And so to shaping the braces (basically parabola shaped to retain the strength but reduce weight) and tweaking the shape of the braces to get the top to resonate with multiple harmonics at as many of the required frequencies as possible - tap tuning.
For anyone interested in this black art (which I only scratch the surface of personally - I know when it's right but I don't know how to get there other than by accident), this is a long but very instructive video. The last 15mins or so has him actually doing the tweaking and by golly you can hear the difference at the end!:
https://youtu.be/Ei5-DkVTrEE
Mine has ended pretty much where his began (then again, he sells his guitars for many thousands of pounds) but is certainly more resonant that when I started with a number of distinctly different notes, with at least two harmonics, ringing out when various parts of the top is tapped. On this dry fit, you can see that some of the non-structural braces disappear to nothing - and where that happens matters!:
The straight brace at the top and the long cross braces are structural and will extend into the kerfed strip, which needs cutting away:
As will be seen later - the outside join will actually be cut away!
So the glue joint of the kerfed strip itself has to be a good one - but remember, the top and back are curved. So they need sanding at an angle to provide a good gluing surface and tight internal join:
While I can see both sides (ie, before the top is glued on), I need to similarly prepare the back.
First a purfling strip is set into the join line:
That is scraped smooth and then the back braces are put on. The back has a 15 foot radius spheroidal curve so has its own radius dish. The bottoms are radiused to fit the 15' dish in the same way the top braces were radiused to fit the 25' dish:
I pre-shape the parabola so use spruce offcut strip to act as the pressure beams for the go-bar struts to press the back into its proper shape in the dish:
And then the dry-fit tweaking of the back join is done in the same was the top was:
Thread is ALMOST up to date. Next post is gluing the top and back onto the sides which is where I've just got to.