As some of you know, I put a jib on my Adventure Island for light air use. In practice, I find I don't use it much, because if the wind is that light I go powerboating instead. However, I left the little piece of braided line that I use as a halyard attached. When I'm sailing, it flaps around up there, messing up air flow over the leading edge of the sail.
I figured I was imagining things, thinking it could really affect performance very much. It's just a little line, right? Well, have a look at this image from Garry Hoyt's website:
Wow, a little wire creates as much drag as a huge foil, and putting a foil fairing around a round mast reduces drag up to 75%! Makes me wonder why all the racing sailboats don't have plastic foil shaped fairings on all stays and shrouds. It also explains why I thought my little line was creating a lot of drag: it was! Off it comes until I actually want to use the jib.
The AI sail, when fully deployed, creates a nice fairing from the mast to the sail. Once we reef, one side of the sail is flush with the mast, while the other side has a big bump. This creates a favored tack. My left handed wife made me reverse her sail control lines, so her sail rolls up backwards. This means that when reefed, my boat sails better on starboard tack, hers better on port tack.