Skip navigation

Category Archives: techniques

V joint finished

I had intended my previous post to be the last on the V joint. But, as I’ve just completed a guitar using the one that I made for the photographs, the series can end in a rather more satisfactory way by showing how it turned out on an actual instrument.

 

 
Here’s a close-up to show any sceptics that the small extra piece of wood glued on to the male part of the V really is invisible in the finished joint – scroll down to the last couple of photographs in this post if you can’t remember what I’m talking about.

 

V joint – final fitting and gluing

Before gluing up the joint, it’s worth taking some trouble to make sure that the two parts fit perfectly. I put the neck in a vise and hold the headstock in place while checking for gaps with a 0.05mm feeler gauge. A bright light behind the joint also helps to reveal places where the fit is defective.

Here I’ve discovered that the sides of the V are a bit loose…

…while the shoulders are tight.

A couple of fine shavings taken off the shoulders of the headstock using a shooting board…

…improves the fit. As a final check, I rub chalk over the male part of the V joint, locate the female part in position and press the joint together hard.

Where the fit is perfect, chalk will be transferred evenly. High spots, on the other hand, show up as a blotch of chalk surrounded by unchalked wood. Here it looks as if there’s a high point on one side near the mouth of the V.

A small file takes off the bump…

…and a second chalk fitting shows that the joint fits pretty well all over, except for a small low spot on one side at the apex of the V. I decide that I can live with that.

The next step is to dust off the chalk, size all mating surfaces of the joint with hot dilute hide glue and leave them to dry.

This is the clamping arrangement that I use. It’s important that the compression force runs through the centre line of the headstock and bears directly on the shoulders of the joint. Chiselling off the front of the V where it projects through the headstock allows the bar of the clamp to sit close to the surface of the headstock.

Once I’m happy that I can get the clamp into exactly the right position, I un-clamp, brush medium strength hide glue onto all joint surfaces, re-clamp it and leave it undisturbed for a couple of hours.

Here it is after taking the clamp off. The shadow below the right hand shoulder of the joint indicates that the headstock is slightly twisted relative to the neck. I suspected that this would happen while I was making the final adjustments but decided that the inaccuracy would be small enough to plane it out after the joint was glued up.

And I’m pleased to say that it was.

The back of the joint looks a bit weird until the extra block is shaved off.

But these two necks show that it comes out all right in the end. Even with a magnifying glass it’s scarcely possible to see that extra wood has been added and after the final shaping it will be quite invisible.

That’s the last of the series of posts on making a V joint. Thanks to anyone who has followed the story this far. Before finishing, I ought to add that there are many variations in the way this joint can be cut. Some makers, for example, prefer to use a template for marking out rather than a ruler and dividers. Please add a comment if you know how to do it quicker or better.

Click on the thumbnails below for larger pictures.

V joint – cutting and trimming

Moving on from my previous post about marking out a V joint, it’s time to cut and trim it to shape.

First, I saw out the V in the headstock, keeping close to the lines but being careful not to saw past them. I try to be brave in sawing up to the line at the narrow end of the V because that’s the hardest part to clean up later.

Next, I stop to put a fresh edge on the chisel that I’m going to use. When it will slice through tissue paper, I reckon that it’s sharp enough.

I clean up the V, paring from both sides towards the middle. Final cuts are carried out with the chisel resting in the knife line that marked out the joint. A small square is useful to check that the sides of the V are flat. The most difficult part of the joint is the apex of the V but a slicing cut with the corner of the chisel will remove the last bit of waste.

Here’s the female part of the V joint in the headstock finished. It shouldn’t be necessary to touch it again.

Now I cut the male part of the joint on the neck, starting with the angled shoulders. I chisel out a ramp for the saw in the usual way…

… and then saw down to the V, keeping clear of the lines.

I mark the starting point of the cuts for the sides of the V on the endgrain…

… place the neck in a vise, tilting it so that the cut will be vertical, and …

saw off the sides of the V with a tenon saw.

I mark and keep the pieces that I’ve just sawn off. They’ll be useful later.

Now I clean up the V and its shoulders with a chisel, paring in from both sides as I did for the headstock.

Here it is almost finished.

The neck and headstock are now tested for fit. Below is the view from the fingerboard side of the neck.

And here’s the view from the back of the neck.

As you can see, there’s a problem at the apex of the V, where a shadow shows that the neck isn’t quite deep enough to fill up the whole of the female part of the joint in the headstock. (My stock of mahogany for necks is planed up at a thickness of 25mm which means that I always run into this difficulty.)

The solution is to add a little extra depth at the apex of the V. This is where the offcuts that I saved come in handy. I prepare a small piece from one of these…

and glue it on, taking care that the direction of the grain in the extra piece is orientated in the same way as the grain of the neck.

When the glue is fully hard…

… it’s sawn roughly to shape…

… and trimmed with a chisel. This addition will be invisible in the completed joint.

The last step is to make sure that everything fits to perfection before glueing up. I’ll discuss how to do that in the next post.

Click on any of the thumbnails below for larger pictures.

V joint – marking out

Although the geometry of the V joint is simple, it’s surprisingly hard to to visualise if you’ve only seen the joint on a finished guitar. So, in an attempt to make the marking out easier to understand, I’ve sketched it below.

As with all joints, the more precisely it’s marked out the better the final result. It’s crucial that the stock is sized and squared up accurately. The headstock needs to be 17 or 18mm thick to give a final thickness of 19 or 20mm after application of the veneer. The neck must be rather thicker – at least 24 or 25mm – or there won’t be enough wood at the apex of the male part of the V where it engages with the female cut out part in the headstock. The side view in the drawings of the joint above will show what I’m getting at. (Even 25mm thickness may not be enough for full engagement but I’ll show how I deal with that problem in my next post.)

It’s also important that the end grain edge at the lower end of the headstock is exactly square to the sides and faces. I ensure this with a low angle plane and a shooting board.

To begin the marking out, I scribe a centre line down both faces of the headstock with a marking gauge, being careful to scribe both faces from the same edge.

Then I mark the corners of the V with dividers, placing points 18mm either side of the centre line to form the base of the V, and a single point 42mm up from the base on the centreline to define the apex. In the photograph, the pinpoints are marked with chalk to make them more visible.

A single bevel marking knife is used to mark the sides of the V, keeping the ruler on the outside of the V. I try not to cut beyond the point of the V, particularly on the back of the headstock. It doesn’t matter so much on the front which will be covered with veneer later.

To ensure that the ruler doesn’t slip, it’s helpful to fix a strip of fine sandpaper to its underside with double-sided tape.

Here’s the V marked out on one face of the headstock. This process needs to be repeated on the other face so that both sides of the headstock are marked. I haven’t bothered to illustrate this.

Now it’s time to mark out the male part of the joint on the neck. Again, I start by scribing a centre line down both faces. Then I square a line across the upper face of the neck slightly more than 38mm from the end.

Using a sliding bevel set for the angle that I want the headstock to make with the neck (10º in this case, so the bevel is set to 80º) I scribe both sides of the neck from the line that I’ve just squared across it.

Then I square across the back of the neck at the point where the angled lines on the sides end. Finally, I mark out the V on both faces using dividers set to exactly the same dimensions that I used on the headstock. The only difference is that, when it comes to scribing the lines with the knife, I keep the ruler on the inside of the V.

Here’s the top of the neck marked out…

…and here’s the back. You can see that, on the back, the V is positioned slightly further down the neck than it is on the front.

In the next post, I’ll show how I cut out the joint.

You can see larger versions of the photographs by clicking on the thumbnails below.

V joints for guitar headstocks

There are two ways to create the angle between the headstock and the upper end of the neck of a guitar. One is to saw it out whole from a large piece of wood; the other is to make it out of two pieces using a glued joint – either the V shaped joint invented by the early guitar makers or a scarf joint. Of these options, the most rational is the scarf joint. It’s quicker and easier to execute than a V joint and wastes less wood than sawing out a neck and headstock whole. What’s more, it has a large glued surface so it doesn’t rely on nanometric accuracy for its strength.

Despite the obvious advantages of a scarf joint, the V joint has become something of a fetish among guitar makers. This is easy to defend where historical accuracy is concerned. After all, if you’re attempting a copy of a 19th century guitar, it’s desirable – even obligatory – to imitate the constructional methods of the original maker. But for a modern instrument, why prefer a weaker joint that takes longer to make?

The answer, I guess, is to show that you can. It’s not a million miles away from the Georgian cabinet makers who made the pins of their dovetails so skinny that they almost vanished at the narrow end, as you can see in this photograph of the drawer of the table at which I’m sitting as I write this post.

There’s no practical advantage either in strength or speed of production in cutting dovetails like this. Indeed, the reverse must be true. But they do provide an understated way by which makers can demonstrate that they care about seldom seen details and show off their skill.

I’ve found myself using a V joint for both these reasons. Here’s a copy of a 19th century guitar that I’ve mentioned in previous posts. The V joint in this instrument was present in the original and it seemed right to keep it.

On the other hand, the V joint in the guitar below could perfectly well have been a scarf joint. The guitarist for whom I made the instrument didn’t notice it until I drew it to her attention. Still, I enjoyed making it and, for reasons that I can’t properly explain, felt that it was worth the extra time and trouble.

I’ve just cut a couple more V joints for guitars that I’ve got planned for 2012 and, although instructions for making this joint already exist (see here, for example), I thought it might be useful if I kept a camera handy to document the process. In the next post, I’ll explain how I mark out the joint.

A mirror aid to drilling free-hand

Although I was sure that I’d read somewhere that there was a way of using a mirror to help judge when a drill bit was truly vertically, I struggled to find an account of how it was actually done. Eventually, after a lot of googling, I came across this letter and illustration published in Popular Mechanics nearly 80 years ago.

To find out if it worked, I bought a cheap handbag mirror.

First I cut off the hinge and trimmed back the plastic mount along one edge.

Placed next to the drill bit, the mirror showed when the drill was vertical…

… and when it wasn’t.

It’s a simple idea but I was impressed by how well it worked. A problem though, is that the mirror only tells you whether the drill is vertical in one axis. You have to move the mirror around the drill to check whether it’s vertical in the other axis and while you’re doing this, it’s easy to lose the vertical on the first axis.

One solution might be to have an L-shaped mirror or, perhaps better still, a mirror with a hole in its centre. Then, all you’d have to do to check that the drill was truly vertical in both axes would be to move your head.

So I ground a small hole in the centre of the other mirror and tried it out.

This is the view when the drill is vertical.

And when it’s miles off.

Of course, you don’t need a mirror to see when the drill is as far out as that. The benefit is that it makes it easy to spot small deviations from vertical.

Does it work in practice? As a test, I drilled ten 2mm diameter holes at 10mm intervals along a line in a piece of MDF and stuck cocktail sticks into them.

Not perfect – but not bad either. Certainly better than I was able to do in a repeat of the experiment when I used a small try square instead of the mirror as a guide, as you can see below.

Obviously, the best way to drill a truly vertical hole is to use a drill press. But there are occasions when this is impossible because the work piece is too large or too awkwardly shaped. It’s then that this trick with mirrors might come in handy.

Thinking about truss rods

As you’ll have gathered from my last post, I’ve been making a steel string guitar recently. That’s something I hadn’t done for a long time, and it got me thinking about truss rods. One puzzle is how they got their name. Doesn’t the word truss conjure up something like the Forth bridge or the roof structure of this magnificent medieval tithe barn¹?

Wikipedia says that, used in an engineering context, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. So it’s surely an exaggeration to call a rod in the neck of a guitar a truss. Still, it’s not seriously misleading and I expect that most readers will think I’m quibbling.

Another puzzle surrounds the purpose they serve. As far as I know, no classical guitar maker finds them necessary. So why is it that steel string guitar makers never build a guitar without one? The straightforward answer is that steel strings exert more tension when tuned up to pitch than nylon strings and that a truss rod is necessary to counteract this extra force.

But I wondered if this explanation really held water. Using information provided by d’Addario, a reasonable estimate of the combined tension of 6 nylon guitar strings is about 40 kgs, while 6 steel strings exert nearly double that at 70kg. A load of 70 kgs certainly sounds a lot – the weight of an adult man – but don’t forget that it’s acting at a mechanical disadvantage when it comes to bending or breaking the neck of a guitar. The pull is only a few degrees away from parallel to the neck’s longitudinal axis and the compressive forces will be substantially greater than the bending forces.

Using simple beam theory, I made some rough calculations to get a sense of how much the string tension of a steel string guitar would bend the neck. These calculations didn’t attempt to take the taper of the neck into account – I simply pretended that the dimensions of the neck at the first fret remained constant all the way along the neck until it joined the body of the guitar – and they ignored the fact that the fingerboard and the neck are of different woods that have different material properties. (More details of the calculation are given at the end of this post in a footnote, if anyone is interested enough to check².)

The answer turned out to be that, tuned up to pitch, string tension would deflect the nut end of the neck about 1.6 mm forwards of its unloaded position. Although this is bound to be an over-estimate (because the calculation neglected the stiffening effect of the fingerboard and the increasing dimensions of the neck as it descends), I was surprised how large the deflection was. And I wondered if I’d got something seriously wrong. To check, I made a primitive model of a guitar neck to make some actual measurements. As you can see in the photographs below, the experimental neck is smaller in cross section than a real neck but it’s modelled realistically with an angled headstock and nut. Loaded with a 14lb weight, I measured a deflection of 1.47 mm at the nut, which compared fairly well with a theoretical value of 1.26mm derived using the dimensions of the model neck. So I’m moderately confident that my calculations for a real guitar neck aren’t too far out.

It looks as if the obvious answer is at least partly right. You almost certainly do need a truss rod to counteract the bending effect of string tension on the neck of a steel string guitar.

I suspect there’s another reason for truss rods too, and that is to prevent creep. Wood that bears a constant load for a long period tends to deform gradually even when the load is far short of its breaking strain. This is the reason why the ridges of old roofs tend to sag in the middle. In his book, Structures, J E Gordon explains that it’s also the reason why the Ancient Greeks took the wheels off their chariots at night. The wheels were lightly built with only 4 spokes and a thin wooden rim. If left standing still for too long, the wheels became elliptical in shape.

So perhaps I’ve ended up proving something that most guitar makers knew already. However, I don’t feel that the exercise has been a complete waste of time. Musical instruments shouldn’t contain anything that isn’t either necessary or beautiful. Since truss rods certainly don’t fit into the latter category, it’s good to know that they qualify for the former.

Footnotes

1. Thanks to Kirsty Hall for the image of the tithe barn.

2. Details of calculation of neck deflection.

Neck: width = 44mm; depth = 21.5mm; length (to 14th fret) = 355mm
Force exerted by string tension = 700 N
Nut taken as being 8mm above centroid of neck
To work out the area moment of inertia, I assumed that the neck was semi-elliptical in cross section and that the neutral axis ran through the centroid.
Modulus of elasticity of the neck was taken as 10,000 MPa.
Deflection was calculated as Ml²/2EI, where M = moment exerted by strings at the nut, l = length of neck to neck/body join, E = modulus of elasticity of material of neck (taken as 10,000 Mpa) and I = area moment of inertia of neck (assumed to be a half ellipse).

Stiffness of soundboard braces, harmonic bars and bass bars

Experienced guitar makers (and books about guitar making) always advise quarter-sawn spruce and vertical orientation of the growth rings for braces and harmonic bars. You hear the same if you ask a violin maker about selecting wood for the bass bar. They’ll explain that wood is stiffest in that orientation, which means that your soundboard will get maximum support for minimum weight.

That might seem the end of the matter but, if you’re one of those disagreeable people who can’t resist probing further and ask if they have ever measured the stiffness of wood in different grain orientations or, if they haven’t, how they can be so sure, you may hear the sound of feet shuffling and detect a swift change of subject.

In fact, as Liutiaio Mottala points out on his interesting website, considering the number of wooden structures that have been built over the years, the information available about how grain orientation influences the physical properties of strength and stiffness is remarkable sparse. In Chapter 4 of The Mechanical Properties of Wood, in USDA Forest Service, Wood Handbook – Wood as an Engineering Material, (available here) there’s a short section on the subject starting on page 4-31, saying that properties of wood do vary slightly according to orientation of annual rings in some species. Disappointingly, it gives no information either about the size of the variation or about which species exhibit the variation. Mottola’s website mentions work done by David Hurd, who found no difference in stiffness between quartersawn and flatsawn wood for the samples he examined but, as far as I can discover, no details are available on line.

Using the rather primitive set-up shown below, I attempted some measurements myself. The wood is straight grained European spruce with around 14 growth rings to the inch. I sawed and planed 9 pieces, each around 35cms in length and between 7 and 8.5mm in width and depth. I used a shooting board to to make sure that each piece was as straight and as square in section as possible and that the growth rings were oriented more or less parallel to one face (and therefore more or less at right angles to the adjacent face).

Each bar was then clamped in a vice with about 22cms protruding horizontally. I then hung a weight of 2lbs, exactly 20cms away from the vice jaws and measured the resulting downward deflection 4 times for each piece, rotating it through 90° between each measurement.

I’ve summarised the measurements that I made in the table below. The deflections I’ve given are the mean of the 2 measurements for each bar in each orientation. As you can see, the way the growth rings were orientated made remarkably little difference to the magnitude of the measured deflection and there was no consistent tendency for the wood to be stiffer in either of the two orientations.

Now, I’m well aware of the many deficiencies in my experimental design. One of the most serious is that all my specimen bars were cut from the same board and it’s possible that other wood from other trees behaves differently. And of course both the way I prepared my specimen bars and the simple test rig meant that all sorts of errors could have influenced individual measurements. However, the consistency of the findings encouraged me to think that these errors can’t have been very large. If they had been, the size of the difference between quarter sawn and flat sawn deflections would have shown much more variation between different bars.

As a check that the sorts of results I was getting were plausible, I used simple beam theory (max deflection = Wl³ ⁄ 3EI )to calculate the size of deflection that might have been expected, using a value of 10 000 MPa for E, the elastic modulus of spruce. This worked out at 0.34 inches, which was close enough to the deflections that I was observing to reassure me that my simple set-up wasn’t completely inadequate for its purpose.

So what do I conclude? Well, probably nothing that would stand up in a court of law. But I’ve satisfied myself that that spruce cut on the quarter isn’t very different in stiffness from spruce that has been flat-sawn and that where wood of the size and sort used for bracing soundboards is concerned, it doesn’t matter much whether the growth rings are orientated vertically or horizontally. In future, when selecting wood for struts and braces I shall feel free to use either orientation, to make the best use of what I’ve got available.

As a postscript, I was interested to learn from Stewart Pollens’ book Stradivari (ISBN-13: 978-0521873048) that the Hill collection of 50 bass bars taken from violins and cellos of the first rank, including those attributed to Antonio Stradivari himself, contains 11 that are flat sawn (that is to say, the annual rings are orientated horizontally). Maybe instrument makers in 17th century Cremona made less of a fetish about the orientation of growth rings than we do today.

Guitar neck support

When working on the top of a guitar, I put the instrument on a carpet covered bench and prop up the neck on a block of wood that has a shallow, foam-lined curve cut into the top – as you can see in the photograph above. But I’ve recently learnt a better method. The device below, made out of 2 semi-circles of 18mm plywood, radius about 3 inches, adjusts itself automatically to the taper of the neck and supports it in a far more stable way.

The danger when using the simple block is that it tips over if the instrument is moved along its longitudinal axis. Of course, one can always clamp the block, but with the new neck cradle there’s no need. I’m grateful to Richard Nice (who invented the plane that I wrote about in my last post) for this bright idea.

A plane for guitar struts

Richard Nice, who among many other things makes guitars, recently showed me this attractive plane that he had designed for shaping soundboard braces and harmonic bars. He made it from an off-cut of beech and a discarded cutter from a plough plane and, so that there could be no doubt about its provenance, he signed it too.

The screw adjustment is simple but ingenious, depending only on a carefully sited screw tapped into the back of the plane and a slot cut into to the upper end of the iron.

The plane is comfortable to hold and works well. Its narrow cheeks enable it to take shavings from the lowest part of the brace and produce either a triangular or gothic arch section according to your preference.

Panormo guitar

Continuing my experiments with smaller guitars led me back to the 19th century and the instruments made by Louis Panormo. One of his guitars, made circa 1840, is in the Edinburgh University Collection of Historic Musical Instruments and, rather helpfully, a workshop drawing is available. I had other assistance too. My friend, Peter Barton, who makes fine acoustic guitars in Addingham, West Yorkshire has a Panormo guitar in his collection, which he generously allowed me to handle and photograph. And Gary Demos has a series of photographs documenting his construction of a Panormo guitar copy on his website.

Here are some photographs of the instrument as it was being built. It isn’t, and wasn’t intended to be, a slavish copy. I felt no need, for example, to reproduce the inexplicable scarf joint at the heel end of the neck that was indicated in the drawing of the Edinburgh instrument and that you may just be able to see below in the Panormo guitar owned by Peter Barton. In the photograph, it runs more or less horizontally from where the neck joins the ribs to the back of the neck, ending around the 7th fret position. (Do tell me, if you understand why Panormo did this.)

I also felt free to to inlay spalted beech for the rosette instead of the mother of pearl set in mastic of the original.

I did however, reproduce the V-joint between the neck and headstock, although the width of the headstock itself was increased slightly to accommodate modern tuning machines. Followers of this blog might recall an earlier post about making the V-joint.


.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

The bridge design is more or less the same as Panormo’s, except that a slot was routed for a carbon fibre saddle to provide a little leeway for adjusting the action later on. His bridge has no saddle. Ebony bridge pins were turned to replicate the original way of fixing the strings.

And here are 3 photographs of the completed guitar. The body length is 450mm, width across lower bout 290mm and scale length 630mm.


Making rosettes for a classical guitar (4)

All that remains at this stage is to cut the inner and outer circles to make the annulus of the rosette. I start by drilling a hole in the centre of the work piece…

… and then use a Dremmel mounted in a shop-made jig to cut the circles. (More details of the jig are available in the ‘Tools and Jigs’ section of this site.)

Here are the two rosettes that I’ve talked about in early posts in this series cut out.

And here are a few more. Going clockwise from top left, they’re made of English yew, laburnum, spalted beech, spalted crab apple and mulberry burr.

It’s probably best to leave them attached to their base until you’re ready to install them on the soundboard but, as you can see from the two rosettes at the bottom, I don’t always heed my own advice.

Making rosettes for a classical guitar (3)

The rosette below is made from laburnum, arranged to show the striking contrast between the light coloured sapwood and the dark heartwood. It’s rather more complicated to make than the spalted beech rosette shown in the previous post and a fair degree of accuracy is needed throughout.

The starting point is a small piece of laburnum. This one has been air drying for a couple of years and I reckon that it should be pretty stable by now. I’ve scraped off the wax that covered the endgrain while it was drying.

The first step is to decide how many individual sector shaped pieces to use to complete the circle. I’m planning to use 20 for this rosette, which means that the sides of the billet must be planed to converge at an angle of 18°. That’s hard to manage on the bench top and it’s worth making a cradle to hold the wood while you plane it to size and shape. Go slowly and carefully because it’s important not only that the angle is right but that there’s no taper along the length of the piece. In addition, the width must be right so that the line between the sap wood and the heart wood ends up where you want it to be in the finished rosette.

Having planed the wood to a near perfect prism, it’s sliced on the bandsaw.

The pieces are numbered as they come off, so that they can be put together again in consecutive order.

Here the rosette is being assembled ‘dry’.

It may be necessary to make some fine adjustments with a shooting board and a block plane.

Here, the first piece is being glued and clamped into position on its plywood base. The base has been marked out in pencil to aid positioning of the individual pieces.

As the pieces are glued into place, the rosette nears completion.

Cleaned up and levelled with a finely set block plane.

Making rosettes for a classical guitar (2)

One of the rosettes is going to be a replica of the one used for the zebrano guitar that I made last year from this remarkable lump of spalted beech.

I used a bandsaw to cut 2 thin (3mm) slices …

… and trimmed and book matched them to create a symmetrical pattern.

A card with a rosette shaped cut out helps give an idea of what the finished rosette will look like.

I use veneer tape to keep the two pieces in registration while they are glued to the base that I described in the previous post.

Clamping up.

Out of the press and ready to be planed flat and cut into shape. The veneer tape comes off easily if a little hot water is brushed on.

The next post will be about the construction of a different sort of rosette.

Making rosettes for a classical guitar (1)

Last July I wrote a couple of posts about making a guitar rosette from spalted beech. But I missed the opportunity to photograph some of the details of its construction and, since I’ve been making some similar rosettes recently, I thought it might be useful if I had a second attempt at explaining the method.

For reasons that I’ve discussed before, I like the visual effect of rosettes made by inlaying wood with contrasting colours or a striking figure and often use this technique when making guitars.

These rosettes are made from at least 2, and usually many more, individual pieces and I’ve found that it’s much easier to assemble them accurately on a base of thin birch plywood (0.4mm or 0.6mm thick*) than it is to inlay them directly on the soundboard. Because the plywood is so thin, it too needs a stable base during the assembly process. But, of course, it must be possible to remove this base when assembly is complete. I start with a square of 6mm MDF, a similarly sized sheet of clean paper and the square of  plywood that will be the permanent base of the rosette.

One surface of the square of MDF is given a thin coat of hot hide glue.

The sheet of paper is then smoothed down…

…before adding a second coat of glue…

Glueing up 3

and the layer of plywood.

The whole thing is then clamped up in a nipping press and left to dry overnight.

If you don’t have a press, a flat board and a weight work just as well.

The point of the paper and the hot hide glue is that, after it has been assembled, the rosette is easy to detach from the MDF base. In another post, I’ll show the next stages of the process.

*This sort of plywood is used by model makers and, at least in the UK, is easily available from the sort of shops that supply materials for people who build model aeroplanes.

Follow

Get every new post delivered to your Inbox.