That's
funny, I had never heard of Cowan lake either until I started sailing
The reason Cowan and Heuston woods are for sailing is becouse they both have a 10hp
motor limit. All the other lakes, like ceasars creek, eastfork, etc... are just completely overcrowded with
motor boats (except during the week, then you have the entire lake to yourself). I actually sailed on ceasars creek several times before finding Cowan, but it was really frustrating being a total noob, trying to teach myself, and literally being surrounded by jetski'ers and tow-behind tubes and all the crazy weekend drunks!
It was so frustrating I almost gave up and
sold the boat... Finding Cowan lake was a lifesaver.
I think there is another lake with sailors, rockyfork, or something like that. They have bigger sailboats that older folks own. They usually raft up in the middle of the lake and get drunk on the weekends, not much real sailing...
Brookville lake has a real sailing marina, real sailboats, sailing association, races (both one design j24's and PHRF cruising boats), cruisers, everything you wouldn't expect to find in a little inland lake

I think the guys at strickly sail are pretty well tied into to all the happenings there, so they are the one's to talk to about it.
I think Hueston Woods has a sailing club and races, (just like Cowan Lake) but I never went there to check it out because Cowan was closer and more than good enough for me.
My boat was a little sunfish type of boat, it's was actually a
Sear's Jetwind. It was a lot of fun, but I'd recommend a different type of boat for these local lakes. The lakes rarely have any
wind worth speaking of. And when the
wind the does pick up, it's too much for this type of boat (a real sunfish would probably be much better, but my jetwind with Nylon sail and my 180lbs did nothing but make the boat hard to handle in anything over 15knts). The problem with sunfish types is you can't ever reef the sail.... I'd recommend a little 'daysailor' type of boat. Something between 14-20' (or so) with a cubby hole, or even a
cabin, to store stuff in, real seating instead of just a footwell and
deck. You want to be able to bring a few things along with you, life jackets (because the watercops will check you out occasionally), cooler for the
beer 
, an
anchor so you can stop and go swimming in the summer,
fishing gear, etc... the sunfish is just sailing and nothing else. A Laser would be a really fun boat if there was enough wind, but the wind around here is either fluky and light, totally non-existant, or 20+knts. It's still fun to get out on the lake though no matter what the wind is doing. All of these smaller boats will do a few knots even in nearly imperceptible wind.