2. Material Selection

2.1 Shell Materials

• Solid Hardwood (Traditional / High-End):
  • Species:​ Chunmu (Ailanthus altissima), birch, oak, maple, walnut.
  • Requirements:​ Knot-free, straight-grained, air-dried to 8–12% moisture content​ to prevent warping or cracking.
  • Character:​ Warm, complex overtones; preferred for concert and solo instruments.
• Multi-Ply Laminated Wood (Professional / Institutional):
  • Construction:​ 6–10 plies of cross-laminated birch, maple, or poplar pressed under high heat and pressure.
  • Advantages:​ Dimensional stability, consistent roundness, resistance to climate fluctuation; produces a focused, reliable tone.
• Composite (Specialized / Outdoor):
  • Fiberglass or carbon-fiber shells: weatherproof, durable, but acoustically brighter and less organic.

2.2 Drumhead (Membrane) Materials

• Water Buffalo Hide:​ The professional standard. Dense, thick (typically 1.5–3.0 mm), with rich low-mid resonance and complex harmonics. Requires careful curing and thickness grading.
• Cow Hide:​ Slightly softer, sometimes used for medium sizes or specific regional tones.
• Synthetic (PET / Mylar):​ Stable, moisture-proof, bright attack; used for education, outdoor, or touring where consistency trumps traditional timbre.

2.3 Hardware and Auxiliary Materials

• Tension System:​ Steel tension rods, cast-metal or stamped lugs, steel or wooden counterhoops.
• Adhesives:​ High-strength wood glue (e.g., Titebond) or traditional hide glue for solid-wood joints.
• Finishes:​ Chinese lacquer (red, black, natural), polyurethane, or oil/wax for natural wood.
  

3. Shell Fabrication

3.1 Solid Wood Shell Construction

1. Log Conversion and Seasoning:​ Timber is sawn into planks, air-dried (months to years), then kiln-dried to target moisture.
2. Stave Preparation:​ Planks are cut into tapered or straight staves. Edge bevels (15–30°) are jointed for tight seams.
3. Joinery:
   • Mortise-and-Tenon (Premium):​ Interlocking wooden pins unite staves—acoustically continuous and structurally superior.
   • Butt-Jointed with Ribs:​ Staves glued edge-to-edge, reinforced internally with wooden ribs or metal bands.
4. Assembly and Clamping:​ Glue applied; shell drawn together with internal/external clamps; cured under pressure.
5. Turning and Sanding:​ Shell rough-turned on a lathe or hand-shaped to final diameter and roundness; surfaces progressively sanded (80–320 grit).

3.2 Multi-Ply Shell Formation

1. Veneer Cutting:​ Thin plies (1.5–3 mm) cut to width.
2. Lay-Up:​ Plies stacked with alternating grain direction for structural integrity.
3. Molding:​ Wrapped around a precision mandrel, inserted into a hydraulic press.
4. Curing:​ Heat and pressure applied to cure adhesive; shell emerges as a rigid cylinder.
5. Trimming and Squaring:​ Ends sawn square; shell cut to finished depth (height).

3.3 Bearing Edge Crafting (Critical Acoustic Step)

• Machining:​ Top and bottom edges chamfered to 30–45°​ bearing edges.
• Hand-Finishing:​ Edges refined with fine sandpaper (up to 600 grit) to remove tool marks. A perfectly smooth, symmetrical edge ensures even head seating, airtight vibration, and clean fundamental pitch.

4. Drumhead Processing

4.1 Hide Preparation (Natural Heads)

1. Rawhide Selection:​ Fresh or salted hides inspected for uniformity, minimal scarring.
2. Liming and Unhairing:​ Soaked in lime solution to remove hair and epidermis.
3. Fleshing and Splitting:​ Subcutaneous tissue removed; hide split to target thickness.
4. Stretching and Drying:​ Hide stretched on a frame, air-dried under controlled humidity. Thickness graded with calipers.
5. Flesh Hoop Assembly:
   • Circular hide cut 5–8 cm larger​ than drum diameter.
   • Moistened for pliability, centered over a wooden/metal flesh hoop.
   • Excess hide folded and secured with tacks, cord, or adhesive to form a taut, concentric head unit.

4.2 Synthetic Head Preparation

• Die-cut from PET film to diameter; mounted on metal hoops with mylar collars; no flesh hoop required.
  

5. Hardware Integration

1. Lug Mounting:​ Lug positions marked equidistantly around shell; holes drilled; lugs installed with screws/bolts. For cast lugs, insert nuts may be epoxied into shell.
2. Vent Hole (Optional):​ A small relief hole (3–5 mm) sometimes drilled to equalize internal/external pressure and adjust sustain.
3. Hoops Fabrication:​ Steel counterhoops bent to perfect circle, ends welded/bolted; holes drilled for tension rods; hoop edges smoothed and plated (chrome/nickel) or painted.
4. Tension Rod Fitting:​ Rods cut, threaded, and test-fitted to ensure smooth engagement.

6. Finishing

1. Sealing:​ Shell interior/exterior sealed with sanding sealer or thinned lacquer.
2. Painting / Lacquering:
   • Traditional:​ Multiple coats of Chinese lacquer applied by hand, often with decorative motifs (cloud scrolls, dragons). Each coat dried, sanded smooth.
   • Modern:​ Sprayed polyurethane or catalyzed finish for durability.
3. Final Polishing:​ Buffed to satin or high gloss.
4. Hardware Final Assembly:​ Lugs, rods, washers, hoops fully installed; moving parts lubricated.

7. Tuning, Voicing, and Quality Control

1. Initial Head Seating:​ Heads mounted; tension gradually increased in star (opposite-lug) sequence.
2. Flexing and Re-Tuning:​ Heads flexed (palm pressure center) to settle fibers; re-tuned to even lug pitch.
3. Acoustic Testing:
   • Tap Test:​ Lug-area pitches matched; center fundamental clear and stable.
   • Stroke Test:​ Single strokes and rolls evaluated for attack, sustain, evenness, and interval purity across the set.
4. Final Inspection:​ Finish, hardware alignment, bearing edge integrity, and overall craftsmanship verified.

8. Rack (Pai Jia) Fabrication

1. Material:​ Heavy-gauge steel or aluminum tubing.
2. Structure:​ Vertical post(s) with telescoping height adjustment; horizontal crossbars with pivoting cradles.
3. Cradle Padding:​ Neoprene/felt-lined to protect shells.
4. Locks:​ Collar clamps, wing nuts, memory locks installed.
5. Stability Testing:​ Frame loaded with five drums; checked for wobble, foot spread, and locking reliability.

9. Regional and Workshop Variations

• Ji’nan / Shandong Style:​ Emphasis on hardwood (maple/birch), precise moisture control, and bright yet full concert tone; often associated with professional orchestral models (e.g., Guyun workshop standards).
• Suzhou Style:​ Softer woods, warmer overtones, traditional lacquer artistry.
• Modern Factory Standard:​ Laminated shells, mechanical lug tuning, consistent CNC-machined edges; prioritized for stability and replicability.

10. Conclusion