Ljungström rig

Ljungström rig is the name for the sailing rig designed by Swedish engineer Fredrik Ljungström with double main sails and rotating mast, but without boom, foresail, forestay and shroud. The early models of the Ljungström sailboat had a stern stay but this was omitted around 1945, before the model 12 (Vingen 12).

The Ljungström rig is competitive towards the competing rigs from that time when close hauled and full run but is lacking at beam reach and broad reach. Its main purpose and advantage is, however, safety and ease of handling.

The first Ljungström rig was developed by the Swedish engineer Fredrik Ljungström to enhance safety at sea. The family had been close to severe accidents with the traditionally rigged Ebella, nowadays named Beatrice Aurore, when in hard weather the crew had to walk on deck to take in sail. Ljungström, in order to not risk the safety of his crew, designed a boomless rig handled completely from the cockpit.

The mast is made of glued clean wood, conical, without stays or shrouds. Boom, pole, gaff, spreaders and such are completely omitted. The mast is supported by two ball bearings, one at the keel and one at the deck hole, and can thus rotate freely. The rotation is created using a wooden collar, with a V-shaped track, around the mast below deck. Around this collar an infinite rope sling runs through two blocks to a winch, powered by hand or an electric motor. In this way the sail is rolled onto the mast when less area is needed or when the sailing is finished. As a result of the conic mast, the clew will move up the less sail that exposed. As a result of the mast taper the clew will end up higher and higher the closer it is to the mast.

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Wikipedia