What you back a bow with depends on why you want to put a back on it.
If you want to improve the bow’s cast, fiberglass will do that. But fiberglass cloth won’t add much because only about half the fibers are aligned with the bow.
If you want to protect the bow from splintering, then there are more options.
I know you don’t want to use rawhide, but I thought I’d mention that it does protect the back of the bow. But it does NOT add any cast. In fact it can dull the bow a bit.
Cloth works really well to protect a bow and can give it a nice look. One of the older members of this forum, Duncan, posted some pictures many years ago of some self bows he made backed with some mossy oak cloth he had. They looked great.
Heavy duty paper works well too. It can be dyed black, brown, or whatever. A lifetime supply can be had from the painting isle in Home depot for a few dollars.
If it was me, I’d leave the fiberglass and epoxy on the shelf. It will add nothing to the bow you are making.
