Wednesday, 1 March 2017

Spliced Yew Flight Bow

Ha! The dreaded "explain more" box has been ticked. Now I'm guessing it's not an interest in expressing cat pee! So I'll ramble on about the flight bow in more detail.
Firstly the billets, these were odd bits that were just too good to throw away but had peculiarities. One had the weird alternating heart/sap wood, this is often visible when you cut a log, this pic shows
what I mean, with areas that are neither clean sapwood nor clean heartwood:-
I maintain continuous heartwood on the belly even if it is relatively thin in parts, similarly I like to have at least some sapwood showing along the entire length of the back. This billet also had some natural reflex (which I left alone) and some deflex which I took out with dry heat (hot air gun and oil) The grain also wandered side to side on this billet and I cut it out following the grain to some extemt, whilst heating to take out the deflex, the tensions in the wood caused some sideways bend which I had to correct with a further session of heat. The advantage of all this heat work is that it toughened up the belly on what had been the weaker limb.
The other billet was mostly sapwood in parts and I had to take care to preserve as much heartwood as possible, by reducing the back rather than the belly, there is a bit of deflex at a knot near mid limb which makes the tiller look weak and a bit ugly.

I've since heat treated it (the right/upper limb) to take out the deflex and stiffen the slightly weak mid/inner limb.(see pics) The pull out the deflex I strapped the limb to the narrow edge of a length of 2x1 timber back downwards (back and sides protected with 3 layers of masking tape) Where I wanted the limb to bend I put three small pieces of hardboard under the back, this forced the tip up and away from the 2x1. by a couple of inches. I clamped side cheeks along the limb and gave it 5 minutes of heat, then strapped the tip hard down onto the 2x1 and heated some more.
I didn't go mad trying to pull out too much bend and made sure I heated over a good long area. This method of just strapping down the ends gives a gentle bend and allows the natural flex of the limb to apply the force evenly rather than trying to force it a one point.
Design wise, I've made the lower working limb as long as the upper to try and keep the strain on the two limbs as even as possible, having said that, the timber in the limbs is so different that the thickess of the limbs is substantially different (I may take some measurements at some point just out of interest)

The general philosophy of this bow was purely distraction and experimentation. If I really wanted to make a good flight bow I'd start with better materials, but it's allowing me to evaluate a short draw ELB and compare it to the long draw heavier weight bows. The distraction element is just to keep me busy and stop me worry about the cat, mind she's much better now anyway and is coming in to watch me work and getting up to mischief.

The pics show it after the heat bend/treatment, you can see the upper limb (right) looks effectively stiffer and much of the deflex has gone, note I haven't tried to bend it hard at that knot.
It's not been back on the tiller yet, hopefully it will have gained a bit of weight which I can scrifice if necessary to get the tiller as good as possible.
I've shot it throgh the chrono' with pretty consistent results, best 187.4fps average of 5 shots 183.2
I was using a bamboo flight arrow 346 grain and 24.75" overall length.
I need to check the draw weight and get a full draw pic, I suspect the weight is prob about 65#.
We hear a lot about 'hand shock' and I think it is often attributed to the wrong thing! First shot through the chrono hurt one of the joints of my left hand like hell, but close examination showed that the corner of back and side was rather pronounced and was right under the knuckle. A few strokes of the rasp to round that edge and the problem evaporated!


  1. Looking forward to the report from the flight shoot. Could the odd wood be reaction wood? Looks similar to what I have seen in other conifers.

  2. Hi, yeah, I've heard it called reaction wood... but what's in a name? It is what it is, can't argue with the wood! Yew is pretty forgiving.I did try a lighter flight arrow and it kicked a bit, didn't get a clean reading, maybe tomorrow!