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long long downlines!! what about fuel clunks in the tank???

Discussion in 'IMAC>>>Aircraft, Techniques, Equipment, etc.' started by orthobird, Sep 6, 2014.

  1. Do-rag

    Do-rag 100cc

    Should have known that [MENTION=17]MattyMatt[/MENTION]; would have this figured out already.

  2. Looks identical to a nitro heli with a header tank set up.

    Vent line from the header tank plumbs into the "feed" line on the main tank. You can use a simple 3rd line on the header tank to fuel the entire system. :)
  3. MattyMatt

    MattyMatt 70cc twin V2

    No pictures, but Bunky is correct.

    The 8oz tank has three lines: One has a straight tube into the middle of the tank, this one goes to your carb. One line goes into the bottom of the tank and goes to the filler fitting on the side of the plane. The third line goes to the top of the tank, like a normal "vent line".

    The 50oz tank has two lines. One is a traditional clunk line, and the other is a traditional vent line that goes to the top of the tank. The vent is routed out of the plane like normal. The clunk line is plumbed to the vent line on the 8 oz tank.

    So when you fill the plane, it fills through the header tank, and when it is full, it pushes all the air out into the 50oz tank, and fills the 50oz until the whole system is full and over flows through the vent line.

    As the engine runs it pulls fuel through the header and pulls fuel from the 50oz tank, the header tank is always full... Meaning your clunk will not run out of fuel.
  4. Pistolera

    Pistolera HEY!..GET OUTTA MY TREE!

    One other thing is the long brass tube, which keeps the clunk near the back of the tank and during extended downlines, or even a long down-hill descend (not vertical).....the gas goes toward the front of the tank and the clunk cannot due to the brass tube. Take that tube out and replace it with Viton all the way to the clunk.

    I have had the exact same issue in two different planes. Removed the tube and problem solved.
  5. orthobird

    orthobird 150cc

    happened again, this time, we got it on film!!!

    look at 19 seconds. I just came out of a 1/2 Cuban 8 and was going to do an Immelman, when the motor wanted to give out. this is about 7 minutes into the flight. DA 170 cc with MTW re3 pipes and Fiji tank with the brass tube inside. once she landed, i checked, there was 500 cc of fuel left. the Tank is 1.5 liters.

  6. orthobird

    orthobird 150cc

    just now, i did this:

    real interested to see if it does that "hiccup" again????

    17982=12346-IMG_6102.jpg[​IMG] 17982=12347-IMG_6103.jpg[​IMG] 17982=12348-IMG_6105.jpg[​IMG] 17982=12349-IMG_6106.jpg[​IMG] 17982=12350-IMG_6107.jpg[​IMG]
  7. Ant

    Ant 50cc

    Cam, I use the same clunk and Viton also,only I have a McDonalds drink straw over the tubing to keep if from curling.. works very well.
  8. orthobird

    orthobird 150cc

    excellent!! thank you Anthony!

    let you know what happens with next flight.
  9. Pistolera

    Pistolera HEY!..GET OUTTA MY TREE!

    I think you will find that with a heavy clunk such as the one in the pic and the flexibility of Viton tubing that the clunk will always find its way to the fuel. Again....a brass tube OR plastic straw WILL keep the clunk towards the rear of the tank....so when you are less than 1/2-2/3 full and are on an extended downline, or descent the fuel will be forward and the clunk will be in air.
  10. The_Wreck

    The_Wreck 30cc

    I with you Earle, I have been running just Viton and a Stens plastic ceramic clunk for the last 6 years, never had fuel issue. When I hold the tank nose down the clunk falls to the front, when I turn it upright it falls to the back. This way the clunk follows the gas. I do use 3W round tanks, mainly because they are easy to setup, and the fuel always settles to the clunk.

    When I used to run tygon in the tank I would put a straw over it to keep it in the back of the tank, I guess the plastic/ceramic clunk held enough gas on a downline to keep it running.

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