I have just finished a new addon to design sails with Blender. Is a bit primitive, but is meant to use as much as possible what is already available in Blender without trying to make specific tools for 3D design.
What is really available is the algorithm to flatten a 3D surface and a couple of algorithm to generate the profile of the sail.
The motivation for this work is, apart from the wish to design a sail, to have a free tool that can accomodate different type of sail profiles and is expandable. Blender was providing an already available 3D manipulation and visualization tool and was a good point where to start.
I have started a website for the addon, that you can find at http://sailflow.weebly.com. There you will find also the link to the videos explaining how to use the tool and what techniques to use to design sails.
I am interested in find people interested in this topic and may be interested in working together to expand the addon.
Source code can be found at http://github.com/blueluca/sailflow
Hope somebody enjoys it.