Sounds like you're looking at a skin-on-frame boat, which at least eliminates the need to scarf plywood.

You may still need joints for stringers and other longitudinal parts. If you don't have access to epoxy you probably don't have access to other waterproof glues like Titebond III either. Scarfing without glue can be done, probably the easiest way is how the aboriginal builders of kayaks would have done it, by binding the joint.

The trick to preventing a bound scarf joint sliding apart without using nails is a simple one, just drill and insert a couple of small wood dowels, or if those aren't available you can carve pegs, called trenails by the boating community; thick copper wire should also work.