Many aftermarket Cub fuel tanks have extra outlets in the forward corners. Has anyone come up with a really good way to plumb these outlets into the existing stock system? I have a lot of ideas, but would like to hear from anyone who has experience with this.
Mark Drath
These full sized front outlets are required if you convert over to the headerless fuel system like a Cessna. If you look at a stock system the RH tank and rear header tank only work for high or low nose angle and not steep RH turns. The outlet of the rear header tank is on the wrong end of the tank in a steep RH turn when running off the RH tank. This is because it is plumbed to the fuel shut off valve. So you really don't have the full benefit of header tanks in all angles on both tanks. Because of the long fuel lines from the rear tank it will run for a while though. I have always been told to cruise on the RH tank and take off, land and turn on the LH tank.
I'll have to play test pilot to see if I can get a sputter on the right tank, sounds like a good excuse to fly.
Here is todays project - One basic Fat Cub with a standard PA18 headered fuel system. Standard size stock shallow tanks with full size front and rear outlets. I'd like to make use of the forward outlets if possible, due to the shallow tanks. The options I can think of are:
1) Plug the front outlets, hook it up like a standard 18 system.
2) Elbow the forward outlets down and rearward, teeing into the standard line low in the wing root. Basically making a fuel oulet manifold in the bottom of the wing root, then connecting to the standard 18 system.
3) Run the left front outlet down through the cabin in front of the window, teeing it into the regular line that drops down behind the window under the window, upstream of the valve. Run the right front outlet down through the cabin in front of the door, forward to behind the instrument panel, left behind the instrument panel, aft along the left side wall, teeing into the standard line that comes forward from the rear header, upstream of the valve.
I can't decide if there would be any advantage to adding the extra plumbing, also need to stay simple and with a proven system to ease the field approval. Would like to avoid going headerless, and want no part of the stock 12 system. Anyone have any thoughts?
Mark Drath
I think #2 would be the least amount of hassel and can only help feed the rear header tank. I used the Cub Crafters drawings and went headerless on the PA-14 I'm just finishing. You have to run the line from the front fitting on the RH tank, down the front door post then forward to the firewall, then across to the LH side then back to a T above the valve maintaining slope all the way. I am not so sure I will like this system. In the OFF position the tanks cross feed to level. Let's say you're empty on one tank and 1/2 on the other, you park and shut the fuel off. You come back and your site guages show no fuel because the balls don't float with low fuel. I can see climbing up and dip sticking the tanks a lot. Also if you land on a beach and park on a slope with full tanks the uphill tank will cross feed into the lower tank and overflow it out the vent. I think this system has it's share of problems. The only reason I went this way, was I have a pass through upper baggage and the rear header tank looked ugly being exposed in the cabin. I'll tell you more after I fly it for a while. Crash
Thank Crash, I am leaning towards #2 for this machine. Glad you brought up the rear header in your 14. I had a idea to get rid of this, but did not mention it, (no extended upper baggage in this one). It goes like this: Take system #3, remove the rear header and run the rear line around the back of the cabin like a stock 12. Install the header behind the instrument panel next to the left one, (lots of room for this in a Fat Cub). Rout the right front outlet line through the header instead of just passing it behind the panel. Bring both lines together on the left side and into the valve. I think it would work. Basically the right tank system would just get swapped front to rear. You might want to use some variation of this idea in your 14 after you fly headerless for a while... Removing headers is the big fad right now, but I think it will die out when more people see how it works in the real world. Does anyone remember drooping ailerons? Same thing, sounds good, but sucks in the real world. Give me a set of heavy duty header tanks and a nice new Univair valve anyday.
Mark Drath
We lost a Fish and Wildlife Trooper last year in a headerless Cub. He was flying it like a headered Cub on one tank when the engine quit in a turn. I still think the stock system is safer no matter what the Richmonds say. Left, Right, Off and Off, duh I'm having a hard time figuring this fuel system out...Crash
Greg,
I thought that Trooper was flying thru IMC on the way to Iliamna and lost sight of the guy in front....? Didn't know it had anything to do w/ the HT.
Andy
Remember the guys that were returning from a caribou hunt, got stuck on top, ran out of gas, lost the electrical, in the dark and lost? Then they spun into an alder covered slope that was covered with deep snow. It was like landing on a mattress. Only injury was a broken ankle. Talk about using up your lucky stars!!pak
Andy, the one you're refering to happened last fall over by Sparevon. The one I am talking about happened in June over by Morrain Creek. Also one other thing. When you go headerless you have to run a vent line between the two tanks across the top deck. It feeds into the vent T at the top of the fuel site guages on both sides. This allows vent air to pass from one tank to the other. Crash
Fat Cub fuel system update.
After much screwing around, cussing, swearing, and AN fitting throwing, I have decided to order a nice set of plugs for the front outlets, and hook a tried and true stock 18 system to the rear outlets and get the thing flying. There is not enough room in the Fat Cub wing root to make any kind of connection between the two outlets that would serve any purpose other than aggravating anyone that has to remove the tanks someday.
I don't want to start a new thread on the subject, even if this one is quite old and asleep - so I hope this pops up anyway.
I have read this and a couple of other threads but I don't understand how the CC headerless system is designed...
I have an L-18C under restoration with standard (I think...) header tanks. There's already a L/R/Both selector installed and there's a full size front fuel port on the left tank. What would be required to get rid of the header tanks?
I have emailed Cubcrafters a couple of times but I don't get any response...
While on the subject of fuel systems:
Can anybody give me the number of Air Energy Service? I need to call them to get some paperwork.
thanks
Tim
tim,
witts # 309-594-2280
message on the recorder is witt's wife,as he has been ill and shop closed,wish him the best,good luck.
happy holidays to all.
jr.
delete
You are talking about an uncoordinated right turn aren't you Crash???Originally Posted by Crash
The most important aspect of this signature line is that you don't realize it doesn't say anything significant until you are done reading it & then it is too late to stop reading it....
Diggler, I asked the same question when I installed the system on a L18C. They told me they got it approved for the 180hp engine and needed the extra head pressure to get the fuel flow required by the FAA.
sekps, The system adds a front fitting in the rt. tank and vents the two tanks together thru the site gauge. I dont ever remember seeing Piper put a both on the L18C. The FAA requires the tanks be vented together if you have a both position.
Steve Pierce
"When everything seems to be going against you, remember that the airplane takes off against the wind, not with it."
Henry Ford
I gotta ask....then back to a T above the valve maintaining slope all the way. I am not so sure I will like this system. In the OFF position the tanks cross feed to level...
Don't the two tanks pipe into two sperate inlet ports on the fuel selector instead of teeing upstream of the valve. That way, left, right, both, and off, mean what they say?
Interesting discussion regarding fuel systems. Amazing how complex a "simple" fuel system can get, eh?
Just a note reference the accident referenced earlier: I don't believe he was in a turn, but he was climbing just after takeoff. Could be wrong, though.
In any case, nothing wrong with either fuel system, just make darn sure YOU know which one you're dealing with today.
MTV
The Both selector on my L-18C was a standard mod French ALAT made. I've always thought it was a good thing. But I think I have to compare my fuel system with the standard to see what I've been flying around with...
Mark,
It's the right scenario that will uncover weaknesses in a fuel system. Heres what I know for sure. In a long decent with a PA 12 you can have one hour of fuel on board and have the engine quit. If not for a discussion with Clyde Smith Jr. and his vast knowledge of the 12 a certain somebody might be repairing his 12. What Clyde had told this owner was if you think your out of fuel in a 12 raise the nose to a climb attitude and it will fire back up. This owner did just that within 200 feet of dropping in on some amish farmers. He climbed 11 miles to his final destination and then started his decent into his field dead sticked again. My point is if there was any way to connect those front fittings to the front header I would. Because I make left hand circuits into uncontrolled fields I think its better to land on the right tank because it's raised for the all the turns thus using all available fuel in that wing or filling the header tank( which ever)and viceversa .This procedure is very important in an airplane with out the headers as in the case with some modified 12's. It has already been implied but the bottom line is with the aircraft gimbaling on the vertical axis the fuel system should supply at any angel- left front down- right front down and so on. You probably already knew these things. Good luck.
One solution on the PA-12 is porting at both the front and rear of each wing tank. I was building an experimental J-5/PA-12 hybrid, and that's the route I went. There was no header, but I ended up with 5 - yes, five - shutoff valves. They appeared to be identical to the Univair $94 models, but were $9.95 at the local auto parts store. (All brass, with a teflon-type ball seal)
A manifold at the rear, with a drain at the low point, fed another cross-tee in front where the two lines came down the windshield posts. The "main" shutoff was just ahead of the gascolator. The main valve would *not* prevent cross-feed when parked on uneven ground, though; both valves on one side would need to be off. In normal conditions, just the main would be turned off, to prevent worries about stuck floats, etc.
I never finished the project, but she's alive and well (or was, last I heard), in Havana, Florida. She's flying behind a 160HP O-320, and climbs like mad. Slow, though; about 100mph cruise.
Jon
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