Spinnaker trim really falls into two categories; sails flown on a pole and sails flown on a fixed sprit. There are also a very few boats that fly asymmetrics on an articulating sprit but in general those articulate through a small enough range that flying them is nearly the same as flying a sail on a fixed sprit. However what you are trying to accomplish is the same in all cases. For that reason this article will focus mainly on trimming spinnakers flown on a standard spinnaker pole with some ideas on how to incorporate the same ideas for sprit sails.

There are four main controls you use to obtain the shape you want; pole position vertically, pole position horizontally, sheet tension, and sheet lead position. Basic wisdom has always been to fly the spinnaker pole pulled aft so that it is perpendicular to the wind, fly it high enough so both clews are level (on symmetric sails), then ease the sheet out until the luff of the sail just starts to curl over. While this will get you close it will also leave you lagging behind the good trimmers that take full advantage of all the controls at their disposal.