doublebass C-extensions

Once in a while I get talked into making C-extensions, and during the summer of 2005 this happened three times. This is, I suspect, the first and the last time so many will be made in one year. Too painful for the fingertips with so much fussy small metal work, and taxing in terms of having to invent so many little things each time. Every extension is in some ways unique, depending as they do on all the geometrical variables of a given scroll and fingerboard, and this usually makes for some stressful figuring out of just how to make the darned things work well.

Earlier efforts were solid enough, but less than satisfying in terms of appearance and in the labour intensive nature of the armature for each capo. I have now adopted an aluminum rail for those with more than one capo, a 'C' cross-section which provides uniform height along the extension and a great degree of stability.

Base price is about $1000 for a single capo extension (your supplied C string), plus about $150 per additional capo. Expect to be without the instrument for at least 2 weeks, and a 50% deposit to be paid in advance. Some design considerations are open for discussion, such as wood choice (usually ebony, but some other woods can work well) or sculpting of the thumb interface.



This is a simpler version. Single capo at the E. The bassist liked the extensions seen at Kansas City Strings, especially the deep curve for the thumb. I made this very comfortable for noting C# and D, and made a similar neck-like area lower down for playing D and D#.

The nut end is reinforced underneath with an inlaid, dovetailed piece of brass, which is threaded to be bolted to the stainless steel capo mount. A single allen bolt into the base of the pegbox holds this steel part in place. Another bolt attaches the top end to the scroll, in a minimally disruptive fashion. A rubberised cork gasket material lines the juncture. The string path with a figure-eight loop around the pulley turned out to have too much friction on the string sides, so I later modified this one to run through the length of the ebony, as shown in the second image:




And the last one for this season is a hybrid of the two previous extensions. This player has used a single-capo extension for about 15 years and has wanted a 4-capo model for his ancient Italian bass for years... since seeing one I made for a Vancouver Symphony member's 7/8th-size French bass in 1998.

His older extension was somewhat sculpted, with a very round/deep thumb area just below the scroll, and he wanted this again. The blank was a considerable volume of ebony, but the cutouts for scroll, thumb hollow, and the tapered end closer to the nut can all be used as bass nuts and saddles, not wasted.

This one is very comfortable to use, with a rounded surface in the E to D position as well, and lots of room there for the thumb. The capos grab the string automatically; no pre-pressing of the string is needed (something I had to The string routing was dictated by the previous luthier's choice to go through the scroll, so a wheel embedded above the scroll was necessary. The finish on the aluminum capo rail is baked enamel.

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It seems that my ambivalence towards C-extension design and building had some influence... as it took until 2008 before I was again asked to make one. Actually the first extension in this year was a partial re-design of one of those above, the single capo model shown as second on this page. It seems the path I chose for the string was not adequately low in friction, some binding happened in use, and a string was broken eventually. So I did some serious frowning and then came up with a rather radically different path for the string - drilling a hole from the top end almost to above the E tuning shaft and setting a wheel there for the string to pass over. This was very difficult to drill, as the hole was over 10 inches long and in a rather narrow piece of ebony, but it worked. The resulting path was very free for tuning and surprisingly easy to re-string, considering how long the string end is hidden inside the ebony. And as a nice bonus the string is nowhere exposed until it comes out inside the pegbox, freeing the thumb area entirely and un-cluttering the look of the scroll a bit.

Two new extensions were made in 2008, both for clients who had extensions made in 2005, but of course on different basses. The first of these was a finely carved Pollmann bass being passed from a father to a son. The second was put onto a German bass bought in Poland the previous winter, to be used in the opera. In the first case ebony capos were requested. As ebony is much more prone to splitting in short lengths than many other woods I extended these back to include 'tails' which may be used in lifting them off the string. This almost doubles the capo length and makes them much stronger. I also used large-headed bolts to hold them in place, further bracing the delicate ebony. Also incorporated into this design was the long string hole as described above, using a second pulley hidden inside the lower part near the D capo.



And this is the last for 2008. A bit different, or a lot, depending on one's perspective, as there is no tunability here. The fingerboard on the bass was pleasing to the player, and to be fair it was nicely dressed and the neck plus fingerboard thickness felt good, but the very thin top end of the board made for a special challenge in fitting an extension. With four capos. After much thinking, it seemed the only practical approach was to use a sheet of stainless steel running through all four capos, cut out between to leave platforms for each. This was inlaid into a long groove in the underside of the ebony and up into the backwards-curving portion of the thumb rest area. What resulted was very solid in feel, though plainly without the versatility of the aluminum rail type. Still, a satisfying solution.




From August of 2009, a two capo extension fitted to a bass by Peter Chandler. Owing to minimal clearance above the scroll edge, the ebony was left quite wide which leaves a strong portion beside the scroll. This offers an advantage in terms of thumb placement; I was able to carve a long hollow from scroll to nut which gives a secure anchor for the thumb, and leaves better access to the pegs for string changes.





gerard@luthier.ca