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3 line tanks - 3rd line bend tubing or use tubing with clunk?

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3 line tanks - 3rd line bend tubing or use tubing with clunk?

Old 11-28-2003, 01:03 AM
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mvigod
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Default 3 line tanks - 3rd line bend tubing or use tubing with clunk?

I have always bent the brass tubing for the 3rd line in a 3 line fuel tank setup so it touches the bottom of the tank to act as fill/drain. I have seen some people mention that they use a 2nd line of fuel tubing with a 2nd clunk for the fill/drain line.

Is there a preferred way to do it or problems with the 2nd clunk method such as lines tangling/twisting/binding during violent 3D? The bend method can keep you from sucking up all the fuel at days end. Curious what everyone else does for the 3 line setup?
Old 11-28-2003, 01:53 AM
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rajul
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

Hi Marc, all my planes (except for the ones with Cline regulators) have three lines - 2 clunks and 1 vent. No problems whatsoever after violent maneuvers like snaps and waterfall. I have actually tried shaking the tanks (before installation) vigorously to see whether the lines get tangled up - no issue. I do have the brass or aluminum tubes extend slightly more into the tank to prevent tangling or the clunks thrown to the front in rough landings. Good luck !
Old 11-28-2003, 11:20 AM
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Richard L.
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

I too use a 2nd clunk connected to the third line for filling and draining on engines other than YS. I like to keep the second clunk slightly ahead of the main clunk in the tank so that it doesn't interfere with the main clunk.
Old 11-28-2003, 11:41 AM
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Flypaper 2
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

I use the same setup you do, Mark. Simple with no problems.
Old 11-28-2003, 01:48 PM
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MHawker
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

Another 2 clunk guy here. I like the added convenience of being able to drain the tank fully (huh? drain it 'fully'.... How would I drain a tank, 'fully'?)... sorry, got sidetracked.

I didn't do this on my Magic and it's kind of a pain to take the line off the engine to drain the tank after a day of flying when there is a fill line (just a tube) sitting right there.
Old 11-28-2003, 04:49 PM
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Cactus.
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

ditch the brass!!!
i use 3 lines, but i don't bend the 2nd, one clunk, on fill line thats either moulded at the top or just squirts inside from somewhere. 3rd is the exhaust which is bent up. to empty i use the engine line, but...!!!!!
i love that idea of a bent tube down ( no clunk ) got a couple of planes that could do with that.
Old 11-28-2003, 07:40 PM
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88xlh
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

i use no clunk on the fill/drain line. i bend this tube down to 90 degrees then put a piece of tubing on it so it just touches the bottom of the tank. i cut a small "v" on the tip so it won't suck itself to the tank bottom when draining.
Old 11-28-2003, 08:59 PM
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mvigod
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

This clunky stuff gives me a clunky idea. How about doing the standard line (tubing plus clunk) from tank to carb, the regular vent line bent to top of the tank and then a hybrid of the clunk/bend concept.

Take the fill/drain line and bend the tubing about 45-60 degrees downward and then you can put a very short piece of tubing on it maybe 1/2" to 2 inches only (depending how large the tank is) with a clunk on the end. This setup would never cross the path of the main clunk line and would have the benefit of being able to fully drain the tank. Also the clunk would prevent the tubing from sucking to the bottom of the tank.

What would be really cool is if somebody made a tank with the 3rd line modled in that reaced to the rear bottom of the tank so you could have a built in fill/drain line!
Old 11-28-2003, 10:26 PM
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

Mark
You need a rest, You are getting to tech. 2 clunk 1 dot 1 vent and go???!!!! Its about time you took a break!!!!!!!!!!!
Old 11-28-2003, 11:25 PM
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mvigod
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

ORIGINAL: RC Outlaw

Mark
You need a rest, You are getting to tech. 2 clunk 1 dot 1 vent and go???!!!! Its about time you took a break!!!!!!!!!!!

I think I got hit in the head with a clunk too hard
Old 11-28-2003, 11:48 PM
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

On third line tanks, I use aluminum tubing for the fill/unfill line, and run it to the bottom left rear corner of the tank. You can bend it enough to avoid any real contact with the klunk. Easy to empty your tank too!

Clair
Old 11-29-2003, 12:49 PM
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MinnFlyer
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

I really like the idea of a "molded in" third line. Have you ever seen those new containers that moter oil comes in? It has a little vent molded into the neck, I don't see why some tank Mfgr could do something like that.

Hey Marc, there's a good idea, you should pitch it to Sullivan et.al. and call it the RCU Tank!
Old 11-29-2003, 01:12 PM
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Cactus.
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

the tanks i use have two extra holes off to one side top and bottom that are blanked off. i always assumed this was for a fuel guage as a bit of silicone between these would show the level, but i could use the lower hole as a drain even tho it's slighty rasied and the plane would have to be put on it's nose slightly to drain.
Draining the fuel on my Capiche before meant turning the plane upside down and draining from the exhaust line, but as i've changed tanks after the crash i'm gonna try this lower hole as a fill and drain. it's not the bung type so i cant fit a pipe facing down, and i'll have to block one of the normal holes.
Thanks Marc
Old 11-29-2003, 01:17 PM
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mvigod
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

ORIGINAL: MinnFlyer



Hey Marc, there's a good idea, you should pitch it to Sullivan et.al. and call it the RCU Tank!
I like that...the RCU tank!
Old 11-29-2003, 07:35 PM
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

I never Drain the fuel from my tanks....just fly em til they quit running!

Tom
Old 11-29-2003, 07:42 PM
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rajul
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

ORIGINAL: iflircaircraft

I never Drain the fuel from my tanks....just fly em til they quit running!

Tom
I'm gald you're not a full scale pilot ![X(] Just kiddin
Old 11-30-2003, 03:29 PM
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

heres my RCU Tank...
please no one tell me expoy won't stand up to a lifetime in 10% fuel
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Old 11-30-2003, 07:48 PM
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

There's certainly no end of suggestions for this one. Seems like a lot of ideas will work. I've never tried this setup for a 2nd. clunk but remember a reply to a similar post a while back. Made some sense if there's concern about the 2 clunks interfering with each other.

Install the 2 clunks by making fill/drain line a little shorter. But, splice a short of brass tubing midway along each clunk line. These 2 lines can be secured side by side. With a piece of fuel line on both ends of the brass slice pieces the tubing and clunks are free to move up and down with virtually no chance of getting tangled with each other.
Old 11-30-2003, 09:46 PM
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Richard L.
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

Even if the two clunks do get tangled up, it's not really a big deal because fuel is still being drawn from the main clunk. Plus, the two clunks will untangle themselves when the plane goes vertical.
Old 11-30-2003, 09:58 PM
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rajul
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

Has anyone actually had two klunks entangled ? It surely will be interesting to see it, although I doubt it can happen.
Old 12-01-2003, 12:09 AM
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BobbyRichardson
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

I have always made both clunks the same length and never a problem. I never used the second 90 degeee bend but it sounds like a good idea.
Old 12-01-2003, 12:35 AM
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mvigod
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

Our very own Erick Royer had a great idea. What he does is place the 3rd line so it is just flush with the back of the tank stopper. This way he just puts the plane on its nose at the end of the day for the defueling. Since you only do a full drain at the end of the day this is fairly easy and foolproof. Now he said that would be better than my tubing bend to the bottom since he can get all the fuel out.

However now as I'm typing this & thinking about it the stopper protrudes far enough into the tank that you actually wouldn't get all the fuel. When the plane is on its nose the and the fuel drains the stopper will be protruding higher in the tank than the inside front thus it cannot pick up all the fuel...hey Erick read this! I think I found a flaw in your system? [sm=confused.gif]
Old 12-01-2003, 09:27 AM
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

Funny, I use 2 clunks, with the filler-drain clunk 2/3rd of the way to the back of the tank and was wondering the exact opposite - I can never get all the fuel out and was thinking of changing it to having a brass tube bent a little over 90 degrees towards the front corner of the tank. I'd have it actually touching the bottom of the tank with a notch cut into the end.

I suppose the tank is always better drained on the other side of the fence.
Old 12-01-2003, 11:48 AM
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

I have one plane that is a 3 line job that has a clunk on a short hose.
This is done so that the fill clunk does not interfere with the engine clunk
Old 12-01-2003, 01:08 PM
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Default RE: 3 line tanks - 3rd line bend tubing or use tubing with clunk?

why do you need a second clunk??
clunks are to keep the line by the fuel as you fly inverted and roll and stuff, how the heck are you guys defueling?

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