Thursday, 23 August 2012

Why a Bow Needs Shooting In

The Hazel bow has had 110 arrow through it and umpteen coats of Danish oil.
I was just rubbing it over when I noticed an odd mark on the back. There is a couple of tiny pin knots where the grain swells up, they are barely visible and I hadn't allowed any extra thickness there. There was a tiny zigzag line for about 1/4" across the back just to the tip side of the pin knots (It's about 3" from the grip).
From each end of the zigzag there was a hairline going tipwards for about 2". Could it be a splinter trying to lift?

My optimistic self said no, it's just a discolouration of the grain, but my realist gut self said its a damn splinter. I knew the bow was still shooting fine so I winched it back to 28" on the tiller and with my fingernail could just feel the zigzag lifting a tiny amount. I flooded it with low viscosity superglue along the zigzag and the hairline cracks, pulled it to 29" for a split second, then let it down and got the string off quick.
I left it a while and carefully examined the rest of the bow.
On the belly side under the pins was a tiny dark spot of a knot only about 2mm in diameter, I hadn't given it any real thought before. I cleaned it out with a drill bit held in my fingers, it had no strength at all, so I filled it with sawdust/epoxy mix.
I don't know if this contributed to the problem, and I don't know if the problem contributed to the apparent slight change in tiller where I feel the lower limb looked weaker than it did in the pic of it on the tiller.
Anyhow I ran my nice new 12" bastard file over the belly of the upper limb to weaken it a whisker and thus even up the tiller an take a little bit of load off the lower limb. I also ran the file over the outer 2/3 of the back of the lower limb to ease the load off the suspect area.
This tiny amount of work has lost a couple of pounds draw weight and evened the tiller.
I sanded the zigzag and filled knot dead flat then popped it back on the tiller at 28", no sign of the splinter, I shot 10 arrows and it's looking fine.

There is a huge temptation not to post this sort of embarrassing setback, but I think it's a vital part of the blog's usefulness.
The big question is have I fixed it? I'll shoot another 100 arrows through and see how it goes.
The good news is it didn't explode so it was probably a very shallow splinter. If it lifts I could bind it with linen thread rubbed over with epoxy or I could chisel it out into a shallow trench which fades out to nothing at each end and inlay a sliver of hazel. I could bind it anyway as a belt and braces fix. Anyhow, I'll leave it a day or so as I have other stuff to do.

There are often several options and not necessarily just one 'right' one.
I'm a lot happier about it than I was a few hours ago when I first noticed it and you could have knocked me down with a feather.

2 comments:

  1. Great post!
    Definitely a worthy addition to your blog and there's no shame in admitting/posting your mistakes. You saw what was about to happen before it did and hopefully the bow will survive for many years.

    Well spotted, I would have missed that flaw for sure but thanks to this post I have a fighting chance if I ever encounter something like it in the future.

    /Håkan

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  2. Cheers.
    It looked a bit more obvious than that before I worked on it.
    It doesn't stand out as much in the pic either, it's hard to photograh as it's so pale.

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