Conventional trimming devices are of complicated design or are little suited to handling (manipulation). In order to provide a sail trimming device for a rig which is better than this, it is provided that the rear boom end (5) can be swivelled out of the common boom spa plane about an axis of a joint with respect to the remaining part of the boom (1). In the pivoted position after fastening of the boom head (3) to a mast and anchoring of the outrunning rear end of the sail to the boom end (5), the desired trimming can be undertaken by swivelling the boom end (5) back. A length adjusting device for the boom (1) offers a support function as a supplement or alternative. The sail trimming device is suitable for a rig. <IMAGE>
