Saturday, 24 November 2012
2nd Stage of Repair and a Dilemma Solved
The back patch has now been glued on and wrapped with rubber strapping. The patch is actually made of the strip of sap wood sawed from the back of the bow when it was first glued up as a stave so it will match perfectly.
It will take at least 6hours for the glue to cure in a warm room, so in the mean time I've been working on Bob's bow, which has now been braced and is coming back nicely.
You can see a fair wiggle on one limb, I've drawn a straight line down the side of the limb to help me see it's true bend as it's flexed on the tiller. Without that line the downward dip near the end looks like a weak point whereas in reality it was actually too stiff and not bending.
My dilemma is that as I'm reducing the thickness of the bow, the belly patch I did at the outset is now in danger of becoming rather thin. Ideally I'd like the bulk of the patch and it's glue line to be about 1/3 of the way into the bow.
I imagine the thickness of the limb acting in thirds, with the back 1/3 under tension, the belly 1/3 in compression and the central 1/3 having a fairly easy time of it, which is why I want any discontinuities or the main areas of glue lines in that middle 1/3.
The pic shows how the patch barely overlaps the knot at its right end.
In view of the problems on the previous bow, I think I shall rasp off the patch and re-do it. It often happens that filled knots and problem areas actually disappear as a bow is reduced in size, this just happens to be a case where, it hasn't disappeared and I think it needs improving. Being half way down the limb a failure would be catastrophic and all my work would be wasted... so better to do a bit more work now.
It's now Saturday evening and I've been busy all day. I re-did the patch on Bobs bow, that's now strapped up and curing.
I've unwrapped the back patch on Brian's Bow and rasped it roughly to shape, looking good. I've now glued on the belly patch and that will cure overnight.
I'm hoping to shoot tomorrow, so I should get some more pics posted on Monday.