Articles - How a Sea Kayak is Made

The Builder, the Baker, the Sea Kayak Maker

Manufacturing a modern composite sea kayak in simple terms is very much like baking an extravagant cake. You need a mould that will give your boat its final shape. Inside the mould are a selection of ingredients whose properties individually would not be suitable but when mixed together form a tasty morsel. Valley Sea Kayaks in Nottingham have been developing and perfecting some of the finest kayak recipes known to man since the early seventies. Jason Buxton and Peter Orton, the proud owners for the last two years, took us on a tour of one of their three factories to show us how the perfect sea kayak is made…

Every composite boat starts with a plug. The plug is a perfect one off model of the final boat. Sometimes a plug is made from an existing design (as in the photo) where small tweaks to the current shape are required or from scratch where a plug would be shaped from wood or foam in a similar way to a surfboard. The shaper uses their skill to carefully develop their design into a physical design ensuring the boats symmetry is maintained at all times.
    

The plug being worked on in the photos is the development of an existing boat. It has been cut across various planes along its length allowing the shaper to alter the length and width of the boat at specific points.
    
Not yet widely used in kayak design are rapid prototyping printers to make plugs. These printers allow designers to draw up designs on 3D CAD systems and then realise them into solid shapes. This process is extremely expensive, and some feel it loses the craftsman’s skill and feel in shaping their designs.
    

Moulds of the deck and the hull to make kayaks are made from a plug. Just like a complex jelly mould there can be no undercuts or completely vertical surfaces that would prevent the moulded parts from releasing easily out of the mould. The moulds are reinforced with layers of glass and resin to make sure they do not flex or change shape during the manufacturing process. The inner surface of these moulds are highly polished to an almost mirror like the finish ensuring the kayaks outer will be free from imperfections or defects. Stalks are mounted onto the mould to hold the brass insets that eliminate the need to drill the finished kayak later to fit the deck fittings.
    

Just as in baking you must first coat the mould in a releasing agent before pouring in the ingredients, however unlike baking a kayak starts with the icing first! A gel coat is sprayed over the surface of the mould and will give the kayak its colour. It will also prevent harmful UV rays from degrading the laminates and will protect from the knocks and scrapes of rocky beaches.
    

Now the cake tin is ready for the main ingredients of the boat. A composite boat uses flexible fibres, such as fibreglass and Kevlar, that are held in place with a glue, called resin, to form lightweight complex shapes. Like all good recipes the proportions of the ingredients are key. Too much resin and the kayak will be heavy, not enough resin and the kayak will be weak and brittle. The most common way of applying the different textile cloths and mats together with the resin into the moulds is by hand. To do this well is an extremely skilful process. Layers of cloth and matting are laid inside the mould and then resin is applied onto them as they are gradually worked into the complex shape of the hull or the deck. A roller is used to compress the fibres together and ensure that there is no air trapped between them or the mould, this could form a weak point in the final boat. The boat builder must ensure all the fibres of the cloth are wetted out to ensure a good bond between them, but must not let excess resin pool in the keel and other recessed areas of the mould. Like any glue the resin begins to set as soon as it exposed to air, so the builder has finite time to achieve perfect results. Critical areas such as the thigh braces and the skeg box are reinforced with further layers of cloth and mat. Laying up the moulds by hand is a very messy process. The builder must wear full overalls, heavy rubber gloves and, where particularly noxious resins are used; a respiration mask and goggles must also be worn.
    

A much cleaner way of moulding the hull and the deck is to use the Earth’s own atmosphere to help. This is called vacuum bagging. Essentially all the components, all the layers of cloth and resin, are put inside a large plastic bag and then sealed. The air is then gradually sucked out leaving a vacuum inside the bag. The builder then massages the resin throughout the mould and the cloth working it into all the tight corners and recesses. If you image a vacuum packed pack of bacon from the supermarket where you can push around the bacon juices you get the idea. The pressure created by the vacuum helps to force out all the air and squeeze the different layers together.
    

A stage on from this is called vacuum-infusion. Valley were the first, and still the only British sea kayak manufacturers, to perfect and use this method in their production process. In a similar way to basic vacuum bagging the mould and the cloths are sealed inside a large bag and the air drawn out. Once the cloth has been worked into place the resin is then sucked into the bag through a series of feeder pipes and gradually moves through the layers of cloth. This allows the correct quantity of resin applied and any excess resin can be sucked out. By using this method Valley have been able to lay-up to five layers of Kevlar cloth, a weight saving of up to three-kilos on a hull and another two-kilos on the deck.
    

Once the resins in the moulds have set the two halves are bolted together. A narrow length of Diolen cloth is then applied along the seam inside the joined kayak and allowed to set before breaking the now joined kayak out of its moulds. Once removed from the mould the flashing along the join, the cockpit and the deck holes needs to be cleaned up. The outside seam between the hull and the deck needs to be sealed with another length of Diolen cloth, this time covered in a gel to protect it from the outside elements.

The kayak shell is still very flexible at this point and is strengthened when the moulded bulkheads are located and sealed into place. The cockpit rim and the tube for the skeg wire to run inside are also fixed inside the kayak whilst the world-renowned Valley hatches are glued into place.

Once all the gluing of parts is complete the hull and deck receive a final buff to make sure there are no surface imperfections before the holes are drilled to locate the foot braces, the moulded plastic seat is bolted in and the recessed deck fittings are bolted onto the brass nut in-sets that were moulded in during the deck manufacture.

Once signed off the brand new sea kayak is all wrapped up ready for delivery to its new home, and awaiting adventures on the water… Where ever that is in the world!




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