I have been learning to use Google sketchup for drawing 3d optics for
work but it has occurred to me that it would be good for designing
boats as well. The basic version is free to download. It does have a
learning curve but after only 4 days using it I have mostly drawn the
types of 3d images I have long needed for my strange optics. It might
take another week for me to get proficient enough to start drawing
complicated objects like boats.