Saturday, July 14, 2012

The Baroque Lute Neck

The design of the baroque lute neck is anything but simple. The fingerboard is cambered from side to side for ease of barring chords. It is thin in the area closest to the nut becoming gradually thicker toward the joint with the bowl. The back of the neck is shaped for comfort. Those are fundamental attributes. Added to this are the preferences of individual lutenists and luthiers.

I work within defined limits for each feature. The thickness of the finished neck (fingerboard, spruce core and  veneer covering) at the first fret is under 19mm. The thickness at the joint to the bowl is under 29mm. These are measurements for large lutes. I think that necks that are thicker will be uncomfortable. If thinner, the structural integrity will be threatened. Naturally this doesn't suit all lutenist. But I have found that  compromise can be achieved by thoughtfully shaping the neck's contour.

I start with a plank of aircraft grade sitka spruce  that is straight and quartered with about 20-24 growth lines per inch. Usually I cut narrower pieces from several planks and re-glue them into a neck-size piece. This relieves any tension that might be in the wood. Having already beveled the front of the lute bowl to the proper width and angle, first with a back saw and finished with a block plane, I then cut the matching angle on the neck wood  using the same tools. I glue and screw tabs to the top of the neck block to help hold the neck in position while it is being shaped and adjusted.

With the rough neck material tack-glued to the front block and held level by the tabs, I drill a hole through the block and into the neck.  Once a screw is inserted I scribe around the joint delineating the contour of the neck. With the contour marked on both ends it is a quick task to remove the excess wood, first with a larger plane and then finishing with a block plane and a thin steel scraper that can flex over the contour or with sandpaper. 

I have never found it easy to apply veneer to the back of a lute neck. There are so many steps that are necessary to assure a good result. Perhaps I make it more difficult than it need be. I bandsaw my own veneer from 3 inch wide ebony boards that are sold as fingerboard stock for bass guitars. I finish the rough sawn pieces to a thickness of 1mm or a little less and bend them over a hot pipe using shaped cauls to ease the ebony into the proper curve.

Since the fingerboard stock is narrower than most lute necks it is necessary to use multiple pieces. I glue each on separately. Here the center piece is strapped down with elastic tape while the glue dries.

Removing the glue squeeze-out is done after the glue dries.
I apply a wet strip of cloth to the edge of the veneer and leave it to soften the glue for a few minutes. Then I run a hot knife along the edge. Any dried squeeze-out is liquified and can be wiped off.

The two edge pieces are bent and glued in place in the same way.

There is one last detail. I like the edges of my
necks to have a substantial roundness.  This is difficult to do with veneer because there is always the risk of it splitting when it is forced over a rounded edge. I solve the problem by planing the edges of the neck flat and adding strips of ebony. These are then contoured flush with the veneer surface. The strip on the right side is still "as glued" while the one on the left is finished.

When the fingerboard is glued on there is a solid edge of ebony that can be nicely rounded.

Next time I will describe my technique for cambering the fingerboard.

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