This decision was made in the interests of manoeuvrability, since the center of thrust is in the outer part of the disk thus giving a larger turning moment arm.
Union Rotoiti was built with a large angled stern ramp that allowed her to unload her cargo at any wharf without the need for a specialist linkspan as required by most ro-ro ships.
She also had a bow door which could be used if a linkspan was present in a port, thus allowing cargo to be worked both forward and aft speeding up turn around time.
It was a feat never before accomplished with two ships of this size, and Captain John Warren of the Union Rotorua later exclaimed: ‘If anyone had previously tried to tell me it was possible … I would have thought them quite barmy’.
[5] On 23 April 1999, New Zealand Transport Accident Investigation committee reported Union Rotoiti as losing power in the Tasman Sea.