Hooking up a surge tank

[LRFitch]

Guys, Some time ago, there was some info and I think a sketch of how to plumb a fuel tank and surge tank together. Can anyone please repost that type of info?

[BobM]

I don't have a sketch, but see if this is helpful:

The main tank (large tank) should have a clunk line (which is the fuel feed) and then one vent line. The vent on the main tank will be the fuel overflow for when both tanks are filled.

The secondary tank (small tank) will have a clunk line and one vent line.

The vent line on the secondary tank is connected to the fuel line (clunk line) of the main tank.

The fuel line (clunk line) of the secondary tank goes to the engine and often can have a T inserted somewhere along the way to be the fill line for the 2 tank system.

Fueling the system is via the fuel feed from the secondary tank to the engine (the T allows you to have the fuel fill be placed where it is easiest to accomplish this....I typically use a fuel dot on the fuselage and my T line goes to the fuel dot).

The secondary tank fills first then the main tank fills from the overflow of the secondary tank. Once both tanks are full then overflow of the fuel goes out of the vent line from the main tank.

I typically use a large main tank, approximately 100 oz, for my tow planes that use a DA 170 or DA 150. The secondary tank is usually somewhere around 8 to 12 oz.

The fuel line for outside the tanks (fuel line that feeds between the tanks, to the engine, to the fuel dot, and the overflow line from the main tank) is usually the clear yellow gas fuel tubing, I think it is called Tygon. They make it in a couple diameters, which I usually use the larger diameter if at all possible. I think both Dubro and Sullivan have this tubing, it is the large tubing (11/64 diameter).

https://www.horizonhobby.com/tygon-g...rge--30-dub506

Inside the tanks I use a different fuel line that does not break down or harden as easily. This is often called FKM by Horizon Hobby:

https://www.horizonhobby.com/medium-...ter%29-evoa102

There are also other brands of this type of fuel line, many auto stores have something similar.

I make sure to use wire clamps or wire that I twist to tighten around all fuel tubing connections to the brass fuel pipe on the tanks as well as the carb fuel fitting. I solder barbs on all the brass pipe that goes in and out of the fuel tanks........the brass pipe used for the clunk feed and the vent lines. This keeps the fuel tubing form coming off easily (when tied with twisted wire or fuel line clamps of some sort).

Hope this is helpful.

Bob

[Sinkhappens86]

Sometimes a picture is worth 1000 words. Shamelessly stolen from RCU.

[LRFitch]

Thanks guys. That is just what I was looking for. Pictures and words! Thanks again.

Larry