The Stitch & Glue method

This method was initially developed using fishing line through small holes drilled close to the edge of plywood sheets to be mated together and the joint strength then obtained by added resin and fiberglass tapes to both sides of the joint.   The system morphed into one using short lengths of copper wire when TV host D-I-Y expert Barry Bucknell used it in partnership with designer Jack Holt for the Mirror Dinghy in 1962-3, (winner of a competition sponsored by the ‘labor red’ newspaper The Daily Mirror in the UK .., hence the red sails on the boat ;) 

Unlike other construction techniques of the day (like clinker and carvel) which required specialist skills and tools, Stitch & Glue kits were claimed to put boat-building within the reach of even teenagers to build, and despite the boat actually being quite complex internally, this Mirror Dinghy is now arguably the most successful 2-person dinghy in the world with over 70,000 examples !   (Footnote:  The Mirror Mk 3 now has a Bermudan rig instead of the original sliding gunter and the newest models are now built in composite with a foam core).

In the United States Stitch & Glue boat building was popularized in the mid-1980s largely through Harold Payson's articles in WoodenBoat magazine and books on building "instant boats" designed by Phil Bolger.  These boats were constructed of ‘wired-together plywood’ with seams filleted with thickened resin, and overlaid with fiberglass tape.   They could be built by Do-it-Yourself amateurs of modest skill and relatively simple resources.

Because the Mirror dinghy made the system so well known, I will use it here to show various steps in the method.

First, one needs to cut suitable copper wire into lengths to suit the plywood thickness. Typically about 2.5” to 3” long.

Then, if it’s possible to lay adjacent panels together, drill through both panels at the edge, (but not too close or the plywood will break!)  Initially, the wire loop should be set up very loose, so that it not too tight to open up the panels.  Once in position, the wires can be tightened before the joint is bonded.

Here are the bottom panels of a Mirror Dinghy being wired up to the transom.

Here is the uniquely vee’d Mirror bow transom all wired in.

And below is the whole external hull all wired up.  As the boat is very flexible at this stage, it’s important to support it with bow and stern aligned parallel to each other in a horizontal plane with transoms square to the centerline, before starting to fill and tape the joints …, typically starting on the inside before flipping the boat to finish off the exterior.  Most of the twisted wire is clipped off and the rest pushed into the gap before filling, rounding off and taping.

Although this all looks very easy (and it is), there are still a lot of holes to make and the wires need to be compacted against the plywood as much as possible .. or the plywood ‘tacked’ together with filled epoxy and then the wires pulled out and holes filled before completing the joint.    And particularly in the case of the Mirror Dinghy, most of the hull work is still to be done as the internals are complex, with many bulkheads, tanks and seats needing to be added. (This is required in order to make this small boat (under 10ft) unsinkable and readily rightable by teenagers; a strict requirement for a public newspaper who was to put its name to the design).

The white blocks are for guidance when setting in the internal seats & bulkheads.

Recent versions of Stitch & Glue now often use nylon ties that are lighter, do not require twisting and their flat section allows the parts to be opened more easily with less damage to the plywood. However, the system still requires holes and additional work to prepare the joint for laying on the cloth tape in a smooth manner.       While this system still works best for multi-chine designs with very open angles, the ABC System can avoid the holes and trimming for designs that are hard chine with joining angles more in the general 80-100 degree range.

See: ABC System

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