Thanks so much for all replies. Jaeger22, the difference between hand held bow and crossbow prods is while building hand held bows a singe piece of horn used at inner side of bow arms. This is quite different for crossbows since large number of strips are used in a specialized structure. Thanks for links I am also interested in bow making I will certainly take a look.
Kenh, eventhough that site is great about archery, it has very limited information about crossbows especially in case of siege crossbows but thanks for suggestion.
Rizzar, you are just a little bit late since I got both the site and the book you suggesting from a friend on facebook.
Both sources are immensely rich in case of heavy prod building. Especially, Die Hornbogenarmbrust has exceptional images about inner structures of such heavy bows which is what I was looking for. Thanks again for suggestions and no, I have neither enough sources and knowledge about building such complex bows.
My aim here to just understand a medieval text. Mardi bin Ali Al Tarsusi, 12th century writer, in his military manual, describes a giant crossbow with 3.4 to 4.8 meter long, one and a half span wide arms and while describing he mentions oak as base wood. He continues giving the information that wood and horn aligned and glued then bound just like ordinary bows but he omits how horn strips were placed on wood. That was what I am looking for and now I have some satisfying answers thanks to you.
I thought there could be some information about in the book, Spingalds and Great Crossbows by Jean Liebel. Could anyone having the book share if there is something interesting about such large crossbows ?
Thanks in advance.