Assembly

Provided the plans are accurately transferred and all faces accurately cut, the assembly of objects poses no great problem other than a good deal of patience. In fact, it comes as a very pleasant surprise that such complex hand-made objects can fit together so well. Objects cut from plywood, particleboard, MDF or wood planks and joined with biscuit joints or dowels, can be glued effectively with PVA glue. Predrilled nails help with the gluing. The old adage of ‘measure twice, cut once’, applies with a vengeance.

When tackling geodesic domes like ‘ShowTent.lig’, start at the top of the dome adding concentric rings of faces until the base is reached. Add two or three faces at the one time so that the correct solid angles are achieved by triangulation, rather than-relying on the half-angles cut into the edges of each face. When adding already-joined faces, do so before the glue has completely hardened. In this way minor angular mismatches can be overcome by slight joint flexing. If all faces are cut to the correct edge lengths and half-angles, the object should automatically assume the correct shape when it is assembled. Minor errors in the cutting of faces are generally accommodated by minor gaps in the joins -- which can be plugged with a suitable wood-filling compound.

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As illustrated, one technique for applying the right forces during gluing is the time-honored ‘twisted rope trick’. Strategically-placed G-clamps are used to anchor each end of a tied loop of rope and the loop is then twisted with a stick or screwdriver to obtain the required degree of closure. In this way, excessive gaps (that inevitably arise during assembly) can be eliminated.

Clamping during gluing can be assisted by large diameter dowels with a flat surfaces cut on one side. Temporary screws are used to hold the flat surface of these dowels to the outside surface of the two faces to be joined, with the dowels parallel to the joining edge. Clamps are then used between the dowels to draw the two pieces together during gluing. Position the dowels so that the clamping force passes through the center of each edge being joined.

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Dowelled joints are more positive when it comes to holding faces together before the glue has set, but they must be more accurately positioned than biscuits. Also, with long dowels the assembly of an entire 3D solid could be very difficult, if not impossible. All joins in the object would have to be drawn together simultaneously. Now there is a challenge for someone to prove me wrong!

Nails can be used to hold faces together while gluing, particularly in conjunction with biscuits, but the start of each nail hole should be pre-drilled to make sure the nail enters at the correct angle, and does not emerge from the front or back of the adjoining face. Nails for particleboard or MDF should be relatively long and thin – say 2mm x 50mm.

Completely enclosed objects, such as a soccer ball, are best built as two separate halves that are then joined together. In this way, biscuit joints can be used throughout. Otherwise, some biscuits have to be omitted if all the faces are to be glued together.

Larger objects, such as large geodesic domes for pavilions or houses, generally require a frame to be assembled first and then covered with sheet material of some sort. L3DD’s plans give the exact lengths required for the framing members. With the help of nails or bolts, these can be joined at each vertex using obtuse cones cut from galvanized iron sheeting. Domes designed to be portable can be built out of faces that are individually framed. The edges of the faces can then be joined together using bolts.