This summer some of my colleagues raced PocketShip #1 in a local PHRF series. It was a summer marked by a lot of dead-calm conditions, and as ever the racers were looking for a way to find more speed.
I devised a "jackyard topsail" of 24 square feet. Our sailmaker stitched it up and we used a pair of anodized aluminum bimini poles for spars.
It came out well. In very light air, the 16-percent bump in sail area DOES make a difference in speed. Some caveats:
1. We had to add a halyard to PocketShip's already crowded masthead. In order to be able to hoist and take in such a sail, you really need THREE halyards: one for the peak, clew, and tack of the topsail. This was going to guarantee a monumental tangle of running rigging, so instead we simply snap-shackled the lower yard of the topsail to the gaff yard. This took a number of tries in the parking lot before we got the snap shackles in the right place for a good sail shape. The only way to get the topsail down is by lowering the entire mainsail (managing topsail halyard, peak halyard, and throat halyard simultaneously). This works with a racing crew of three good sailors, but would be a handful to work singlehanded.
2. Such a sail is helpful only in VERY light air. 7mph or less, with little or no danger of gusts or rising conditions. A strong puff would knock you flat. Again, not a great sail for casual use!
3. The topsail yards are almost ten feet long, making it hard to stow the sail when not in use. The bimini poles are telescoping, and I thought I'd be able to reduce the length enough to stow the sail in the cabin. But the friction-adjustment on the bimini poles wasn't strong enough and they had to be riveted to length permanently.
Certainly looks the business in photos!