Building a traditional crossbow
By Wesley Kuhn
It was about five months ago that I got, what my loving wife calls, on a mission – a time when she can get nothing out of me, unless it requires me going into my workshop. Then getting me out is more work than it's worth, so she has learnt not to bother. I've been on this mission a few times, trying to build a number of backed and unbacked self-made bows from the hand-picked hickory and ash boards I had stashed over the years. However, none have ever lasted more than a few shots before exploding in my hands.
Well, I'm a nut for anything that casts an arrow and the more traditional the better, but I was getting over hours of work filing and shaping firewood. So the idea was born to build a crossbow, an old one, and they don't get much older than Medieval. After few hours on Google, joining a few forums and talking to the wealth of knowledge around the world, I set off on my adventure (mission).
I spent a few hours getting my dimensions together and drawing a template with all the relevant slots marked for the moving bits. I selected a beautiful piece of kiaat for the tiller (Medieval for stock) and traced the pattern onto it. After routing and drilling the slots for the nut and tickler, parts of the trigger, I laminated the two halves together and let it cure for twelve hours, at which point I squared it up on the planer and started work on shaping it with a rasps, files and a Dremal tool. Now you have to be careful how much wood you remove and where, due to the huge amount of pressure you place on the tiller, with the high poundage prods (bow) which the Medieval crossbows were known for. If the grain of the wood doesn't run top to bottom, you risk splitting it right down the middle.
My intention was to hunt with this crossbow, so I was careful to make it as easy to carry and to point to target as I could, while being comfortable against the shoulder. The original crossbows were never shot like a modern rifle; rather the tail of the tiller was placed on top of the shoulder and the thumb used to release the bolt or the cheek rest against it. I found this very unstable and used some creative design to come up with what I had.
After a few good days' working on the shape and sanding it smooth, I glued the deck on with the slot for the bolt to sit in. I had made this from African Blackwood and installed the nut, which I had made for me at a machine shop.
The next bit was the prod. Problem number one. I could get the steel, but what were to be the dimensions, what thickness by length and depth would give me the poundage I wanted? I had thought about 300 pounds should give me the power I was looking for. Back I went online and a few emails to Germany got me off on the right foot. What I learnt here is, never build the tiller before the prod is complete with hardening; spring steel will break if overstressed and can, as I have been told, shatter with rather nasty wounds if it does so while you are sighting down your bolt, something I wish not to experience. As it turned out, I managed to get a draw of 9,2 inches at 400 pounds, which worked for me, so I started to put it all together.
After binding the prod on to reduce the forward weight and installing the bolt clip and trigger, ironing out all the nitty-gritty bits and pieces, it was time to build the string. 60 strands of B50 on a string jig and served with some 3D serving from a DIY serving tool and we were ready to get it on and do some test shots. I had made a few very traditional bolts which had hand-fetched feathers bound to a beechwood shaft and a 35-grain judo on the end. They came out at about 500 grains total, a bit light but would do for now. Initially the arrow flight was very erratic, so back to Google and some overseas help. It turned out that I had the prod angle wrong. Quick fix and back to the target.
I'm very pleased with the way the crossbow turned out. It is heavy but stable, very consistent and now has stable bolt flight. My judo-tipped bolts nearly go right through the butt at 30 metre, so plenty of power. I think a field test is needed.