Billy from Primitive Pathways, came out with a new movie and he had some piaute bow fragments. They had a strange V notch at the tip. Billy said he thinks it was there to wrap the sinew around the tip and I don't think he is wrong at all. In fact I think he is very much correct, but I think it may have also served another purpose. A string groove that you can wrap the string around! I have done some testing and it has a lot of benefits actually. You are able to reduce the weight at the tips significantly, it wears less on the string, and you can leave the string tied onto the bow from both ends.
Here is the bow I tested on, before I changed the tips to the piaute v notch, I had just normal side string socks. It was 46" ntn and 40lbs at 23" draw. It flung a 400 grain arrow 130fps, not awefil but not great either. Then I cut the tips off and did the piaute style v tip notch and it was still 46" ntn and 40lbs at 23" draw, but now it flung a 400 grain arrow 150fps! A major increase in speed. So if somehow that is not what it was for, i found a new way (new to me at least) to string a bow.
