I built an Arctic Tern and found the sheer edges very easy to bevel with a cheap ($6) mini (1"x1"x3") block plane that I found at a woodworking shop. Assuming you don't have a small block plane and it's not worth the time to go out searching for one, a coarse wood file will do a fine job and won't take much more time at all. After using the block plane on the main part, I used a file at the very ends to get a nice, sharp point on the panels.

Happy building! Dean