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Fuel system minus header tanks question.

B

BrentBostwick

Registered User
Seattle, WA
The Cub Crafter drawings show a 1/4" line split off of the upper sight gage ports that connects the left and right tanks together. It is labeled as a vent line.

My questions is: if both tanks have an independent vent (at the cap) why the interconnect between the two tanks? Would this have something to do with the gages or redundant vent source?

Thanks

Brent
 
Brent I have the same question. Is it necessary with both caps being vented?

I want to run a LEFT/RIGHT/BOTH/OFF valve. I don't know if you can do this or not without a header. But my question was the same about the vent line.
 
Grant - regarding your valve question

I used a Weatherhead fuel valve and drilled out one side of the plastic insert that creates the additional channel for Left/Right/Both/Off selections. The only problem I see with this is that although in the off position the fuel is shut off to the engine (that is a good thing), the left and right tanks are interconnected and could/will crossfeed if on an incline (left or right wing low).

Only way to stop that is to select either left or right tank while on the ground.

Brent
 
The 1/4 " line is a redundant vent line. if one cap gets clogged for some reason, it would still vent throught the other tank. It is the same as on Cessna's
The tanks do cross feed when on both or off positons. Select either right or left and they won't.


John
 
That is correct. If you get into impact icing, the tank vents could ice up pretty fast. The CC-18 has not only the "snorkel" vents on the caps, but an underwing vent behind the jury strut on each side.

I'm sure that's an FAR 23 thing.

MTV
 
Grant
I have a new Andair left/right valve you are welcome to if you decide to go that route. I decided not to use it.

Dave
 
mvivion said:
That is correct. If you get into impact icing, the tank vents could ice up pretty fast. The CC-18 has not only the "snorkel" vents on the caps, but an underwing vent behind the jury strut on each side.

I'm sure that's an FAR 23 thing.

MTV
Click to expand...
I drilled small hole on the back side of the fuel vent, for this. Works good.
PR
 
OK... I've read through the original (?) thread on this subject that Kase posted for me. My question now is:

Has anyone run the vent line forward as opposed to aft as shown in the CC drawings? It seems there is additional height forward which would help eliminate the crossfeed/sphioning between the tanks through the vent line while on the ground. I suppose the line will be exposed inside the cockpit but I don't think it would be a problem.

Thanks

Brent
 
I've been trying to figure out the fittings used to T this line into the top of the sight gauges. CubCrafters calls for a Piper part number. How did you all do this?
 
Gerald,
I used a "T" in the rubber line connection between the tank and the guage.

Steve,
I 1st ran mine across at the rear spar, but after some debate I changed it to the front spar carry through. I removed one end of the line and tried to blow through it. There was fuel trapped in the line, not allowing it to vent in the event one side gets plugged. I would imagine the fuel in the line came from overfilling or sloshing while taxiing on uneven ground with full tanks.
 
I ran the vent line in front of the front carry through spar. attach it with small plastic clamps to the spar angle. Paint it the same color as the fuselage tubing and it's hardly noticeable.

John
 
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