Hi all,
The type of instrument we are building requires the case sides to sit ON TOP of the case bottom so the next component we need to build is the Bottom of the case. It would be easier to build the Bottom out of ½” plywood but, for tonal reasons, we can’t. Instead, we will build the Bottom out of ½” thick Select Pine boards. Because we want to control the direction of wood expansion we must build the Bottom in two sections. In the front of the instrument, the section where the jacks will pluck the strings, stability in the left-to-right direction is critical. Therefore, we build the front 17 11/16” section of the Bottom using boards that run from left to right (as seen front the front of the instrument). Since wood swells significantly more across the grain than with the grain this will give this area the most left-to-right stability. Any expansion of the wood in this area will be front-to-back which is not a problem. The remainder of the Bottom is built with the boards running front to back. Let’s build it!
The following illustration shows the plan of the Bottom.
The first photo shows the 4 pieces of stock that will make up the front portion of the case Bottom. The wood has been planed to ½” and all edges have been jointed.
The next photo shows the 4 pieces being glued up into a panel.
Next we have the glued up panel which has been cut to size and sanded.
The next photo shows the 7 pieces that will make up the rear portion of the Bottom.
In the next photo the longest 3 pieces are edge-glued together. This is a rather low tech but effective way of clampling. My workbench has rails on two sides that can be raised to act as a stop. The edge of the 1st piece is butted against the rail. Then wedges made out of scrap are used to apply pressure. One half of each wedge is nailed to the workbench with a couple of brads and its mate is wedged in to apply pressure. Weights are placed on top to prevent buckling of the pieces but the pressure applied is modest. Of course the boards must be well jointed. Small, thin strips of plastic are placed underneath each seam to prevent the panel from glueing itself to the workbench.
In the next photo the next two pieces are added to the panel. The brads are removed from the wedges and their positions are adjusted for the new pieces and re-nailed to the bench.
In the next photo the remaining two pieces are added to the panel.
In the next photo the panel has been cut to its correct width and the front edge is cut square to the sides with a router.
Next, we glue the front panel to the rear panel. The same wedge system is used. A couple of brads driven through the rear panel prevent it from moving backwards under pressure.
After the glue has dried we remove the Bottom from the workbench. We place the full-sized plan of the instrument on the bench and place the bentside on it. We move the bentside on the plan until we find the best match and place a mark on the bentside to show its front and rear locations.
The Bottom panel is placed on the workbench and the tail line is drawn onto the panel. Then we place the bentside onto the Bottom panel and trace its outline.
In the next photo the dark lines are the outline we just drew. The faint line is the line taken from the plan with carbon paper. The lines match perfectly except for the front several inches where our bentside has a little deeper curve than the plan. More than good enough.
The next photo shows the tail line being cut using a jig-saw and a wood guide.
The next photo shows the bentside being cut with a jig-saw. Unfortunately this must be done freehand so great care is taken to do this correctly.
The last photo shows the completed Bottom.
In Part 6 we will add the sides to the Bottom and, for the first time, have something that begins to look like a harpsichord. See you then.
Ernie
Part 1 - The Keyboard Part 2 -Keyboard con't. Part 3 - Keyboard con't. Part 4 - The Case (Bentside) Part 5 - Case Bottom Part 6 - Case Sides Part 7 - The Lower Braces Part 8 - Case Finished Part 9 - Building the Registers Part 10 - The Stand Part 11 - Jackrail & Moldings
Part 12 - The Music Desk Part 13 - Building the Benchhttp://www.ncwoodworker.net/forums/f101/harpsichord-project-part-12-music-desk-18962/
The type of instrument we are building requires the case sides to sit ON TOP of the case bottom so the next component we need to build is the Bottom of the case. It would be easier to build the Bottom out of ½” plywood but, for tonal reasons, we can’t. Instead, we will build the Bottom out of ½” thick Select Pine boards. Because we want to control the direction of wood expansion we must build the Bottom in two sections. In the front of the instrument, the section where the jacks will pluck the strings, stability in the left-to-right direction is critical. Therefore, we build the front 17 11/16” section of the Bottom using boards that run from left to right (as seen front the front of the instrument). Since wood swells significantly more across the grain than with the grain this will give this area the most left-to-right stability. Any expansion of the wood in this area will be front-to-back which is not a problem. The remainder of the Bottom is built with the boards running front to back. Let’s build it!
The following illustration shows the plan of the Bottom.
The first photo shows the 4 pieces of stock that will make up the front portion of the case Bottom. The wood has been planed to ½” and all edges have been jointed.
The next photo shows the 4 pieces being glued up into a panel.
Next we have the glued up panel which has been cut to size and sanded.
The next photo shows the 7 pieces that will make up the rear portion of the Bottom.
In the next photo the longest 3 pieces are edge-glued together. This is a rather low tech but effective way of clampling. My workbench has rails on two sides that can be raised to act as a stop. The edge of the 1st piece is butted against the rail. Then wedges made out of scrap are used to apply pressure. One half of each wedge is nailed to the workbench with a couple of brads and its mate is wedged in to apply pressure. Weights are placed on top to prevent buckling of the pieces but the pressure applied is modest. Of course the boards must be well jointed. Small, thin strips of plastic are placed underneath each seam to prevent the panel from glueing itself to the workbench.
In the next photo the next two pieces are added to the panel. The brads are removed from the wedges and their positions are adjusted for the new pieces and re-nailed to the bench.
In the next photo the remaining two pieces are added to the panel.
In the next photo the panel has been cut to its correct width and the front edge is cut square to the sides with a router.
Next, we glue the front panel to the rear panel. The same wedge system is used. A couple of brads driven through the rear panel prevent it from moving backwards under pressure.
After the glue has dried we remove the Bottom from the workbench. We place the full-sized plan of the instrument on the bench and place the bentside on it. We move the bentside on the plan until we find the best match and place a mark on the bentside to show its front and rear locations.
The Bottom panel is placed on the workbench and the tail line is drawn onto the panel. Then we place the bentside onto the Bottom panel and trace its outline.
In the next photo the dark lines are the outline we just drew. The faint line is the line taken from the plan with carbon paper. The lines match perfectly except for the front several inches where our bentside has a little deeper curve than the plan. More than good enough.
The next photo shows the tail line being cut using a jig-saw and a wood guide.
The next photo shows the bentside being cut with a jig-saw. Unfortunately this must be done freehand so great care is taken to do this correctly.
The last photo shows the completed Bottom.
In Part 6 we will add the sides to the Bottom and, for the first time, have something that begins to look like a harpsichord. See you then.
Ernie
Part 1 - The Keyboard Part 2 -Keyboard con't. Part 3 - Keyboard con't. Part 4 - The Case (Bentside) Part 5 - Case Bottom Part 6 - Case Sides Part 7 - The Lower Braces Part 8 - Case Finished Part 9 - Building the Registers Part 10 - The Stand Part 11 - Jackrail & Moldings
Part 12 - The Music Desk Part 13 - Building the Benchhttp://www.ncwoodworker.net/forums/f101/harpsichord-project-part-12-music-desk-18962/
Last edited:
