oldfart
Elite Veteran
Location: Vancouver, Canada
| "header tank"Hi Ed,
Just a correction on your three points...two are correct. It has been proven that contrary to what was initially believed, the "header tank" does not "keep a constant fuel draw pressure" at the carb. If it did one would have the same presure after the maintank empties, even when the center line of the main tank was different then that of the header tank. The only type of tank arrangement that keeps pressure at the carb the same from the top of the tank to the bottom is one plumbed in the "uniflow" manner.
People used to think that the carb would then only see the pressure head of the "header tank" at all times. If this were true then there would be no change as the main tank emptied and the only fuel was left in the header.
This is also why, in many other countries, it is called a "sub tank" and not a "header tank". It is basically there to trap the air bubbles that get sucked into the fuel line from the main tank whenever its clunk comes out of the fuel through aerobatic manoevers.
In fact if the sub tank is plumbed with a clunk it too can feed air bubbles to the carb. As it collects air from the main, it too will end up with air at the top of it (even when their is a good bit of fuel in the main). Then when inverted, if both clunks come out of the fuel and into air, then air will get into the carb line. This is why many plumb the sub tank such that it can only draws fuel from its volumetric center. Then if they never run their engines until the fuel in the sub tank gets below the volumetric center of the sub tank then the carb line will never see air bubbles. |
