By the way, it's definitely not medieval. And neither really is animal hide glue for fletching, based on all the extant arrows we have.
I dunno if you've read my SUPERBLY written article on the EWBS page
but evidence suggests that the "fletching adhesive" was actually a compound made of pine resin, tallow and beeswax. It goes on like a liquid, sets almost instantly and the fletchings are bound down into it. It's then reheated and that causes the compound to become liquid again, flow over the bindings and around the quills and secure everything extremely tightly in a sort of plastic-like casing.
You can just use pine resin - cooked down gently it becomes a glassy liquid which is extremely sticky until it sets. On it's own it sets in a few seconds and goes brittle like glass, but cut with some wax it becomes just right.
