How much performance do you want as opposed to ease of handling, affordability, long life and simplicity? Do you expect to add more sails to the wardrobe over time? These are the factors that will affect the sails you purchase. Start out by making decisions about these factors and talk them though with your sailmaker.
The mainsail is pretty straight forward, and apart from possibly adjusting the mast height the main thing to consider is the width of the head or square top. Wider is more powerful but requires good leech tension and it can take more effort to raise and lower the main.
Headsail selection is more complicated and the decisions will be based on how many headsails you are planning on, where they will sheet to, and where the tack point will be located.
By headsails I mean any sail with the tack point forward of the mast, not just windward sails,
Selecting a headsail wardrobe has always been complicated and potentially confusing. Well its not getting any simpler. New developments such as the structured luff, top down furling, and upwind screachers/code zeros are further complicating the issue.
You really can't finalise your sail plan without making decisions about where you're going to tack the gennaker and asymmetic spinnakers if you're going to have them. These three images help to demonstrate why.
Above we have a really neat setup with an extendable pole designed and built by Alan Carwardine for his Stealth 42 cat Coconut.
Don't try this at home . It's a fairly complex to build but Al is a master at rigging details and this is not his first attempt. The pole mostly lives inside the tube and it can pulled out to fly the assymetrics.
I'm not sure about the sail arrangement here but I expect the inner furler is for the Code Zero or Screacher, the furler on the forebeam is the genoa, the furler on the pole is gennaker, with a standup block on the pole extremity for an asymmetric spinnaker. The pole can be removed is required to save on marina fees but probably lives as shown here most of the time.
This is a simple and relatively compact arrangement that can be built economically by any rigging company. Note that you need sturdy local reinforcement on the inboard side of the the hulls to carry the side load from the brace wires.
This is the bow pole arrangement on trimaran Venom. It is similar to the setup on Coconut in that it is partially retractable, but is different in that it spends most of its life extended but can be retracted when not in use.
The ideal basic setup if the budget and deck arrangement allow is a three headsail arrangement not including the storm jib.
1. A working headsail tacked to the bow, most commonly a self tacking jib. For a little more power the working headsail can be sheeted on separate tracks either side and slightly aft of the mast. For the self tacking system the headsail sheet leads back to the cockpit after going forward on the deck close to the tack point, or leading up the mast, back to the deck and then aft to the cockpit. If the sheet is to go up the mast this needs to be communicated to the rigging company in the design phase.
2. Screecher or Code Zero
This sail fits the range between a genoa and spinnaker and in recent years has become popular as an upwind sail on multihulls. Screachers and Code Sails can do the same thing. The name Screacher is derived from combining reacher and spinnaker, so they were generally intended as downwind and reaching sails, as were Code sails which are still regarded as reaching sails on monohulls, typically with a mid girth measuring between 50% and 75% of foot length.
For multihulls the Code sail has developed into an upwind or close reaching sail largely as a result of the way it was rated under the OMR, tacked forward of the bow and providing substantially more area than the working genoa. It sheets inside the shroud and its size is limited by the foot length available before the leech engages the shroud. It is normally set on a furler and to be effective upwind it needs to be able to be tensioned with a tight luff.
My preference is that we drop the Screacher terminology and simply refer to these sails as Code sails, with the defining difference within the category being the area and the intended angles.
The code zero has lagely taken the place of the genoa on cruising catamarans because it avoids having tracks on the cabin top and the complication of leading sheets down to deck level.
3. Gennaker or Asymmetric Spinnaker.
This sail maximises downwind performance, especially in light air and gains maximum are by being sheeted outside the shroud and as far aft on the deck as possible. On a cruising boat the tack point might be the same point used for the Code Zero. On a high performance boat it is more likely to be set from the tip of a long bow pole. A variety of equipment can be deployed to make it easy to raise and lower the gennaker including furlers and snuffers of various types. If it is set on a furler of has a structured luff then its a gennaker, not a spinnaker.
4. Asymmetric Spinnaker
A free flying headsail that is designed for downwind angles and does not have a structured luff or furling gear. It generally requires a couple of fit crew members to deploy and retrieve the sail so is not a common addition to a cruising wardrobe.
For Asymmetric spinnakers you can safely call them A1, A2, A3 etc, with the number increasing as the sail gets smaller, gets tacked further aft, and generally gets hoisted lower on the mast, although two or more sails will sometimes share a common hoist. The A1 is typically hoisted to the masthead and and the tack is located at the forward point of the bow pole for maximum exposure.
Designer's Advice; Don't get too hung up up on what the sail is called. They will get called different names from loft to loft, from crew to crew and their design features will continue to evolve and confuse us if we let them.
Time Machine susing a large asymmetric spinnaker for power in the light air. The long bow pole not only enable more sail area but provides a large slot between the jib and the spinnaker, helping to clean up the air flow in the slot..
Sail Plan for Trimaran Venom. Sailmaker Ben Kelly worked closely with the owner on the development of the sail plan but the builder Jamie Morris and rigger Joel Berg were also closely involved int he process.