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Gas tank - two line plumbing plan

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Old 01-12-2013, 10:27 PM
  #26
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Default RE: Gas tank - two line plumbing plan

i use to run 3 i run 2 now a days along with i never drain my tanks... works well 4 my needs...
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Old 01-13-2013, 12:07 AM
  #27
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Default RE: Gas tank - two line plumbing plan

No need to clunk the fill/drain as you should always leave at least some fuel in the tank to prevent fuel system issues. I run 3 line systems in my planes (one's more complex as it has a primer on the carb so there's a tee in the fill/return/drain line). I store my planes nose down so I only leave a splash of fuel in them but I've had the same fuel lines in my plane for over 3 years without issue, just a standard tank with Dubro stopper...
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Old 01-13-2013, 04:23 AM
  #28
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Default RE: Gas tank - two line plumbing plan


Quote:
ORIGINAL: av8tor1977


Quote:
ORIGINAL: BobH

Many years ago when I worked in the chain saw industry felt filtlers were the standard. The only issue with them is that after a while they tend to harden and restrict fuel. If you are aware of that and change them befor that happens you are fine. No fibers get in the carb etc. These filters are made specifically for their intended purpose.
Walboro carbs take about 10psi or more to over come the inlet needle valve. So fueling on the two line system would only be an issue if you have a lot of fuel pressure in that line. FYI I've always used a 3 line system but I don't see big problems with either situation provided you do the right things in the first place.
But what I didn't like was each time you fuel the plane, you are filling it through the wrong side of the fiilter clunk and it is possible to introduce crap straight into the line the goes to the carb.

AV8TOR
I've been torn between the two for a long time. I like the idea of the two lines because the fuel doesnt pour out if the model tips up, but as you say, filling it through the 'wrong' side of the clunk doesnt sit well with me. All thing weighed up, i decided to go with the three line.
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Old 01-13-2013, 05:05 AM
  #29
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Default RE: Gas tank - two line plumbing plan

If you run a loop in your vent it wont drain gas when you tip it up
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Old 01-13-2013, 05:16 AM
  #30
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ORIGINAL: BarracudaHockey

If you run a loop in your vent it wont drain gas when you tip it up
I didnt realise this untill recently. I have both lines quite long just to make it easier to fill but when i shove them back in the model the create a loop themselfs, i actually wondered if one of them was kinked. It was one of those AH HA ! moments, then you realise - of coarse it does.
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Old 01-13-2013, 05:19 AM
  #31
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Default RE: Gas tank - two line plumbing plan

Another way is to use a coarse thread self tapping screw in one of the lines.
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Old 01-13-2013, 05:47 AM
  #32
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Default RE: Gas tank - two line plumbing plan

..........or this:

http://www3.towerhobbies.com/cgi-bin...&I=LXK138&P=RF
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Old 01-13-2013, 06:32 AM
  #33
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Quote:
ORIGINAL: Lnewqban

..........or this:

http://www3.towerhobbies.com/cgi-bin...&I=LXK138&P=RF
Ah, not quite. Sorry i should have been more specific, i meant the self tapper with the head cut off or not pushed up tight against the fuel line. It stays in the fuel line all the time. The point being the air gets by the threads and still works as a vent. The item you posted from Tower is just a bung with an air tight seal which i do use.

I do apologise for the confusion.
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Old 01-13-2013, 07:55 AM
  #34
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Default RE: Gas tank - two line plumbing plan

Thanks for the pictures of Libby and Sarah.
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Old 01-13-2013, 08:37 AM
  #35
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Default RE: Gas tank - two line plumbing plan

Interesting topic. I run both but am aware that people have issues with the 3 line setup. I notice Pe' weighed in and while I certainly respect his opinion, I never really understood WHY the 2 line arrangement causes the occasional problem. People who have had issues simply say when they switched to the 3 line system their problem was resolved. I know, "You can talk to an Engineer, you just can't get them to understand". In this case your right.
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Old 01-13-2013, 10:31 AM
  #36
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Default RE: Gas tank - two line plumbing plan

I use both 2-line and 3-line systems, whichever suits the application at the time.
If you use a T connector, just make sure you have the correct size barb and secure it properly to eliminate any minor air leaks.
In fact, a properly fitted T is no more likely to cause a leak than the fuel dot on the third line.

Like RMH, I have a felt filter in my fuel can and toss it if the pumping slows down.
If the plumbing is done properly, you are highly unlikely to have problems with either 2-line or 3-line setups

Quote:
ORIGINAL: rmh
If there is no crap going into the tank - there is no crap going into the carb. That is my approach.
In line filters , especially he felt things, do plug up- and or restrict .
I do use a big felt filter in the fuel can and toss it if pumping slows.
If you have no problems with your setup - use it
I have no problems with mine either .
I know you have been at this for quite a while -
so have I .
There is more than one approach which works .
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Old 01-13-2013, 11:31 AM
  #37
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Default RE: Gas tank - two line plumbing plan

That's true. I think it's another one of those "Ford vs. Chevy" things....

AV8TOR
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Old 01-13-2013, 03:04 PM
  #38
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Default RE: Gas tank - two line plumbing plan


Quote:
ORIGINAL: apalsson

I use both 2-line and 3-line systems, whichever suits the application at the time.
If you use a T connector, just make sure you have the correct size barb and secure it properly to eliminate any minor air leaks.
In fact, a properly fitted T is no more likely to cause a leak than the fuel dot on the third line.

Quote:
ORIGINAL: rmh
If there is no crap going into the tank - there is no crap going into the carb.
'zactly.....2 line set-ups are simpler; less connections means less failure points. BUT, I always triple filter the gas going in to begin with. The first filtering happens when I fill my field can. Nothing fancy, just a coffee filter fitted to the funnel. Funnel is cleaned first actually. Then dual filtering on the field can line that fills the tank

You can't overfilter your fuel.....As they say in the army, "a penny of prevention is worth a pound of manure"

ASALWAYS...YMMV
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Old 01-13-2013, 04:01 PM
  #39
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Default RE: Gas tank - two line plumbing plan

As far as points of failures goes, three line wins hands down. A two line setup adds 4 extra barb/tubing connections, 3 for the Tee, and one for the fuel dot, all in the line to the carb. Three times more connections than a three line setup.
Pete
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Old 01-13-2013, 04:29 PM
  #40
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Default RE: Gas tank - two line plumbing plan

YEP......

AV8TOR
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Old 01-13-2013, 05:06 PM
  #41
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Default RE: Gas tank - two line plumbing plan


Quote:
ORIGINAL: pilotpete2

As far as points of failures goes, three line wins hands down. A two line setup adds 4 extra barb/tubing connections, 3 for the Tee, and one for the fuel dot, all in the line to the carb. Three times more connections than a three line setup.
Pete
a fuel dot? never use em
as for failures- only one was a line coming off the clunk line inside the tank- once
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Old 01-13-2013, 05:39 PM
  #42
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Default RE: Gas tank - two line plumbing plan

I have been re pluming my gas planes this winter and a installing small header tanks in my 3D planes as
I have gotten some air through the system when the tank is low at the worst times. It is more complicated
but I will be much less concerned with where the fuel is during crazy tricks down low. Any one else doing this?
The Jet guys always do this, I just wondered why us prop guys do not do this more.

Cheers
Tim

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Old 01-13-2013, 05:45 PM
  #43
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Default RE: Gas tank - two line plumbing plan


Quote:
ORIGINAL: TimT2000

I have been re pluming my gas planes this winter and a installing small header tanks in my 3D planes as
I have gotten some air through the system when the tank is low at the worst times. It is more complicated
but I will be much less concerned with where the fuel is during crazy tricks down low. Any one else doing this?
The Jet guys always do this, I just wondered why us prop guys do not do this more.

Cheers
Tim

I always run a header tank on my glow helis, too.
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Old 01-13-2013, 08:46 PM
  #44
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Default RE: Gas tank - two line plumbing plan


Quote:
ORIGINAL: pilotpete2

As far as points of failures goes, three line wins hands down. A two line setup adds 4 extra barb/tubing connections, 3 for the Tee, and one for the fuel dot, all in the line to the carb. Three times more connections than a three line setup.
Pete
That was OTOH since to me, it's a simpler set-up.......Lesse, I use water bottles with fittings:

3-line, vent has 1, fill has 4, 2 inside tank and 2 outside, and fuel supply has 4, 2 inside the tank and 2 outside; assumes no extra filters and any loops in the vent are done with fuel tubing

2 line, vent has 1, fuel supply is also the fill.....2 inside tank,6 outside the tank; also assumes no extra filters and any loops in the vent are done with fuel tubing...

How 'bout that, they are the same # points. Never wooda thunked it.......

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Old 01-13-2013, 11:18 PM
  #45
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Default RE: Gas tank - two line plumbing plan


Quote:
ORIGINAL: rmh


Quote:
ORIGINAL: pe reivers

I rather have a filter in the line than crap in the carb where it can really block fuel flow.
If there is no crap going into the tank - there is no crap going into the carb. That is my approach.
In line filters , especially he felt things, do plug up- and or restrict .
I do use a big felt filter in the fuel can and toss it if pumping slows.
If you have no problems with your setup - use it
I have no problems with mine either .
I know you have been at this for quite a while -
so have I .
There is more than one approach which works .



Crap can get in via the filler line. Dust, dirt on the fuel dot, dirt getting into the filler line etc these are all sources of eventual fuel filter blocking. Without at least one filter in the "to carb" line the mesh screen in the carb is going to get blocked real quickly. A filter has a much higher dirt carrying capacity than the mesh screen in the carb.
A filter in the fuel sorts out any dirt in the fuel or fuel can, it does not sort out the plane.

By your thinking, motor vehicles should nt have fuel filters on board either. Remove those filters and see how it works out for you.

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Old 01-13-2013, 11:20 PM
  #46
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Default RE: Gas tank - two line plumbing plan


Quote:
ORIGINAL: TimT2000

I have been re pluming my gas planes this winter and a installing small header tanks in my 3D planes as
I have gotten some air through the system when the tank is low at the worst times. It is more complicated
but I will be much less concerned with where the fuel is during crazy tricks down low. Any one else doing this?
The Jet guys always do this, I just wondered why us prop guys do not do this more.

Cheers
Tim



Because the carb has a reservoir that stores fuel before it is metered and released into the venturi airstream. This negates the need for a header tank

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Old 01-14-2013, 12:07 PM
  #47
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Default RE: Gas tank - two line plumbing plan


Quote:
ORIGINAL: TimBle


Quote:
ORIGINAL: TimT2000

I have been re pluming my gas planes this winter and a installing small header tanks in my 3D planes as
I have gotten some air through the system when the tank is low at the worst times. It is more complicated
but I will be much less concerned with where the fuel is during crazy tricks down low. Any one else doing this?
The Jet guys always do this, I just wondered why us prop guys do not do this more.

Cheers
Tim



Because the carb has a reservoir that stores fuel before it is metered and released into the venturi airstream. This negates the need for a header tank


This true with some carbs that have float bowls, but these carbs need to run mostely up right. The walbro carbs have no reservoir and can run at any attitude. They do pass an air bubble rather quickley, but 2 or 3 seconds out of the fuel and she will stumble or quit on you. This will be my first year with header tanks so we will see how it goes.
Cheers
Tim
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Old 01-14-2013, 12:37 PM
  #48
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Default RE: Gas tank - two line plumbing plan

I dont see the point of a header in a gas plane.
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Old 01-14-2013, 01:15 PM
  #49
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Quote:
ORIGINAL: BarracudaHockey

I dont see the point of a header in a gas plane.
Me neither....The competition flying I do requires dead verticaldownlinesofabout800' in length. At80 mph that's about5 seconds where the klunk is out of the fuel. I have yet to have a gas engine die on a vertical downline but I run my tank of the cg meaning I have at least a foot of gas line from tank to carb. That's a reservoir in itself and its enough
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Old 01-14-2013, 03:11 PM
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Default RE: Gas tank - two line plumbing plan


Quote:
ORIGINAL: TimBle


Quote:
ORIGINAL: rmh


Quote:
ORIGINAL: pe reivers

I rather have a filter in the line than crap in the carb where it can really block fuel flow.
If there is no crap going into the tank - there is no crap going into the carb. That is my approach.
In line filters , especially he felt things, do plug up- and or restrict .
I do use a big felt filter in the fuel can and toss it if pumping slows.
If you have no problems with your setup - use it
I have no problems with mine either .
I know you have been at this for quite a while -
so have I .
There is more than one approach which works .



Crap can get in via the filler line. Dust, dirt on the fuel dot, dirt getting into the filler line etc these are all sources of eventual fuel filter blocking. Without at least one filter in the ''to carb'' line the mesh screen in the carb is going to get blocked real quickly. A filter has a much higher dirt carrying capacity than the mesh screen in the carb.
A filter in the fuel sorts out any dirt in the fuel or fuel can, it does not sort out the plane.

By your thinking, motor vehicles should nt have fuel filters on board either. Remove those filters and see how it works out for you.

Been using my simple setup for many years - no problems - filters in the plane get blocked as well as filters in the carbs
start out clean and filter at the nozzle and it all stays clean.
PS I have cars with electronic as well as cars with mechanical FI (Mercedes classics )
Filters must be used in the cars simply because the fuel you pump in is typically not finely filtered .
If your setup works for you - have at it - -
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