Making and fitting the tail block correctly is essential for all acoustic instruments. The tail block is key for holding the edges of the sides in place and providing additional strength for the strap button and general abuse as the instrument is usually set on its butt. Key is the shaping of the sides to the tail block so there is a consistent gluing surface.
Tools and Materials Required:
120 Garnet Sand Paper
Feathering Disc Adhesive
(2) Large Cee Clamps
Wood Clamping Cauls
Dovetail Saw -or- Japanese Pull Saw
1/2″, 3/4″ Chisel
After you remove the sides from the Side Bending Jig, place them in an Inside Form using Spreader Jacks, to maintain the form of the guitar. Make sure the top of the guitar is facing downward and that the sides are evenly resting against the bottom of the form.
Trim The Side Ends:
Take the Aluminum Retainer off the tail block end of the Inside Form to expose the cutting slot. If you have a bandsaw, take the form with the side clamped inside the Form and run the sides through the saw to trim both sides at one time. If you don’t have a band saw, carefully mark the center of the guitar of each side (use white pencil on dark wood sides). Remove the sides and trim with a fine-toothed dovetail saw or a Japanese Pull Saw. Now insert the sides back into the Form and re-clamp.
Final Side Fitting – Inside Form:
Next, fit the sides back into the Inside Form, install the form retainer block(s) and apply the Spreader Jacks make sure the sides are exactly symmetrical within the form and that the joints at the Tail Block are exactly on center. If not, adjust by cutting or sanding with a sanding stick.
On a side note, we don’t have to have Tailblock joint hairline tight as the butt of the guitar receives a purfling strip.
Cut the Tail Block to shape using the layout of the Guitar Building Plans. Be sure to cut the blocks to exact height as the blocks will be a couple of our references for the proper side depths.
Shaping The Tail Block:
The Tail Block could be cut on a table saw, a band saw or with hand saws to match the proper outline of the block. Depending on the guitar shape the side of the block that is glued to the sides will be flat or have a slight curvature. If it is flat, just finish sand the block.
If the butt of the guitar is curved slightly, slowly sand from the center of the block toward the edges with a sanding stick. Just take a little at a time and check your progress often by fitting against the guitar sides. Flip the block upside down and check again. When you have a hairline joint between the guitar sides and the block, you are set to go.
Shaping the Classical Guitar Tail Block:
The classical block is similar except the classical blocks are usually almost semi-circular. Shape front and back of block with rasps and sanding sticks. Check your work often to get a hairline joint.
Gluing the Classical Guitar Tail Block:
For the Classical Guitar, cut wood cauls and shape them to fit the outside contour of the Tail Block. Place leather cushioning in the inside of the caul and take (2) large “C-Clamps” and glue the Tail Block to the guitar sides. If you are using a highly resinous wood, clean the sides with Acetone and be sure to use protective gloves and eye shields. Check that the bottom of the block is resting securely on the bottom of the Inside Form. Tap with a hammer if needed. Place a piece of waxed paper behind and beneath the sides and the Tail Block to prevent the sides from being glued to the Inside Form.
Gluing the Acoustic Guitar Tail Block:
Do final fitting of the Acoustic Guitar Tail Block. Apply glue to the block and the sides. Apply a small gluing caul to protect the block from the clamps and clamp similar to the Classical Guitar Block above. Be sure to place a piece of waxed paper behind and beneath the sides and Tail Block to prevent the guitar from being glued to the Inside Form.
Tail Block Shaping Tips:
Here is one way to get the glue joint of the tail block absolutely perfect. Glue a piece of medium grit sandpaper against the sides where the tail block will be installed. Make the sandpaper about 1″ wider on either side of the block. Be sure to use a release-type of adhesive like feathering disc cement or something similar. Now take your Tail Block and sand it either up and down or sideways a bit. In a very short period of time you block will be perfectly contoured. Remove the sandpaper and adhesive and check the joint.