Miami-based Sunstone Ships is poised to sign the third shipbuilding contract in a series of expedition cruise vessels to be built in China.

Sunstone ordered four firm vessels, with options for a further six, in a contract allowing the newbuildings to range between 100 and 200 passengers.

A steel cutting ceremony, attended by Sunstone’s chief executive Niels-Erik Lund, was held recently in China for the first ship in the series, the Greg Mortimer.

Simultaneously, a ceremony was held to mark the contract signing for the second ship in the “Infinity” series, which is scheduled to start delivering from August 2019.

The contract is now being inked for the third of the firm quartet which will be ice class 1A or Polar Code 6.

They are needed as replacements for older vessels in the Sunstone fleet and will be the first expedition cruiseships to use the Ulstein group's X-BOW hull technology.

Ulstein Design & Solutions is responsible for designing the ships, as well as delivering and supervising the entire European-sourced technical package.

But actual construction will be handled by China Merchant Industry Holdings near Shanghai.

Tillberg Design in the US is handling the interior design and Makinen of Finland the cabins and public spaces.

Lund describes the 120 metre long, 20 metres wide “Infinity” vessels as European cruiseships assembled in China.

The Greg Mortimer has been chartered to Aurora Expeditions whose shareholders have bought a 50% stake in the ship.