Buoyancy testing in the dry

Buoyancy testing in the dry

There are two ways to test the buoyancy tanks in a Wayfarer, wet and dry. The dry test is much preferred as it can be done ashore with a minimum of incovenience, although it is considered to be more stringent than the wet test.

The dry test consists of creating a pressure differential between the inside of the buoyancy tank and the air outside, either a partial vacuum or modest inflation. This can be created by removing a drain bung in the tank and connecting a plastic hose instead, with a suitable airtight connection, and either sucking or blowing into the tank. The larger the diameter of the pipe the easier it will be to inflate or deflate the tank. 8mm (bore) clear plastic pipe from B&Q is highly recommended.

In order to measure the pressure differential you will need to use a manometer, easily made from another length of clear plastic pipe. This should be connected to the first pipe with a 'T'-piece, as shown in the diagram. The manometer must be partially filled with water (food colouring in the water makes it easier to see). The pressure differential is measured in terms of the difference in height of the water in either side of the manometer.

To conduct the test you need to establish a pressure differential of 5 inches initially. Then seal the tube (with your thumb for example) and record the pressure differential remaining after 30 seconds. This must be at least 2 inches to pass the test. Repeat the test on the other tank. The test is fully descibed in WIC rule 34.7.

If the pressure differential cannot be maintained then you have a leak. It is best to inflate the tank on a quiet day and initially just listen for the source of the leak. Hatch cover gaskets are a favourite source of such leaks, other possibilities being any penetration of the tank by screw fixings, and joints between hull or bulkhead and deck, especially on older boats. Soapy water can help to locate the source of such leaks. If this fails to find the source of the leak then more drastic action might be needed - refer to "Buoyancy Testing with Tears" by Alex Crook for some valuable advice on the subject.