Make a Bundle Batten fom Trash
Bundle battens are simple shop-made tools for drawing fair tight curves. This is one of those tools you can make while taking advantage of what would otherwise be scrap and if you’re lucky, you can use materials that don’t require any extra processing. In this case, mine happened to be a bunch of consistent offcuts from the table saw.
If you can’t find or don’t have some copper rivets, go ahead and improvise some other fastening method such as some clenched over nails or even use some wire to bind the batten together.