Hi Guy,
Nice bow, you found. Where exactly was that fleamarket ?
I tried to find something on African bows in my books, but it isn't easy.
I can only say that rattan is often used for making bowstrings.
Some months ago, I acquired a bow in Amsterdam. It's a small one, measuring only 84 cm. It's made from wood with some rattan weaving on both ends and in the middle.
I was able to identify this piece by the two 'knobs' on the end of the bow. These are also made of wood and are used to hold the bowstring.
According to 'Dodelijk mooi' (deadly beauty/beauté fatale) this bow originates with the Luba people in Congo.