The relieving valves and tubes

The 'Alfred Corry' is rather like a large lifebelt. Air tanks surround a space in the centre that can be filled with water and emptied to provide ballast when necessary (deck mounted pumps pump this out). Should the deck be swamped the boat will not sink because of the buoyancy of the air tanks. However water must be cleared from the decks quickly so she can regain her balance. This is done by way if relieving tubes and scuppers. The original plans for the 'Alfred Corry' do not show the scuppers, and it is not known whether they were added to the boat before or after she was commissioned at Southwold.

The scuppers are copper pipes passing through the waling (fender) at deck level. Each scupper measures 5 inches by 4 inches approx (125mm x 100mm). The 'Alfred Corry' had four each side. The relieving tubes pass from the well deck (central portion of deck, 1 foot lower than the main deck) and out the bottom of the hull. To do this they have to pass through the water ballast tanks. Each tube is 6 inches (150mm) diameter, and she had 18 of these. The combined scupper and tube drainage area from the deck is just over 4 1/2 square feet (0.4 square metre).

The top end of each of the relieving tubes has a valve. The valve flap is designed to rest in the closed position, but should water enter the top of the tube it opens to let water drain down. In certain rough sea conditions it is possible that water could jet up the tubes, thus reversing the flow, and should this happen the valve will close (if not already closed) and prevent water from welling up onto the deck.

No drawings existed for these valves, and they had to be designed 'from scratch'. David Cragie is a product designer, and he used his C.A.D. modelling system 'SolidWorks' to design and '3D model' the valves. Then he made a prototype valve in plastic (David usually designs plastic injection mouldings). John Cragie then evaluated the prototype and concluded that it would fulfil its (original) intended function. The files were then sent to Mr Ben Jones-Fenleigh at Metalfacture in Leicester, a specialised metal fabricator. Here the parts were laser cut, formed and welded. Finally an epoxy powdercoat finish was applied in a bronze colour. Originally these parts were made from bronze, but this was deemed to be un-necessary and too costly for the Museum. Likewise the brass tubes are now made from plastic.

Valve in situ on well deck

Design copyright David Cragie BA. For enquiries please email.

Metalfacture can be contacted on 0116 2440606 or sales@metalfacture.com

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