Hey blacktail,
I've made several sinew bowstrings. When I make my loops, I just make a plaited loop for the top loop. It's illustrated on pg 223 of the Bowyers Bible, Vol. 2. The bottom loop you can just make with several half-hitches, but I prefer something not so permanent because sinew strings will stretch in high humidity, so they sometimes need adjustment.
I use leg sinew for my bowstrings, but I had a friend tell me that back sinew works much better and you can make a string much faster with back sinew because you don't have to make nearly as many splices. Leg sinew bowstrings usually take me 2 hours to make (sometimes more, depending on length), but that's also because I chew every bit of sinew before I twist it into the string. It would be much faster if I made them from dry sinew, but I prefer chewing it because it activates the natural glues and makes for a more cohesive string. Although when my chewed sinew strings finally dry, they are really stiff and somewhat unwieldy until they break in. That makes tying knots a challenge. Hope that helps. If you have any more questions just send me a PM.
Billy
