100K sounds like a ridiculous sum of money for daysails and occasional weekending on a boat you aren't totally happy with. I might get my head chopped off for sticking my neck out here, but I suggest you use no more than 1/10 as much and invest the rest for the catamaran in another 8 - 10 years. 10K can get you a very nice first timer's mono cruiser, including the first year's cost of ownership.
Alternatively, join a sailing club and use their boats. You'll gain access to sailboats, other sailors, their collective knowledge, and you'll forego many of the headaches associated with boat ownership. Or, another approach: last summer I met a woman here in Maryland who simply crewed for others; at the end of the season I asked her how many times she had gone sailing. Her answer shocked everyone in the room: 35 times!