Friday morning I gave it a good going over with the scraper and cleaned up the back a bit more. The (fairly fine) rasp & scraper combination works well.
I wanted some off the right limb so I drew a pencil line along the belly where I wanted to take it off. I rasped off the pencil line and got it back on the tiller.
I repeated the procedure a couple of times, it's now back to almost 26" at 55#. The scraper cleans off the rasp marks without effecting the weight too much.
Near the tips I use a coarse file as there is less wood to remove.
I shot one of my heaviest arrows into my foam back stop just to try it the penetration looked pretty good.
The set in the bow has come up to about the thickness of my thumb now.
It's virtually there now except for some fine tuning to check the string alignment and clean it all up.
It's odd, I've got it back to about 26" and it doesn't seem to want to come back the last few inches despite a lot of scraping and rasping and tweaking, (Usually the last couple of inches of draw take very little work to get there).
I then got another 1/2" and BANG.
The whole thing disintegrated, interestingly, it hasn't simply gone at one of the features or slightly suspect places, the whole thing seems to have gone at once, splitting along the neutral plane about halfway through the bow.
More pics and autopsy later. You have to be philosophical when making bows, I got away with some nasty knots on the last one, so I don't begrudge some kindling for my Sister's wood burning stove.
I think the break probably started at the knot which protrudes through the back despite there being plenty of sapwood there .
I've sawn a section through the area of the knot (at an oblique angle to show it better). It looks pretty sound and you can see the extra sapwood I had allowed around the knot. (The pencil line shows the profile of the rest of the limb)