How do I fly a cruising spinnaker?
Eric Waters responds:
There are typically two ways that cruising spinnakers are flown—with or without a dousing sock, or what's occasionally referred to as a spinnaker sally. Most short-handed cruisers on larger boats prefer the safety and simplicity of using a sock.
Flying the sail with a dousing sock, I would attach the sheets while the sail is still in the bag. AirForce sails provides a tack pennant roughly 15 feet long spliced to the tack ring. The bitter end is then led to a foredeck cleat. The sheets should be led as far aft as possible, and should be 1.75 times the boat length and preferably led to a snatch block on the stern quarter. The sail with the sock covering it is then hoisted, Typically, I recommend that you sail with the sock and spinnaker in the lee of the mainsail when deploying and dousing the sail for the first few times.
You are now ready to raise the dousing sock, or uncover the spinnaker. At this point, as the sock is fully hoisted, you will begin to change the boat's heading so that the spinnaker is no longer blanketed by the mainsail and then sheet in on the spinnaker sheet.
Of course you don't have to have a spinnaker sock, and many boats don't. If you don't have one, just be sure that you coordinate all of your movements and have all of the lines ready before you hoist the spinnaker. Before you set the spinnaker, remember that the tack pennant should be adjusted relative to the apparent wind angle. The deeper you sail, the more eased the tack should be. And the closer you sail to the wind, the more you should pull the tack line down so that the tack itself comes closer to the deck. This helps keep the right amount of luff tension in the sail for the heading of the boat.
To trim the spinnaker, you essentially want to do a little early experimentation to find out just where the sail will "break" or collapse. To do this, get the boat on the heading you intend to sail, and then, with the spinnaker flying, begin easing the spinnaker sheet. As you do this the sail will initially get full and then the luff will begin to fold in and ultimately collapse. With most spinnakers, you can afford a little bit of fold, but beyond a foot or so of cloth, you'll risk collapsing the sail too often. If you intend to set the sail and not adjust the trim frequently, it's best to over-sheet. Just ease the sail until it begins to fold and then trim it in until it won't fold on that particular heading and it should be fine until the wind angle changes significantly. Like any other aspect of sailing, all of this will vary relative to the boat and the conditions you're sailing, so spend a fair bit of time getting to know the sail and how it trims before you let it tend itself for too long.
You might also want to have a look what Brian Hancock has written here at SailNet on this topic. He has two articles: Using the Asymmetrical Spinnaker, and Refining Your Downwind Sails. Best of luck to you.