A good friend at school recently asked me if I thought it was possible to convert a 6 string into a 12, at first I thought the neck would need to be widened but I thought I'd try. So here you go Seb, proof that it is possible.
I hope that if you are reading this you give it a go,
Step 1: What You Will Need
An old normal 6 string guitar(mine was an old encore 3/4 size which my grandad was going to chop up for fire wood) :O
6 new geared tuners £7
Wood for the head (pine)
Wood for the strengthener (Mahogany)
Wood for underneath the bridge (Pine)
12 Sting nut 99p
And you are ready
Step 2: Modify the Head
To start with I took of the original pegs(to prevent damage), all the strings and the bridge(later on I came to wonder why I did as there is no need to unless you want to reglue it or make it stronger)
After doing this I marked on where I was going to cut the top of the head because it had a curvy bit.(Photo 1) After this I took a tenon saw to it and cut it.
For the new head I had 15mm pine, this was the same thickness as the original head. As the original head went from 65mm to 75mm over 130mm I cut the new head to be 75mm at the bottom and 85mm at the top.
Step 3: Add the New Head
I decided to use 2 wooden 8mm dowels and a hollow 10mm dowel. I carefullly marked out on both heads, and then drilled, check before glueing that they fit together.
I used titebond wood glue, clamped it and left it.
When I took off the clamps I was very surprised about the strength, I put alot of weight on it and it didnt budge.
For extra stength I glued andscrewed on a 100mm length of hardwood on the back. They were self tapper screws so I drilled a little pilot hole.
(As an after thought, when i had put the guitar back together, I decided to shape the head. As it was only to have 11 strings as the neck was too narrow for 12. I use a coping saw and gave an asymetrical curved shape, as well as sanding it.)
Step 4: Installing the Pegs
The pegs are 10mm from the edge of the head. I marked them out according to a Tanglewood I have. When you think that the positioning is right drill them out. These pegs also had tiny screws on the back so I used a 1.5mm drill bit.
When the holes are drilled instal the pegs and watch the guitar take shape.
At this stage I also glued on the nut. Here was a dilema, as the guitar is only 3/4 size the original nut was 45mm and I couldn't find a 12 string nut that small(48mm), so the decision was to make it an 11 string and miss off the low E.
Step 5: Glueing on the Bridge
As I took the bridge off (yet I don't remember why) I glued it with titebond glue an put it in the vice. To cope with extra tensile strength from the strings I put a strip of pine underneth the bridge in the body and screwed the bridge into this.
Step 6: Restringing
The strings I usually use have the "nuts" on the end, so instead of drilling new holes for the strings I threaded the pair through the end of the other one.(Have a look at the photos). To adjust the width between the strings I put in small screws between the pair, the theory being that the futher the screw is in the wider the strings are. This limits any buzz between the strings and on the saddle
Step 7: Clean Up the Guitar
I used a palm sander on the head to smooth it all over and to prep it for the varnish. Unfortunately the original guitar stain is very dark and I couldn't match anything to it. In the end I settled for a dark mahogany stain. I pulled all the glue streaks off to finish the bottom of the guitar. As I mention earlier I modified the shape of the head but this would have been easier to do earlier.
Step 8: Finish
As you can see that it is not a peice of artwork and certainly no Martin, but it works and it sounds good, futher more I didn't pay much to do it. I may get round to cleaning it up, if I do I will add it on here, but I like its rustic appearance.
I Hope you enjoyed this instructable and feel encouraged to have a go.