Building a Kaiser Theorbo bowl

Assembling lute bowls is demanding and sometimes frustrating work. I took this photo on Sept 11 when I had seven ribs in place. I usually only spend part of my work day on this activity; averaging three ribs a day. Each rib takes 1 1/2 hours unless there are problems. This bowl has 27 ribs. My assembly technique differs little from other makers. For narrow rosewood ribs like these I dampen the rib with hot water and bend them on a very hot iron -- spit jumps off of it. This model of bowl has a moderate flattening in the cross-section which means that the ribs are different shapes. They vary from "spear" shaped where the two edges are mirror images or nearly so, for the ribs in the center, to crescent shaped, for the ribs on the shoulders of the mould, to "S" shaped where the rib twists in opposite directions at each end. It is possible to cut this variation of shape into each rib but it is time consuming and wasteful. However, when assembling bowls with fewer ribs it is often the only choice that is possible.

The technique for planing the rib edge doesn't vary according to the shape. After the rib is bent to the contour of the mould I hold the rib against its neighbour and estimate where it needs to be trimmed and by how much. The excess is removed with a fine blade on a bandsaw, with a broad chisel or on the plane board as in the photo to the left if only a little is required. After the "rough shaping" a final fit is achieved using the plane board with an ever finer setting. This is time consuming and frustrating when a mistake is made. But this is only one edge of the rib. I shape the second edge by measuring the required width as determined by the lines on the mould, transferring those measurements to the new rib, and shaping  accordingly. The rib is then glued into place using hot hide glue, push pins and plastic wrapping tape to secure and seal the joint.

When the contour of the mould requires a rib that is crescent shaped or "S" shaped I bend the demanding portion sideways. Only certain woods will accommodate this technique: rosewoods, ebony, snakewood and yew. And only with ribs of a narrow width such as those found on multi-rib bowls. I use a simple technique of damping the part of the rib that is to be bent, using a very hot iron and wearing thick deer skin gloves. While the rib is held in the proper longitudinal contour against the iron with my left  hand -- I'm left-handed -- I push or pull slowly, but firmly with the other hand. This is exacting and delicate work. I am always amazed at the properties of wood that make this possible. It is also this property of certain tonewoods that resulted in 16th century lute makers inventing complex bowl designs.

I finished this stage of the bowl several days ago. Since then I have applied the rear apron and papered the inside of the bowl. Today I will glue in the inside apron and report on these in my next post.

Gluing the Lacote Back and Starting a Theorbo Bowl

Last week I explained my rationale for gluing the back struts separately to the rib linings and then stretching and gluing the back over the struts. In the photo i have done just that. All of the clamps are in place. You can see that I have used a traditional method for gluing the edges.  Passing through the mould at regular intervals are threaded metal rods that are equipped with wooden blocks and wing nuts. These secure the edges. The two ends are secured separately with small extension clamps and wooden blocks. Four other clamps with long wooden cauls are place directly over the area of the back that is supported by the arched struts. Remember that I have fitted pillars under the struts to support the clamping pressure. The cauls have a concave surface that is a match for the arch of the struts. An even application of clamping pressure is assured by a layer of high density foam that is placed between the caul and the back. Since arranging the clamps is a lengthy process I use a slow drying fish glue from that has a long "open" time.

I have cleaned up the glue squeeze out and inspected the joints. The sound board, in the background, is nearly ready to glue to the body. I will use the same method of stretching the belly over arched struts as I did with the back.

I have made rapid progress on the bowl for the Kaiser theorbo and since I have a definite delivery date for this instrument it will be the focus of my work from now until it is finished. I will explain the design of the bowl for this lute and demonstrate my technique for shaping the ribs in my next posting.

Welcome to my workshop

In my last post I mentioned that I was working on three instruments. In the foreground left is the Lacote guitar, the Kaiser theorbo mould is in the centre and the Voboam guitar with ebony sides and a light coloured cypress back is to the right. I usually have two instruments under construction at the same time. It is just an economical use of time. Having three is a whim on my part. The Voboam has reached stage where I am waiting on the delivery of a parchment rose from Italy. The back, sides, neck and peghead are assembled and the soundboard is awaiting the rose. As soon as the rose arrives the Voboam will become the focal point of my activity. In the meantime, I decided to start a Lacote. Although I don't mention 19th century guitars on my website I have been building them in a limited way since the late 90's. This particular guitar is based on an 1823 instrument in a private collection in Brooklyn, NY. When it is finished I will put it on sale on my website.

For those of you who are not instrument makers this represents a typical Lacote arrangement of the side assembly. The front and rear blocks  are wide and shallow and nicely contoured. The linings that stiffen the side ribs at the joint between the side and soundboard and the side to the back are fairly deep. Four arched cross struts are glued into the back linings and will support the back. What instrument makers may find odd is that these struts are glued to the side ribs rather than glued to the back as in the usual method. My method is too stretch the back over the struts like a skin. The struts have been   heat bent to a 3mm arch rather than cut and shaped. Bending the struts preserves the longitudinal fibres of the wood in their natural alignment. This combined with putting the back under tension increases the degree of stiffness that can be obtained from a minimal amount of wood. One always remarks on how light these guitars are! This method of assembling the back is described in detail in Jose Romanillos' book on Antonio de Torres. Although this may not be a French technique for assembling guitars I think it adds a particular tone quality to the guitar's character. The dark blocks of wood under the cross struts are temporary supports for the gluing operation. Besides numerous clamps placed around the edge of the body, four or more clamps will be placed over the back at locations matching the cross struts. The temporary blocks support the clamping pressure.

Cavalli's Giasone in a cabaret setting

Opera Omnia launched their second production, Giasone by Francesco Cavalli at New York's Le Poisson Rouge last week. Their  inaugural production, Monteverdi’s The Coronation of Poppea, played to sold-out houses in 2008.  The very special thing about this production is that the final show Wednesday night, September 7 at 7:00pm is being streamed live! Watch it here:


http://concertwindow.com/lpr    


This posting is the first for my new blog and I wanted to direct attention to the wonderful musicians who have become friends and clients. Daniel Swenberg and John Lenti are playing theorbo and baroque guitar. Thanks to Dan for sending me the link.


I am working on three instruments now: a baroque guitar that will be finished in a few weeks, a 19th century Lacote model guitar that is more long term and a Kaiser model theorbo that is due for completion in October. My future posts -- hopefully frequent -- will concern the building details, stories and backgrounds, both contemporary and historical, of those instruments and the musicians who play them.