ASSEMBLING THE BODY -- 2
After the back is glued on I locate and install the top. Step one, shown here, is to flatten the ribs to match the top. As you can see, I use a high tech tool -- a level with sandpaper glued on the edges. This photo is slightly deceptive -- normally I have the spreaders in place when I do this to provide support to the ribs. Otherwise they tend to vibrate when I do this step.
The next step is slightly tricky. If the top is perfectly flat there is a problem with the neck angle. A guitar neck must be set back (angled) slightly from the flat plane of the top -- if it is not, the bridge will be too low for good tone. But if the neck is set at a slight back angle, the fingerboard will bend slightly down at the body when it is glued to the top. This is unsightly and causes the action to be (slightly) too high over the body. There are three solutions that I can think of. One is to place a slight wedge under the fingerboard over the body so that it is straight. (Few if any makers use this technique) Another is to make the top with a slight dome shape -- the makers that do this typically use a dome with a radius of about 25 feet. This will give the top a slight angle where the neck joins and will allow the fingerboard to lie straight. This method is quite common. The third method, which I use, (and which I learned from Jim Olson) is to cut a slight wedge out of the ribs (from the sound hole to the dovetail) so that the top angles down slightly at the top end of the guitar. This angle begins at about the top of the sound hole and extends to the top (dovetail end) of the guitar. If this "wedge" cutout exactly matches the back angle of the neck, the fingerboard will lie straight. In practice this is relatively easy to do, The two boards you see mounted on the mold have this taper built in. (I cut them on my table saw with a taper cutting jig). The router, with a long supporting base, rides on these angled boards and is then set to the correct depth of cut. This will then cut a small amount off of the rib and creates the taper that I am looking for.
After the ribs are tapered, I cut the notches for the braces. I notch in all four ends of the X brace and the two braces under the fingerboard extension. All others are cut slightly short of the linings and the linings are not notched. I use a locating pin at the dovetail end of the guitar (where it will be hidden under the fingerboard) and simply carefully center the "back" end of the top. Then I use a small thin saw to outline the braces I will notch in. After I have marked them, I cut the sides of the notches with a fine fret saw (this helps keep the router from cutting too wide - the wood will chip out on the saw mark), and then cut the notches with a laminate trimmer (using a 1/4" spiral cut bit. These steps are shown in the next four photos.
If I cut the sides of the notch with a thin saw, the routing of the notches is easier. As the router bit approaches the saw cut, the wood will tend to chip out right to, but not beyond, the line. This makes for a very precise notch.
Here the top is being glued onto the walnut body. What doesn't show is that the work board under all this -- on which the top is resting, has a wedge or ramp to match the wedge cut out of the ribs. (I cut the wood to make this ramp at the same time and with the same jig as I cut the boards which guide the router.) This ensures that the assembled body really will have the slight taper on the top.
Another photo of the same. Notice that the work board is elevated above the workbench. This makes it easier to apply the clamps, and the device I use (a carvers clamp) enables the work board to rotate as well. This is really quite efficient. I can also mount the work board for the back on this device.
This shows a repair - gluing a back onto an old Dyer Brothers harp guitar. It took two people working carefully and fast - and 32 clamps. Proof of the old adage - you can never be too rich, too thin or have too many clamps.
Here the cutaway is being glued to the neck block. The tricky part of this is shaping the end block so that it exactly matched the slight curvature of the cutaway. Currently I do this with an oscillating drum sander. For a long time I resisted getting this tool thinking it would be expensive and of limited use. WRONG!! It is now one of the most used tools in the shop and I kick myself for not getting it earlier.
Here is Michelle holding a cutaway she is building. Note that the lining for the cutaway is solid -- something I have always done. I feel (rightly or wrongly -- I don't know) that this is an area where the extra rigidity is helpful to the structural integrity of the instrument. There is another photo of this HERE.
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