The mainsail and jib on the Star 45 are self tending. That is they can swing from side to side as the model tacks without requiring the sheets to be tended.
Originally on the old model the jib was loose footed and did not use a jib boom (aka a jib club). The addition of a jib club allowed the jib shape to be controlled.
Like the main sail the foot of the jib will fly up is some type of vang is not in place. Typically a swivel is placed along the forward end of the jib boom and clipped to a deck fitting (aka jib rack).
Look at the jib as a triangle. The halyard pulling the head of the jib places a force on the jib swivel. As the swivel is moved forward and aft along the jib boom the leach of the sail has more or less ability to rise. The head of the jib also moves off center.
It is possible to find jib boom fittings that anchor the forward end of the jib to the bow and use a vang to control the lift of the boom. These are known as radial jib fittings. The jib stay attaches to the radial fitting. This has the advantage of staying taught against the back stay as the sails are trimmed,
The jib boom and swivel also pull against the back stay. Since the jib stay attached to the jib boom in this arrangement moves off center and is subject to varying wind forces the tension on the jib stay and back stay will vary.
The driving force of the sails is changed when the slot between the mast and jib changes. Finding the best spot for the mast and jib swivel/radial fitting adds the challange of setting up the sails prior to sailing.
