Saturday, 2 April 2016

60 Pounder Coming Along

I've been rather busy with other stuff but I've been teasing the 60 pounder back, I've filled some small knots and been carefully working down the knot near the end of the right (upper) limb. The stave had about an inch of natural deflex overall, that is to say with the tips on the floor the belly (at the grip) was 1" off the floor. The tillering and working the bow had increased this to about 1.5"
I strapped the bow down (back down), straight with a couple of bits of hardboard under the deflex portions having first covered the sapwood with layers of masking tape to keep the heat off. The hardboard helped to force it into a slight reflex to allow for it springing back after heat treatment.
It's just about straight now with tips and grip touching the floor together. By the time it's finished it will be maybe back to 1" which is good. Un-treated it would have crept up to about 2" which would have been loosing performance.
I may do a hint of reflex towards the tips later, but it's a good honest shape now with a bit of waggle just above the grip which is still visible when loaded up to 60 pounds. A bow at full draw should still reflect the shape of the unstrung bow, that's what makes tillering character bows particularly tricky.
This post of a bow with a real dogleg shows what I mean:-

It's getting close now, 60# at nearly 24" (at a low brace height ~4").I need to get the outer 1/3 of each limb coming round a bit more, but it's tricky with that big knot... It needs to work but not to get over stressed.
I see some horrid tillering where people leave a knot proud on the back (which is correct) but then make it proud on the belly too which just leaves it ludicrously stiff and creates a weak spot either side of the stiff spot. If the back is proud and the belly stays in line there is already extra thickness and stiffness and if there is no knot just a bump, the belly should follow the shape of the back.
If anyone is in doubt, they just need to measure the thickness at the bump and cube it. Measure the thickness below the bump and cube it. Comparing those two figures will give some indication of the relative stiffness of the two areas, it needs very little extra thickness to stiffen an area.
(Other opinions may vary, terms and conditions apply)


  1. Looking good Derek, really

    Taking shape. What do you fill the knots with and she you heat to bend it is it steam or direct heat?

    1. Damn predictive text! What kind of heat do you use to bend it?

  2. The knots get plugged with Yew if they are big, but these were just small so I use Yew dust mixed with epoxy.
    The heat is dry heat from a hot air gun. Here's a video of how I do it:-