I construct the rims of four laminated strips of domestic hardwood, usually white oak, black walnut and/or black cherry. I choose a laminated structure because the bending process is simple. Also, the structure is much stronger and less prone to warping than a single thick piece of wood. Contrasting hardwoods can be used as inside and outside pieces. Boards are selected free of knots or cracks. Highly figured wood is fine as long as there is not too much endgrain in the long section. The boards are sawn to four inches in width, resawn on a bandsaw to 3/16-inch thickness, then sanded to 1/8 inch thickness on a drum sander with an adjustable table. The resulting strips are then cut to length on the bandsaw. For a bodhran with an outher diameter of 18 inches the boards are sized as follows: (diagram 1). The inside and outside layers are tapered at their ends using the top of the drum sander or belt sander so that they can overlap when glued.
The strips are then soaked for two hours in a soaking box lined with a plastic sheet after which they are bent over a hot pipe, then fitted and clamped to a bending form. Steam bending is an alternative method and should be used for boards that are thicker. The method I use is a very common one for bending the sides of stringed instruments. (diagram 2) Starting in the middle and using gentle pressure I rock the strip lengthwise over the pipe until it bends to the desired approximate curve. This process is repeated every 2-3 inches proceding toward either end of the strip. Too much force and impatience will result in a sudden crack, as will knots and too much endgrain. When bent, you should be able to easily press the strip until its ends meet.
After the strips are bent they are clamped in a bending
form overnight. The next day the four strips (still damp) will have assumed
a round shape. If allowed to dry outside of the form the strips become
irregular in shape, which causes difficulty in gluing the laminations and
causes gapping to occur between the laminations. The damp strips are hung
up until completely dry. I wrap a bicycle inner tube around the strips
to hold them in shape. If damp wood is glued the boards may subsequently
shrink and cause the laminates to separate.
When the strips are completely dry I sand them with 180-grit sandpaper. Next they are generously coated with yellow carpenter’s 7glue and set in the clamping form overnight. (See diagram). The outside and inside strips have tapers at their ends which overlap, the ends of the two inside pieces almost touch. (See diagram). I line the form and the clamping blocks with waxed paper to discourage stray glue from gluing the rim to the form. In gluing it is important that the laminates have no space between them. Not only is the resulting structure strong and artistically aesthetic, it also contributes to a deep, resonant sounding drum. Sound is the primary consideration in building a good instrument. If the musician taps the beater on a rim with gaps between the laminations the sound will be non-projecting and hollow. When covered edges hide the laminations tapping on the rim is a good test for gaps. If gaps do occur they must be filled with something like epoxy glue and wood dust.
After the rim is glued up I plane the top and bottom edges flat with a block plane, or have them sanded flat on an industrial sander.
The edges of my bodhrans are covered with hardwood
strips. Though not a feature of traditional Celtic drums, covered edges
are both artistic and practical. Without covered edges moisture from the
skinhead, dampened by the musician or by the skin attachment process, would
inevitably find its way in-between the laminates just under the skin. The
strips of wood I use to cover the edges of the drum are 1/8 inch thick
and curved to the radius of the drum. I cut out six pieces for each rim
edge on the bandsaw. The edges are fitted by tracing the edge of one piece
against the juxtaposing edge of the next. The traced edge is sanded to
the pencil line on a disc sander. I use Elmer’s Cascamite glue to glue
these edge strips to the rim, further discouraging moisture from finding
its way to the laminates, and clamp as diagrammed for six hours at 70 degrees
F. (Diagram 3)
A 2" sanding drum with 80X sandpaper attached to a drill press is used to sand the inside and outside tapers flush with the rim as well as to sand the edge strips even with the rim. The entire rim is then finished by scraping and sanding to 400X. After the goatskin head is attached, I finished the rim with three coats of tung oil.
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Attaching the Goatskin Head