skoemba

Morning boys 'n girls,

I have a Extra 330L from World Models. How do you wise people fill the tank of a cowled aircraft and know when the tank is full? Someone seggested that I fill it until the fuel runs out off the muffler. Sounds like a waste te me! Is there any other way?

I have a Dubro filling valve installed in the cowl and only two lines into the tank.

perreback

Funny you should ask that, I was just about to ask the same question myself, so if I may, I'll just tag along and add another: how do you know when the tank is full if you aren't using a pressure line to the muffler? I have an O.S. FS-70 II Surpass that isn't supposed to need a pressurised tank, so I'll just need a fill/drain line through the cowl. How do I know when the tank is full?

DGrant

My Feedback: (4)

I've set them up several ways.. the easiest and cleanest by far I've used for the last 5yrs are what's called "fuel-dots", which are small machined aluminum devices, that are essentially a mount/plug for your fuel lines, to and through your cowl. It amounts to a small dot on the outside of your aircraft when installed correctly.
As for the plumbing... in a cowled install... where the inlet to the carb is not readily accessible, I use a 2-clunk set-up.... and it's actually a 3line/2clunk set-up.. whereby you have 2 clunk lines, and 1 vent line... which the VENT is your overflow... in any case it would seem. Anyways.... one of the clunk lines goes direct to carb(with a fuel-filter preferably), and you never need to touch it again(you should for service/inspection about once a year).. the second clunk line comes through the cowling in a convenient spot(usually on the side, however your preference might be the top), and the third line is vent/overflow... this takes just a tad more planning if you dont' have muff pressure... in that case.... you can still tack it somewhere to lower firewall so it exits down and away(an inch or so if that) from your firewall/airframe, and you still have easy access to monitor it when filling. I DO NOT recomend just letting your tank fill until it comes out the muffler. This could create problems at one point none of us like to deal with.. so I just eliminate those before they start.
Try this link.... it'll give you an idea of what I'm talking about with dots. Good luck guys.
http://www.centralhobbies.com/fuel/f...ngs/CHFLD.html

Drag

I have the 3 line/2clunk set-up.. But I can't get to the vent line on the muffler under the cowl ??

Drag

skoemba

That is precisely my problem. I don't have any difficulties with filling the tank, I struggle to see when it is full. In my stick, I remove the back-pressure line and fit it to a small container. As soon as the fuel runs into the container, I know the tank is full. With the cowl I cannot get to the pressure line, and therefore cannot see when the tank is full.

The dubro filling valve works like a charm.

da Rock

I've just been replumbing a couple of my cowled models. I got tired of the lack of precision that results when you use the "dripping muffler" method of filling your tank.... not to mention the waste of fuel and the pit area where grass don't grow no more.

With today's excellent fuel tubing and hardware, it's a slamdunk to replumb the suckers.

I want the capability of draining my tank after each flying session. My choice of plumbing layouts requires me to drain the tank from the fuel line to the needle valve. Turns out that there is an excellent place in the line from the tank to the needle valve to plug in a T fitting. I then ran the extra line over to the cowl and out a small hole. I'm plugging the end of that line with a cheap plug that bulges the line slightly. I made the cowl outlet hole the right size so that the silicone tubing bulge very lightly squeezes through the hole. It's basically a poor man's "fuel dot". It cost nothing and works great.

Needless to say, the drain hose is long enough that I can pull on the plug and pull out enough hose to have a grip on it. Pull the plug and connect the fuel pump and drain the sucker. Punch the plug back in, push the hose back into it's hole until the bulge grips, and the airplane is good to go.... good to go home, that is.

My fuel system uses muffler pressure and the fittings I made are more than adequate to hold that pressure. I also used the little black plastic plugs from the LHS. They come 4 to a pack. There are two big ones (that're too big for my use) and two small ones in the pack. The small ones have round ends that barely hold in the fuel tubing. Hey, I'm a modeler so I can fix anything right? So when I have some good strong epoxy mixed for some other task, I dip the round part into the epoxy and TAA DAA..... the "bulb" end gets bigger.

Now about the overflow deal...............
All of my models right now have cooling air openings that provide pretty good view into where the muffler pressure outlet is on the mufflers. I use the absolutely clear fuel tubing for my muffler pressure. I no longer use the translucent blue hose, because the completely clear hose is so much easier to see through. The transparent blue actually isn't as transparent as you'd think.

So when fueling, I bend down a little and watch the muffler pressure line. Turns out that when the tank is full, a very solid line of fuel pops into that hose, and I stop cranking. BTW, I count the number of turns of the crank when fueling. It's a habit I picked up flying Precision Aerobatics where each flight had a max time limit and nobody used engine shutoffs. That counting has helped me spot a fuel system problem more than once and it's warned me that I got "old" fuel in the tank etc etc

One of my clubs is about to institute a "no raw fuel overflow" rule. They figure the reason the pit area won't grow grass now is from the wasted fuel that gets squirted on the ground before every flight. They are thinking about requiring everyone to have an overflow bottle to capture that fuel. It's a good idea. The fuel does kill the grass and ruin the soil for seeds. As it is, I'm not overflowing any fuel out the muffler, but a couple of the officers say they don't want me "flaunting" the rule. I'm good with that. So I'll put a T fitting in the system and still count. And maybe put a one-way valve between the T and the muffler too.

I was originally worried about the T fittings being a weak point. You know, there are guys who warn that putting filters in your fuel line is bad because they could leak. LOL.... You know, with today's excellent fuel tubing, and my outstanding ability to put tubing on a fitting (an idiot ought to be able to put fuel tubing on a pipe good enough that it'll stay) I haven't worried a bit about the fittings causing any problems.

But I did pressure test them with my compressor. They'll take a hundred times the pressure a muffler pumps into the airplane's fuel system.

T fittings....... they're the hot tip

Richard L.

My Feedback: (24)

I do it all the time via fuel dots. Just fill up the tank until fuel runs out of the vent line into a small canister:



Your dubro filling valve might work like a charm now, UNTIL it starts to leak.

Drag

I use fuel dots from PSP Manufacturing in all of my planes now Thanks ! to Richard L. I did install one dot to fill the plane My problem is I can't get at my muffler vent line after the cowl is on.

Drag

Richard L.

My Feedback: (24)

You can try to install a one way check valve in the line between the muffler and the fuel tank. Then install a tee between the check valve and the tank with a piece of fuel tubing going from the tee to a second fuel dot. When you fill the tank, open the second fuel dot to let air and fuel out since the check valve will prevent fuel from going into the muffler. Under normal engine operation, the muffler will still provide pressure to the tank when the line to the second fuel dot is closed.

Joe14580

Nevermind [&o] ,

Drag

I will try to install a one way check valve in the line between the muffler and the fuel tank, And a norther dot and a tee

Thanks

Drag

mikeboyd

On the vent, I usually run a little excess tubing down and out of the bottom of cowl, behind the muffler, cut it and put in a small piece of aluminum or brass tubing. When I refuel I can disconnect this section so I don't start dumping excess fuel in the muffler and don't have to struggle to try to reconnect to the Pitts muffler fitting.

I have also put in a tee with a small piece of tubing hanging down with a plug in it. Pull the plug out when refueling and replace it before flying.

For flying, like the above recommentations, I like the two clunk system with the aluminum fuel darts on the side of the aircraft. Don't overcomplicate your fuel system with check valves and the like, the exhaust system does blow out stuff that can cause them to malfunction from time to time. The KISS principle is the safest on your fuel system. You need good, clean fuel delivery to your glow engine in order for it to perform and be reliable.

skoemba

Mike,

If I understand you correct, I have to tee off the pressure line before the muffler (between the muffler and the tank), and then put a dot in that tee which I will remove during filling? Are we on the same page here?

My last question (I think) is, what prevents the fuel from running via the tee and not running straight into the muffler when refueling?

Drag

I run a little excess tubing and some brass down and out of the bottom of cowl, That gave me some room to get to the vent line. That was a good fix.

Thanks

Drag

2slow2matter

My Feedback: (1)

Peereback,
I don't know if your question got answered, but you need at least two lines running to your tank, regardless of whether or not muffler pressure is used. If muffler pressure is not used, then you need a vent line that will purge the air as you fill the tank, and will allow air to replace the fuel once the motor starts drawing it out. Without a vent line, your setup will never work. Simple physics.
In your case, I'd hook up a vent line (connected to a brass tube leading to the top of the tank--as if you were installing a pressure line), and then just run the end of the line out the bottom of the fuse somewhere it's not so noticeable. Fill the tank until fuel runs out of this line, and you're full!

Drag

I have the 3 line 2 clunk set-up,and I run a little excess tubing, and some brass down and out of the bottom of cowl from the muffler so I can Pull the line apart at the brass. I Fill the tank until fuel runs out of this pressure line

Thanks

Drag

Deadeye

I was facing this same dilemma on my nearly finished TF 182. Everything fits under the cowl, with now way to disconnect the muffler line. Here is what I have decided to do, time it. I use an electric fuel pump that fills a 14oz Sullivan tank in 40 seconds. So, that is how I will l know.

DGrant

My Feedback: (4)

I T'd off my pressure/vent line....for the overflow.. the T is lower then the point the line meets the muff, so it overflows first.

As for "raw-fuel" .... I catch it all in a used tank I just hook up to my overflow... it's about a 4oz. square tank that came out of a wreck. At the end of the day(or if it gets full).. I just drain it right along with the main tank..... Alot of good info here though... There's got to be an answer to the original question.... ya think....

Buteos

I installed a return line to my filling station with a small section of brass tubing slid into the fuel line. I attach this to my drain line after the dot is removed so that when filling the excess fuel returns to the fuel can. No spill, no waste and no problems...this is KISS "Keeep it simple stupid"!

BWooster

I count the cranks on my hand pump: 4 to the oz, I believe. So for a 4 oz tank, it's 16 cranks. It's surprisingly accurate.

mikenlapaz

Lots of good suggestions Visually this should be a good reference.
No drip fuel plan cowled engine.

JohnBuckner

My Feedback: (1)

Fueling valves are notoriously unreliable and have witnessed many folks experiance much frustration and lost flying days trying to figure out what is wrong. Many also require a special fitting on your pump line.

Three line systems with or without a second clunk work OK but still offer up lost flying time in if that tiny plug is lost (a common occurence). In addition a second clunk if used reduces your fuel capacity.

Filling through the feed line with a simple plugged T is dangerous to your engines health especially if you have a 135 degree or inverted engine due to hydralic lock.

The most reliable method is always the KISS method, a simple two line system exactly as used on a trainer. Its very simple on a fully cowled engine. The feed line is run external at the front of the fuselage or just out of the cowl and then right back in with a small amount of slack. This allows the flush little loop to be pulled out a little and at this point the line is cut and a short tube is inserted. If you desire the same can be done with the pressure line which will of course give you your full tank indication as usual.

The procedure is to pull the little loop out and separate at the break and same at the vent line if needed then fill just like a trainer, simple. The replug both lines and your done, hydralic lock is not possible. On my inverted cowled installations or 135 degree mounts I don,t bother with the vent. the drip at the muffler is almost as instantanious as an open vent line and due to the muffler being at the bottom no fuel can reach the combustion camber to cause hydralic lock. You can see this setup in this picture, the right engine has the feed line neatly tucked in and the feed line of the left engine is pulled out where it can be separated for fueling.

John

mikenlapaz

Quote:

In addition a second clunk if used reduces your fuel capacity

LOL What percentage of tank fuel capacity do you figure and how much run time does that relate to? I build too heavy, I worry about the added weight!

Nice plane, had to maginify like crazy , Is that an opened cover on the starboard fueling location? If I understand after you cut tube(s) where they exit, you insert a small section of brass tubing to create a splice joint that slides back into one of the holes to leave only a nice curved piece of hose on exterior.

Maybe an oversized to carb fuel line up to the fill location would offset the fuel capacity loss of using a second clunk!

JohnBuckner

My Feedback: (1)

Thank you and apologys for my poor photografic skills. Perhaps these two photos are more self explanitory.

Not every one flys for the same purposes and indeed in some cases one ounce of fuel is critical. These airplanes are used for warbird pylon racing, in addition to weight being a critical factor and difficulty in getting sufficient tankage in the proper spraybar/height relationship its a matter of survival. A typical heat will last 2.5 minutes and add starting, launching, countdown start and post flight landings with four other airplanes all low on fuel then yes that extra ounce is very important.

Its also typical for many sport flyers always try to stuff as much fuel in as they can for whatever reasons. This is frequently unsuccessful due to poor installations and never utilize all their tankage. I am just offering insight into the fuel system that I beleve that offers the simplest and most reliability as a fuel system. I also use this on many sport airplanes that are completey exposed engines when a rear needle is used. Frequently the inlet nipple on rear needles is difficult to get to.

The blue airplane will maiden soon for my team mate to fly in the next race and notice the slots are already cut for the loop of fuel line. This also allows easy cowling removal or installation.

Laugh if you will its just some very effective alternatives.

John

mikenlapaz

John, my comment was result of my lack of experience. If it offended, I apologize. I learned more about another aspect of this hobby from reading your reply, thanks for taking the time to explain.

Those planes are awesome, including those hanging in the background.

This is second reply as the first, longer one, got cancelled due to operator input.