9-string Acoustic Guitar

The purpose was to make an acoustic guitar to my own preferences which are

(1) 9 string (lower three duplicated)

(2) wide fretboard, as wide as I wish (like a classical guitar)

(3) loud and long sound (i.e. a big jumbo body)

(4) as simple as possible (no embellishments)

(5) as cheap as possible

I am located in the UK, so I am somewhat limited with materials in comparison with the US. So I will indicate where I bought them. I followed instructions of some articles already published here and on the Internet and from the book "Build your own acoustic guitar" by Jonathan Kinkead.

Step 1: The Mould

The solid mould is needed to keep guitar body in position when you work on it, especially to keep curved body sides curved.
The guitar body sizes : 532 x 430 x 132. I bought some 18mm MDF boards in B&Q and got them cut in B&Q into rectangles 282 x 607 mm : Figure 1.

Made a template of 4mm MDF to draw body contours : Figure 2.

The next step is to cut out the required body shape by an electric jigsaw : Figure 3.

Both cut parts will be needed : one for the mould itself (inner), another for outer mould to bend guitar sides. Then I fastened the two piles of MDFs into the two left and right halves of the mould by 8mm bolts, nuts and washers bought in Screwfix : Figure 4.

No glue was used. The next step is to smooth the inner surface of the mould with a drum sanding kit (Screwfix) and a drill : Figure 5.

This is what it looks looks like after sanding : Figure 6.

It is very useful to make the construction detacheable with an aluminium angle (B&Q), bolts, nuts and screws (Screwfix) : Figure 7.

Step 2: Side-tapering Jig

Sides of a guitar taper to the neck. This tool is placed on top of the mould to facilitate cutting of guitar sides : Figure 1. It is attached to the mould by screws.

It is made of 4mm plywood and some pine planks (B&Q). I used a jigsaw to cut plywood and small screws to attach planks to the surface : Figures 2,3,4.

Step 3: Stop Blocks for the Mould

Use stop blocks (see pictures) to provide support for the guitar body when processing its other side. The body lays on the stop blocks. They are inserted/removed into/from holes drilled in the mould.

The blocks are made of pine planks (B&Q) cut into pieces with 8mm wooden dowels (Screwfix) glued into.

Drill holes keeping in mind that the top of the body is flat, but the bottom is tapered (two rows of holes).

Step 4: The Neck

We finally start making a guitar part. Start from the neck. I made the neck from pine planks bought in B&Q. It does not mean that it is a good choice, the only thing I wanted was the lowest price. People normally make necks from mahogany and I suppose it will cost something like 45 pounds and more. B&Q pine wood is dry. I bought it before and the planks did not lose their straight shape. I do not say that it would be a great choice, I simply do not know what will happen with time.

Another choice is oak (available in B&Q, but at twice higher price than pine), but people say that oak is not good for guitar parts as it contains oil which prevents it from glueing. I however, used oak for fretboard (see below) and it was OK. Before glueing, I sanded the surface and cleaned it with spirit - I am not sure that it is really needed.

So, I bought some pine planks in B&Q, one being 25x68x2400 at 11 pounds(? - all prices here and below are approximate) and another plank for the head of 15 mm thickness. Try to buy planks which

(1) have no knots and cracks

(2) more-or-less quarter-sawn (look at the Internet what it is)

So, make a neck head plan on the paper (Figure 1). The main important thing is that strings from the nut to the machine (inner point of tuning machine) must be straight not touching other machine heads.

Figure 2,3 : the neck is glued from two parts : the neck and its head.

Figure 4,5 : the head of 15mm wood is glued of two parts, cut by jigsaw and the cuts sanded with a drum sanding kit with a drill and round files.

Glueing the two parts. I used classic Titebond glue. At first, the task looks very simple, however, the problem is the glue makes the two parts VERY slippery and one part WILL (100%) slide under clamp's pressure. We need to use a metallic pin between the surfaces to keep them in place. This is Figure 6.

Figures 7,8 : templates for neck shape made of 4mm MDF - the process is exactly the same as in shaping ship model body with frame templates : rub the inner surface of template with pencil, then rub the template around the blank - the marks will show you where to remove wood.

Figures 9,10,11 : neck heel is glued from the three parts of the same pine plank. It is cut into shape with a Japanese Shinto saw rasp - very useful tool (16 pounds) (on Figure 8). It cuts wood very easily, so be very careful, especially when trying to make a plane surface - in a moment it will spoil the shape.

The next step is a trussrod groove (Figure 12). Trussrod is adjustable two-way 355mm in length (Tonewoods, 5 pounds). The groove must be 6mm wide with height to cover the rod. I used an Embauer router (70 pounds, Screwfix) to cut the groove. Keep one side of the neck blank straight line and parallel to the plane of symmetry (Figure 13) to let the router slide along this plane (Figure 14). The gap length should match the length of the trussrod (Figure 15).

Step 5: Top and Back

Top and back. A real problem is where to buy the wood at an acceptable price. The only place I could find it was Touchstone Tonewoods - I bought a top of two parts of spruce at 10 (?) pounds and back plus two sides of mahogany sapeli at 27 pounds. They arrive at 4-5mm thick and you must make them 3-2.5 thick.

But first of all, glue two parts of the top together. Glue - Titebond.

First, you need to make glued surface ideally straight. For this, use the construction shown on Figure 1 : straight MDF board with one side on top. Use a big planer to cut top edge to the straight edge of MDF board. For both halves.

Then, you need to glue these two haves with straight edges together as shown on Figure 2 : underlay a plank of some 6mm height below the glued edges, some paper under the glued edge to avoid it sticking to the table, insert nails at opposite edges and then glue the straight edge and remove the underlay. Place some weight in the edge with glue (Figure 3).

As a result (the down side after removal of underlay paper) is shown on Figure 4. Now we need to make the whole wood thinner. It is a problem. Even with ideally sharp planer, it may leave big cavities on the wood surface (Figure 5). So be very careful.

The same procedure is applied to the mahogany back (Figure 6).

After some planing, I used a Triton band sander (50 pounds, Screwfix), which was useful, but of course I was unable to make ideally thickened wood. And the dust. Everything, including myself, was in dust. The target thickness of top wood must be 3mm, the back - 2.5 mm.

In general, a drum sander for 250-300mm wide wood with regulated target thickness would be very useful but I was unable to find anything in the UK at an acceptable price - everything is huge at some thousands pounds.

I plan to make such a sander myself but still not sure about the design.

Step 6: The Bending Mould

Another useful tool is a mould for bending sides. It is simply another part of every MDF board cut for the inner mould (Figure 1). I made a similar construction of piled MDFs and connected by bolts (Figures 2, 3).

Afterwards, I covered the whole mould with "waterproof" PVA glue (Screwfix) to somehow protect it from wet guitar sides when bending.

Step 7: Forward and Back Blocks

The two blocks keep the two curved guitar sides, top and back (i.e. the whole body) together. The neck is attached to forward block by glue and two bolts (Figure 1).

The height of each block must fit the distance bewteen the back and top surfaces. On Figure 2 the forward block is placed on the surface of "mock" top surface, the block's upper surface must conform to the taper of the back. The same is related to the back block (Figure 3).

Step 8: The Neck-to-body Joint

I use the "bolt and tenon" type of joint as the "dove tail" seemed to me too complicated. Probably it is not at all.

Figure 1 shows the cut lines for the joint. Figure 2 - the cutting process.

Figure 3 : the neck with forward block attached. Look at the gap between the neck and the block - it will be filled by sides, and the vertical position of the block : it will hold the top wood on top.

The two details separate - Figure 4.

Two threaded brass inserts in the tenon - Figure 5.

Step 9: Steam Box

Bending the two guitar sides was quite a problem. I finally achieved an acceptable result, but will not do it this way again.

I made a steam box of MDF (Figure 1) to accomodate a guitar side (Figure 2) and covered it with waterproof PVA glue (Figure 3).

The sides of the box were connected to each other with screws. The "door" was on screws as well. A big side of the box had a hole to let the steam in.

Step 10: Simple Rosette

The hole in the soundboard is 100mm in diameter, the rosette itself - 120mm. It is impossible to make such a hole and the groove with an Embauer router I bought, but I found a way to modify the router - I drilled a hole in a router leg to rotate the router around this point. And it worked fine.

The router is rotated around the nail at the circle centre in the Figure 1.

Figure 2 - two purfing strips each of 1.5 mm wide are glued into the groove. I used a Grip thick superglue (ebay) here. Do not use much of the glue! Use just a small amount to glue strip bottom. The problem is the dry glue is MUCH HARDER than the wood around, and, when sanding, dents are generated around the strip.

Finally I managed to create more-or-less flat surface arond the strip by machine sanding at the expence of wood thickness (Figures 3, 4).

Step 11: Bending the Sides

As I already mentioned, side bending was the most complicated operation. The sides, as the top and the back, were sanded to the width of 2.5 - 3mm. I used a steambox to put a side in hot steam and then attach it to bending mould. Figure 1 shows the original construction : a plastic tube at the most curved part of the side. The pipe was later replaced by a stronger cut-to-the-shape MDF block.

Figure 2 : the tools used in the bending process : steam box (at the upper right corner of the picture), KARCHER K2 full pressure washer used as steam generator (borrowed from my wife) and the sides pressured to the mould. So, the process is :

(1) put a side into the steam box

(2) fill it with steam with the steam generator for half an hour or more

(3) attach the side to the mould, fix it in position

The problem was that the side straightened and did not keep the shape after it was released and it did not bend "smoothly" at the point of its highest curvature, not fully breaking though (Figure 3). It was a pain.

I even tried to keep the second side in hot water in the bath (Figure 4) and it helped somehow but not very much (Figure 5).

Step 12: Assemblying the Body. the Sides

Despite the sides were not of correct shape (Figure 1), it was possible to keep (almost) desirable shape inside the mould (Figure 2).

I use a manual jigsaw to cut the sides to the size (Figure 3). Figure 4 : the two cut sides inside the mould.

Now is the time to use the side-tapering jig and cut the side to the tapering shape (Figures 5,6). Please note : the back (Figure 7,6) is under the sides to keep a proper side height.

Now we connect the two sides together by gluing them with the forward and back blocks (Figure 8). Do not forget to put some paper or masking tape between the glued edges and the mould. Othewise the sides will be glued to the mould!

This is what it looks like now (Figure 9,10).

And, finally, cut out the forward side part with a rotary tool or/and stencil (Figure 11).

Step 13: The Top Braces

I tried to copy the X-brace system from the Kinkead book by extending its bracing system to my jumbo contour and adding one more brace to help cope with additional tension from the three more strings (Figure 1). My braces are made up of pine planks from B&Q. Most of them are of 6-8mm width with various heights. I did not do scalloping (people say the sound would be better), for simplicity.

I used a stencil to shape them (Figure 2) and the router (Figure 3) to round their edges.

Figure 4 shows the original bracing system from the Kinkead book with all brace lengths increased to fit countour of my jumbo guitar.

Figure 5 - this is how I glued the braces to the top - I was just using some weights. I used standard Titebond glue.

Figure 6 - glueing additional small braces which connect to main braces.

Step 14: Gluing All Body Together

Now we have sides, top (soundboard) and back. They must be glued together.

Kerfing is used to increase area of glued surfaces. I did kerfing strips myself : I bought two pine 6x21x2400 planks in B&Q, cut them into four 800mm pieces (two for the top and two for the bottom). Planed them to 18mm height. Rounded one corner with the router.

Then, made many small cuts to make them bending with a jigsaw as shown on Figure 1 with a period of 6-7mm. This is not very fast - takes some time. Some ready kerfing strips can be seen on Figure 2 in the upper right corner of the pricture.

This picture also shows the process of glueing the kerfings into the sides. It is important to glue kerfings protruding vertically from side edge some 1-2mm. I used Titebond (wood to wood glue).

The result is shown on Figure 3. The next step is to level the kerfings with the sides with a small block plane - Figure 4.

Figure 5 shows how the top looks from the inside of the guitar - all its top bracing system. The lowest brace is an additional one I added to withstand more tension from the three string duplicates.

Figure 6 : how the full kerfing systems looks right before glueing top and back.

Figure 7 : before glueing the top. You can see how three main braces stand out. They must be cut and glued into holes in the kerfings (Figures 8,9,10,11).

Glueing the top ... (Figure 12) and the result, view from the inside - Figure 13.

Then, we need to trim the top with the Japanese saw rasp and a stencil : Figures 14,15,16.

The same procedure is applied to the back (Figures 17,18). The back braces are much simpler : just four horisontal braces.

This how the whole body looks : Figure 19.

Step 15: Binding the Body

I used binding only between the sides and the top. I bought a plastic binding strip in Tonewoods.

First of all, I needed to cut a rebate along the top side. For this purpose I used a "depth controller" from the standard Erbauer router which is actually used for other purpose. Anyway, by setting the router this way (Figures 1,2) makes a perfect rebate. The rebate must have a proper size to let the binding strip slightly stand out above the top plane.

Here we need to glue wood to plastic, therefore I used Grip Thick Superglue (ebay). I remembered the lesson with the rosette, so used the glue very sparingly.

Figure 5 : the body after scotch removal; Figure 6 - after sanding.

Step 16: The Bridge

I made the bridge shaped like Gibson J200, from rosewood. Originally I bought rosewood for fretboard and the bridge, but I spoilt the fretboard and made only bridge from rosewood. Looks like it would be OK to make it from a regular B&Q oak, like I did for the second version of fretboard.

The tool on the pictures is used to cut an inclined gap for the saddle with a router.

Step 17: The Fretboard

I used oak from B&Q to make the fretboard. Oak is twice as expensive as pine. People say oak is never used in acoustic guitar construction due to its oily nature, they say that oak is hard to glue because of it. However, I made some precautions (sanded the glued surface and cleared them with spirit), but I am not sure that it is necessary.

I glued the fretboard of two halves (Figure1) exactly as I glued two pieces of top and back with standard Titebond glue.

Then another subtle thing : cutting the fret slots. First, you need a special fretting saw which produces accurate slots of 0.6mm wide. I bought a Hosco at Tonewoods at 24 pounds or so - quite expensive. But it does its job.

The slots should be located from the neck at accurate distances which are given in the Kenkead book with hundreds of millimeter accuracy. I do not think it makes much sense as, anyway, it is impossible to cut a slot even with a tens of mm accuracy. I understand the maximum you can achieve is something like 1/3 of mm. Anyway, the important parameter is the string length TO THE SADDLE, not to the nut, which is much greater and therefore more accurate in a relative sense.

The fret slots must be perpendicular to the centre line and the cut must be ideally vertical. When using a manual saw, the cut may be a little inclined, therefore I do not think it is a good idea to cut slots and then provide the fretboard with camber - after planing, the final fret position maybe impermissibly far from the nut. Therefore, I think the best way is to provide the fretboard with camber and THEN cut fret slots (Figure 2).

The next step is fingerboard inlaying. The inlay dots are glued to the fretboard with a spare amount of Superglue (Figures 3,4).

Step 18: Attaching Neck to the Body

Neck must be attached to the body to provide correct distance from strings to frets. The Kinkead book recommends to incline the neck at 2 degrees "otherwise the instrument could be unplayable". I understand this is OK for a domed soundboard, but my top is absolutely flat and a simple solution is to attach the neck to the body with no angle. It is also makes fingerboard attachment a much simpler task.

I used a wedge (Figure 1) to provide a proper neck position. Not very elegant, I understand. In addition I tried neck installations with screwing the two inner bolts via the top hole, what was not very easy, and I did that multiple times as rehearsals.

Then I inserted the trussrod at a proper position (Figure 3) pushing it a little bit (10mm) forward (Figure 4).

And the glueing is shown on Figure 5. Do not forget a couple of pins (small nails with their heads cut) between the two surfaces to avoid sliding! The final result was not very good : I should have spent some time to make a tool to press the fretboard to the top, like the one I used to glue the bridge. I have already made this tool and will not repeat this mistake in the future.

Step 19: Fretting

I bought fret wire at Tonewoods (Figure 1) and cut the wire to a required length at each fret (Figure 2). Each fret end was filed smooth (Figure 3) and glued into the fretboard with a standard epoxy glue (wood to metal) (Figure 4). Use the glue sparingly because it wold be hard to sand the fretboard between frets.

Frets were NOT re-crowned.

Step 20: A Tool to Glue the Bridge

The bridge will be glued after lacquering. We need a tool to press the bridge to the top to achieve good glueing quality, as all the tension of strings is applied to the bridge. The tool is shown on Figure 1, how it works - on Figure 2.

Step 21: Sanding Before Lacquering

I made a simple tool for manual sanding (Figures 1,2) and also used a rotary tool on flat surfaces (Figure 3).

Step 22: Cover With Lacquer

First, we need to cover non-paintable areas with a masking tape (Figures 1,2,3).

I used Dartfords clear nitrocellulose guitar lacquer aerosole (ebay, 18 pounds) as I never tried a waterbase lacquer and trust nitrocellulose more. The aerosole label says that a tin contains enough aerosole for 2 coats, I am not sure about this - I covered this big guitar 6 times by this amount (Figure 4). The full tin weights is 410 grams, empty tin - about 100 or something like this, if I am not mistaken - you can judge by this how much is left.

I did not do any polishing, just left the surface as it is.

Just wanted to test a waterborne finish - bought from NorthWest Guitars. They sent me a wrong one : plain for electric instead of an advertised special type for acoustic and I discovered in small fonts that it contains cancerogenes. No, thanks. I will use nitrocellulose.

Step 23: Finishing

And the last steps. We need to glue the bridge to the top (Figure 1) using the pressure tool (Figure 2). After glueing, I drilled pinholes and widened them with a reamer (Figure 3) and then installed the saddle into the bridge groove (Figure 4).

Then, I prepared the nut (Figure 5) to fit into the nut groove (Figure 6). Installed tuning machines (I bought them at ebay, 12 pounds for 6 machines, I needed two sets).

Other things we need are pins and strings - I bought extra-light d'Addario for 12-string guitars. Better to buy normal 0.012 .. 0.052 strings - it will help avoid wrong intonation.

One important thing here - all the distances :

(1) from the nut to the bridge (saddle)

(2) nut height

(3) saddle height and compensation shape

Normally, I would copy these sizes from a guitar of a reliable manufacturer, I copied it from an acoustic Fender.

Nut height should be as such as to avoid fret buzz near the nut, together with saddle height.

One idea about saddle compensation is as follows : next time I would leave the saddle upper surface flat, measured each string intonation and after this decide how long it must be. Provide a required length by filing the saddle. It would give a required compensation for a given set of strings.

Step 24: Conclusion

All this work took me 5 months of work after my normal job.

Most part of efforts and money was spent for making moulds and tools, maybe 50%, like for a head ship, which is normal. The total amount of money spent is moderate.

I made some mistakes and will try not to repeat them when making a next guitar. I mentioned them in the text.

Most of problems were associated with side bending - next time I will buy a silicone heating blanket to try. Another serious problem - thicknessing the top, back and sides to the required thickness of 2.5 - 3mm. It would be great to make a special sander for this purpose.

The guitar sound is very good - long and loud (at least it seems to me). The tuning is stable, compared to other manufactured guitars (I have got an Epiphone, a Fender, a Harley Benton and others). Tuning is smooth. The fretboard is wide enough to play duplicate strings which make unusual impression with finger picking and reach tone with a pick. There are no high-tone duplicates for bass strings and it seems good to me - you do not need to find a bass string to pick, as in a 12-string guitar.

So, that's great. This is what I wanted.

Step 25: Some Scientific Background

When making the guitar, I thought it would be great to calculate an optimal brace system. I have got lots of experience in writing finite element code for fluid mechanics, so I thought I must have a look at the acoustic equations to get some idea how complex it would be to solve them to minimise losses (optimisation problem). The acoustic equations happened to be not trivial, highly non-linear, even worse than Navier-Stokes. It is not a surprise : any time you start thinking about losses, the whole thing becomes non-linear. Anyway, it is easy to find articles related to this.
Another thing is structural mechanics : brace system must be strong enough to withstand string tension. I suspect this structural mechanics part should be linear.

These two systems of equations is quite a challenge. But solveable if to have time.

Step 26: Intonation Problem Fix

Intonation problem (the internet) is a guitar sound of wrong frequency at frets while an open string is tuned correctly. I noticed that my first fret sound at the sixth E string is not quite F when playing and I measured tones of all strings at frets with a chromatic KORG tuner and noticed that all strings emit sharp tone. It means that the strings must be longer.

Electric guitars have a saddle with which you can easily change string lengths, and it is very good (Figure 1).

There are the two ways of fixing : (1) move saddle to make strings longer (2) move nut (actually lay something, like a piece of screw etc. under the string or make nut thicker). I tried (2) first (Figure 2) and it was working, but it seems to me not very good and I cleaned the nut (Figure 3) and chose more radical solution.

First, I decreased action by decreasing saddle height. Appeared fret buzz was fixed by the truss rod adjustment (counter clockwise rotation) to increase neck bulge down. I had the action 4.5 mm before, now it is 3.5 mm. This measure made intonation much better and playing easier. I still did not change the saddle compensation nor the saddle groove - maybe I will do it later, I do not know.

With the next quitar, I will try to change the groove cut process - make it after necessary string length experiments for correct intonation (Figure 4).

By the way, wrong intonation is a very common problem : only one of my four professionally manufactured acoustic guitars (Fender) has ideal intonation; all others (a nylon string Chinese, Epiphone, Harley-Benton) all display wrong tone at frets : nylon strings should be shorter, steel strings - longer.