sweetpea01

My Feedback: (10)

Can someone please post a diagram of a 3 tank setup (4 if you include the hopper)

Is it important for the lines to be the same length?

I've only done gasoline engines (single tank)and want to make sure I plumb every thing correctly.


Also why do most people plug up the ventline? I assume you unplug it during flight.

Billy

My Feedback: (15)

Here is one from the Skymaster manual. Lines must be even from the main tank to the saddle tanks. And yes you will unplug the vent during flight.

USSCAT

Hey Sweetpea01,

Is it important for the lines to be the same length?- Yes, if you are using the main tanks in parallel, having same size and length tubing will help empty the tanks at the same rate.

Also why do most people plug up the ventline? I assume you unplug it during flight. - Ther are two lines that get pluged when the aircaft is at rest, one is on the bottom of aircraft asnd one is at the UAT. When fuleing the aircraft, you would remove both plugs and use the UAT line to fill with fuel, hook up your taxi tank to the bottom vent when fueling. After the tanks are full, plug the UAT line and remove your taxi tank and fly with no plug on the bottom vent line.

Regardss,
Mike

frothingslosh

My Feedback: (6)

Don't confuse the vent line with the fill line . . . the vent line lets air directly in to the main tank(s) and also serves as an overflow when filling and a hookup point for the taxi tank. The FILL line goes directly to the UAT (air trap) and MUST be plugged except when filling.

Most people plug the vent to keep fuel from accidentally venting from the tank when handling the plane. The vent plug should have some sort of ribbon, flag, etc. for visibility so you don't forget to remove it before starting the engine. Most turbine fuel pumps will collapse the tank as fuel is consumed if the vent is plugged.

Ask me how I know!!!

causeitflies

Because Jet-A and K-1 really stink before it's burned and the stink lasts a long time.

sweetpea01

My Feedback: (10)

Thanks for all the help. This is what I gathered about plugging the vent line. Gasoline stinks as well but we typically don't plug the vent line.


This should do me just fine.

highhorse

My Feedback: (2)

pulled this off the site some time back, hope it helps !

d_wheel

I don't understand the "Y" going to the main tanks. It appears that if one emptied before the other it would start pulling air from the empty tank instead of fuel from the one that is not. Why not run them all in series?

Later;

D.W.

Harley Condra

My Feedback: (4)

Heres a good tip.
Eliminate the tee fitting, and install another fitting on the header tank. Plumb the saddle tank pickup lines directly to each of the two inlet fittings on the header tank. Each saddle tank has it's own feed line.

This is a good idea for larger engines such as the P-180's and P-200's, but I have been doing this since about 2002 on RAM 1000's and P-120's and Titans in order to ensure a good supply of fuel under any conditions.

For an example, look at the BVM website under jet Kits/Ultra Bandit/addendums. You will find a step by step tutorial on how to accomplish this modification.

RCISFUN

My Feedback: (44)

I have run mine with Large diameter (i.e. .187 id) in series with no problem on my Jet Central Falcon.
I use this large diameter for my vent lines and interconnecting lines to reduce the back pressure when fueling.

CraigG

My Feedback: (40)

I too have noticed an issue with 3 tanks in series (and with fairly long fuel line runs) that pressure builds up in the main tank during fueling and then tends to collapse somewhat during defueling. I have checked and doubled checked that there is no restriction in the system but it just seems the more tanks, more fittings, more clunks and longer the lines get that resistance builds.

Doesn't seem like this should be the case when it's just air being drawn or pushed in the system but that's what's happening. Like Rich, I have resorted to larger diameter lines in the aux tank and vent line.

Craig

Harley Condra

My Feedback: (4)

Craig,
I have always used 6MM line in an effort to avoid the situation you are experiencing.

The 6MM O.D. tubing (.236) has a 4MM bore (.1575 dia.) which is much larger than Tygon, which only sports a 1/8 (.125) bore.
The difference in bore is almost a full millimeter. This is a very large difference in fuel delivery capability.
I use the 6mm tubing on all of the feed lines on the suction side of the fuel system, and 4MM on the pressure side.

I also drill my clunk weights out to maximum size, and enlarge the tank fittings as much as possible.

CraigG

My Feedback: (40)

Good suggestions Harley, thanks.

Craig

joeflyer

My Feedback: (48)

I do as Harley does, except I use 5/32" (0.156" id) tygon and 5/32" brass tubing on the suction side then 4 mm. tubing on the pressure side.

Keep in mind that the part with the most restriction will dictate your system restriction. Drill out your clunks, upsize the brass tubing in your tanks, and use oversized tees (force 5/32" tygon onto 3/16" tees, available at your local auto parts store). If you fill with your taxi tank attached, that also needs to be upsized.

Joe

sweetpea01

My Feedback: (10)

Gotcha.


from the drawing of things in parellel.......will it matter if my tanks are setup in this manner?


I have 2 saddle tanks (each on the side of the jet)and 1 small tank at the top of the jet. It rests just over the top of center of the fuse. Would I want to empty that tank first or last or does it matter?

frothingslosh

My Feedback: (6)

Go back and look at the diagram submitted by High Horse. THAT is the way it should be done.

highhorse

My Feedback: (2)

Sweetpea, I think Harley gave some great advice ref eliminating the T and installing a second "in" line in the nose tank ("small canter" tank in your app).

Don't neglect to use an air trap, it's pretty good insurance.

One other piece of advice I found useful: You should DEfuel your jet several times through the feed line leading into the UAT and see if your parallel tanks are feeding evenly, while also looking for evidence of air leaking INTO the system during the hi-vacume defuel. This is the time to even up the fuel feed by triming or adding to length of the fuel lines, as well as trouble shooting air bubbles which turbines HATE. They just dont eat bubbles well.

Enjoy, Don.

sweetpea01

My Feedback: (10)

I was referring to that diagram. In an F-16 you cannot put the 3rd tank in the front left. It goes centered of the two saddle tanks but sits higher than the saddle tanks. That was my question.....

If you drain the center first, then start draining the saddle tanks, is it an issue to draw the fuel up into the center tank instead of laterally or down on your way to the UAT?

joeflyer

My Feedback: (48)

Sweetpea,

It's the way that they are plumbed that's important, not the tanks relative position. The two saddle tanks should feed the center tank and that should feed the UAT, just like the diagram shows. Because you have a fuel pump and are not relying on gravity it doesn't matter which is higher. The center tank will help eliminate any bubbles from the saddle tanks.

I'm not sure which F-16 you have. I have mine plumbed as Harley suggests with each saddle tank feeding directly into the center tank instead of a tee. Perhaps a picture of my FEJ F-16 will help.

Joe

Harley Condra

My Feedback: (4)

Remember this:
Look at the fuel system as a two sided system: side 1., Suction side (all tanks and UAT), and side 2., Pressure side (pump to engine). This is if you use the recommended system in the drawing submitted a few post ago.

The fuel pump must suck fuel from the UAT first, then pump suction must draw fuel from the header tank, to keep the UAT full. It simultaniously draws fuel from both of the saddle tanks, in order to keep the header tank full.
The little pump has to work to draw fuel from both saddle tanks to feed the header tank from the farthest tank in line.

Be mindfull that the pump suction also draws fuel from the start and taxi tank, (if you use one) so it's work is heavier yet....until you unplug the start and taxi tank from the system vent just before takeoff.

That is why I recommend using dual feed lines from the saddle tanks to the header tank.
The pump doesn't see a reduction in it's workload until the mains (saddle tanks) are dry and you are on header fuel.

Also, the header should be large enough to make a couple of trips around the pattern before being exhausted. The size is determined by your engines fuel consumption. A 16 oz header is the least I would use on a P-120 sized engine.

To answer your question another way, drain the saddle tanks first, drain the header tank next, and never drain the UAT........

sweetpea01

My Feedback: (10)

I think your words are confusing me slightly (header/UAT/etc etc). I'm going to show a diagram of what I plan.....let me know if this is good.

So we are all on the same page.

Jet Legend 1/8 F-16 w/Jet Central Rabbit Turbine (it gets here Tuesday!!!! ) about the size of a P-80

I had only planned 4 tanks.

2 fuse saddle tanks
1 center mounted tank
1 UAT (Hanson super trap or BVM UAT)

I had not planned on a header tank (didn't see that in the drawing either).


Also by my drawing I believe the center tank will drain first then the saddles......or am I wrong?

sweetpea01

My Feedback: (10)

My next question......

What is the deal with a start tank connected to the vent line?

I understand connecting to the line during filling as to not lose fuel on the ground. But after fueling why do people leave it on during engine start and taxi?

causeitflies

The vent goes on the two saddle tanks, tee'd together for one overflow and not on the center tank. Other than that it looks good.

The start tank is simply to not lose fuel on the ground as you said but also not to waste any fuel if you have to taxi a long way or are waiting for someone else to land/takeoff or clear the runway. Often at jet events guys are lined up waiting to take off and burn fuel from the extra tank while waiting. It connects to the vent from the saddle tanks. It is optional.

By the way the Rabbit is two sizes smaller than the P-80 but puts out nearly the same amount of thrust.

sweetpea01

My Feedback: (10)

Sorry, that is what I meant on the P-80 comment. Its about the same thrust as the P-80.


So why does the vent have to go on the saddle tanks vs going on the center tank? Just wondering.

causeitflies

When you suck the fuel out of the center tank air has to come in somewhere. If air comes in your vent the center tank would fill with air not to mention that you couldn't even fill the saddle tanks because the fuel would overflow out the vent instead of going to them, because they don't have a vent..
When fueling, the fuel has to push the air out of the center tank and then push the air out of the saddle tanks before going to the vent overboard. As the engine runs the reverse has to take place... air into the vented saddle tanks and then air into the center tank as the fuel is sucked out.

The center tank actually does have a vent, but it/they are connected to the feeds of the saddles. So instead of sucking air they (vent/vents) are sucking fuel from the saddles.