Part II: Bridge and Soundboard
Updated: Feb 6
If you missed our previous instalment about building the case, here it is.
Now, with the structure of the case mostly done, and with the liners screwed in properly, it's time for us to fit the 8' bridge to the soundboard. A quick note about terminology: 8' (i.e. "eight-foot") refers to the pitch of the strings. This originated in the pipe organ: the 8' pipe played at "normal pitch": 'A' above middle C sounds at 415hz (or whatever pitch standard you happen to use). For a 4' pipe, the same key would sound an octave higher; while a 16' pipe would sound an octave lower.
For our harpsichord, we chose to have the 8' pitch for both sets of strings -- a set of strings is called a choir, and how the pitches of the strings are laid out is called the disposition of the harpsichord. So our instrument is disposed at 2 X 8', whereas an original Ruckers single manual would have been at 8' + 4', meaning that if both choirs of strings were engaged at the same time, the key for middle C would simultaneously sound two notes: one at normal pitch, and another an octave higher. Our choice of 2 X 8' was dictated by the usefulness of the disposition to our needs, which is primarily continuo playing.
Once we trimmed the soundboard to the correct size (it arrived a bit larger to account for warps in the other parts), the thing to do is glue the large 8' bridge to the soundboard. For the 2 X 8' disposition, this bridge will eventually take two strings per key for the harpsichord's 56 keys from GG to d''' and we need to get it absolutely right. The bridge arrives a bit straighter and longer than it needs to be -- the final bending at the treble end must be done by us. and the extra length helps us do this (you can see roughly how it compares to the drawing, above). The idea is to bend it into shape, glue it, and affix it to the soundboard by driving a series of nails into it, through the soundboard, and into the bench below. The idea of it caused U-En several sleepless nights, until Lin had a very good idea: Where in Kuala Lumpur would there be a workbench and all the tools necessary to do this job... as well as professional advice in a related field of instrument-making? We wrapped up the soundboard and bridge and packed them into the back of U-En's ancient motorcar for a little trip to the workshop of our friendly local luthier (and Wicked bassist) Ong Ket Wei.
Ket Wei had a great idea. Instead of bending the bridge with the glue on, and simultaneously trying hammer nails through it into the bridge, how about bending the bridge into its intended curve first, using the hot iron thinggie that he uses to bend the ribs of violins?
It's simple in principle: we need to wet the area-for-bending with a bit of water, then heat up both sides of the bend by pressing it up against Iron McIronface (correct name: "bending iron"), then bendddd. And repeat. And repeat again. And again. The steam loosens the fibres and allows the shaping, all along the bridge until it matches the drawing.
For convenience we'd transferred the lines directly to the soundboard by tracing them out in pencil. This has to be done very accurately as a misalignment would be disastrous.
After we got it properly shaped, we got the glue on it quickly, making sure it spread over the entire surface of the bottom of the bridge -- but not so much that it would squeeze out and smudge everywhere -- then hammered in some 'padded nails' through pre-drilled holes (using a 0.1mm drill-bit). These are simply nails that have been driven through a couple of pieces of cardboard so that the nail head sits some distance above the surface of the bridge. Driven through the bridge and soundboard and into the bench, the nails act as clamps; and after the glue dries, we can then remove the cardboard in order to provide a fulcrum to remove the nails. Eventually, we'll plug the holes with 'toothpicks' made from the extra length of the bridge on the treble side, which we've cut.
As the glue dries, it's time for lunch!
After lunch, we were joined by a couple of visiting UK celebs -- Ibi Aziz (left) and Leong Lee (centre) -- who helped us get the nails out. This was a lot trickier than we thought: the nails were quite soft and we broke a couple of nail heads, but got them all out with a bit of perseverance. Then, after packing up the soundboard again in the sheets of cardboard and saying goodbye to Ket Wei, we headed back to our respective homes.
Back at U-En's the work continued to thin the underside of the soundboard according to the practice of the original builders. The soundboard is about 3mm thick all over, but some areas needed to be 2.5mm and some at 1.5mm. The idea was to plane the soundboard to these thicknesses but U-En opted to use coarse sandpaper instead, graduating to finer and finer sheets as we got to the ideal thickness.
As the bridge was already in place, thinning the underside meant balancing and securing the upside-down soundboard on something -- in U-En's case, some books of the right thickness matching the height of the bridge -- then simply mark, sand, measure, vacuum, repeat. Note about vacumming: the wood dust from sanding is very fine and we always wear some kind of respiratory protection (masks) because it gets everywhere. Regular vacuuming helps keep everything manageable.
Once sanded, we needed to glue on the ribs (for stability and sound transmission) to the underside, and then scallop them, which involves shaving off bits from the ends of the ribs to make gentle curves that strengthen the structure:
And then it's time to put the whole thing together, which is just a simple matter of gluing the soundboard to the liners and the upper belly rail at the front end of the soundboard:
Here you can see all the work we've done so far from underneath the instrument (it's upside down on the floor): There are lots of supporting structures both at the bottom of the instrument and underneath the liners holding up the soundboard. There is a new piece on the right of the wrestplank (left of the photo). This is a long piece known as the lower guide, with little oblong holes cut all through and is held in place by three screws and washers. It's function is to serve literally as the lower guide for jacks that pluck the strings.
Finishing the casework
Now with all the inside parts sorted, it's time to put the bottom on the harpsichord, and prepare the lid and flap for the top. Like the soundboard, these major pieces are sent to us oversized in case humidity causes other pieces such as the bentside to warp (and indeed they do warp!) and the new shapes must be accounted for, so the first task is to cut them all to size like so:
And we also needed to do a bit of metalwork. Here are the hinges that will eventually secure the lid to the spine. They are brass and are sent rough directly from the foundry. We need to hammer them (gently!) so they are completely flat; smooth out the edges, which are sharp and rough from the casting; and cut and file off the sprues (the bits sticking out) before sanding and polishing them.
In the video below, Lin is trimming the sides of the lid to size while Andrew is cutting and filing the hinges. Later, he'll take them home to sand and polish.
And finally, Lin and Andrew are hammering down the two panels that make up the bottom of the instrument. Once everything is secure, we'll be moving the harpsichord to Lin's house where we will begin the final stages of the construction: