The Bottom Inlay (this would be the Purfling on the very bottom, or butt of the guitar), can be quite a challenge by itself. Most luthiers make this Purfling wedge shaped, or tapered. This varies from luthier to lutiher and you can decide which best suits your taste. Typically I make this inlay on my guitars with a curved/tapered shape, which carries through a theme of my guitars. Some of the less expensive guitars eliminate this trim to save time and money. The wood sides are then sawn to length and butt glued to the tail block.
Start By Planning Your Design:
Before you forge ahead with routing the binding channels and Bottom Inlay channels, you have to know how you will design the guitar’s appointments for purfling and binding.
Classical guitars are usually quite simple. The edge binding typically is the same wood species as the back and sides and there is usually only one feature strip between the bottom of the binding and the guitar side. This is usually true between the binding and the back too. I make these feature strips (commonly referred to as purling) from maple veneer.
If this is the case, you will want to make the Bottom Inlay to match the design of the binding/purfling strips.
Acoustic Guitars can be just like the Classical Guitars if you like and the simplicity of this design is very elegant. There are other designs that become much for difficult and a real challenge for the luither. For the purposes of this article, we will keep things simple and straight forward.
The Bottom Inlay:
The first step is for you to make the bottom inlay. For simplicity make it tapered, with the widest part of the taper at the top of the guitar. (otherwise it looks funny and like you made a mistake if it is reversed). Cut the wood from a section of guitar back hardwood that you have left over. Tradition (and for strength purposes) calls for this grain to run at a 90 degree angle to the side wood grain. This wedge shaped purfling should be slightly longer than needed for right now.
Once you have cut the taper and checked the balance of the piece to make sure the taper is mirrored exactly, and the sides are sanded perfectly straight and square, it is time to add the maple feature strips. The easiest way to do this is to cut the Maple just a bit wider than the purfling strip. Spread Epoxy or Titebond on the pieces and tape the Maple to the purfling with 3/4″ masking tape, being careful to use enough force and tape to make the joint tight.
When dry, take off the tape and carefully use a scraper and plane down the Maple so it is flush with both faces of the Inlay.
Mark The Inlay on the Sides:
Carefully lay the Bottom Inlay strip on the guitar butt and center the Inlay on the Global Centerline of the guitar. Now take a sharp Marking Knife and strike a sharp line directly next to each side of the Inlay. Run the knife a second time if necessary.
Now take a metal straightedge and your Marking Knife an very carefully strike directly on the line several more times. This will give you a great starting point for your saw joint that is coming up next.
The Inlay Saw Joints:
Next take the metal straight edge and set it directly adjacent to the line. Place a fine toothed Japanese Pull Saw next to the straight edge and make sure you will not cut past the line, but inside of it just a bit.
Carefully make your first few light cuts and then you can remove the straight edge. Cut completely through the side and just deep enough to graze the tail block.
Repeat with the other side of the Inlay.
Remove the Waste:
Your next step is to remove the waste that is between the two cuts. Take a very sharp 3/8″ or 1/2″ Wood Chisel and cut against the grain to remove the guitar side waste. Use a very low angle of attach for the chisel and be sure to work carefully along the saw cut areas.
Work your way down to the tail block until all traces of the side wood is gone, as is the wood that was holding it in place.
Test Fit The Bottom Inlay:
Slide in your Bottom Inlay to test the fit. If it does not slide in far enough you will need to carefully trim off a bit from the channel. Work carefully with light strokes of a sanding stick or file to take just a bit off at a time. Repeat until the Bottom Inlay fits snugly in place without force and there are not any gaps showing.
GLS Tip #1:
If you make the tapered Bottom Inlay piece approximately 12 – 25 mm longer than necessary, because of the taper, you will have much greater latitude when fitting your Inlay into the channel. Then it is just a simple matter of trimming off the ends of the piece.
If you will be using plastic binding for your guitar, you can use either plastic or wood as it is discussed in this article for installing your Bottom Inlay.
GLS Tip #3:
If you want to remove the waste from the Bottom Inlay Channel quick and dirty, just use a Dremel Rotary Tool, a Router Base and Carbide Tip Bit to easily and quickly remove the material to the proper depth. Just be real careful new the saw cuts and hold the Dremel firmly so you do not get any kick-back from the wood grain.
Note: Most often Classical Guitar Bottom Inlays are square to the bindings and not tapered.