The most commonly replaced sails, therefore, are the No. 1 genoa, half-ounce spinnaker, and then the mainsail. In most sailing venues, No. 3 jibs are not used as much, so they tend to retain their design shape longer. Baxter and Keyworth both say careful planning is a must, so when it does come time to replace the No. 3, an owner can slot it in.