I managed to mend the mast with a piece of alum pipe 3' long by inserting it into both broken ends and then lightly welding the exposed seam, pipe fits snug, and seems to be quite strong. this mast was broken near the bottom.
fixed a few small holes and pushed her into my lake where she floated for days without sinking. I figured then that I must have gotten an ok deal on a free boat and tryl.
after downloading the owners man. for this boat "Prindle 18" it seems that all my parts are pretty much accounted for.
Does anyone know where a newbie such as myself might find a inexpensive set of used sails that would be sufficient for my self taught cat-boat primer and swimming lessons???
Its been my experience to "BEWARE OF FREE BOATS", but I would say to watch Ebay, every now and then stuff comes up at a good deal. The reason I say beware free boats is that often you can buy a boat with sails for cheaper than you can buy a set of sails. I hope you find some though, you might also try www.thebeachcats.com, they have a parts section. There might be one here on catsailor.com as well. Also, contact any local sail lofts, sometimes they commision used sails. And last bet, call http://minneysyachtsurplus.com/ there is no telling what they have floating around.
I don't know.. It sounds like an accident waiting to happen. I hope it's a shallow lake, so worst case scenareo you just get wet and walk to shore. If the mast broke the metal is probably fatigued. And that may be true for all the other metal parts as well. There are so many parts that can break on these boats that would just leave you stranded.
If you do get this boat running, do stick close to shore and sail where people can help you.
good luck
Geesh fred - cut some slack! 
The boat is probably fine - welding alumuminum can be tricky but anyone that can do it and end up with one piece is probably pretty reliable at it. A mast has very specific bend characteristics, but reliable repairs at the base will have little affect on things. Prindles are pretty good and solid boats - biggest problem I've seen from them is soft fore decks (as a lot of catamarans from that era had). For used sails, try a couple of places. Dan Berger (who frequents this forum) sells a bunch of used parts on ebay as username 'catreaper'. The Sailing Pro Shop (www.sailingproshop.com) in Long Beach, CA occasionaly has some used stuff too. Buying another used boat for it's sails and/or mast might be an economical solution (as Josh suggested above) too.
P.S. Fred - will we see you in Hollywood again next year?
wonderful, this site kinda kiks ???
thanks everyone for the help 
Yes - it does! But if you're going to hang around here, I might suggest replacing your avatar with an image of that resurected Prindle instead of that monodull!
Not that it helps now, but a sailing school had NEW P18 sails with their logo on eBay a couple months ago for next-to-nothing.
Here are a couple "used parts wanted" sites that might help:
Yacht-sale.com
tedknowlton.com
I guess from the original description I pictured a dilapitated piece of S**t. With my boat, which is in pretty good shape for its 20 years of age, I'm always wondering if there are any unseen areas that are suddenly going to let go and leave me stranded in the bay. With a boat like what I imagined, I could just picture every component, from tang to tang, being a possible failure point. Including the mast, which has apparently already failed. Having said that though, I would be the first one to probably take a free boat if I thought I could fix it.
I'll be in Hollywood......will you??
I knew my name would come up in a discussion like this (thanks, Jake!). I do have a set of P18 sails that I was just about to put on eBay. eMail me at: danberger@mindspring.com and I'll send some pics and particulars.
The P18 is one of the best boats I have had! They are good and solid and just a pleasure to sail. However, some of the parts are a bear to find. I would start collecting rudder castings and rudders because they break easily and you can't find them when you need them..
I have access to a main at least. I can get some particulars. I think we're a little closer together if you might want to pick it up. email me if you're interested. try stiletto444 at catsailor dot com ... you know the drill.
Clayton
about the mcgregor boat in the picture, I grew kinda close to it after 5 straight days with it in stormy weather, the last 1 of witch I was aboard her belly 11 or 12 miles out in the gulf. she is just a relly good friend