I'm pretty new to gas power and I'm trying to decide on a two line or three line fuel system for the Dave patrick Extra with BME 44 that I'm assembling.

Should I use a two line system with a vent to the top of the tank, and a filler or "T" in the line to the carb? Or should I use a three line system? If three lines, how should it be configured?

I have an old used gas powered airplane that I bought, and it uses a standard two line "glow" type system, with a fuel filler and muffler pressure feeding the vent to the gas(oiline) tank. I'm thinking that this isn't a good idea, but it did fly this way.

Many thanks.....

Hello Katmandew

Three lines

1> with clunk to carb

2> with clunk to fuel dot (fill)

3> vent out of bottom of fuselage

I make the fill clunk line just a little sorter then the carb clunk line.

Hope this helps
Doug

Thanks Doug. Are there any problems with the two clunk lines getting tangled?

I have tried both 2 and 3 line systems. I finally settled on a 2-line system because it is very simple. Put a T in the line (I use brass T's that I get at Wal-Mart in the aquarium section) between the fuel tank and the carb. Run the line to a fuel dot for filling/emptying. The carb on the BME44 won't get flooded when you fill, so crank away without worries.

Ken

I forgot to mention--no need to pressurize the fuel tank with the muffler/exhaust. The carbs on gas engines (Walbro type in the BME) use a diaphram to create suction from the tank. Pressurizing the tank will only cause you problems.

Ken

Quote from KEN's post.
"The carb on the BME44 won't get flooded when you fill, so crank away without worries."

With the diaphram carb, you don't have to worry about flooding the carb anyway.

Stomper mentioned that he uses a line with a clunk for filling. This is good for emptying as well (and most likely his purpose) You do not have to have that line with the clunk in your tank. Just turn your plane upside down and tip it forward so you can use the vent line to do the defueling. Helps keep the weight down.

I use the 3 line method and the only added weight is the little brass tube at the fuel tank. Works great.

Jeff C

CAPtain232 has it all summarized! The only difference I use on my gas planes is to use only two lines at the tank (weight!). I have a T in my carb inlet line that goes to my fuel dot, and I fuel from there, and turn it upside down to defuel.

Lynn

Thanks for all the info! Is it not a good idea to use the gas version of the Dubro and Great Planes fuel fillers like I use on my glow planes?

I have been told to use a flet clunk from a lawn and garden supply. Is this the kind they are talking about?

Yes, those are the ones to use! I have been using those felt clunks and had good results with them.

I'm a believer in using filters - I use one of these felt clunk filters in my gas jug, then another in the tank. I no longer use a filter between the tank and carb because I'm already using one on each end to do my fueling.

Just be sure to use a nylon zip tie over the connection when you attach the tubing. It's a big, heavy clunk. I am now using the smaller Tygon tubing with these clunks - I've had the black neoprene lines split where they go over the large diameter nipple on these clunks.

They are also so large that you are restricted to specific brands of tanks to use. My preference was to use Hayes tanks, but had to go to Sullivan/Dubro tanks to use the felt clunks.

Lynn

Why are some of you people turning your planes upside down to defuel?????

I don't get it. I use 2 lines, one to the carb with a T and fuel dot and the other from the tank vent with a few coils then out the bottom of the plane.

A hand pump will remove every drop of fuel from the tank provided the clunk is back far enough.

Maybe I'm missing something.


Dave

A few coils on the vent line? That sounds like a great idea.

No trouble with sucking air from the carb when defueling with a T in the line from the clunk to the carb? (I don't know about this kind of stuff)

Interesting stuff guys. Thanks!

If when flying your airplane, the carb draws all of the fuel out of the tank, there is no need to invert your aircraft to defuel. Just plug you fuel pump into the T that you have coming off of your carb line and suck away. You will draw every drop out of your tank from the clunk that serves as your pick up line going to the carb. If you can't drain your tank this way, then your clunk is not far enough to the rear of your fuel tank. There is never a need to invert your aircraft and drain from the vent line. You will not suck air from the carb. I have always used the two line system on my gas engines, with a T coming off of the pick up line for fueling and defueling. Never have I given it a second thought because it has always worked flawlessly.

I have to agree with davham. Inverting anthing bigger than about a 25% airplane is a problem. It would take 2 guys to accomplish this with a 35%, and you would find a field full of laughter if you attempted this with a 40%. Keep it simple--2 lines with a T. No problems, very simple, easy to maintain.

As for the felt clunk in the tank. I have heard of people having good results with this, but I have also heard of people having problems. I have one of these clunks in my 2 gallon jug that I fuel the plane with, but I just have a standard clunk in the tank. That way, the fuel gets filtered as it enters the tank. Either way, DO BE SURE to use a filter--felt instead of the glow-type screens. Gasoline will have some small "crap" in it. And it will gum up your carb in a hurry.

Ken

I flip my 1/4 scale gas planes over to defuel simply because immediately after defueling, I can then take off the wing. I usually defuel only when I am done flying the plane and ready to head home. If I need to defuel it for any other reason, I defuel through the T dot.

Also, using the felt clunks, I can't actually get all the fuel out of the tank, but using the vent line will pull every drop out.

Lynn

I use three line tanks, because once, I forgot to put the cap back on the fill line.
The engine started and ran fine until I lifted off the ground, pointing right at this ugly barbed wire fence. From that time on, I have used three lines, I don't worry about defueling, and if I forget the fill line cap it just becomes another vent, without killing your engine.

What would be the purpose on using the felt clunk you show on your picture? Would it be much better than the dubro fuel clunk that came with the tank? If so, Why is that? Would there be more fuel traveling through the fuel clunk?

Santi

At first I built my Stinger with a fuel dot so I could fuel it thru a 3rd line. I had a line to the carb and a vent line coiled and run out the floor of the plane.

With the 3 line setup I often ended up with an air bubble in the carb line after fueling. After fooling around with this for a while, I realized that I could get to the carb nipple and just pull off the line to the carb for fueling/defueling. Felt kind of stupid adding a 3 line system when all I needed was the 2 lines.

The moral of the story is - if you can get to the carb, just pull the line and fuel from there.

At least I was able to use the fuel dot as a fill port for my smoke tank.

I am running a 2 line system in my 35% Giles with a ZDZ80. One line is vented out the side of the plane using a fuel dot the other line is hooked up to a dubro large filler valve. I used a large filter on the line running to the carb and secured all the lines with wire clips. I had heard that the fuel filler valves leak but so far I have not had a problem with it. I can fuel and empty the tank through the same line.

After reading all of the above posts, I've decided that we are all a bunch of granite headed son's of b_____s. We are going to do it the way we've been doing it and there is not one single solitary reason to change it, because it's the way we've always done it.
So.... you guys that are turning your plane upside down to defuel, keep doing it, it'll at least give you big biceps. And those of you that like running and extra line to the tank, keep right on doing it because you like an extra hole in your tank plug and that extra line that can come off of the inlet tube, or get tangled around your pick up line. If you fill your take up and forget to plug that line, it will at least drain your tank to the level of the inlet tube and if you get a good siphon going there, it'll drain your whole tank. But, not to worry, at least it won't be on take off. It'll probably wait until you are going up wind at 10 feet of altitude, right over the runway.
If it ain't broke, don't fix it. That's the spirit.

Hey Santi
The felt Is a filter so you don't pick up any crap from the tank. You will find them In the better chainsaws.


Fighterpilot> LOL

Doug

Quote:

If you fill your take up and forget to plug that line, it will at least drain your tank to the level of the inlet tube and if you get a good siphon going there, it'll drain your whole tank. But, not to worry, at least it won't be on take off. It'll probably wait until you are going up wind at 10 feet of altitude, right over the runway.

Fighterpilot:

You can't get a good siphon going if you don't use an extra clunk.

KatManDEW,
Can you supply more information about the filter? Where can I get one?

Hey Geistware

You can find them at any good chain saw shop. My oldest saw (056 super) Is over twenty three years old and still filltering fine. I use all Stihl stuff, works great!

Doug

Fighter Pilot has it right - no matter what - we will continue doing it the way we always have because it works! So, here is how I do it. THREE lines - the fuel line to the carb is fitted with a felt clunk filter. I also use a felt filter in my fuel can - so the gas gets filtered twice before it reaches the carburetor. A dirty carb is very rare using this system. The other two lines are routed to the bottom of the airplane, where one is used to fill, the other is the vent. When you are through filling, the fill line also becomes a vent.

I only fly giant scale, and the smallest engine that I own is a G-62. All of my planes use a one quart size fuel tank, and all are a simple plastic bottle that oil comes in for your car. Like Pennzoil, Quaker State, the standard bottle that we are all familiar with. I place the bottle on edge, slightly slanted, with the neck to the top. The neck sticks thru the firewall so that the cap can be unscrewed. I use yellow tygon fuel line. I drill three holes through the cap - all 1/64 smaller than the O.D. of the tubing - cut the tubing on a diagonal, and pull it through those three holes. That eliminates the need for any fittings, and they do not leak.

So if you haven't figured it out yet, my tanks are very reliable and very inexpensive. Try it sometime - you just might like it.

I like the 2 line system-BUT- if you use a filter type clunk any crap in fuel will collect on engine side of your clunk- filter when fueling and guess what, the crap will go direct to your carb when you start engine. My way of thinking is to use very good filter on the pickup in your fuel can and just a plain clunk in tank in plane. Any comments on that????? Thanks Captinjohn