The first is a hemp sling with sinew wrapped round and round on the places were wearing occurs the most severly :the release cords fist ~6 inches as the stone slides on it.Also the release knot sometimes get's blown off..so the last 2 inches are also wrapped with sinew. I would bet it will longer the slings life quite a bit.
The second picture as braided entirely of sinew,and it feels as sturdy as paracord. Again, i'll have to test it
@ Dan:No dogs ..yet
@ Bill Skinner: here, also it's quite humid,and I suppose waxing generously should keep it sealed
@ Thearos: I knew about the reference about sinew being used for balearic slings..this gave me hope that it should work.
I love hemp,but with local stones it deteriorates quickly...and i seem to blow off the knots fairly quickly too..so i hope a half hemp(retention) half sinew(release cord sling should last much longer.