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| S&S Swan General - Fitting additional fuel capacity |
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Join Date: 01 February 2007
Posts: 234 |
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Fitting additional fuel capacity I am trying work out how to increase my current fuel capacity on my Swan 411 from 120 litres. Has anybody ever converted one of the water tanks inot an additional fuel tank? What are the technical issues I have to consider. John |
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Join Date: 16 May 2009
Posts: 252 |
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John -
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Join Date: 02 January 2008
Posts: 1547 |
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John It is not a big deal to modify a watertank for fuel. At least the following to be considered: - An additional tank connection for the fuel return is needed - The vent line to be led to the outside (now at galley sink) - The requirement nowadays is that all connections - also the filler line - are on the top of the tank. The intention is that in case of a leak the contents will not end up in the bilge. - An additional deck filler line to be arranged - Approved fuel hose to be used - A shut-off valve on the tank recommended for the feed line Kind regards Lars |
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Join Date: 02 June 2007
Posts: 43 |
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John You might also want to consider the effect on heel trim as fuel is consumed. It may be a good idea to locate the fuel (and therefore also water) tanks on opposite sides of the boat. If you do this though, there will be considerable additional pressure head developed on the low side tank top when the boat is heeled and the tanks are full, which would not occur if both tanks were on the same side. You will need to make sure the inspection hatch seals will not leak due to this additional head. Closing the crossover valve installed between the tanks might be a good idea to counter this. I just carry additional jerry cans. John |
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Join Date: 02 January 2008
Posts: 1547 |
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Referring to tank valves: The general recommendation is to keep only one tank valve at a time open. This refers for both for fuel and water, particularly when there are tanks on opposite sides. If several tank valves are open and the yacht heels the contents in the high tanks will, as Pleiades rightly points out, flow into the low tanks, and may cause overflow through the vent line. If you see fresh water flowing out through a vent pipe at the galley sink when heeled it is advisable to close some water tank valves. For fuel tanks the vent line is outside, and you may not notice overflow. For diesel engines there is a fuel return line, and if the return is directed to another tank than the feeding one this may cause overflow even when the yacht is upright, particularly if the other tank is nearly full to start with. It is good practice to direct the return fuel to the feeding tank, this has been cared for on newer yachts which have feed and return valves interconnected so they automatically open and close together. Monitoring of tank levels will be much simpler if the contents are not allowed to flow arbitrarily into other tanks. On the other hand tank valves can be used to deliberately transfer tank contents, both by gravity when heeled or using the fuel return line, but then an eye should be kept on the tank levels. If fuel tanks are nearly empty, and it is important that the engine works even in heeled condition, it is preferable to use a fuel tank on the windward side. The reason is that the tank suction is at the deepest point, which is towards the centerline. On the leeward side heeling will cause the tank contents to flow to the outboard side, and the suction may suck air. The same comment refers for water tanks. Lars |
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