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| One of my long standing dreams has been to build a bowlback mandolin. Over the
last few years, I feel I have learnt enough by making my own instruments and
repairing many bowlbacks, to at least make a start. This will be a record of my
project.
Problems: The biggest
issue I feel I need to deal with, will be.....'How to build the bowl!'
...the rest will be similar to building a flatback, I guess. I have done a fair
bit of research on this, and discovered that they are built either on a frame
of some kind, or on a mould. With the exception of a superb site
chronicling the building of an Oud, and Lundberg's book on lute construction,
whose bowls are rather different from that of a mandolin, there is nothing on
the net that really deals with the technical difficulties of bowl construction.
I do have a plan for a bowl, but it is very simple, with only 7 ribs, and does
not explain anything about the construction at all. |
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Resolutions: I have decided to build on a mould,
and model it on a 1932 Embergher, since I have discovered a superb set
of posters, providing enough detail to build a plan. I have also decided to
build a bowl based on a Loveri I have on a frame.
These are some of the
bowl-related issues as I see them, and their possible answers.....
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Q: How to decide on the shape of the ribs, and how many
ribs.
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A: Taken from the models.
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Q: How to attach the ribs to heel and neck blocks whilst
glue dries?
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A: Evidence from several disassembled bowls seems to
suggest some were pinned at the tail, the hole subsequently hidden beneath
the end clasp. 'Thick' hide glue also 'grabs' quite quickly, so the neck
end may be held with elastic I think.
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Q: How to hold ribs in correct alignment during
construction, and force together for a good join?
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A: No answer here, so I
will have to try a combination of elastic bands and clamps!! Or I have
seen pins.
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Q: How to bend the very thin stringing material?
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A: I have tried taping several together so they are
then wider than tall, and this seems to work to some extent.
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Q: How to trim the sides of the ribs, so that are the
correct angle to meet the adjoining rib?
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A: By fitting odd ribs to
damaged instruments, I have discovered that a pre-bent rib, sanded on a
flat surface, will give a good edge to glue to another treated the same
way. Or even better, an upturned plane.... new jig to build there!?
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Q: Do I start with the sides and work up, or the keel rib
and work down?
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A: The consensus seems to be start with the centre rib
and work outwards.
Some of the other practical issues
that I must address are...
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Q: How to construct the heel and tail blocks?
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A: In both systems, the heel and tail blocks will need
fitting to the mould /frame first, then shaping to receive the ribs. I
have seen a photo which apparently shows a whole head and neck, apparently
unfinished, attached to a bowl mould.
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Q: What system is best for joining the neck to the heel
block?
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A: Provided I can manage
the complex curved heel, I have decided carving the heel as part of the
neck, is stronger than wedge joins.
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Q: How much dome to put on the table?
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A: I will take the amount of dome from the 'models'.
I have been measuring, and there is a fair difference in dome height,
which bears no obvious relation to sound. Is it just a structural device?
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Q: How much to cut out of the table centre below the bend,
before gluing?
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A. Have solved this one, by
re-building the top of an old fluted Stridente.
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Q: How to glue the table in 2 sittings at different
angles?
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A: I have discovered that some tables had segments
removed, whilst others didn't. Similarly, some tops were glued to the bowl
first, half at a time, joined above the bend, then glued below the bend,
while others were made as a piece, bent, then fitted whole. Removing a
section should make for a much stronger shape. On the Stridente, I glued
the top half, after planing the 'v cutout', and will glue lower half
after.
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Q: Positioning and shape of the struts?
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A: Taken from the models.
The links below will be
hyper-linked once I begin each stage, and have something pictorial to put on
them.
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