: As I would someday like to build boats of my own design, I wonder where to
: start. An obvious place seems to be to take lines from boats that are
: close to what you want as a starting point. Is this stealing a design?
: Richard

If you just build the boat based on the lines, yes. If you use the measurements as a starting point for creating your own, original design, maybe not. It depends on how much you change it. If you just change the width, length and/or height, yes it is still stealing. If you harden the chine, add more rocker, change the rake of the bow, move the volume aft, and draw a completely new deck, no it is your own design.

If you take a few pictures of a boat, measure the length and width and generally try to match the performance features of a kayak you like, but do all the work of creating your own set of lines, it is your own design. But taking a full set of lines from a design and then tweaking it slightly is probably stealing.

There is no hard-and-fast line between stealing and being inspired. If you feel you are getting away with something, then you are probably on the wrong side of the line. But if you aren't taking any risk with the design, because it is almost identical to a good one designed by someone else, then you are stealing. If you think there is a risk it might suck, then it is definitely yours. If it works well, be proud of your design.

If you want to design your own kayak, I would suggest trying a lot of different designs. Check out their hull shape. Look at the lengths, widths and heights that work for you. See how much water they draw when you sit in them. Watch them move through the water as others paddle them. Feel how they ride over waves, how they lean, how they turn. Listen to the water flowing. Try to learn all you can about how their shape effects their performance. Then draw something up based on what you have learned. Build it. Paddle it for a year and start drawing up another...

If you have the interest in designing your own kayak you probably already have definite ideas about how the shape effects the performance and you probably want to implement your ideas. If you don't have these ideas, and the best you can think of for starting a new design is to copy someone elses, then you really probably shouldn't attempt "designing" a kayak yet. You are ready to design when you think you could improve on every design you paddle.

The first requirement for designing your own kayak is having ideas of your own. When you have them, go ahead and try them out. If they are your ideas, then the implementation is your design.