I've used both G Carlson's program and the program from Blue Peter
Designs, both free.

Carlson's program is for plywood boats or boats made of other "sheet goods"
I suppose, eg steel or aluminum. These boats are made by cutting out flat
panels and attaching them along the edges. The program even produces
coordiantes for cutting out the panels, and a computer file for automatic
cutting of the panels (Carlson sells automatic panel cutting equipment).
Carlson's file includes hulls contributed by other users, and there are
some add-ons and instructions written by users on various websites on the
Internet. The program also creates files that let you transfer the hull to
other CAD programs. You can get help with his program by asking here as I
have done. About the only thing I don't like about this program is it
won't let you have straight lines anywhere. It uses the usual curve
fitting algorithms between points and will not just draw a staight line.

The Blue Peter program I used was for DOS but I've heard they now have a
free Windows version. It can be used for smooth hulls, not just flat panel
hulls like Carlson's program. It also calculates more design metrics than
Carlson's program. You can get it to change the curvature in the curve
fitting algorithm, or draw straight lines, but it's, um, technical and I
was not able to use it.

I used both programs on a study for a plywood micro-cruiser and documented
the process on my website (see below) for other amateurs who might want to try
their hand at designing a boat. Look under "Boats" then "Designs".

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