Open back 5-string (Clawhammer) Banjo notes:
OPEN BACK 5 STRING BANJO DIMENSIONS:
SCALE=25 3/4"
FRET:____DISTANCE FROM NUT:
1________1-7/16
2________2-13/16
3________4-3/32
4________5-5/16
5________6-29/64
6________7-35/64
7________8-9/16
8________9-17/32
9________10-7/16
10_______11-19/64
11_______12-7/64
12_______12-7/8
13_______13-19/32
14_______14-9/32
15_______14-59/64
16_______15-17/32
17_______16-7/64
18_______16-41/64
19_______17-5/32
20_______17-41/64
21_______18-3/32
22_______18-17/32
NECK:
OVER-ALL LENGTH WITHOUT DOWEL ROD: 24 3/8"
MAXIMUM WIDTH OF PEGHEAD: 2 1/2"
PEGHEAD THICKNESS: 1/2"
WIDTH AT NUT: 1 1/4"
DEPTH AT NUT: 7/8" , includes 3/16" fretboard thickness
WIDTH AT 5TH FRET: 1 5/8"
DEPTH AT 5TH FRET: 1" , includes 3/16" fretboard thickness
WIDTH AT 15TH FRET: 1 3/4"
DEPTH AT 15TH FRET: 1 1/8", includes 3/16" fretboard thickness
DEPTH AT HEEL: 2 9/16", includes 3/16" fretboard thickness
LENGTH OF HEEL: 1 7/8"
POT:
OUTER DIAMETER: 11"
THICKNESS: 11/16"
HEIGHT: 2 3/8"
TONE RING: 11" O.D. X 3/8" BRASS TUBING
DOWEL STICK: 10 3/8" + ADDITIONAL 2" SHAPED TO 3/4" DIAMETER
TO GLUE INTO HEEL
DOWEL STICK 7/8" SQUARE AT HEEL X 5/8" SQUARE AT END
NECK ATTACHED WITH FRETBOARD 1/8" HIGHER THAN TOP OF TONE RING
Introduction to 5-string banjo construction shop notes
The following are my shop notes detailing the methods I used to construct my first 5-string open-back banjo. The notes generally follow the construction sequence . A fair amount of detail is presented, but they are not all-inclusive. They are meant to be a referance on which to build from, and not a step-by-step "How-to guide". I find that it is best to form a clear picture in the mind as to each of the steps involved, and then let common sense, logic, and innovation direct your progress. The notes proceed through building the rim construction form, the rim, the tone ring, the neck, joining the rim to the neck, and finishing. The basics are presented and may be further embellished by whatever method you choose.
Rim form
This form has two purposes. It is used as the inner support while the rim is formed from successive layers, and for truing the outside of the rim after each layer is added. It is made by cutting four disks 10" in diameter from 3/4" particle board. Stack laminate these 4 disks to obtain a 3" thick circular form. After stack-laminating the basic form and drilling a centered 3/4" by 2" deep hole in it's center, insert a section of 3/4" dowel 2 and 5/8" long. Cut a 12" long piece of 3/4" plywood 9" wide and drill a 3/4" hole 5" from it's end. Position the circular form on this board by matching the form's protruding dowel to this hole. The plywood is loosely bolted to an extension drill press work table so the overhanging section of the circular form can be brought against a 2" drum sander held in the drill press spindle. Clamp a stop to the table to limit the amount of contact the form can have with the drum sander. Swing the form into the drum sander and sand by turning the form in the opposite direction of the drum's rotation, keeping hands away from the contact area. Sand only about 1/16" off at a time. Relocate the spindle and lock in position to adjust the vertical contact point. Reduce the form to 9 and 3/4" outside diameter. This form is now used as the inner support for the glue-up jig.
Glue-up jig
(Image)
Fabricate this by cutting two pieces of particle board 20" square. One piece is used as a base and the other will become the clamping wedge support. Cut two 9" disks from 3/4" particle board and stack glue them at the center of the base. Drill a 3/4" hole at the center to locate the inner form dowel. Cut a _____" diameter circle from the other 20" square and remove the cut-out. The outer section will become the wedge clamp support. Sand and radius the inner edge of this piece with a 3/4" roundover router bit. Screw the clamping wedge support to the base using riser blocks to align the top edge of the wedge support board to the centerline of the inner support form. Cut 36 wedges from 3/8" particle board approximately 7" long by 3" wide and tapering to 1" to allow wedge clamping any thickness from 1 lamination to the full 3/4" rim thickness. Sand the two long edges to facilitate wedging action when lightly tapping the wedges into the space between the form and the wedge clamp support board.
Rim
The rim is made by laminating 1/10" thick strips around a 9 and 3/4" circular form until the 11" finished diameter is attained. Begin by cutting 40" long strips 2 and 5/8" wide and sanding them smooth to prepare them for lamination. Soak the strips in very hot water for 1/2 hour and pre-bend them around the 9 and 3/4" circular form. Band clamp each strip on form until dry. After strip has dried, it can be removed from the form and the ends clamped together to retain it's shape until ready to use. Successive laminations can be produced in this manner until a sufficient number are produced to complete a rim. A lesser grade of wood such as common hard maple can be used for the inner plies, with a better grade of figured wood used for the innermost and outer laminations.
Laminating the Rim
Select the strip which will become the innermost layer of the rim, keeping in mind that it will be visable. Trim one end of the lamination strip square, wrap tightly around the form, mark overlap and trim at mark leaving a slight gap to ensure lamination closes tightly on form when clamping wedges are tapped into place. Cover the outside of the inner form with aluminum foil or plastic food wrap to prevent glueing the lamination to the form. Cut a small piece of veneer 3" X 3" to reinforce the seam where the lamination ends meet. Place the veneer reinforcement against the inner form and glue the lamination in place with the joint centered over it. The veneer will later be sanded off after the rim is completed. Orient the veneer's grain parallel to the rim to maximize strength at this joint until the second lamination layer is added. Glue and clamp in place using wedges and let dry completely. Remove the wedges when dry and add the second layer, staggering the joints between the first and second layers.
It is recommended that after the first two layers are completed, the rim/inner form be returned to the drill press drum sander. Thereafter true after each strip is glued in place. Each additional lamination is added by trimming square one end of a pre-bent strip, wrapping tightly around the previous lamination, and marking the overlap. Trim this strip to produce a slight gap when test-fitting around the rim to ensure a tight fit when glued. It is best to dry-fit each successive layer before glue-up.
Plan out the amount of sanding necessary on the final two laminations so the finished outside diameter is exactly 11 inches. Stagger lamination joints equally as they are added, and orient the final layer with the joint at the same location as the inner layer joint. Remove the rim from the form by supporting the edges of the rim and tapping the form lightly with a hammer to drive it from the rim.
Use a safety planer to surface both sides of the rim and reduce the width to 2 and 1/4".
Rim bottom trim wedges
Fabricate a wedge-shaped inlay approximately 6" long and 1/8" thick to cover the inner and outer lamination seams. Add thin contrasting strips of wood to the wedge's outer edges for decorative porposes. Sand the finished wedge down to a uniform thickness. Trim in half to produce outer and inner wedges. Hold them in place centered over the seams, (widest inlay on the outside lamination and wide part of the wedge to the rear of the rim), and scribe their location on the rim. Carefully backsaw on the inside of the lines to a depth of 1/2 the lamination thickness and remove the waste between the lines. Cover mating surfaces with glue and lay the wedge in the slot. Lightly tap the wedge to seat it in the slot, cover with plastic wrap and clamp in place using a padded caul for uniform clamping pressure. Remove cauls when dry and trim wedges even with the outer edge of the rim.
Capping the rear of the Rim
Mark the bottom of the rim in 8 equal sections, extending the lines to the outside and inside edges of the rim. Continue this line 1/8" down the outside and inside edges of the rim to facilitate marking the rim cap stock. Invert the rim and rest it on sections of 1/8" thick stock wide and long enough to span between two of the previously drawn lines. Orient the grain to run in the same direction as the plane between these two lines. Transfer the rim outside and inside curvature to the stock and mark the intersecting radial lines. Trim the outside contour 1/8" outside the marked lines and trim the end lines precisely, touching them up on a disk sander. Glue one section at a time, securely taping the section to the rim until the glue has dried. Proceed with each section until the rim is complete. Route or sand the rim cap flush inside and out.
Binding the rim
Route binding ledge around the outside and inside of the rim. My preferred method is a rotary hobby tool adjusted for the correct depth of cut and fitted with a stop to limit the depth of cut to slightly less then the thickness of the binding used. I have generally adopted the use of wood bindings, so these will need to be soaked and pre-bent using a 12" long section of 3" copper pipe heated with a propane torch. Instructions for heat-bending can be found in numerous referance sources. After binding has been bent and dried, glue in place by wrapping the rim with heavy twine to pull the binding into position as it is fitted to it's binding ledge. Binding can meet in a butt or lap joint, prefferably under the area which will be covered by the neck heel. Scrape and sand the binding flush with the rim and round over the edges gently.
Bracket holes
With the rim laid flat and facing up, place four 1 and 7/8" blocks adjacent to the rim and set the tension band on them with the area of the neck notch oriented exactly opposite the rim"s end wedge decorative inlay. Mark the tension band's notch locations directly on the top of the rim. Continue these lines lightly down the outside of the rim, and draw intersecting marks 1 and 1/8" up from the rim's bottom edge to mark the location of the holes for the bracket shoes. Drill through the rim at these locations using a drill press fitted with a bit slightly larger than the bracket bolt diameter. Swing the table to one side and clamp a board whose top has been radiused to match the inside diameter of the rim to the table. The inside of the rim can be supported upon this surface while drilling the bracket holes to prevent tear-out on the back side of the rim. Set rim aside until neck is completed.
Tone ring
This was made of joined sections of 3/8 inch o.d. brass tubing commonly available in hardware stores. Pinch off one end and fill tube completely with fine sand. Tap tube lightly on a solid surface and continue filling and compacting the sand until the level approches 1/2 inch from the top. Fold over the end of the tube and crimp tightly. Bend tube around a circular form approximately 10 inches in diameter. Some springback will occur. Ideally, the outer diameter should match the outer diameter of the banjo rim. This should be 11 inches in diameter. The ends of the sections are joined by inserting pre-bent 1 inch sections of the next size smaller tubing inside the mating sections and soldering them together. The hobby tubing is designed to telescope snuggly into the next size, so a very good mechanical joint will result. The tone ring is assembled by joining as many sections of tubing as is necessary together to form the completed circle. This can be easily accomplished using a ordinary propane torch and common solder for electrical circuits providing the mating surfaces are first cleaned with fine steel wool prior to assembly. File and sand joints flat and smooth to finish the tone ring.
Neck construction
The neck is formed by tracing the side profile onto three pieces of surfaced flat-sawn lumber. Cut out a template, making certain the top surface representing the fetrboard plane is straight and extends the additional width of the nut before the rear-slanting angle of the peghead begins. This is to ensure the peghead overlay will seat firmly against the nut when glued into position. The two outer sections are cut from 1" stock, and the center section is cut from stock that has been reduced to 5/16" thickness.
Plan out the location for the truss rod channel carefully so the rod ends are 1/8" below the top of the neck blank and the rod arches to it's maximum depth around the 10th fret location. Keep in mind the mechanics behind the truss rod principle. Tightening the rod which is anchored at both ends causes pressure to be applied in an upwards direction in the area most likely to be deflected by the string's tension. Route the pocket using a 1/4" round-ended bit set to a 1/4" depth, leaving 1/16" of material remaining at the channel's bottom. I use a guide which is fabricated in the following manner. Cut a piece of 3/4" stock to the desired arch and sand the arch sooth. Make this wide enough so it can be clamped in place with c-clamps. Glue this to a piece of 1/4" plywood or hardboard, with this 1/4" piece extending out about 4" past the arched edge. Insert the 1/4" router bit and set to a depth of 1/2". Run the router along the arched guide board to remove the waste overhang. This remaining jig can now be clamped in place directly on your layout line, the router set to cut to the correct depth, and the channel routed directly on the center neck section. This is a very versatile technique, and can be adapted for many uses. Different tools such as circular saws will also adapt to using these types of guides, their great advantage being that the cut is exactly represented by the guide, therefore eliminating layout time and innacurracy.
Drill a 1/8" locating hole through the center section side profile at each end. Clamp the center section against one side at a time and extend these holes for a short distance into the two side sections. Cut two pieces of 1/8" dowel to insert as alignment guides in these holes, making certain that they are not longer than the total depth of the holes. Glue all three sections together. Draw a small piece of cloth through the truss channel several times to remove excess glue. Let this blank dry thoroughly before further work.
Truss Rod
The truss rod is formed from a 24" piece of 10X32 all-thread rod. It's anchor end is a 3/4" long half-moon keystock (available at any hardware store) which is drilled and tapped for the 10X32 all-thread. Drill the hole close to the flat side of the key. This will be recessed into the heel end of the neck just below the fingerboard. Spin the tapped key onto the all-thread far enough to expose about 1/16" of the shaft beyond the key, clamp the all-thread in a vise, and peen over the end of the threaded rod to prevent it's coming back out of the key. Form the rod into an approximation of the channel's arch and push it through the truss channel ontil the key seats against the heel. Mark the key's shape on the heel, remove the rod, and route out the recess for the key. Form the pocket for the truss rod nut at the peghead end, and insert the rod again. Mark the rod where it should be cut, remove and cut the rod, and remove any burrs on the threads and make certain the truss nut threads onto the rod smoothly. The truss rod may now be removed and set aside until final assembly.
Fretboard area surfacing
After drying, surface the fretboard area by clamping guide blocks to the neck blank sides. These guides will ride evenly on the drill press extension table, assuring even surfacing of the neck's face. Adjust the blank to be perfectly leveled with a light cut of the safety planer. Remove the guide blocks and flip the blank to clean up the bottom edge with another light pass beneath the planer. Lay out the top view of the neck and mark out the profile of the fretboard area and nut location. Extend the rear line of the nut to the sides of the block and mark the peghead slope on the sides of the blank. Carefully saw out the front slope of the peghead. Draw a parallel line 3/4" behind this cut and trim away this area also, being mindful to leave the area of the thumbstop intact. Glue and clamp ears of wood to the side of the blank to increase the width for the peghead profile. Sand the area where the peghead overlay will be glued, making certain you do not sand below the nut's rearmost location. Disk sand the nut end of a peghead overlay at an angle to match with the face of the nut. Temporarily clamp the squared fretboard and nut onto the top surface and glue the overlay into position, butting the angle tightly against the nut.
Shaping the rear of the neck
Clamp the neck to a solid surface and shape the neck profile. My favorite tools for this are a curved surform file and a 2" drum sander held in a portable drill. After roughing out the neck, drill the 3/4" hole in the heel end of the neck in which the end of the dowel stick will be fastened. Clamp the neck upright and drill this hole in it's correct location, making certain the hole is parallel and square to the fretboard plane. Drill 2" deep using a Forstner bit. Verify the alignment of the hole by inserting a 18" length of 3/4" dowel in the hole and placing the fretboard face down on a flat work surface. Check to make certain the dowel stick is parrallel to the table. Sight down the centerline of the rear of the neck to verify that the dowel stick is also in a straight line with the length of the neck. If either of these two checks indicate anything other than a very slight misalignment, the hole will need to be plugged and redrilled.
Fitting the neck to the rim
After drilling the heel for the dowel stick the heel may be fitted to the rim. Clamp the rim and the neck face down to a support which will ensure the neck is in proper alignment with the rim's centerline. The rim is supported upon spacers equal to the tone ring height before clamping it down. This will place the finished fretboard high enough above the head to produce the proper string clearance. Butt the neck heel against the rim. The heel will need to be matched to the rim to eliminate the gap between the heel and the rim before the dowel stick can be joined to the neck. Using a small piece of stock slightly thicker than the maximum gap which exists between the neck heel and rim, hold the piece against the rim and transfer the rim's profile to the neck heel area by scribing along the intersecting line of the stock and the heel area. Remove the neck and connect the tops and bottoms of these two lines with arcs which match the rim's outside diameter arc. Carefully remove the stock at the heel to form a tight fit with the rim. Work slowly and carefully using a 2" drum sander held in a drill press. Holding the fretboard to the drill press extension table will ensure the neck will be profiled in a way as to keep the fretboard parallel with the head surface. Removing slightly more stock in the center area will ensure a tight fit between the sides of the heel and the rim. When satisfied with the fit, orient the neck with the fretboard facing up. Position the tension band on the fretboard surface, and mark the outside 1/4" back from the heel's edge. Mark this area to 1/2" down from the top of the board and remove the waste piece. Finish this recess with the drum sander to create the finished recess for the head and tension band.
Peghead
Lay out the peghead shape and tuner hole locations on the face of the peghead. Drill from the front to the rear of the peghead with a 1/16" drill bit to mark the location of the tuners. Thin the back side of the peghead to 9/16" using a safety planer, staying clear of the thumbstop area. Drill the tuner holes to match the size of the tuners you will be using (probably 3/8") from the backside of the peghead using a backer board under the peghead face to prevent tear-out. Cut a block of scrap stock to attach to the back of the peghead to serve as a base when cutting out the peghead profile on the bandsaw. The top of this block must be cut with an angle that matches the rear of the peghead so when it is attached by means of pan-head screws through the tuner holes the bottom will be parallel with the fretboard plane and even with the bottom of the neck blank. This attached base should be as wide as the blank. This base is used to support the neck blank when sawing the profile, as banjo tradition dictates the profile lines be perpendicular to the plane of the fretboard. Cut the profile for the peghead and sand it's edges with a small sanding drum held in a drill press. Use a light touch to maintain the correct contours. Sand any other contours or flat areas of the profile while the base is still attached to help maintain straight edges on the peghead sides.
Dowel stick
Form dowel stick with a 14" piece of stock 7/8" square. Measure 2" from one end and taper the stick on all four sides from 7/8" square to 5/8" square on the other end. Reduce the first 2" of the 7/8" end to a 3/4" diameter and test fit this end into the hole previously drilled in the heel. Place fretboard surface face down on a flat work area and ensure the center of the dowel stick is at the same level on both ends. Sight down the length of the neck and verify that the dowel stick is also in a straight line with the centerline of the neck. If either of these two inspections reveal a substantial misalignment of the dowel stick, it's time to make a new dowel stick. If the fit is correct, rotate the dowel stick until it is square with the plane of the fingerboard, place the neck face down on the drill press table and drill a 1/4" hole through the 3/4" dowel and extend approximately another 3/4" past the opposite side of the dowel. Remove the dowel stick tenon from the heel hole, coat all mating surfaces with titebond, and glue and assemble by driving a slightly pointed 1/4" length of dowel through the 1/4" dowel hole. Trim off any protruding dowel when dry and fit a 1/8" thick piece of contrasting wood over this area to form the heel cap.
Fretboard
Plane and sand a fretboard blank to a uniform thickness of 1/4". Saw and sand the first string side of the board. Trim the board to the maximum width needed. Lay out fret locations using a square held against the first string edge. Use this edge as a guide edge to saw the fret slots at this time if using a miter box or other guide to be referenced to this edge. A small backsaw that will cut the correct slot width can be purchased from the suppliers of fret stock. After all slots are cut, lay out the fretboard profile, being certain that the fret slots remain at a 90 degree angle to the fretboard's centerline. Trim the board just outside the profile layout lines. Carefully finish sand the outer profile to it's finished dimension.
If it is desired to saw the slots after cutting the board to the appropriate profile, a guide block can be fashioned from a scrap of hardwood with sandpaper adhered to the bottom. This block is held firmly in place while it's edge is used to hold the fret saw square to the fretboard to saw the slots. A piece of masking tape is positioned the entire length of the blade slightly above the teeth on the saw to indicate the maximum depth of the cut.
Gluing the fretboard to the neck
Position the fretboard on the neck and drill two small holes through the board at opposite ends of the board and at the location of the fret slots so the holes will be covered after the installation of the frets. Drill down through the fret slots and far enough off center to miss the truss rod / neck reenforcement area. Use a small drill bit sized to match a small brad and about the same size as the width of the fret slot. Cover the surface of the neck and the bottom of the board with Titebond and position the board on the neck using the locating brads. Clamp firmly in place using clamping cauls to distribute the pressure evenly. Let dry for 24 hours before removing clamps.
Position markers and peghead inlay
The position markers can now be inlaid into the surface of the fretboard. A proper description of inlay proceedures could easily fill an entire book in itself, so I will touch only briefly on the subject here. Inlays can be composed of any number of materials, with shell composing the vast majority. My first inlays were created by sanding large pieces of old mussel shell found along local stream banks to the correct thickness of approximately .060". This is easily accomplished with a belt sander. If you choose to replicate this technique, be aware that shell dust is considered to be toxic and use the proper personal protective gear. The designs are cut from the inlay stock using a jeweler's saw which passes through a notched support board firmly clamped to a sturdy surface. After the profile is cut, the edges are lightly sanded to remove excess saw marks. The inlay is held down at it's desired location with a small piece of double-stick tape attached to the bottom to prevent it's shifting while scribing around it. After marking it's location completely, remove it and rub lightly with chalk to emphasize the scribed line. Remove the waste with a small rotary hobby tool held in a router base to a depth slightly less than the thickness of the inlay. Fill the inlay recess with epoxy selected to match the color of the wood the inlay is being inset into. Insert the inlay in the bed of epoxy and push it firmly down into the recess. Permit it to thoroughly dry. Sand the inlay flat to the surrounding surface using a small wood sanding block and progressively finer grades of sandpaper.
Assembly
Assemble the pot temporarily using all hardware. Tighten the head evenly, alternating the tightening of the hook nuts to ensure tension is being evenly applied. Insert the dowel stick into it's hole until the end contacts the rim's opposite side. Measure the distance between the heel and the rim, remove the neck, and carefully trim this amount from the end of the dowel stick. Re-check the heel-to-rim fit and adjust the length of the dowel stick accordingly. Once satisfied with the fit, slide the dowel stick yoke over the dowel stick, hold it at a slight angle to simulate it's position when tight, and mark the location of the cross-pin. Remove the dowel stick and drill a 3/16" hole through the dowel stick at this location, ensuring the hole is oriented 90 degrees to the stick's centerline.
