I just posted a reply specific to your Mill Creek question on your original thread.

A sailrig for your kayak/canoe is a great idea. I've sailed CLC's red demo boat (CH17) a few times and it was a blast. It's a little different from sailing a "normal" sailboat. First, it feels a lot faster than it is since you're so close to the water. Second, since you're so close to the water it can be quite wet. On a hot summer day it's wonderful, but if you have colder seasons you may need some warm boating clothes. Third, it's very stable, to the point that with a strong wind it may submarine or dismast itself instead of going over. Don't worry, it takes a lot of wind to do that and it's pretty easy to see that trouble is approaching, but you have to know to be looking for different signs than in a "normal" sailboat. Finally, tacking is very different than in a sailing dinghy because of the amas (outriggers). You can't just push the rudder over and expect it to finish the tack on its own. You need to sail it through the turn. In his Life of Boats blog article, John Harris has a very nice discussion of the sailrig, including boat recommendations. He says "Shorter recreational kayaks won't match the top speeds of traditional sea kayaks, but they will be easier to handle. " so an MC13 sounds just right. FWIW, I am building a sailrig for my WD12.

All that said, if you want to build a boat specifically for sailing instead of just adding a sail to your kayaks, I'd recommend the Tenderly dinghy. It's 10 feet long but feels bigger on the inside, very stable and forgiving but capable of some really fun sailing and is very suited for a learning boat that can be used later for big adventures. The sailing skills you pick up with that boat will easily transfer to any other. With the boats that you've already built you have all the skills needed for building the Tenderly. It's also really easy on the eyes.

Laszlo

   Thanks for the information the Tenderly dinghy look like a good option. The information on the kayak sailing rigs was also very helpful. I think I probably really want to build another boat, imagine that.