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Kayaks – types and materials
Here we are talking about sea kayaks. Though some sit-in have also been moulded as sit-on, most sit-on kayaks are beamy and used for short part day paddling or for fishing where some can rival a deep-sea trawler for the gear carried.
Polyethylene – the most common are roto-moulded. A two piece metal mould is loaded with polymer powder. This is rotated bi-axially inside an oven where the polymer melts onto the inside of the mould forming the kayak. The hull is removed after the oven has cooled. It is then fitted out with seat, decklines, etc. New Zealand’s high UV can lead to some hulls being limited to about a 10 year life.
ABS – thermoforming or vacuum moulded. A sheet of extruded plastic is heated and sucked into/onto a mould to form half of the kayak. The two halves are then joined. It is then fitted out. UV can damage plastic hulls though this should last up to 30+ years.
These are built in a mould, a hard resin, gelcoat, followed by fibreglass and a polyester resin and more recently vinyl ester resins with kevlar and carbon fibre. In some cases epoxy resin is used. An old hull can be refurbished by painting or even a new gelcoat. Life, 50+ years.
Strip-built – strips of wood over a former, hull and deck separately then joined after glassing the interior. This is followed by a glass outer coating.
S&G (Stitch & Tape) – plywood planks, stitched together on the seams, usually single chine but some are multichine. The stitching (short lengths of wire) is used just to hold things together until the epoxy has cured, then they are removed. Some builders glass both inside and out however to make maintenance easier, to save weight and save cost, glass is only used on the seams. Done this way they will probably only last 100 years.
SOF (Skin on Frame) – basically the way the Aleutians and Inuits built their kayaks but without using seal skins. Canvas or plastic sheeting fastened over a frame. Can be very light but hard to add good floatation. A cockpit sock is probably the best method. The life can be extended by reskinning – 100+ years.
KASK's aims are to:1. Promote and encourage the sport of sea kayaking
2. Promote safety standards
3. Develop techniques and equipment
4. Deal with issues of coastal access and protection
5. Organise sea kayak forums around the country
6. Publish the Sea Canoeist Newsletter and the KASK Handbook