The replica of the F. Schenk's Bogengitarre

(The photo gallery is further down on this page)

This replica of the Schenk's Bogengitarre (the original is now part of the Berlin Musikinstrumenten-Museum collection) was ordered and made for the project "Die Bogenhauser Künstlerkapelle (1897–1937) – Eine vergessene Avantgarde der "Alten Musik"".

Friedrich Schenk and his Bogengitarre

According to Alex Timmermann (in: Ivan Padovec , Zagreb 2007, p. 118-120) Friedrich Schenk (c 1800 - c 1865) worked in Johann Georg Stauffer's workshop in the beginnig of his career and sold his instruments via Stauffer's shop. He was probably Stauffer's student like for example Georg's son Johann Anton Stauffer or later Gottfried Scherzer. His own labels are traceable from the end of 1830's when he started to work independently and was active in Vienna. His workhop addresses were:

from 1836 Margarethen 150
1839-1841 Margarethen, Lange Gasse 151,
1841-1847 Schottenhalt Felt Gasse No. 491
1847-1848 Wien-Margarethen Grohgasse No.179
1848-1855 Margarethen Grohgasse No. 186

Friedrich's son Johan Decker-Schenk (1826-1899) the singer and guitarist left also some composition for "Pedalgitarre", a type of multibass guitar with pedal attachment which was also built by Friedrich Schenk.
Schenk's "Bogengitarre" model was copied by guitarmakers Raab and Müller for example. Schenk built Bogengitarren with eight, nine or ten strings and also a lyra form of this model with two arms.

Thanks to friendly help of Heidi von Rüden I was able to measured the original Schenk Bogengitarre in Berlin Musikinstrumentenmuseum and also to see the Müller technical drawing of the Schenk's model. This technical drawing is in fact a close copy of this very model, with some changes described later in this text.

This Schenk's instrument can be described as a "Terz Bogengitarre" thanks to its short main string length of 540mm. What seems as a nice round number is in fact 539,6mm which equals 21,5 Viennese inches. The three extra bass strings are progressively longer, each of about 1-2 fret distance. This enables the use of the standard guitar sixth string for these, providing the usual diatonic tuning of these basses.
The outline of the lower part of the instrument is forming an ellipse with the bridge laying on it's long axis. This is the shape recommended for example in the introduction to Bathioli's Guitarre-Flageolett-Schule issued 1833 in Vienna.
The acoustic chamber is connected in this guitar. This means that there is not any barrier between the main body, the arm and the hollow head with tuners. This is not the case with all these Bogengitarren as some of them have a wooden block dividing the inner space to two separate chambers: the main body and the arm with the head although the soundboard does not show any interruption here. Also the Müller plan shows some kind of barrier in this place. The Schenk's guitar has in this place a visible interruption - the part of the purfling - but it is supported with only small piece of wood glued on the inside. The purpose of these two different solutions is maybe in experimenting with several body resonances which influence the acoustic output.
One of striking details of this design is a fact that the guitar has both ends of the neck fixed to the body. The neck although very thin becomes very rigid which is supported with the veneering even more. The standard guitar's neck and head are always more or less flexible but in this design are the strings' ends fastened with more stability which results in better tone response in my opinion.

The Schenk's guitar has a spruce top, flammed maple back (one piece) and sides (six pieces) with a reddish varnish, the neck and heel veneered in ebony, ebony fingerboard. The inner parts: the bars, linings and six blocks are spruce.
The original label says:

Friedrich Schenk / Instrumentenmacher. / Margarethen, Grohgasse, Nr. 179, / in Wien.

The condition of the original Bogengitarre is good but there are some extensive repairs. It was repaired by Halbmaier (repair label: Reparirt / F. Halbmaier / München / 1907 ) and possibly in that time was the whole back of the guitar reinforced with spruce layer with the grain running perpendicularly and the back bars were removed. I was able to trace their presence and position by the filled cut-offs in the back linnings. Anyway their position is indeed typical and is marked accordingly in the Müller plan. The present fingerboard is likely non original. The bridge's base part is original but was modified by adding some material to raise the string's action over the fretboard. Also the small bridge behind the nut which serves to press the stings down behind the nut, is modified.

Comparing the scaled Müller drawing with the Berlin original I can confirm that the model is the same with regard to the body shape. The most important of these changes are the barring of the soundboard and the different solution of the neck geometry relating to the soundboard plane. This last thing is especially important because the side view as drawn by Müller seems as a mistake. On the drawing there is top of the head and top of the body in two different planes which would be barely possible. This is because Müller picked the back plate as a reference. With real Bogengitarren (and majority of guitars of the period) is the sounboard flat and can be as such used in the actual construction process as a real plane (base) to which you can calculate neck angle. This was my method too.
There is also slightly different style of the bridge ornamentation. The fingerboard extension over the soundboard is also different but I think that originally was this form present on the Schenk's guitar too. The same style which has also more frets can be seen for example on the photo of the Hammerer's collection. The side height's as marked on the Müller plan are not exactly the same as on the original.

The description of the making process

The whole replica of this Bogengitarre was made using the historically correct materials (traditional hot hide glue, oil and spirit varnishes etc.) and technologies to get as close as possible to the original.
When planning the actual building I decide to work without the mold or form. Although the Schenk's guitar was probably constructed with the help of some inner mold which makes it easier to get the correct shape and rectangular sides, sides and back assembled first and the top glued on last. In our case when there is only one instrument to be built it is not economical to make a mold. The freehand building has historical support too as is illustrated for example in the G. A. Wettengel's treatise for luthiers (Vollständiges, theoretisches-praktisches Lehrbuch...,Ilmenau 1828).

Bogengitarren have long top and back plates but the advantage of this particular model is that the top plate is divided in length so it is easier to find good quality piece of spruce for it. After the main part of the top plate was joined and the exact shape was cut, it was fitted with a simple rossete made from the alternating strips of natural white and black dyed maple. The top was then hand planed to desired thickess which turned out to be 2,6 mm for the main part around the bridge. It is roughly the same thickness as on the original. The spruce bars were glued and shaped. Barring of virtually every Viennese guitar in the 19th century is similar, so called ladder bracing. According to the descriptions, the idea was to have just enough counter force to balance the string pressure. A combination of two bars above the sounhole and two below was maybe most common. Often we can see these two bars below the soundhole to be located above the bridge with the lowest bar slightly angled towards the treble side. In this Schenk's design they remain paralell, one above and the second bellow the bridge.

The blocks with carefully shaped surfaces for receiving the sides (ribs) were glued to the exact places on the top. The bottom block is usually very wide on these guitars with long bridges. Small supporting wooden pieces are temporarily glued on the back side of these blocks. These will serve for better clamping of the sides to the blocks and will be pared off afterwards.

The same procedure was made for the upper part of the top (the arm and the head). These two halves are now joined to create the whole top.

Then the material for guitar sides is cut progressively from a piece of flammed maple. Sides were thinned with planes to cca 2mm and they were bent over the hot pipe (bending iron) carefully controlling their exact shape with the template.

The set of spruce linings are then glued to the still free sides and the corresponding cut-offs with a chisel are made in the linnings for the ends of soundboard bars. The gluing of such prepared sides to the blocks and the top follows. Those two "corners" where the upper bout starts are not possible to satisfactorily cover by bent sides, because such tight bend is not convenient. That's why are added two extra pieces of maple glued to those corner blocks on the original Bogengitarren and this replica too .

Second set of linings to which the back will be glued are fitted and the fine tuning of the rib assembly rim is made to receive the back plate. The long one piece back is cut from a big slab of flammed maple. Its thickness is planed to cca 3,5mm and the arched back bars are glued to it. This creates domed back on the finished guitar.

After the guitar is closed the overhangs of the back plate are cut flush with the sides and the channel for the purfling and binding can be cut in the top plate.

With the purflings and bindings the guitar body can be prepared for varnishing. The style of Schenk's varnish is not so common among guitarmakers of that time. Usually the guitars were just plain yellow, without any pigmented or colored varnish.

The neck blank with already prepared tenon (heel to body joint is a shallow tapered mortice and tenon) is shaped and veneered. I pick the maple wood for the neck core, the original is not known but I have seen maple used on similar viennese Bogengitarre from the same period. The ebony fingerboard is prepared and fitted with brass bar frets, the same as were used in the period. I had to make a decision if the fingerboard extension over the body will be floating as per Stauffer design or glued on the top as in this original which was nevertheless modified so we do not know what it looked like originally. The floating extension is present on many Bogengitarren and would be my choice but Bogengitarren have thanks to their design a flatter neck geometry (lesser neck angle to the plane of the soundboard when seen from the side) then can a standard guitar have, so the extension can be only very thin which causes bending of the fingerboard when playing in the highest positions. This results in short sounding highest register. The floating extension is really needed only when the neck is screw adjustable which is not possible on the Bogengitarre. So for the better stability I have chosen the glued-on-top extension.

The fingerboard with frets was glued on just after the neck was installed, an operation which required a precise adjustments to end with the right calculated string action over the fingerboard - ie. good playable instrument. Finally the carved and black dyed pearwood bridge was glued, the cut-off for the tuner made, the small ebony bridges and nuts manufactured.

The tuning mechanic for this Bogengitarre was manufactured by Rubner in Markneukirchen according to my technical drawings, tracing of the engravings and templates.

Jan Tulacek, guitar maker