This is a simple winder for KAP. KAP generally uses strong single-string kites as lifters: you get the kite and the camera up there, and you don't do a lot with it once it's there. Meanwhile, you want to be working your controls to take photos.
This is a design that I've seen around on the internet for a while. I'm sure the resemblance to a Klingon bat'leth is entirely coincidental.
Step 1: General dimensions
You'll need a piece of wood about 26" by 7". A lifting kite can put plenty of force on you, so choose something thick and strong - a floorboard or a bit of sturdy plywood is ideal. I've got MDF, because that's what was handy.