Thursday, 9 August 2012

Tricky Tillering and Smashing Video!

Wednesday Evening:-
The bow was trying it's best to bend sideways.
The two factors contributing to this are the string line being a bit off centre and the cross section being about as thick as it is wide and is some places even thicker! (One of the billets was rather narrow to start with)
I've got it flexing now better now and thinned it a bit ad teased it back to a reasonable brace. The tips are getting pretty narrow where I've tried to adjust the string line. It feels a bit unstable and was making some ominous ticking noises on the tiller, it sounded like cracking glue, but I don't think it's the splice failing.
I'm fully expecting it to explode as it come back further, I think the bug holes in the sap wood will cause it to explode, but you just don't know.
Making a bow is a road travelled in hope rather than certainty.
It's back to about 40# at 21" , I'll be sure to get the video running before I take it back any further.
Thursday Morning:-
Ah the wisdom of sleeping on it!
It doesn't look so bad this morning. I strung it and adjusted the string line a bit more and flexed it a little.
The sideways bend isn't so pronounced, although the whole stave seems to have settled at a slight angle. That is to say if you look at it as a cross section through the grip, it seems to have rotated a few degrees from the expected, but if that's how the wood is balanced then that's fine I'm not going to fight it.
Here's a video of the first real test up on the tiller, it looks surprisingly good.
The right (top) limb is doing most of the bending. Note I've taken the rare precaution of donning a cap and safety glasses, an indicator of my confidence level!
If you look at it full screen you'll see the tape and pencil mark on the scale at 45#, I think the draw is about 22". I went a hint past the 45# but it seemed to get pretty hard. I'll work on the left limb over the course of the day (that's the one with the bug holes) and report back.
video

I did some work and got it back on the tiller, it was looking good, then BANG. A close examination showed a bug hole right across inside the sapwood where the break is. The video is at the best resolution I can download (slowed down to show it better, but it really needs a high speed camera to actually see it fail).
video

Here's a pic of the break in the sapwood you can see the curve of the bug hole along the break and a neat round hole where it turns down into the wood...

I've run the next two billets through the bandsaw to take off the sapwood, but I may need to buy (wince) a bench mounted belt sander/linisher to thin down the bamboo I'm going to use for a backing. 
Just noticed someone has ticked the 'boring' reactions box... LOL! Maybe they need to have a bow explode above their head to see how boring it is?

3 comments:

  1. Oh Del, that was painful to watch. Sorry about the blow up. Better luck on the next one. I hope the backing with bamboo works!

    -JW_Halverson

    ReplyDelete
  2. Man-o-man! I'm feeling bad this wood is failing you!! Guess my billet choice was not so good eh?! Sorry Del, I really am.

    Joe

    ReplyDelete
  3. No prob' Joe.
    It's still fun and there are a couple of good bows in there still.
    I may even find some English Yew with too much sapwood on it and be able to take a thin slice off and make a transatlantic Yew bow... now that would be cool!
    If nothing else I've shown the theory that bugs don't eat Yew 'cos it's toxic is wrong!
    Cheers
    Derek

    ReplyDelete