Not sure, but I imagine that the hulls could be assemble for less than £10.
And that would be one for you and one for your dad...
If you have or can pick up a small hand jig saw, or coping saw, you can probably have
your springer(s) framed up in a weekend.
- Use the small hand saw to cut a pair of sides.
- Then cut some rectangles for the front and backs.
- Glue and Nail the front and back pieces in place.
- Then sheet the bottom with thin plywood, or balsa...(or what ever is handy...)
- Then Laquer or fiberglass to waterproof the wood.
After that we can get into how to add running gear. (motor, propeller, rudder)