When I was 11 I started to build a sailboat. I built it through a non-profit called The Youth's boat builders (Ungdomarnas Båtbygge, UBB). At UBB children and teens get the tools and instructions to be able to build wooden sailboats. The boats are built by kids with close to no help. For some more complicated and dangerous steps grown-up help is required.
It took me about 8 months to get the boat seaworthy, by that time I had turned 12.
CAD drawings of the plans for the boat
Things I learnt
Even if it might not look like it the boat is mostly built out of wood. The hull is 4mm Gaboon plywood sewn together and the reinforced with glass fiber.
The main, jib, and gennaker are all sewn in house. While I was too young to use the industrial sewing machine, I got to cut out and tape all sails. I got to sew the boat cover and some sail-bags on a smaller machine.
The boat was spray painted with two part automotive varnish and paint.
The mast, boom, and bowspirit are all made out of hollow composite tubes. The tubes are made by laying up the carbon fiber on a flexible form, the form is then closed and a balloon inflated on the inside to lock the round and hollow shape.