I've been through some of my Yew and found that a load from last year was all but worthless, but I did manage to get two short clean lengths for the crossbow limbs from 4 staves. I'd paid good money for the Yew while it was in the tree, but some you win, some you loose, I've had other stuff for free, so I can't complain.I'd also gone through my billets too trimming them down and eventually I ended up with 7 potential limbs, from which I chose the best two.
Doing all that has cleared some of my wood storage shelves, so that's a result, I can get some Yew off the garage floor and onto the shelves now.
The new Yew limbs are clear of any knots this time, although it took a bit of careful laying out to achieve that. I've done the Z splice, which is slightly tricky. As the limbs are angled back in deflex they have to be supported at that angle when the splice is cut, I did this by making up a block of plywood and sticking the limb onto it with double sided tape to support it at the right angle as I sawed the spliceMeanwhile I'd glued and clamped the cracked limb and I've actually braced it and pulled it almost to full draw! I may pluck up courage and pull it all the way, but it will just be for curiosity and test purposes, I'll never really trust it.
Hopefully the pics will show what I mean.
I think I can see why the string went up and over the limb. The tip of that limb is bent up very slightly and I think the reason for that is that the lower edge of the limb is thicker than the upper... the reason for that is the bamboo backing being thicker in the middle than the edges. The top edge of the bow corresponds to the edge of the bamboo (thin edge). The lower edge of the limb tapers upwards and as it narrows it goes from the thin edge of the bamboo slat to it's thicker center section.
So the top edge of the limb is say 5mm Yew plus 1mm Bamboo, where the lower edge is 5mmYew plus 3mm Bamboo. This difference causes the limb to twist up slightly towards the weaker top edge.
On the mk II I will try and keep the thickness more even.
Del you talk about your crossbow yew/boo bow having an off centre crown. I'm working on a yew longbow at the mo(when I get the time)and for about 28 " in the middle of the stave the crowns offf centre by loads. Were talking 10 mm across the width. As you can imagine when strung it's trying to roll over. I've still left the belly even Steven along it length as just not sure what to do. I've already reduced the sap wood too one yearly growth ring,hence discovering the problem. Do I try to even up the crown and lose the growth ring on the back? Or sin bin the stave and mark it down as a complete lack of experience(being only my second yew bow project) cheers del love reading your blog,watch your vids. Please keep it up :)
ReplyDeleteAh, an excellent Q' like a lot of these things there are several approaches and it seems like you've tried one, but often the answer is a little of 'A' and a little of 'B'.
DeleteThis post may offer some ideas:-
http://bowyersdiary.blogspot.co.uk/2011/04/different-approach-to-twist.html
There is also heat treating or applying heat and twisting which may heat. I find these challenges are a great learning opportunity, even if you don't fancy it now, you can set it aside and have a play some other time. Just try to remember we do this for fun! ;-)
Thanks del you light a floodlight in my darken mind. You da man :)
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