Stitch and Glue

from Wikipedia, the free encyclopedia
Schematic representation of two different stitch-and-glue seams in cross section

Stitch and Glue (German: sewn and glued) is a modern method of joining wood in boat building in order to produce light, stable and at the same time durable wooden hulls . Originally developed for canoe construction , the method was later further developed and also applied to larger boat hulls. Stitch and Glue is considered to be a simple method of boat building that is suitable for laypersons, because shaping frames or special tools are unnecessary.

technology

Two pieces of wood fixed by twisted wire were glued together with epoxy resin
Canoe hull, the seams are fixed with cable ties
Cured fuselage shell of a lobster 12.5 , the wires fix a clinker planking

First, the wooden components are cut and provided with numerous small pairs of holes for the connecting wires at the seams. The components are fixed ( stitch ) in place with the help of twisted pieces of wire , so that the fuselage supports itself. Then all seams are filled with epoxy resin ( glue ) . If the epoxy resin has hardened after a few days, it has a higher adhesive strength and breaking strength than natural wood. The seams change from the weakest to the strongest parts of the trunk, they form the backbone in the static sense.

After the epoxy resin has cured, the wire can be dispensed with and - as far as possible - is removed, with permanently bonded residues usually remaining in the resin compound. Hardened epoxy resin can be sanded and planed so that protrusions and adhesive residues can then be smoothed. Due to the form-fitting edge connection of the wooden panels, the resulting wood-resin body is waterproof and dimensionally stable. The hull is often designed with a wall thickness of only 6 mm in order to ensure optimal flexibility of the wood before gluing and also to obtain a light hull. Fine-ply veneer plywood made from open-pored and soft types of wood such as okoumé , which is then impregnated with epoxy resin varnish and thereby hardened and protected against swelling, is particularly suitable .

In the area of ​​the underwater hull, the finished wood-resin body is usually reinforced from the outside by a glass fiber mat embedded in epoxy resin in order to prevent damage to the thin hull when it comes into contact with sharp-edged objects.

The disadvantage is the high price of the epoxy resin, of which several kilograms are required per meter of the hull. In addition, it is laborious to process because it is a two-component adhesive that - like all polyaddition adhesives - must be mixed in exact proportions and processed within a pot life of 15 to 60 minutes. Both components are to be regarded as hazardous substances with a high allergenic potential until the resin has cured . Protective gloves and goggles must therefore be used during processing and good ventilation must be ensured. Cured epoxy resin is a high quality plastic that is physiologically harmless and permanently impermeable to water.

Epoxy resin is attacked by the ultraviolet radiation of the sun, which is why the hull should finally be coated with a UV protective varnish based on polyurethane to extend the service life .

Web links

Commons : Boat building  - collection of images, videos and audio files

Individual evidence