The bow was a fun piece to model. Included below is my reference image for the bow and my model beside it.
For the string though, it was a bit difficult to see the details of how the bow string was tied, so I used an image from this website – https://www.cowanauctions.com/lot/plains-sinew-backed-bow-plus-arrows-3963843
Hovering over the images of the bow enabled me to see an enlarged version of the bow end, and I ended up basing my model on it.
I blocked out the bow in Maya and brought it in Zbrush for detailing. Similar to the arrow binds, I brought in a simple cylinder for the bow string from Maya into Zbrush and turned it into a dynamesh. Then I used the Dam standard brush to sculpt the details of the string. The ties were cylinders made in Maya, then brought into Zbrush, zremeshed to a higher resolution and inflated to fit the bow.
I made the following variations by tweaking the shape of the bow and moving around the ties that were used to either strengthen the bow, or to add comfort while holding the bow. This website also provided some modelling reference-http://misterios-historia.blogspot.com/2017/09/