The Bryn Production

Rob,

That's certainly coming along nicely. Interesting bracing. I think "parabolic" is a much abused word for bracing profiles, I call it tapered - i.e no big changes or scallops - and that's what you seem to have going on there. As to how far to take it down you can only learn that by trial and experience. When you flex the top along it's length you want good stiffness there and can have more flex from side to side. When you tap around the top I would be looking for a good "musical" ringing and sustain everywhere.

Good on you making your own purfling for the rosette

So now it’s neck time. My mahogany table top, which I used for the neck of the first build almost built, is exceedingly dense; I calculated it recently at around 900kg/m3 and it’s resulted in a neck which is a bit heavier than necessary. Not really a problem but this time I thought I’d try to modify it a bit with a lighter timber down the middle and what do I have loads of? Douglas Fir. Unconventional to use a softwood in a neck perhaps but it’s tight grained and 80 years old and most of it will be routed out to accommodate the truss rod and carbon fibre so there won’t be a problem unless it gets dented a lot. I’ll just call that “patina”. Here’s the resulting blank:





and, for all you timber experts, here’s the end-grain of the mahogany:





Whatever it is, I don’t think it’s available in Wickes.



Next I sliced of the headstock and a bit at an intended 11° but which came out as 14°, which was an accident but serendipitous since I then remembered I’d intended to increase the angle to about this much anyway. Here’s a picture of the slice:




Like one of Nadiya’s, isn’t it? And, just to show how high-tech I am, here it is cramped up with a laser, no less, shining a nice straight line on it!



(The brickwork looks pretty straight as well.) I avoided slippage here by putting a couple of pins through the join before gluing it up.



Here’s the angle, by the way:




I like to have the join this way round so that the fingerboard reinforces the joint.

Two more bits of table-top and a few strips of quarter-sawn Douglas Fir make up the heel-block blank. By the way, I initially glued the Douglas Fir pieces to each other with fish glue but there was a distinctly dark area around the join where it had soaked in so I had to re-do it with something unmentionable. I suspect it only does this when the grain is orientated like this because it hasn’t happened along the Douglas Fir/Mahogany join.



Flattened everything and then routed out the neck ready to receive the truss-rod and two carbon-fibre pieces; I finally paid up and bought proper luthier’s 8 x 4mm strips despite what I talked about above (a long way above).



I decided to keep up the Douglas Fir theme by utilising the door panels. These are always very decorative but are, in fact, plywood. However, it is very substantial 3-ply and the top is quite easy to slice off and clean up. Again, I’m not sure how many knocks it will take before looking a bit battered. Call it patina.




While I was about it, I drilled and shaped the headstock to almost final size using one of my trusty paper cut-outs:





I hope some of you realise that my headstock is in fact an homage à Westone, incidentally. Here is a Westone headstock, which also gives the strings a nice straight run through to the machine heads:



Another slight error coming up. The plan is to run the “heel-block” under the soundboard so that they can be glued together; this is easy when building on a solera, of course, because you are building from the face through to the back. However, I forgot about this when installing the truss rod so it didn’t make life easy for me when I was trying to first flatten and then gently curve the end bit so that it would make good contract with the underside of the soundboard. Next time I will sink the truss-rod a little deeper!



You can see the housings for the ends of the “A-braces” in the top of the heel-block in this picture, too. Anyway, having removed a small channel from the soundboard, the heel-block now sits nicely where it should, though it’s not yet glued in place:



Not yet glued in place because I have to cut housings for the rim to enter in the sides of the block and generally shape it to fit. I’m wondering at the moment whether to leave it as a hefty block in the middle of an otherwise fairly light guitar or whether to trim off all excess and leave a skeleton. I know it’s good to have a light and therefore responsive guitar but that surely refers to the box alone rather than to the neck and blocks etc. Advice welcome (though not necessarily followed).

Afraid I don't know what it is exactly, which is why I included the picture of the end-grain; that is usually conclusive if you know your timber. As a furniture restorer/french polisher I suppose I ought to know the difference but most of what I do involves making bits of wood look like the bits of wood I am attaching them to even if I have to paint in the grain on occasion to complete the illusion. However, I do suspect this is "Spanish" or "Cuban" - something that you can't get hold of any more for love nor money but which used to be sent back as ballast on ships taking goods and passengers out to the New World in them days.  Definitely a Swietenia species anyway, which makes it a "genuine" mahogany.

Rob,

Great progress and a nicely executed change of design and direction on the hoof with the cutaway. Looks good and is pointy enough to inflict serious damage in a barroom fight



Could well be Cuban and the white specs in the wood would be consistent with that - lucky you. Unfortunately the original "passengers" you mention weren't so fortunate and were non paying coming from Africa. That's how the South American hardwoods got to Europe as ballast on the return journey and were dumped on the dockside to the surprise and delight of furniture makers.

I gather the idea of a solera is to build the guitar from the face through to the back. My solera took a lot of effort to built (since it is made out of slices of mdf glued face to face and then sanded down to their final profile, which matches the arc of the face of the guitar). The mdf was a big mistake since it delaminates alarmingly easily and I doubt that it will keep its shape accurately once I start asking it resist any kind of cramping. Anyway, I’m stuck with it for the time being until I find time to make another out of some nice stout pieces of pine – or even Douglas Fir! This is where the build begins then; I have a neck and I have a soundboard and the solera is all set up to line them up correctly and glue them together. Unfortunately, I haven’t arranged any means of cramping the heel-block on to the end of the soundboard yet so I have gone a bit Heath Robinson with my half hundredweight of iron to hold them together while the glue goes off. (I’ve just deciphered the writing on top of the iron block and it reads “56 lbs” when the light’s in the right direction, which, as many of the old folk hereabout will know, is 4 stone or half a hundredweight).




Here’s a more dramatic view with the iron block lowering like a thundercloud:




You can also see here that I have at least started to shape the heel. It’s not symmetrical because of the cutaway and because I trimmed the other side of the rim away too far without thinking it through so it looks a little bit odd with the stripe down the middle which isn’t down the middle! Despite all these misgivings, I am content that the line of the neck is pretty well spot on in both planes: i.e. the centre line points straight down the join down the middle of the soundboard and the angle the face of the neck makes with the face of the soundboard is correct; that angle is… 180° - better known as a straight line! I know that necks tend to be canted back one or two degrees but I have planned this so that it can be a straight line. Here are some drawings to prove it:





I have the centre of my saddle at 12.3mm above the soundboard and estimate an action of 2.18mm above the fret (which stands 1.19mm above the fretboard) for strings 3 and 4 at the 12th fret. If I taper the fretboard from 5.5mm to 6.34mm at the body end, then I can have a straight line running through from the face of the neck (not the fretboard) to the face of the soundboard. However, this taper is difficult to do precisely so I tried various thicknesses of fretboard to see how they would do. Here is the 5mm fretboard:




As you can see, I have to start canting the neck back at a very subtle angle for the strings to hit the saddle 12.3mm above the soundboard (if the action etc. are kept constant). So I kept going with thicker and thicker fretboards until I reached one which meant I didn’t have to cant the neck back at all. Here it is:




You will observe that it is 6.75mm thick. I don’t think that’s outrageously thick so that’s what I am going with on this guitar. If you have (a) followed what the hell I am talking about and (b) think it is outrageously thick, please let me know as soon as possible so that I can perform another volte-face before your very eyes.



Meanwhile, in another part of the workshop I have been gluing together two pieces of walnut to make up the back of the guitar. I used the traditional tent method with fish glue and a row of nails down either side but had to “encourage” the tent to lie flat with various heavy tools; Heath Robinson makes a second appearance:




While that was going off and settling down, I removed the ½cwt and examined the neck-soundboard union. It’s tempting to see if it flies (like a paper dart) but I resisted the urge and took some photos instead:





I did notice a small oversight; where the soundboard is cut away for the cutaway, there will be an undesirable line of Douglas Fir between the mahogany of the cutaway and the fretboard. I therefore trimmed the Fir back slightly and glued in a piece of mahogany to mask the edge:



And this (below) is a bit messy; need to sort myself out a bit so that bits like this, which are almost on view, don’t look quite so amateurish:



Meanwhile, back in the other part of the workshop, the back board had gone off sufficiently to stand the strain, so I set about sanding and planing to get the board down to a reasonable thickness:



It gave me a headache and irritated my lumpy knuckles but I think it’s just about down to under 2mm in most places now – and it’s starting to look like a back:



though that could have something to do with cutting it out to be back-shaped!



Well, that’s the way things stand as of this evening and, since it’s half-term and I have children, we are away for a few days from tomorrow so this is the way things will stay for a little while.



Thanks for reading.

Rob,

More great progress. Adrian Lucas (ajlucas) would be in a better position to comment as he builds with Spanish heels but the top where the bridge is usually domes up slightly under string tension and the string tension will also pull up the neck at the headstock end changing the actual neck angle into a slight positive one and you have to allow for this "wriggle room" in your calculations. This is why steel string guitars usually have a slight negative neck set angle - in your case you'll probably need the fingerboard to be thinner than you are planning now.

On second thoughts I think that should be "thicker" than you are planning now.

Great input Adrian . I used a Douglas Fir top once and it was a great top wood.