A guy E-mailed me with a pic of his bow which I'd made for him a while back, (Bamboo backed Yew) it had developed a bit of a pinch by a filled knot on the belly.
He brought it over so I could have a look, it needed a repair, better safe than sorry.
Looking at it, I could see some buckling in the parent wood on the corner and a hairline crack across the filled knot.
The Yew belly had been heat treated and the knot filled before the bamboo backing was done and I was a little surprised to see the crack in the filled knot.
Rather than do an inadequate half arsed repair I thought I may as well get the patch to completely cover the knot and to extend over a good part of the belly and about 4mm down the side as a curved scallop. I make sure I rasp down until all signs of the pinch have disappeared.
The pics are pretty much self explanatory. I took the finish off the bow first with wire wool soaked in white spirit and protected the surface of the bow with plenty of masking tape. The masking tape is good as it provides a guide when rasping the patch down to the shape of the limb. You can feel and see when it's getting very close. What you don't want to do is to end up rasping in to the limb and creating a weak point, in fact I tried to leave the patch just a whisker thick so I can check the tiller and adjust if necessary.
It just needs a bit of shooting, a tiller check and Danish Oil re-applying. The finished patch will look better than the original filled knot. I've had a quick look on the tiller and that limb looks maybe a hint stiff at the patch, but I'll shoot it in a bit before easing it off at all as it may settle down.
I should mention, when doing a patch, I try to get the run of the grain and growth rings in the patch to match the wood of the limb, and in this case I gave the patch a good 10 minutes or so under the heat gun to get it close to the properties of the rest of the belly.
This really illustrates the value of checking over your bow. I've had people ask if I offer a guarantee with a bow, I always tell them that my pride in my workmanship is the guarantee, and it they keep a close eye on the bow I'll keep in in good condition for them. There's not actually a lot of hours involved in doing work like this, there is a fair bit of experience though and it helps a lot to have a bandsaw, belt sander and a good supply of nice Yew offcuts!