ASL Breakdown Page 1 Rim Wednesday, January 16, 2013 9:35 PM Similar to the plates, begin with the side blanks, determining the "show face" and taper angle. Then make the taper cut. The diagram shows these considerations when laying out the side blanks. Sides: Heel Top X Butt Back Orient the sweep of the grain to sweep up with the taper of the side. Side should be thickness sanded to 0.085" (about 2mm). - - - X marks the following: Show face Lower bout Soundboard edge Decide this when you evaluate the side blanks Sled with side taper template in place for locating taper cut. When this cut is made, the edge that will join to the soundboard is inboard on the sled. The saw cuts the edge that will join to the back. NOTE: before this step, figure out which side will show, which will be front and back, etc (see above).
ASL Breakdown Page 2 Side bender, waist compression. On each side of waist, 7 small panels (1/8" each?) of Masonite conform to the contour of the waist as given by the guitar form in the bender. Once the contour is set, tighten the bolts to hold the Masonite "leaves" to the correct shape. Note 3 parallel cutouts for the guitar shape. separated by dowels. Fox bender Another view of bender machine at waist. Note on pipe bender (to tune up sides after they have been on the Fox bender): Best material is copper, but aluminum is good. Bending machine is heated with the metal and heat blankets fully bent in order to have metal contact the heat as much as possible. Note the (very) small red arrow at the waist pointing to the upper bout. The work should have this spot marked as well. The sides to be bent are placed (one at a time) between pieces of butcher paper. This prevents wood resin
ASL Breakdown Page 3 1. 2. 3. 4. 5. 6. from building up on the metal in the bender. The paper is marked, using the side template, to indicate the waist and the spot corresponding to the red arrow (above). The sides must be bent considering that one is left and one is right - line them up on the workbench correctly and don't move them out of the correct configuration (use the X mark made previously). Soak the wood and paper with a spray bottle. The bender is loaded with the sides between the 2 metal strips underneath the heating blanket. A 3rd metal piece goes over the heating blanket. Make sure the straight (soundboard) edge of the side piece is square with the bending jig so the side does not come out with a twist in it. Ideally, the heating blanket can be controlled with a switch similar to a stovetop cook unit. A probe, like a digital oven meat thermometer, can be used to check temperatures. The bending cycle is: Pre-heat to 300 degrees Insert piece to bend. Bring the waist down and then back off 1 1/2 turns. Bend the upper bout, then the lower bout. Re-tighten waist. Set heat blanket for 250 degrees for 15 minutes. Allow to cool to room temp With the sides still in place, go through a second heating (250 degrees) and cooling cycle View of completed sides showing curvature from dish. Note that the butt end (foreground) is lower than the sides at the waist. Also note X mark indicating top/butt end/show face.
ASL Breakdown Page 4 Setting up the mold for a specific body shape. The large dowels are pieces of closet pole. All Charles' guitars have a 20" radius at the head and foot blocks. Building mold and center caul Make sure head and tail blocks are properly aligned and tightened in place. Properly adjusted mold with guitar sides and caul spanning the waist in place. Note that in the form, the guitar is build face down with the floor square to the reference plane. My mold with head block bolted in place. When working with the mold, adjust the bent wood work pieces (sides, linings) to find the "natural" spot for the waist. Then work out from there to determine where the pieces will intersect the other sides or the neck and tail blocks. Blocks are covered with packing tape and side of head block is taped as well to help clean up glue run out. Head block inner curve is fine sanded for appearance.
ASL Breakdown Page 5 Radiusing rear of tail block to 20" radius prior to gluing in mold. Tail block radius sander Tail block clamping. Like head block, tail block is raised on 3/16" shim. A caul shaped like an ] is used to spread clamping force to bottom of tail block. Cam clamps used - one on either side of cauled (lower) clamp.
ASL Breakdown Page 6 Final clamping Note cams of clamps are all outboard of the mold in a position to be (nearly) fully thrown.
ASL Breakdown Page 7 To fit linings: - Find "natural" waist. - Compress lining along the sides toward the front of the guitar. Cut front of kerfed lining at the kerf closest to the head block. If possible, cut the kerfed piece at an angle to fit closely to the head block. - Cut solid lining so it is proud of the head block and roughly at the angle needed to meet the head block to make a clean joint. Trim with sandpaper until the solid lining and head block join well. - Repeat this process at the tail, making sure to keep the linings solidly butted against the sides so that the overall length is correct when gluing. <--- Completely installed and clamped top lining. Note spreader at waist. Be as conservative as possible with glue when gluing in linings. It leaves less to clean up.
ASL Breakdown Page 8 Next, the frame is cut down to size and to a 12' radius on the back side. This begins with a rough cut of the frame using a scribed mark and a plane. My frame with a peep hole cut to the depth of the head block. Such a hole is cut into both head and tail blocks. The scribe tool should be set to scribe a line at the height of this window. This should be the same at both the head and tail blocks. If it is not, raise the lower of the 2 sides with shims until the proper cut can be scribed with minimal loss of side material. Scribing 25' radius line around sides when top is face down on the dish. The line is drawn with a white pencil held in a protractor-like jig with a flat bottom that moves across the surface of the dish.
ASL Breakdown Page 9 Preparing to plane the top to the scribed line with a block plane. Taking off top side of frame with a block planer. The waist is not much accessible to the plane, but the rest planes nicely. Keep the plane at a tilt so that the lining is proud of the sides themselves. Also, plane across the lining at an angle so as not to split it.
ASL Breakdown Page 10 After the rough planing, the frame can be cut so as to put a the 12' radius arc on the lining, which will be the gluing surface for the radiused back plate. <--- Setting frame into radius fixture for cutting the back to a 12' radius arc. Radiusing the frame can be done with an electric potter's wheel and a radius plate. The wheel can be mounted sideways on a wall to take up less room. New wheels aren't cheap! Guitar frame aligned in fixture so as to be level. Adjusting router cut to be just proud of the head and tail block surfaces. The reference plane is to the top of the guitar. When routing the back (as here), the top of the frame is face down in the jig. The supports are adjusted so the sides and lining that face the back of the guitar are level to the router. Rim trimmer fixture with router Router head of radius fixture. Note the arm that controls the distance of the bit from the guitar is radiused. As the bit travels closer to and further from the center pole, it travels along the radiused guide beams.
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ASL Breakdown Page 12 Final radius shaping on 12' radius dish with course paper. Use the pencil test to be sure sanding is complete. More fixture pix.
Finished frame. ASL Breakdown Page 13