Re: How to make my own sail?
There is a company that sells Tyvek in sufficeint size for small sails but I forget their name.
What you want to make is a Lateen (like a Sunfish) sail because it is "cut flat" meaning it has no curvature. A lateen rig is about the simplest way to put a sail on a small vessel. I made many for my homebuilt 12' MiniCup sailboats beginning with the duct taped version and finally sewing an overlap at the edges thru which I put grommets. These grommets were used with big zip ties to hold the sail to the spars. My latest sewn Tyvek sail has lasted for years.
For spars, I went to Metal Supermarket and bought thin walled Aluminum tubing for the two that carry the sail and a shorter piece of 1/8" wall for the short mast.
You might consider building a modern version of a MiniCup as the plans are free on the Stevenson Projects website. Somewhere out there, I think I still have my old site called MiniCup Madness about my adventures with them.