Fuel Systems

Gang --

Help an old-timer out. What are good setups for backyard and casual stunt? How about competitive stunt?
Let me date myself a little. In combat and rat (late 50s, early 60s), we drilled and tapped the backplate, and ran an extra tube to the tank. We had to solder an extra tube into the tank. Later, some engines and some tanks came set up that way. In stunt and sport, most folks just ran tanks with two tubes (other than the engine fuel line) that were open to the environment, facing the wind at a 45 degree angle.
Now you guys run some kind of pressure from the muffler or something? I am truly ignorant of what a modern fuel system looks like. Never had a muffler. (Guess I will have to get one in today's world).
Describe the choices in modern fuel systems, and how mufflers fit in.

Welcome back. I imagine someone else will tell you about plastic tanks with clunks. Many top flyers use them but I have had no experience with them.

So far I have used metal tanks. All my tanks are uniflow. The fuel pickup tube is where you would think it would be. There is an overflow which is capped while flying, and a uniflow tube which lets air into the tank (fill through the uniflow). The end of the uniflow in the tank is at least 1/2 inch ahead of the fuel pickup so it doesn't dump air bubbles into the fuel pickup. It is also over toward the outside of the tank so that it will be covered with fuel until the run is almost over.

The important point about the uniflow is that the engine thinks it is sucking fuel from the end of the uniflow that is submerged in fuel. The engine doesn't know that the amount of fuel in the tank is changing so it runs steadily through the whole tank. The end of the uniflow is more or less lined up with the needle valve vertically. Running rich right side up and lean upside down can be cured by moving the uniflow opening down and vice versa. (You can move the whole tank to accomplish this or move the uniflow itself within the tank.)

Let me describe three of my tanks: (1) A flat wedge tank on a profile airplane with a TD 09, TD backplate tapped for pressure, a Kustom Kraftsmanship one-way valve in the pressure line. Pressure line attached to the uniflow. Uniflow centered in the wedge. The tank has a piece of 1/32 ply wedged so as to tilt it down a hair and runs fine.

(2) Flat wedge tank, K&B 40 with weird venturi, Spraybar 1 inch above crank centerline (upright engine). No room to move tank up. Uniflow is 1/2 inch in front of top outside corner of tank, soldered to top to tank. Pickup down in the wedge where it belongs. Muffler pressure from tap on top of stock muffler to uniflow line. Runs fine.

(3) Fatter flat wedge tank with upright Oliver Tiger repro diesel. Uniflow put where I thought it ought to go to line up with spraybar. KK one-way valve plugs onto uniflow, after filling, to prevent syphoning and keep uniflow uninformed about changes in outside air pressure with maneuvers. Flown twice. Need to jack up back of tank maybe 1/32 or 1/16 to get run same right-side-up vs upside down.

We are talking airplanes I fly competitively in Stunt at a middling Advanced level. Works for me. Thanks for your patience.