Sailing downwind in light wind (say 3-8kts) can be a little frustrating, especially if there’s any sea left over from earlier winds and your sail inventory doesn’t include light-air or downwind sails. In those conditions, the mainsail typically slats back and forth as the boat rolls about, and the jib collapses and fills, often blanketed by the main. Dropping the main and sailing under jib alone quiets things and saves wear on the rig, but a modestly-sized headsail doesn’t provide the area needed to move the boat adequately – as is the case on the cutter-rigged Cape Dory 36 with a Yankee jib.
A great solution for gaining a bit more speed without the expense of a spinnaker, and without too much fuss, is to hoist two headsails. In our case, we pole our Yankee jib on one side and sheet the drifter off the end of the boom on the other side. Since the Yankee is on the furler, the drifter is set flying (or loose), attached only at the head, tack and clew. If you don’t have a drifter, the same configuration with a genoa and jib would work.
Here is a short video of the twin headsail configuration we use aboard Ariel, a Cape Dory 36.