DIY Network

Handmade Mandolin, Part 3: Creating the Curved Sides From "Handmade Music" episode DHMM-105

	Lynn Dudenbostel creates the curved sides for the mandolin using a custom-made bending form.
	Andy Leftwich of the band Kentucky Thunder provides a worthy workout for a newly minted Dudenbostel mandolin.

In this episode of DIY's Handmade Music, Lynn Dudenbostel continues the process of creating an instrument that looks and sounds like a vintage F-5 style mandolin. In this segment he focuses on the body of the instrument. Earlier Lynn crafted a top from two joined pieces of red spruce and then carved a back from one solid piece of curly maple. Now his focus shifts to the sides that are formed by bending curly-maple strips.

Materials:

Curly-maple stock
Mahogany stock
Band saw
Drum sander (or thickness sander)
Bending device (custom-made using metal pipe and propane torch)
Bending form
Instrument-maker's glue
Straight-edge
Carpenter's pencil
Safety glasses or goggles

Safety Alert: Always wear safety goggles or safety glasses when
working with wood, power-tools, saws, drills, routers, etc.

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Creating the Curved Sides

• Strips of curly maple are cut to size on a band saw, then brought to the proper thickness using a thickness sander.

• Some curves of the mandolins sides are extreme and some are subtle. The bending is aided by a device that uses a propane torch to heat a metal pipe. The wood strips are moistened, then gradually bent over the hot pipe. The hot metal surface turns the water in the wood to steam, allowing the wood to bend more easily (figures A and B). Lynn designed this device in a way that he can bend the wood on the hot metal while keeping his hands a safe distance from the heat.

  Figure A

  Figure B

  
  
  
• The goal in this phase of the construction is to bend three strips to form the perimeter of the mandolin. It's a slow, gradual process, and a template is used as a guide (figure C).

• The extreme curves of a mandolin make this a tricky process. Ultimately the strips will fit inside a form that will hold the sides together while they cool. As he works bending the strips of wood, Lynn references the form as a guide as well (figure D). Forms like the one Lynn uses can be purchased from luthier-supply shops, but Lynn built his forms by hand.

  Figure C

  Figure D

  
  
  Each side piece receives equal attention in the bending process (figure E).

  After a few hours of work Lynn has formed all the needed side elements (figure F). "You put the pieces in the form," says Lynn "and hold them in the form until they dry and have cooled off -- which is normally just a few hours. Then they normally take a set to that shape."

  Figure E

  Figure F

  
  

  Figure G

  
  

• With the side elements bent to their proper shapes, Lynn begins work creating and gluing in the head-block, tail-block and point blocks. These interior parts are made from solid mahogany and cut for precise fit using the band saw. The use of mahogany for these parts is based on the traditions of the original instrument makers of the 1920s. Templates culled from vintage instruments are used to create these precisely sculpted pieces (figure G).
  
  
• Once the pieces are all cut to the proper size and shape, Lynn begins gluing them in place around the rim he's created using instrument-maker's glue. The head block goes on the inside of the rim on the upper side where the neck will connect later (figure H).

• The tail block is glued to the lower part of the instrument, and the point blocks fit inside the triangular shapes created by the joined strips of maple (figure I).

  Figure H

  Figure I

  
  
  
• After the glue is dry Lynn can remove the rim for the first time and see the shape of his newest creation (figure J) .

• There's some sanding to be done (figure K)and a little more essential crafting.

  Figure J

  Figure K

  
  
  
• Once the sanding is complete, Lynn installs kerfed lining around the rim (figure L). "Kerfed lining is a small, flexible strip [of wood] that has saw-kerfs cut in it," says Dudenbostel, "so that it can make those real tight bends on the inside of the instrument. It's glued on the rim where the top and back will join together to give you more glue surface-area. When you put the binding on an instrument, you actually rout away most of the glue joint between the sides and top or back. You need something else there to give you more glue surface. That's where the kerfed lining comes in."

• After removing the pins that serve as clamps for the delicate kerfed lining (figure M), Lynn checks and removes any excess glue.

  Figure L

  Figure M

  
  

  	Figure N
  	On the stage at the world-famous Ryman Auditorium in Nashville, host Jeff Wilson holds the instrument that introduced the world to the unmistakable bluegrass sound -- the Gibson F5 style mandolin.

  
  
• Finally, once the pins have been removed, Lynn sands the edges even with the sides (figure N).

RESOURCES :

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