ORIGINAL: ww2birds
I was surprised to see that some of the Kingcats have their two main tanks plumbed in parallel with a "Y" connector .. with the hope that they drain evenly.
Seemed like a dull idea to me since if they do not drain evenly the fuel left in the "fuller" one is useless when the other one goes dry and draws air. Seemed to me a better idea to plumb with the usual series connection of vent to fill .. but the owner told me they did this deliberately to get even weight distrubution as the fuel drained (the series plumbing would guarantee worst case distrib since the tanks are on either side of the centerline).
He told me that if all tube diameters and lengths are identical, it really does drain very evenly. Somewhat surprising, but there you are...
Dave
The parallel tank setup was pretty much mandatory back in the glow engine ducted fan days. With series tanks, you would get a big change in flow resistance after the first tank emptied, and that meant the engine would go very rich.
Its not a critical deal for turbines, since the ECU compensates for resistance variations, as long as all the plumbing is large enough diameter that the extra resistance of the series tanks is not a problem with full fuel and full throttle (but you need some big fittings if you want to run a 40 lb thrust engine with series tanks!)
The parallel tanks worked just fine, and if you did them carefully, they would always empty within a fraction of an ounce of each other.
Bob