. OAC is a semicircle with diameter OA. The area of the semicircle OAC is twice the area of the sector OAB.

(i) Find \(\alpha\) in terms of \(\pi\).

(ii) Find the perimeter of the complete figure in terms of \(\pi\).