The Bryn Production

Rob,

Don't panic yet grasshopper Again ajlucas will be in a better position to comment but from the looks of it you haven't glued the back on yet. With the Spanish heel construction - even with the slot angles in the neck/heel you have the neck angle in relation to the top can be adjusted to the one you require by moving the neck up or down a little and the angle won't get fully "locked" until the back is glued on to the neck block completing the box. Indeed neck resets are done by "slipping" the heel joint - releasing the back from the bottom of the neck block, adjusting the neck angle and re-gluing the back on. I don't think you need to do any tapering of the fretboard thickness.

The rule of thumb for string height of 1/2" above the top at the bridge is just that. Much higher and the torque will increase and could cause structural issues and much lower means that the torque driving the top reduces, plus you have less room to lower the saddle to compensate for string tension increasing the action over time.

Of course it does ...

You have ideas, drive, and talent.  Just keep going.  Don't think too hard.     

Right.  I think I've got back to where I was about 10 days ago;  that was when I originally glued the neck (via the "heel-block") to the soundboard.  

Once I had realised I needed to be pragmatic and allow for a slight "give" in the neck once it was under the tension of the strings, I decided that I ought to un-glue the joint, modify the angle and then re-glue.  I know davewhite said I could avoid major trauma by shifting the back-plate a little but, since I didn't want to encourage any longitudinal curve in the soundboard, which in my case is only arc-ed side to side but is flat along its length, I decided to bite the bullet and re-set the joint.  Good advice, Dave, but I really don't want to allow any curving along the length of the soundboard if I can discourage it.

Now reversing a reversible joint isn't as easy as it sounds especially when one side of that joint is softwood and less than 2.5mm thick.  Anyway, after several hours (during which I tried rigging up a modified wall-paper stripper amongst several other things) I got the two apart with only minor warping and without disturbing bracing etc. (I hope!) through the use of my trusty clothes iron and a set of hot feeler-gauges.  Here is the result:



This did give me the chance to tidy up the end of the block which, as previously mentioned, looked a bit "amateurish" and, more importantly, made it easy to take a sliver out of the housings in the sides of the block to minutely alter the angle at which the sides enter it and thereby modify the angle of the neck to the soundboard.  Finally, I put a very slight angle on the face of the heel-block and glued it back on to the soundboard.  Back to where I started but with an angle (of about 0.6^o) on the neck, which required a 3.5mm shim at the end of the neck;  my geometry is slightly different to yours, ajlucas, but it comes to the same thing with a 1mm action at the 12th fret - I think.  Here is a familiar picture of the re-gluing operation:




Determined to make some kind of progress over this period, I did manage to make a caul to fit under the bridge when I come to glue it on (one day).  Here it is:

Nipped down to the workshop first thing and removed all the cramps and, as I had come to expect, there had been a bit of unpleasant seepage which I had failed to mop up so that the guitar was (a tiny bit) attached to the solera in one or two places.  Eased it off with an upholstery tool and only lost a tiny bit of wood right on the edge: 




Back down the garden and sliced the missing bit off the solera and glued it back where it belonged:





I'll be routing most of it out when I come to do the binding and purfling anyway.  Reminder for next time:  line the solera with baking paper when gluing.  Also failed to drive my carefully prepared wedges fully home on one side so, although the joint is tight, there is a tiny gap between heel and side.  I'll be able to sort it out with a sliver of mahogany but a totally self-inflicted wound;  don't do it again!

Apart from this, I was very happy.  It really is beginning to look the part now and, with the soundboard attached all round, I can begin to hear what its tap-tone sounds like.  (Whether it's supposed to sound as it does is another matter but I can't help thinking that, now that it's attached at its periphery, it must be nearer the way it will sound in situ.)  Here are some pictures;  don't feel you have to study them with as much delight as I do!














Having looked at it for a bit, I then drilled some tiny 1mm holes through the braces from the back to the front of the soundboard to help me locate my bridge dowels more accurately when fixing the bridge on later;  I wanted to make sure I hit the braces down the middle:



(Particularly fascinating picture, that one.)

And finally, today, I turned to the back.  I'll be needing braces soon so I made them from the pieces I sliced off the doors (you may remember) several months ago when the whether was bright and sunny.  Here they are being sanded in my sanding trough:





And that's where I am today.  Too much information?  Possibly.

On the guitar or in general?

I'm never quite sure about guitar backs but my understanding goes something like this:

The soundboard is supposed to vibrate and the sides are, first of all, supposed to support the soundboard but not soak up any of the vibration energy generated in the soundboard;  I therefore make the sides as rigid as I can.  The back and the sides together should help provide resistance to the pull of the strings and therefore have a structural job to do but the back should also help broadcast the vibrations of the air inside the box and reflect the vibrations radiating back from the soundboard out towards the listener.  That makes me keen to put a hard shellac surface on it but leaves me a bit lost as to how to brace it.  There seem to be two approaches:  four or five side-to-side braces (ladder bracing), which would seem to stiffen it across the grain;  or a cross together with a couple or three side-to-side braces, which provides the stiffening across the grain but also helps strengthen the structure against the pull of the strings.  On my first flat-top I used a version of the former;  now I plan to use the latter (copied directly from pictures on this here forum).  Now I gather I ought to be considering whether I want the back to be "active" or not and I should also be wondering whether the end user has a big belly (or, perhaps, is in the early/late stages of pregnancy) and will be standing or sitting etc. etc. but, in the end, I don't really know enough about it and wonder if there will actually be an "end user"...  

(I'm happy to be put straight on anything I've got wrong here but neither should anyone feel duty bound to explain it all to me;  a push in the right direction as to what I might read on the subject might be helpful, though - as long as it doesn't cost over £160 plus postage from Australia or the States!)

So here's the plan, which should be very familiar to some of you:




Looks convincing, doesn't it, though you may also have guessed that the new design also fits better around the labels, which have already been printed - all right, photocopied.  The ends of the braces will also be let into the linings to some degree.

Today was spent fiddling around with the braces until they fitted everything properly





and then finalising the thicknessing of the back.  I also cleaned up the inside of the box (i.e. tidied up areas visible from the hole and fine sanded the whole thing and even shaved some of the braces a little more) ready to seal/polish with shellac.  These little things take a lot of time but you can't leave it looking scruffy, can you?

The scientifically minded amongst you will have noticed that by now I have changed so many variables that, if this guitar sounds utterly amazing or utterly awful, I won't have the first idea which of the changes is/are responsible.  That's probably why I'm not a scientist - or a successful guitar maker, for that matter.