Hello all. Well I have decided to buy another plane. I bought the BH T-28 Trojan and Magnum 91 2 stroke. It is supposed to be here saturday 6-7-08. Come on Fed Ex. Any hoots, this is going to be my first cowled airplane and I am not sure if I have should do a 2 or 3 line fuel tank set up. Also, Minn or RcKen if you would post a diagram of a 3 line set up I would greatly appreciate it. Thanks and look forward to everyones humble opinion.

Below is the graph that RCKen posted, I believe that is what you are looking for.

Or you could use one of these fueling systems
http://www3.towerhobbies.com/cgi-bin...?&I=LXD745&P=7

I highly recommend using the 3 line system with a fuel dot for cowls. Anything that you add extra will be potential for airleaks. Keep it simple, and avoid having to chase down potential tuning problems later.

This is even simpler, requires NO fuel dot, uses only two lines and has the advantage of letting you perform pinch tests on your cowled engines.

It basically brings the fuel line out of the cowl, so you can fuel/defuel and perform pinch tests.

The picture of the 3 line tank plumbing has 3 labels for the lines.

The top label says VENT. Most glow engines nowadays run best with muffler pressure. This line is very often connected to the pressure tap on your muffler. When you fuel the airplane using the line labeled Fuel Dot, you discover that the tank is full when fuel overflows out that VENT line, wherever it goes. If it can quickly and easily get out of the muffler, you have no problems seeing that the tank is full just as soon as it is full. If the muffler layout doesn't do that, many people put a T in the vent line and run the extra line to wherever the Fuel Dot line goes. They have two lines sticking out somewhere and both are plugged. The attached picture shows how I do most of my airplanes.

The two lines are pushed into the cowl in the picture. That's how they are except when fueling. Pull them both out and remove the plugs to fuel. Into the front one that goes where the Fuel Dot line in RCKens picture goes, and when full, you'll see overflow out the rear one.

works like a charm

The T's available at most LHSs are absolutely adequate and dependable with today's excellent silicon fuel tubing.

The plugs are sold in packs of two. They do what Fuel Dots do. There is really little difference in function or reliability. Both the plugs and dots are as reliable as your ability to stick a plug into a hose.

Thanks SHD3920, that is exactly what I was needing.


Thanks DA ROCK I appreciate the information. I have only used 2 line set ups before. I'm still not sure how your set up is working though. I have alway experience pulling the exhaust line off and seeing the fuel run out and I know the tank is full. How does putting a T adapter in the line keep the fuel from going into the muffler?

I posted a drawing of what I think you are saying. Sorry I didn't go to art school. lol I hope I am making sense and don't sound stupid about this. Thanks for the help.

I actually didn't describe my plumbing setup because I use two different ones. I use uniflow most times, but will use what RCKen's picture shows for airplanes I'm not going to stunt much.

When you have all of your fuel lines enclosed and unreachable inside a cowl, you have to make at least one of them available to the outside world. You need the fill line available. A plugged line that comes through a cowl hole or a fuel dot on the cowl itself work for making that fill line available. But if your muffler isn't in the right place to show you overflow immediately, then you're going to need two lines available to the outside world. And that second line can be plugged or dotted too.

How does the T line work? Great. It's only use is to show the tank overflow. And that won't happen except when the tank fills and fuel starts to flow out the overflow. Yes, the overflow goes to the muffler and out the T line, but as soon as you see that fuel you stop fueling. It isn't a big deal. And if you want, you can arrange the T in the line so the overflowing fuel's momentum goes straight through the top of the T to the outside world instead of the muffler. Works great and the muffler pressure doesn't care if it's got to make a right angle turn.

With either uniflow or conventional when you have two lines showing to the outside world, you unplug them both to fuel. One will be the fill and must always be used for that. You unplug both lines and fill into the correct one. When the overflow appears out the overflow line, you stop pumping and plug both lines.

BTW, have you noticed the different color silicon fuel hose in the LHS? I've found that having at least one color other than clear works really well.

3 line system and use 2 clunks in the fuel tank so you can de fuel

Two stupid questions:

1) Stated above in post 9 jetmech05 says to use two clunks. Is this correct? One on the pickup line to the carb and one on the fuel dot?
2) When you refuel, disconnecting the vent line to the muffler, and using the fuel dot won't the pressure of fueling push some of the fuel up into the carb through the pickup line? Or does the clunk prevent that?

I am going to use this setup with my now completed PT40. And if all goes well I will be converting all my planes to the 3-line.

If you can access the pressure line at the muffler, use that line to fill the tank. Stand the plane on the spinner and if you think about it, close the intake window on the crank. Now simply gas it up until fuel spills out the carb. If you are a "neatness freak", just fill a pre-measured amount with a syringe.

My big question here would be "WHY?" I have plenty of planes that I use a 3 line setup on, but if the truth be known I will strive to use a 2-line setup whenever I can. I subscribe to the K.I.S.S (Keep It Simple - Stupid) theory in building planes. If I can make do with a 2 line setup there is no need to go through the added hassle of a 3-line setup.

But to answer your questions above. Yes, you can have two clunks in the tank. The first one is on the fuel pickup line that goes to the carburetor. The other clunk is on the fuel fill line. This will allow the fuel to be pumped out of the tank. You can forego the clunk on the fill line and put a simple piece of tubing bent down to the bottom of the tank at the front of the tank. To pump out the fuel simply lift the plane up on it's nose so the fuel flows to the front of the tank.

The only time that fuel will come out the carb when fueling with a fuel dot is if you have a T-fitting in the fuel line, with the "T" hooked up to the carb, tank, fuel dot. But you can simply close the carb before pumping in the fuel. In a 3 line setup this usually isn't a problem because overflow will go out the muffler pressure/vent line first.

Ken

My big question here would be "WHY?" I have plenty of planes that I use a 3 line setup on, but if the truth be known I will strive to use a 2-line setup whenever I can.

Simply because I wanted to do something different from my other builds, I did this mod as well as other simple mods (taildragger, rear-mounted servos, dual aileron servos) and I like its looks. Also it is a tight fit at the carb for my hand to reach in so I have to use pliers to hook the line on, and I am thinking that continued hookups this way will puncture the line.

All two line systems. Never agine have to use pliers to fuel a rear needle valve engine. Never agine go looking for a lost dot in the grass. Enjoy the added reliability and fewer failure modes of a two line system. No need to sacrifice fuel capacity to second clunks and lines. very easy fueling with or without cowls. Finally enjoy the ability to use the pinch tuning method when using two strokes. All are two line systems:

You could use one of these.

http://www3.towerhobbies.com/cgi-bin...?&I=LXK135&P=0

This allows you to have only two fuel lines. Mount it on the cowl or inside the cowl to fuel.

I am doing this with my new cowled model but I'm not sure how I will know when the tank is full when I cannot get to the exhaust line? Someone said when you use an electric fuel pump you can hear the pump change pitch as it reaches full?

You can actually have NO plugs or trick fueling devices at all in a 2 line system on a cowled airplane.

Beginners, there are a LOT of plumbing strategies. This discussion actually is confusing a couple of different ideas that have nothing to do with each other.

Why use a 3-line system? Because Uniflow needs 3 lines and Uniflow is worth having to solve problems that happen with some airplanes. Or because you've got a cowled setup and want a carb pickup line with no interruptions. And you don't want to buy a device that overcomplicates a system that doesn't need it. Or a number of reasons.

I've got a couple of models that have benefitted from having Uniflow. I fly the hell out of them and the engines run significantly better with Uniflow. How do I know the engines run better with Uniflow? They started out without it. Do you need it? Probably not. Not yet. But if you ever do, it's there to try. It might help, it might not.

Do you guy's put a fuel filter on the carb fuel line? i.e. Tank-fuel line-fuel filter-fuel line-carb. Fairly new to the glow world so all my engines have been new, but a couple getting older, someone suggested this at the field the other day. Thanx.

If you have a high quality filter in your gallon jug and keep the rest of your fueling operation clean [not hard to do], there is no need for an onboard filter. I fly mostly .049-.074 powered stuff and they need the fuel to be immaculate.

That picture is an older one I did.

This is the new and improved version.