Fuel tank vent line

[Birdseyeview]

I'm looking to replace the fuel tank vent line to the header tank in my old kit but the many different varieties of Tygon tubing are confusing. From my research it's clear that the Tygon brand vinyl tubing is superior to the clear vinyl tubing one can buy at most hardware stores. Although I'll probably buy this tube from Kitfox, I'd like to better understand what is the preferred tubing material. What is the preferred version of tubing for fuel vents?

[aviator79]

I used Gates Barricade fuel line for all connections between the header tank and wing tanks. It has low vapor permeability, so my cockpit never smells like gas. (Or, if it does, I need to check for leaks!).

In fact, I think I have a bunch left. I can send you some for the cost of shipping.

[Slyfox]

blue bing fuel hose. 1/4 inch size. all my fuel lines from tank to header is this stuff.

[HighWing]

I like the Tygon vent lines. To me it is another indicator of fuel system continuity - being able to see a second verification of fuel level. Once when returning from Idaho, because of tail winds, I decided to eliminate the fuel stop in Winnemucca, NV. Then when descending from the Sierra Nevada mountain crossing to my home airport, I was able to visually watch the fuel level drop to the low fuel sender trigger point. The Model IV and earlier had one fuel outlet on the wing tanks at the rear. In a descent, it is possible to unport the outlet resulting in no fuel flow from the tanks with as much as 6 gallons remaining. At that time, I reduced the rate of descent and all good again. In this instance it was a deliberate test. And all worked as designed. As far as type, I tend to favor the local outlets - motorcycle or lawnmower - as CA has nothing available, for any engine, but ethanol containing mogas and these places are pretty much on top of it.

[jrevens]

I didn't think that the plastic line was what I wanted to use at first, but I agree with Lowell. It's nice to be able to see the fuel in that line. The material that I got in my kit is a light yellow in color.

[Flying Felix]

Hello everyone.

I use for my vent line direct from the header tank to the roof of the KF 1/4" blue polyurethane tubin. (see picture)

I had new aluminum tanks made for the KF sometime ago, since the old ones leaked due to fissures. Eliminated the root cause of the fissures and the factory vent on the RHS fuel tank.

The little blue line has been doing it job for a long time and I can see the fuel level sloshing in the hose.

Happy flying!

Flying Felix

[Slyfox]

Hello everyone.

I use for my vent line direct from the header tank to the roof of the KF 1/4" blue polyurethane tubin. (see picture)

I had new aluminum tanks made for the KF sometime ago, since the old ones leaked due to fissures. Eliminated the root cause of the fissures and the factory vent on the RHS fuel tank.

The little blue line has been doing it job for a long time and I can see the fuel level sloshing in the hose.

Happy flying!

Flying Felix
I'm guessing that's the bing blue fuel line that I have. it will turn green with auto fuel after a while.

[Slyfox]

one more thing you buy it at aircraft spruce.

[Slyfox]

https://www.aircraftspruce.com/catalog/appages/bingfuel.php?clickkey=32455
this is the only stuff to use

[ken nougaret]

Been using the yellow tygon f-4040-a 1/4" id, 3/8" od. On amazon.

[SilverFox5]

Hi Steve (slyfox)
Or anyone else that may want to comment.
Couple questions to clarify please.
I will start by saying I am building a Kitfox5 outback originally supplied in 1994 by Skystar.
I have upgraded and purchased an aluminum header tank and 2 new wing tanks.
My first question concerns the size of the gas line.
Earlier you posted that all of your fuel lines from the header tank are the blue bing fuel hose. 1/4" size.
On my older Kitfox 5 the 2 main lines from the wing tanks to the header tank are 1/4"NPT x 5/16" barbed fittings. (For 5/16" ID hose)
The vent line form the header tank to the right wing tank is 1/8" NPT x 1/4" barbed fitting.
Are the newer kits not the same size as my older kit?
Or did you just omit that because the subject was type of fuel line, not size?
But I see Aircraft Spruce does not carry the 5/16" dia blue fuel line.
.
Next question.
Do you get fuel odors in your cockpit from the fuel lines as I have read in other posts?
I see others recommend the Gates Barricade fuel lines.
.
Question for John Evens,
Do you get fuel odors from your lines?
It sounds like you are using the tygon f-4040-a yellow colored lines.
Did you use this for all the fuel lines?
I do like the idea of being able to see the fuel flow in the lines.

Thanks in advance for any feed back!
Joe

[Slyfox]

all my lines from the header to tanks are 1/4 hose even the vent. I have had the vent line going to the tank plug off, not a nice thing, it will empty the header tank and stop all fuel to the engine. yes I had an off field landing. I found the hose closed off and fixed it. than went and changed out the vent line for new after I got back to the airport. interesting thing is the low fuel sensor is on the vent line and that thing didn't work when this happened. anyway. my thought is 1/4 is better than 1/8 in size. I would change things over to get the 1/4 line on the vent, my thoughts anyway. since you are doing this, call kitfox and get the low fuel warning system very important. I won't fly without one. my old one finally gave up the ghost after over 10 years, I called kitfox and got a whole new one. now if it quits I call them for a new sensor. I also use the bing hose on my tank fuel level on the tanks. barb fittings top of tank to bottom and join the two with the bing hose. when this stuff gets green it's still good, just can't see inside it very well. just change it out. I also have individual ball valves on each tank. most people will say why? I use it for two things, one I can turn just one tank on and regulate how I use the fuel in each tank so I don't have old fuel in one or the other. two, to test the low fuel sensor. if you turn off both tanks, the fuel goes down in the header tank and the sensor goes off, I check that often.

[n85ae]

Curious with the header vented outside of either tank, how is your fuel flow from the tanks? Is it fairly equal
or do have the normal Kitfox issue of uneven fuel flow from right/left main tanks?

I always thought it was related to the header vented into one side tank, which has been argued in previous
threads.

Thanks,
Jeff



Hello everyone.

I use for my vent line direct from the header tank to the roof of the KF 1/4" blue polyurethane tubin. (see picture)

I had new aluminum tanks made for the KF sometime ago, since the old ones leaked due to fissures. Eliminated the root cause of the fissures and the factory vent on the RHS fuel tank.

The little blue line has been doing it job for a long time and I can see the fuel level sloshing in the hose.

Happy flying!

Flying Felix

[Slyfox]

worse yet, the tanks can have 1 gal each of unusable fuel. a lot of that is from the fact that the fuel drains out sort of in the middle of the tank. since I have individual valves on the tanks I generally will empty one tank and than turn on the other one. to drain the tank sometimes I have to slip the plane to get more fuel out of it. I estimate about 1 gal on each side. just something to think about.

[jrevens]

Hi Steve (slyfox)
Or anyone else that may want to comment.
Couple questions to clarify please.
I will start by saying I am building a Kitfox5 outback originally supplied in 1994 by Skystar.
I have upgraded and purchased an aluminum header tank and 2 new wing tanks.
My first question concerns the size of the gas line.
Earlier you posted that all of your fuel lines from the header tank are the blue bing fuel hose. 1/4" size.
On my older Kitfox 5 the 2 main lines from the wing tanks to the header tank are 1/4"NPT x 5/16" barbed fittings. (For 5/16" ID hose)
The vent line form the header tank to the right wing tank is 1/8" NPT x 1/4" barbed fitting.
Are the newer kits not the same size as my older kit?
Or did you just omit that because the subject was type of fuel line, not size?
But I see Aircraft Spruce does not carry the 5/16" dia blue fuel line.
.
Next question.
Do you get fuel odors in your cockpit from the fuel lines as I have read in other posts?
I see others recommend the Gates Barricade fuel lines.
.
Question for John Evens,
Do you get fuel odors from your lines?
It sounds like you are using the tygon f-4040-a yellow colored lines.
Did you use this for all the fuel lines?
I do like the idea of being able to see the fuel flow in the lines.

Thanks in advance for any feed back!
Joe

Hi Joe,

First off, I believe that if you have an 80 hp Rotax, the 1/4" ID line is ok, but with 100 hp, 5/16" is recommended by Rotax (to my knowledge). I wouldn't use anything less than that, IMHO. I used 1/4" ID plastic hose for my vent line, and no, I haven't detected any fuel odor. I actually used a lot of 3/8" ID line for my main lines - SS braided Teflon lined between the shut-off valves, that I installed for each tank, to the header tank. Then I used aluminum (3/8"ID) from the header tank to the firewall. I used 5/16" Barricade hose from the main tanks to the shut-off valves because of the necessary routing and flexibility. I used 1/4" aluminum for the fuel return line from the firewall, through a check valve, to the header tank. I'm not using an aux. fuel pump.

[efwd]

Regarding pinching off fuel lines. Be careful using zip ties to secure the hose to the vertical frame up to the wing. I zip tied, and covered them up with the interior fabric. For some reason, I removed the fabric one day (this was all before flying it the first time) and found that although they were fine when I put the zip tie on, they got warm in the hangar and the zip tie had collapsed the hose down. Probably not all the way occluded but Im certain the ID was not the same as when I did the fuel flow tests. No need to put any kind of pressure on the hose with zip ties.

[Slyfox]

yes indeed, do not use zip ties to secure fuel lines. better to let them hang over the rails. once upon a time I did this and it really collapsed the line after some time. definitely a nono. as for the hoses bigger than 1/4. never had an issue with mine. I had a 912ul and went to the uls I did nothing for the fuel lines. runs great with over 600hrs on it.

[SilverFox5]

Hi John,

I have the Rotax 912 uls 100 hp engine. It is not yet installed.
We are ready to install the wing tanks and I want to be sure we had the fittings arranged in the correct way and fitted for clearance before we mount it in permanent with the 739 sealant. It looks like we have 5/16" ID barbed hose fittings for the 2 main fuel lines from the wing tanks to the header tank.
And we have 1/4" ID barbed fittings for vent line from the header tank to right wing tank. I like the idea of ball valves from each wing tank and header tank. I will just need to decide if I want the "Barricade" hose or the blue bing or yellow 4040 fuel lines for the 5/16" lines. Its been fun trying to sort out all the fittings for the fuel system. Most of them are just thrown in a box without the part numbers to match up with the manual and drawings. But it does look like we have some fittings to use aluminum tube from the header tank to the fuel shut-off valve that was also supplied with our kit.
Thanks for the good info from all.

Joe