Beefy Bryn Flat-top

Rob,

I think you will be OK - go with your muse and instincts. The stiff rim and front to back "skeleton" connecting the neck and tail blocks will give a lot of strength to resist the "folding soundboard" forces. Adrian Lucas (ajlucas) has used radial bracing for both steel and nylon strung instruments so he may comment more. To me that bracing pattern would tempt me to use a floating bridge with tailpiece with a more compressive rather than rotational torque at the bridge.

You will learn a lot and the worst that can happen is that you may have to put a new top on with a modified bracing pattern.

I did consider one slim brace right down the middle from top to bottom but that's not really in the spirit of the thing so I'm going with




which, in case you can't tell the difference, has the more longitudinal braces extended further under the bridge whilst maintaining the clear lines of flexibility both across the middle of the bridge and up/down through the middle of the bridge.  This will, unfortunately mean replacing the four braces which are already glued in place:




No problem.

And now with the A-brace or, more accurately, the /\-braces:





I had better come clean as well about the strange little marks you can see on the soundboard.  They were little screw-holes in the door that provided the Douglas Fir:



You can see I made them into little diamonds hoping it would help disguise them when patched:



But it didn't really work:



As usual, I blame the glue.  I'm going to revert to cascamite if things don't improve!

Mmmm Cascamites, where the insecticide...

They used to make motorbikes by building a frame and then bolting an engine on to it as I understand it;  nowadays they build an engine and then bolt bits of frame on to it so that the engine is an integral part of the frame.  It saves weight amongst other things.  Well, I think that's what I'm trying to do with the bridge and the braces.  The trouble is, of course, that in trying to brace and then voice the soundboard I'm lacking that central link - the bridge/engine - which holds the whole thing together as a unit.  Consequently, I haven't really got something I can do much "voicing" with.  It fools you into thinking it's a unit because you can pick it up as one and it looks a bit like a soundboard but, particularly from top to bottom along the mid-line joint, it's very very flimsy;  it feels like a book in your hands, ready to fold down the middle.  Here's where I've got to:

First I trimmed the tops down to something like their final shape though nowhere near their final height yet:



I then went into some very brave carving:



Yes, it looks more like a spider than a motorbike but spiders don't bend down the middle.  (Neither do motorbikes...  I'll have to sort out my metaphors).

I toyed with the idea of of putting a very light brace across the join near the bottom - and I still might do this - but realised that, once the soundboard is glued to the rim, there won't be much pressure on that mid-joint any more so it would only really be temporary scaffolding.  Then I had my epiphany - No, not an Epiphone:  if you want to fine-tune the frame of your motorbike you have to start by bolting it all together so that you've got a frame to test.  So I suspect that I can't do much else with this soundboard until I glue a bridge - or something very like it - on to its face.  Haven't quite decided whether to actually make up the real bridge itself at this early stage and glue it on because that will raise questions about final preparation of the face of the soundboard, polishing, precise positioning and so on...  quite an exciting moment though.  (I don't get out much).

And what else have I done lately?  Well, I made a neck blank and filled it with metal and carbon fibre.  Here are some pictures of that:





Neat bit of sawing, eh?  I know it looks a bit wonky but it'll all come out nicely when I run a plane down the sides of it and carve it to proper neck shape.  All the wood is from my old table top and is (Cuban) mahogany - very heavy, very dense.  You can even see the polished surface on the side of the block in the first picture.  I try to mix up the angle of the rings/grain when gluing these together so that, should the components decide to start moving, they'll move against each other and the whole ought to stay true.  I later capped the truss-rod (2-way) with a thin piece of mahogany because that's what you do.  The carbon fibre was glued in with carefully placed Araldite and the truss rod with Evo-Stick, which I fondly believe might prevent any rattling - but what do I know.  The machine-head is angled back at about 14 degrees as was the last one (The Bryn Production) but it was intentional this time.

(The tabletops I am using, incidently, are worth almost exactly 2 neck+headstock length with only about 4mm spare.  This makes the whole thing a bit tight when you bring in the kerf (cutting width) of the saw and so on.)