DIY Network

Handmade Guitar, Part 4: Back Bracing From "Handmade Music" episode DHMM-101

	The bracing on the inside of the guitar's rosewood back provides structural support to compensate for the channel cut for the marquetry inlay and for the curve of the guitar's back surface.
	Figure A

In this segment of DIY's Handmade Music, bracing and tone bars are added to the rosewood back of the guitar.

There are several reasons why a guitar's back requires a substantial amount of bracing. For one, recall that the marquetry strip along the back of the guitar (figure A) was added by first cutting a channel along the joint where the two book-matched halves of the guitar-back come together. Routing the channel for the strip compromised the joint somewhat. Bracing on the opposite side will help offset this compromise and strengthen the back. Additionally the back of a guitar is not flat but, in fact, bends on a slight curve from the neck to tail-piece. Bracing also counters the stress inherent in the curve.

Materials:

Rosewood and spruce stock
Band saw
Belt sander
Plans for bracing
Sharp chisels
Finger planes
Sandpaper
Caliper
Straight-edge
Carpenter's pencil
Wood glue
Hot hide-glue
Clamps

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	Figure B
	Figure C
	Figure D
	Figure E

Back Bracing

• As he did with the top, Lynn Dudenbostel sketches a brace pattern onto the rosewood back-piece (figure B). His pattern mimics the vintage guitars he has studied over the years.

• With the pattern drawn out, Lynn then cuts the brace pieces from the spruce stock left over from making the top, carefully cutting across the grain. "You want the grain to run the length of the brace," says Dudenbostel, "You don't want it running diagonally through it. It's like splitting firewood."

• Once the strips of bracing are cut, Lynn processes them into rectangular cross-pieces. He glues those brace strips into position to strengthen the bond where the two rosewood pieces were joined earlier (figure C). The gaps between the adjacent strips will be used to form an intersection with more spruce bracing later. Using a block plane and sandpaper, Lynn creates a gentle radius on the brace.

• The rest of the bracing is actually curved. "Braces on the back of the guitar have an arch to them," says Dudenbostel, "They're not just straight. They have a curvature to them that helps allow the wood on the back of the instrument to expand or contract with changes in temperature and humidity." Without the curved braces, the back piece could come apart under the resulting stress. Lynn forms the curved braces using a block plane and belt sander (figure D). He then uses a sharp chisel to cut paths through the back-center brace to allow intersections with the curved braces.

• The curved brace is attached to the back with wood glue. The fit at the intersections must be snug, so Lynn carefully trims in small slices and checks the fit frequently as he joins the braces together (figure E).
  
• Some carving is required on the back braces but, unlike the top's brace wood, scalloped design is not required. A radius shape is carved into most of these using chisels, planes and sandpaper (figure F).

• Using the chisel, Lynn tapers the brace wood along the back's perimeter to where it meets the rosewood (figure G). This is where the back will eventually join the sides, so this tapering will help allow that fit.

  Figure F

  Figure G

  
  

  The hands of an artist and a work of art: Cody Kilby of bluegrass band Kentucky Thunder strums the strings of a vintage-style guitar.

RESOURCES :

Kentucky Thunder
For more information on the band that appeared in DIY's Handmade Music, Kentucky Thunder -- and to hear streaming audio and download samples of their music -- visit the website for Skaggs Family Records, www.skaggsfamilyrecords.com.

Stewart MacDonald's Luthier Supply Shop
Website: www.stewmac.com

Luthier's Mercantile International, Inc.
Website: www.lmii.com

Pioneer Valley Luthier Supply Company
Website: www.pioneervalleyluthier.com

GUESTS :

Lynn Dudenbostel, Luthier
Dudenbostel Stringed Instruments
Knoxville, TN

John Arnold, Luthier
Newport, TN

Ted Davis, Luthier
Loudon, TN