Not being a nautical engineer, my guess would be that the size of lee or center board is linked to the total sq. footage of sail. I am just guessing.
I was wondering why would a barge have a sail. Most barges here aren’t powered at all. They’re just large cargo carriers pushed around by tugboats on the lakes or the rivers. But if you want to run one up the coast, I can see why you would need a sail.
Yes, a Chinese junk. Jbee, I thought the same thing when I saw the photos.
Duane