A simple diamond bow kite, like we used to buy from High Flier for 10 cents, is about 50% longer than it is wide, a slight bow in the cross stick with some string, and about 5 or 6 feet of old bed sheet for a tail. We used to make these out of willow tree sticks and news paper, and string recovered from the local fields that others had left behind. Google High Flier or paper kites and I know there are several web sites devoted to them.
Good luck and have fun,
Dan McEntee