I'll add my agreement with what others have said. Women-only classes can be a fun way to learn, but don't think that you have to teach differently to women.
I've had too many experiences with watered down, touchy-feely, don't-be-scared-little-girl kinds of classes that were changed to be geared towards women. Yuck. Men and women both can fall into this teaching trap.
On the other hand, I've been in wonderful learning situations in women-only classes where the instructor had the attitude that she loved what she was teaching, and so would we.
As others have said, good instructors recognize and address the learning styles and challenges of the students, regardless of their gender. While there are some general trends, either gender can be aggressive or cautious, overbearing or timid....
I say go ahead and offer women-only classes and see if there's interest. Market it simply as being fun to learn with a group of other women. If you want to also offer a class geared toward those of both genders who are nervous about sailing or who need to learn enough to take over in case of emergency, do that too. Just please don't assume that all women are nervous, cautious, timid, etc.
-- An aside: I once took a 2 day women only ski class where the time on the hill was fun and challenging. The first day, after 3 cold action filled hours they served us a small half sandwhich with a tiny side salad. I guess women aren't supposed to get hungry

The next day I wasn't the only one with snacks in her pocket just in case.