In reply to Bill Roberts

I found a lot of things didn't scale to 14 ft. In fact I have deep respect for a designer who can create a 13-15 ft cat, that can hold normal sized people, go fast and not do something strange when it hits the edge of it's envelope.

In response to Maugan.

Yes auto designers use CAD. However, it is not like magic. The CAD program does not do all the work. The CAD model acts like a common interface to let the engineering teams perform their work and then return their inputs. That does not sound like much until you realize that normally, a project engineer sends a design to the engineering teams. The engineering teams laboriously create models using their tools and return their results. Finally the project engineer iterates with the teams to produce an acceptable design. This is great until one night the project engineer wakes up in a cold sweat thinking, how can I be sure all the teams are modeling the same thing? Did acoustics include my 5th wheel or they they think it was a coffee stain on the drawing?

There are some Analysis/CAD systems that will let you design and analyze simple systems, like catamarans, but they are very high dollar and still require experience to interpret the results. Also they need to be calibrated against reality for every type of system you will use it for, at least once.