Of the 9 extant wood crossbow laths I am aware of, 2 are backed, one of which (Royal Armouries Sweden) is definitely sinewed, the other (Alhambra) may be sinewed, or might only be backed with sinew but translations of the Spanish are not perfect . Sinewing offers significant advantages for crossbows but I am not aware of references in medieval texts to sinewed wooden crossbows. It could be that translators only picked up on crossbows and didn’t expound further, or they were sufficiently commonplace as to not be described separately from other wooden crossbows Does anyone know of any texts/sources mentioning adding sinew to wooden laths, or alternatively any papers or articles on the subject?

In some Italian sources of the fourteenth century, there are references of "baliste de nervo", i.e. crossbows of sinew. Probably these crossbows were, so to speak, something in between wooden and horn crossbows.

That’s really useful.! I don’t suppose you could give any references to this?

A while back I read about Andreas Bichler repairing a yew prod with sinews after it was damaged during tillering. Unfortunately, it was only as part of a preview online, and I am not able to read the relevant section now. I don´t know if he explains the historical background to repairing bows with sinews, but it works.

https://www.google.de/books/edition/Jahrblatt_der_Interessengemeinschaft_His/EJQvEAAAQBAJ?hl=de&gbpv=0

In that instance, the string caught in the nock and split a section of the lath which was glued back in and bound with a sinew wrap. He wrapped the other end as well just to be safe. Sinew is amazing stuff, I’ve seen it described as natural fibreglass by one modern bowyer.