Early last summer I finished a Johann Anton Stauffer 7 string with an adjustable neck and a René Lacôte 7 in time for several instrument exhibitions. The story about this is July Update - a new Stauffer 7. At the time I was working flat out and didn't take enough photos to fill a post about the Stauffer. Now I have finished a six string version of the same guitar with plenty of photos so I can show you the similarities and differences in the construction of the two versions. Also, I described building a Stauffer terz guitar in three posts in November and December 2015. Since the three guitars share the same major construction features I omitted many steps in this post. Consult the Terz posts to see these steps.
Building a Stauffer Terz Guitar
a Photo album
I have been surprized to find very few structural differences between 6 and 7 string guitars in my investigations. I'll describe those shortly. The obvious feature is the suspended 7th string. So let's start with that.
The 7th string is mounted on a simple appendage that mirrors the figure 8 design of the peg head. The peghead of the original guitar was clumsy because the neck was made unusually wide probably to accommodate the wishes of a client. I don't think this was done to strengthen the neck because Stauffer eight string guitars built around the same time had standard necks. Since I intended to use a standard nut spacing decided to design a new peghead. I wanted to position the nut on the new peghead so I could use the same diameter of string as the 6th with both at the same tension. Remember, a string will remain at the same tension if the pitch and length are in the correct ratio.
|Harris Becker photo|
The usual tuning for the 7th string is D, a full step below the 6th string. I did the math and found the string length that was necessary to make the guitar's regular nut (640mm) equivalent to the second fret of the 7th string. The answer is 718mm or 78mm from the regular nut. This placement allows the 7th string to be the same diameter and tension as the 6th.
The 7th string nut is a piece of ebony 4mm thick, 13mm wide and about 17mm high. It is embedded in the face of the peghead and stands upright. The design requirements are fairly tight. The 7th string peg can't be too close to the nut or it will make tuning difficult and it must be clear of the other pegs so as not to interfere with them. Everything has to fit somewhat elegantly in a limited space.
This is the template I designed. It is laid out on a half inch grid. The seven peg holes and 7th string nut positions are noted.
Here is an the interior of the Stauffer 7 just before the back was glued on. I used a barring pattern with three bars beneath the rose. I don't know how the original guitar is barred but both Stauffer's eight and six string guitars use this pattern so it must be appropriate for a 7.
I did make several structural allowances for the additional string. The front block is wider on the 7 to counteract the lateral pull of the off-set 7th string. It measures 90mm x 43mm as compared to 75mm x 43mm for my 6 string version. The bridge plate is extended to the bass side to support the wider bridge. The tail block for the 7 is a little wider to provide more support for the pull from the wider bridge.
The bridge is made a little wider to accommodate the seventh string. The spacing between the 6th and 7th string is also a few millimeters wider than the spacing between teach of he other 6. Nineteenth century makers used a wider separation than this but discussions with players has led me to adopt this solution.
Also I made a few changes in how I construct certain parts of the guitar. Until this last guitar I cut the recess for the neck in the front block before I glued the block in place. I worried this would lead to a mistake in alignment that would cause a lot of trouble later on. I devised a complicated system to check the alignment of the parts before they were installed. This was silly and way too much work.
After making the preliminary cuts I clean the waste with a chisel and finish the sides of the recess with various files and sanding sticks. The back of the recess should be square with the top of the guitar and this is easy to check with a small try square. The work goes quickly and accurately.
At this time I also drill the holes for the neck adjustment mechanism. In this photo the large clamp is securing a wood block that helps to align the drill bit for drilling through the heel. When this is finished I can align the neck in the front block recess, hold the neck to the proper angle and drill on through into the block. The anchor nut for the screw is then secured in the block and finally the back can be glued on.
Sue found this old photo of me cutting a flitch of English sycamore into back and side rib lengths for 19th century guitars. I'm still using the same wood.
All photo by the author unless otherwise noted.