Saturday, 12 April 2014

Monkey Bow on the Tiller

I've got the Monkey bow at a 4" brace (note the limbs are naturally deflexed to start with). Here's a frame grab from some video which shows some interesting points.
The digital scale was great from me to see while pulling the bow back (it was reading 50#) but it's not legible on video!
The levers  aren't coming in to play yet. E.G The string is still resting on the tips of the bow and has not lifted off.
If we assume I wanted the string to be just lifting off, I can work out where I'd need a string bridge at some point on the levers to make this happen. (See diagram) I can make some adjustable string bridges to try various configurations, but first I need to get it to full brace as that will effect the geometry.

Improving the tiller (although it's surprisingly good already) will reduce the draw weight a tad and also let me get the brace up.
By the time I've done that the levers will be coming over a bit more and the string bridges won't need to be as large as shown in the diagram.

Here are some pics of a decent Siyahs cut from Ash with a natural curve to the grain and splice in with a good length of joint. The joint is then bound with linen thread soaked in epoxy. This bow was actually faced back and belly with a fibreglass lamination.
I'll post a pic of the much shorter V splice on the Monkey bow in my next entry.

If I decide on different lever geometry, I can always find a bit of curved Ash and re do the levers with a longer stronger joint (assuming it doesn't explode first).

I've done a bit more and got the brace height up a bit, I thinks the limbs are pretty close to how I want them, but I thnk the levers are just at too extreme an angle.
I'll have to see if I can find some Ash with a slight curve in the grain and re-do the levers. At least I just did this quickly, another triumph for my WAQAP quality philosophy! (That's Wrong AS Quick As Possible). I could have wasted ages doing drawings models, geometry and arithmetic only to find it needed re-doing anyway, I've a sneaking suspicion that string bridges are actually a fine tuning mechanism.
You can see that the levers on the Asiatic recurve are at too shallow and angle, somewhere in between is the Goldilocks zone where they are just right.


  1. Could you post a closer picture of the glue joint. There is going to be a helluva lot of strain on that joint. I would never have attempted it but I don't have anywhere near your experience. I was thinking maybe you could continue the bowstring around the end of the lever and terminate it about 3 or 4 " from the tip, if you get my drift. This would take some strain off the joint. That scares me.

  2. Yeah, will do, The join is a V splice, they are normally a lot longer than I've done here. This is just a bit of a mess about. I'll see if I can find some pics of how I did it on the Asiatic recurve too