Squib Bouyancy Every so often the question of Squib buoyancy, or more to the point “lack of” comes to the fore. A couple of years ago at the inlands we came very close to a sinking, and recently in Ireland and Burnham we have had boats broaching and filling up. Fortunately at Burnham the buoyancy was sound and after much bucketing the boat sailed on. However the Incident in Ireland was not so fortunate. The buoyancy tanks were not sound and the result was a boat on the bottom. This pertinent reminder is worth reflecting on by all Squib owners. It is your responsibility to ensure the seaworthiness of your boat. If the woodwork is sound and well maintained a Squib will stay on the surface, but the loads on the tanks from the best part of ¾ of a tonne wanting to sink are very high. If they are not in sound condition, the hatches are not properly fixed, and the glass taping around the joints well bonded, trouble will result in the unlikely event of a broach and filling up. A few years ago Bryan Riley wrote an article about test equipment the Lowestoft fleet made after a similar sinking experience there. Below are his words. “The Lowestoft fleet have made a set of test equipment which comprises of a commercially available manometer, a selection of hatch covers fitted with tube connectors, rubber bungs and tubing and a T-piece. The test is carried out by fitting one of the replacement hatch covers, this is connected to the manometer with a length of rubber tubing and the manometer is tied on to the boat so it hangs vertically. “Manometer” is simply a ‘posh’ name for a piece of clear plastic tube bent in a ‘U’ shape and half filled with tap water, the other end of the tube is left open to the atmosphere. A second length of tube is connected to the hatch cover and this is used to blow air into the buoyancy chamber to the required pressure, the tube can then be folded over 180 degrees and held with a cloths peg, so you do not have to keep blowing. If there are no air leaks, the air pressure will force the water in the manometer up the ‘U’ bend and the graduations on the tube can be used to measure the difference in the water level in the two legs of the tube. This difference in water level should initially be 125mm (5 inches) and should not drop to less that 50mm (2 inches) after 30 seconds. This test method is standard procedure for testing all new gas installations (although for obvious reasons no pressure drop is allowed). It is an onerous test, the smallest leak from a hatch cover or old screw hole makes it impossible to pressurize the tanks in the first place. Manometer, rubber tubing etc can be purchased from any Plumbers Merchant for about £20.00, the manometer I used was supplied by Monument Tools - www.monument-tools.com. I have also seen a manometer made from clear plastic tube nailed to a piece of wood with cable cleats. The largest cost was the selection of hatch covers required to fit different boats, these were drilled and fitted with metal tube connectors. A lower cost alternative would be to insert short lengths of copper pipe held with Araldite. The Lowestoft Fleet kit cost approximately £80, not much spread over several boats and an investment well worth considering.”
I did use Bryan’s equipment several years ago on my tanks and was very surprised just how tight the hatch covers had to be to get a good seal. I also had an unnerving experience when I took off my back tank hatch cover when putting the boat to bed for the winter. The O ring came out in two pieces. Now did that break when I screwed it down, or when I took it off. I will never know, but it reminded me that the O rings on my hatches are 12 years old. Maybe its time to invest in new ones a little sooner in future! Yes I know they seem expensive, but relative to the cost of sinking and the consequences of that, maybe a few O rings every year is a cheap investment, and so is a piece of test kit similar to that described by Bryan.
Food for thought hey what? Another job for the list for the winter, or perhaps sooner.
Bryan Riley (Brimstone)