The recent thread on crossbows reminded me of my desire to make one of those. I had recently read "crossbows" by Frank Bilson, writing back in the 70s/80s trying to get crossbows as a sport in America. It includes instructions and templates to make low powered crossbows and only used wood. I'll happily make one of those to toy with but I'd like one with deer taking power. If you look at a sports store you can spend thousands of dollars on a modern crossbow.

I've looked and I can't find much info on what the ceiling of a wood prod would be. Any sources or info?

You could get into some pretty serious draw weights if you used Osage and backed the bow.  Especially if you backed it with sinew.

Second, the string on medieval crossbows stretched.  That's why a lot of them were as thick as your thumb.  They took advantage of that.

But I think C_A is right, why use wood when you can get a steel prod so easily.

I would think pretty seriously about building one of the lower powered wooden crossbows first to see what sort of problems I could run into.

Perpetualstudent, yeah there is next to no infromation on wooden prods, when i try to make a wood prod, i make it as if it were a small bow and then reduce the stress on it, example: if its supposed to be 36" long with a 4" brace height  and a 14''  draw, i make it 38" long with a 3'' brace and a 12" draw., the most powerfull wooden bow i have pulls 90 pounds with a 11 inch powerstroke, i made it from the best red oak board i could find and glued 3 layers of fiberglass on the back of it, feels barely powerfull enough to take deer tho,. You could also just buy the prods and be done with that part at least, you can buy some 150 pound fiberglass prods on Amazon for about 20 dollars, the one i have on my red crossbow cost me 12 dollars, or you could buy a steel one with for about 65 dollars plus shipping, you can buy one from Alcheminc.com or slowbows in whatever poundage you like, those steel prods are expensive but will last several generations, they're also quite heavy,. Alternatively you could make a steel prod out of a leaf spring, its much cheaper once you have the tools, all you need is an angle grinder(or a hacksaw if you're harcore) a steel vice and 1 or 2 steel files.

Parmenion, i was just pondering about how i would use a hacksaw to shape a leaf spring, i think i would draw my design and start to work on it on the weekend, i would probably start one saturday in the morning, find a nice spot in the shade under a tree in my backyard, grab a beer, maybe put on the lord of the rings or something to get motivated between rests and take my time, and by the second day i would probably switch to my angle grinder because  if i had to continue to use a hacksaw i would probably loose my mind,. Anyway here is a PDF of an article on crossbow making by "Popular Mechanics" (in it you can read about using a hacksaw to shape a leaf spring).

I assumed the price for the prods would be much higher. What you say tempts me very much Onager lovac. Although I think my wife might kill me if I don't finish a project or two before I start one of that magnitude.

I had been leery of working with steel prods. Theoretically of course spring steel, so long as it is not taxed beyond it's rated ability, can handle an indefinite number of compression/release cycles. But theory and practice tend to diverge and the idea of a shattered steel prod makes me far more leery than shattered wood.

That said I just found this https://youtu.be/JPc1tAUo01E
and that makes me want to toy with this idea more.