Re: Boat blew up in jacksonville because the gas was overfilled?
Guys, you are over thinking this in regard to airplanes. Fuel dumping on large aircraft is done to reduce the gross weight of the aircraft to an acceptable landing weight. This is done because you can cause major structural damage if you land overweight, and there is even a specific inspection that must be done in the event that this has been a necessity. If you are at or below the maximum landing weight, and have an emergency, you land immediately, regardless of what your remaining fuel load is. In fact, if the emergency warrants doing so, you land overweight and deal with the consequences later.
As for explosivity of fuel vapors in tanks, some of you may remember TWA Flight 800, which exploded in flight due to arcing of an electrical connection inside of a nearly empty center wing fuel tank. For those poor folks, there just happened to be a spark inside of a fuel tank that had a lot of vapors in it, and the fuel/air mixture just happened to be within the parameters for ignition. Because the tank was nearly empty, and there was so much vapor in the tank, the resulting explosion caused a massive overpressure as a direct result of not being able to escape the enclosed space rapidly.
In terms of achieving the correct fuel/air ratio for ignition to occur, the number of holes in a tank (especially one at sea level), really doesn't make any difference. If the tank is partially empty, the atmospheric pressure inside of it will equalize with the outside of the tank, whether there are few holes or many. What determines the ratio of fuel to air, per cubic centimeter (or any other metric that you may prefer) is temperature and air density. The minute the tank is less than completely full, which is essentially all of the time, there is opportunity for the optimum vapor ratio to occur. What is key, however, is that the smaller the amount of liquid fuel present in a tank, the more vapor there will be. It all boils down to having a little or alot of vapor to burn rapidly and expand.
Where the number and size of the holes in any containing vessel does come into play, is after the rapid combustion takes place. An open tank (no top), which allows for rapid dissapation of pressure, will obviously cause less of an explosion than one that has nothing more than a vent tube in it.
In the case of this boat, what seems to have happened is that the enclosed hull of the boat became the confining space, after excess fuel ran down into it. Whatever vapors were present, filled the engine compartment and a nearly optimal fuel/air ratio occurred. My guess is that something hot on the engine created a small area where the temperature/density relationship created
exactly the right condition for ignition, and a rapidly expanding ignition of all the vapor around the "epicenter" ocurred in a wave. Bearing in mind that this would happen in a split second, the result was an explosion of fuel vapor trying to escape the hull of the boat.
The bottom line is really that getting
all of the fuel out of the bilge is important, because it is from the fuel that the vapors come. Once the fuel is completely eliminated,
all of the vapors must be purged to avoid a potential explosion. Similarly, when a boat has internal fuel tanks, it is extremely important that all fill hoses and vent hoses are devoid of any leaks, so that no raw fuel and/or vapors can end up in the bilges.
PS: I kept typing "ration" too!
