Re: fiberglass powerboat into a sailboat
Okay, sounds like you've gotten a great view of your options from the various naysayers.
I won't add to what they've said about the hull or mast, since you seem aware this is a very unlikely hull to perform well. I wouldn't even worry too much about lightening it.. you can remove anything you won't need, like a windshield, mechanicals, wet foam, etc. You won't be able to take off more than about a quarter of the weight that way... a lot of it is in the hull itself. Unless you can lighten this hull by half or more it won't make much difference to your performance, therefore don't bother.
Plus, I hate to say, you're not half done. With a basic sail, centerboard, and mast set up you're still going to spend a lot of time getting the build done. You need to work on a mounting for the mast, at least two stays to hold it up, a way to attach a boom to the mast, sheets to control the boom, pulleys and winches for raising sail, etc. The hull is the least of the work, I'd just pull out the wet parts and call it good.
Edit: Just read that you realize that already... 3-4 months of full time work sounds like a realistic estimate. You'll need probably a few hundred Euros worth of materials too, minimum... glass, foam, etc.
Your Mom might be happier with a smaller project... one of the two sheet plywood designs would go together fast and have roughly the same ability to handle seas as this hull would, plus it'd be cheaper.
All that said, it WILL sail. Especially with a decent centerboard and mast. People make things sail all the time that aren't custom built displacement hulls. Including log rafts and bathtubs.
So, as long as you acknowledge that while it will move, it will be difficult to handle due to weight, and your top speed will be less than about 4 knots, I'd say go ahead and try.
The speed is due to weight and the limitations of the amount of canvas you can put up... your sail area is going to be smaller than optimal because you aren't going to have a super-strong mast or rigging.
I'd recommend you salvage a mast if you can't buy one. That tree wood won't work very well, and it'll add a lot of weight. If it was a different species, maybe. Small plywood sailboats use electrical conduit for masts, but that won't work well for you given the sail size you need. Consider looking for a sailboat with a broken or otherwise messed up hull and taking the mast and rigging... this will also determine the sail type you need and show you what kind of stays you'll need to keep the mast upright. Or look for any piece of metal or fiberglass tube that's at least 30 feet long and very stiff.
I salute your initiative and encourage you to post pictures of your progress here, so we can offer suggestions.
Erik
PS: If your Mom is worried about you not getting a from-scratch hull done, isn't she worried about having a torn up old boat sitting around?