The Americans whalers, when working close inshore would tow their whales into port for processing, but when working far from port would boil the oil onboard, whilst still at sea.

In this drawing the upperjaw and attached whalebone is being hauled onboard ship. The blubber is being removed in long strips. These will then be chopped into smaller pieces and boiled on-board ship, in copper vessels known as "try-pots". The smoke from a try-pot can be clearly seen mid-ships.

National Oceanic and Atmospheric Administration
Flensing a whale and removing the baleen