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  1. #1

    Replacing the Air in a Jug

    Anyone using something like nitrogen in their fuel to try and keep the bad air out? I've noticed once I get to the bottom of a jug my engines start to run finicky. I was thinking putting a gas layer on top of the fuel might help preserve it to the end. I don't get to fly as often as I use to and it can take me a few months, or maybe longer to get through a jug of fuel. I would like the bottom of a jug to burn as good as the top. Thanks.
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  2. #2

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    RE: Replacing the Air in a Jug


    ORIGINAL: bolar

    Anyone using something like nitrogen in their fuel to try and keep the bad air out? I've noticed once I get to the bottom of a jug my engines start to run finicky. I was thinking putting a gas layer on top of the fuel might help preserve it to the end. I don't get to fly as often as I use to and it can take me a few months, or maybe longer to get through a jug of fuel. I would like the bottom of a jug to burn as good as the top. Thanks.
    Remove from the jug whatever fuel line, connectors and adaptors you are using and put the original neck plug and cap back on the jug.
    This will keep the water out whne you are not using it.
    If you already have water in the fuel.....well....wait till the next gallon and keep it sealed when not using it.
    Forget Mixing Your Own Fuel....It's Easy But No Longer Needed!

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    RE: Replacing the Air in a Jug

    I usually run a jug down to less that 1/4 full, the put it back in the carton and start on a new jug. Once the new jug gets down enough, I pour the old jug in it. I've never noticed any problem and I am presently flying on four year old fuel.

  4. #4
    countilaw's Avatar
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    RE: Replacing the Air in a Jug

    It helps to keep the container of fuel out of direct sunlight. Store it in a dark cool place. Like Jim says, mix the older fuel with the newer.

    I heard some guy once say that he squeesed the jug to get the air out then tightened the cap on the jug. All it did was suck the methanol out of the mix. Bad news.


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  5. #5
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    RE: Replacing the Air in a Jug

    Here is something that might work.

    http://www.innate.com/Paint/DIY/Must%20Haves.htm


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  6. #6

    RE: Replacing the Air in a Jug

    That's interesting. Wow, the price in the description went up quite a bit from the "add to cart" price, ouch!
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  7. #7
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    RE: Replacing the Air in a Jug

    The price stayed the same. It's the cost of shipping that doubled the price. I've ordered a lot of stuff from this company and the postage remains at $9.99 total. They have a lot of stuff that is usable in the hobby. I like their mixing cups and sticks. They have squirt botles that work great for fuel and after run oil.

    I don't know if the Oxyblow will work for perserving fuel, never tried it for that. Works great for paint though. Especially if you are using paint that cost $200. a qt.

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  8. #8
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    RE: Replacing the Air in a Jug

    If you are pumping fuel from the planes tank back into the fuel jug you are putting more water into the fuel jug than you would get from any air in the jug.  When fuel burns it creates a lot of water from the hydrogen atoms in the alcohol  that combines with oxygen.  This is far more water than that in ever very humid hot air.  I wouldn't worry about it, but do keep it sealed.
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    RE: Replacing the Air in a Jug

    If you don't burn much fuel dividing it up into half gallons or quarts would help. That way most of your fuel is in full sealed jugs until you need it.
    No kid, I said break ground and fly into the wind!

  10. #10
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    RE: Replacing the Air in a Jug


    ORIGINAL: jester_s1

    If you don't burn much fuel dividing it up into half gallons or quarts would help. That way most of your fuel is in full sealed jugs until you need it.
    This is not required. If you only have a few ounces of fuel in a jug the air in the jug does not have enough water to be a problem. The most water you can expect to have is probably about .03 pounds of water per pound of dry air and at about 15 cubic feet per pound of dry air. The condensed moisture from less than a gallon of very humid air is only about 2 tenths of water. Since this is air that is over 90 degrees and 100% relative humidity this is just not enough moisture to worry about. How ever a loose cap exposes the fuel to an unlimited amount of air and moisture.
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    RE: Replacing the Air in a Jug

    I just cleared up all my "engine problems" by testing my fuels against new fuel. Turns out I had three old jugs that were definitley bad. I attribute it all to water. I now plan to keep much closer track of my fuels. I did have one older jug that was still good. I no longer trust the standard DuBro fuel system be fully sealed and I will take it off and put a cap on the jug when not activly flying. I bought several 2 quart jugs from Great Planes to minimize exposure. I gave up on electric pumps and just use a DuBro hand crank pump. I also decided to not pump fuel out of the tank and back into the jug. I will either pump it into a "used" jug, or keep it in the tank.

    I have wondered if those box wine containers could stand up to fuel. That would be an ideal system for keeping moisure out. . If fuel were sold in a one gallon [or larger] box with a hose barb outlet you could gravity feed it into the aircraft tank. No pump, no moisture , no problems.

    If anyone knows a way to pour fuel from a gallon jug into a smaller jug, let me know. I use a large funnel and drippage is minimal but it would be slick to find a spout for a gallon jug because the stuff loves to follow down the side of the jug.

  12. #12
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    RE: Replacing the Air in a Jug

    Again not worth the truouble. Although a poor seal will cause fuel to asorb more water, and a poor seal or hole in the jug would do that, the major problem is usually thatthemethanol evaporates leaving a fuel with lots of oil and nitro. A collapsing jug would not prevent that.
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    RE: Replacing the Air in a Jug

    I heard that some guys use glass marbles/ beads and fill their jugs with it as the fuel level drops. Otherwise, shouldn't one use an air drier to suck air into the jug as you pump fuel out (air displacing fuel)? These air driers are installed on large transformers and consist of cobalt crystals. The crystals absorb the moisture in the air and turns from blue to pink over time. To regenerate it you just need to dry them in the sun/ low heat in the oven.
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    RE: Replacing the Air in a Jug

    It would be extra work to dry out the dessicant, which is constantly exposed to the atmosphere. Still, if you could get the color-changing crystals in a glass tube, and have only a small air hole, it would be excellent for removing water. However it would not prevent the methanol from evaporating out [see below]. I top off my working jug with a second jug. I found a flexible spout at the Walmart auto section for $ .50. Otherwise, pouring fuel out of a jug requires a big funnel and then you can't see very well. I have also upgraded my two working jugs with Slimline caps [expensive !] because the DuBro and Great Planes do not seal completely. I think for a low cost solution, epoxy two short brass tubes thru a jug cap. Put a short piece of fuel tubing on the outside of the vent tube. When not in use put your fuel filler fitting into the vent line tube. Then you have a completely sealed system. I had never though about the methanol evaporating out [thanks, Sports Pilot !], just water coming in but sealing the system prevents both.Unfortunately Slimline is undergoing some problems. Ron's Heli South has inventory of parts and pumps.

  15. #15
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    RE: Replacing the Air in a Jug


    ORIGINAL: Bobhend

    I just cleared up all my "engine problems" by testing my fuels against new fuel. Turns out I had three old jugs that were definitley bad. I attribute it all to water. I now plan to keep much closer track of my fuels. I did have one older jug that was still good. I no longer trust the standard DuBro fuel system be fully sealed and I will take it off and put a cap on the jug when not activly flying. I bought several 2 quart jugs from Great Planes to minimize exposure. I gave up on electric pumps and just use a DuBro hand crank pump. I also decided to not pump fuel out of the tank and back into the jug. I will either pump it into a "used" jug, or keep it in the tank.

    I have wondered if those box wine containers could stand up to fuel. That would be an ideal system for keeping moisure out. . If fuel were sold in a one gallon [or larger] box with a hose barb outlet you could gravity feed it into the aircraft tank. No pump, no moisture , no problems.

    If anyone knows a way to pour fuel from a gallon jug into a smaller jug, let me know. I use a large funnel and drippage is minimal but it would be slick to find a spout for a gallon jug because the stuff loves to follow down the side of the jug.

    That is the quickest way to end up with rusted bearings and crank.

    Of course it's true, I read it on the Internet.

  16. #16
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    RE: Replacing the Air in a Jug

    I keep fuel in the tanks all the time, I just disconnect the feed line to the carb and connect it to the pressure line on the tank. I then run the engine until it won't fire anymore and leave the piston at BDC. Works fine for me.


    I do not worry about the air in the jug, never had any problems with fuel once I started mixing my own fuel.
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  17. #17
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    RE: Replacing the Air in a Jug

    I have never bothered with the fuel containers as they emptied out from use. I use it until the container is almost empty. I then dispose of the small amount left and refill the container. I also empty the airplane's fuel tank back into the container when I am done flying that plane too. I have never had a problem with the fuel so far.

    I think the problem is not having a good container that is sealed up Ok so it doesn't leak or allow it to breathe (as the temperature changes the air is drawn in when cold and pushed out when hot). Also my containers are sealed all the time. I have seen folks leave their fuel container open at the flying field for hours like that, and then they complain about how the fuel goes bad so fast on them.

    I have had problems with those plastic jugs leaking in the past, especially from the bottom, so I use the metal gallon containers for my flight box fuel container.

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  18. #18
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    1QwkSport2, when you leave fuel in you tank all the time, does your silicone clunk line tend to get soft and mushy on you? Mine sure does inside of the fuel jug. For the original question about water getting in your fuel. You said the DuBro jug system might not be sealing well enough. Usually they have an o-ring on the probe that has to be in good shape. When you store your jug and it gets cold at night or the next week, do the sides of the jug tend to suck in a bit? If so it is sealing very well. I use the Sullivan (or is it Slimline?) cap and probe system with a tiny o-ring and it seals remarkably well. An extra o-ring came with it but after about 5 years it is still sealing well. If there is a small amount of fuel in the jug it works great the following summer.

  19. #19
    Sport_Pilot's Avatar
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    Not enough water in the air in the jug to worry about. But if your cap is loose then it is exposed to moisture outside of the jug. If you keep your jug capped you will get most of your moisture from pumping fuel back in the jug from your tank, which gets moisture from the exhaust gas from the muffler pressure line.
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  20. #20
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    Quote Originally Posted by Ernie Misner View Post
    1QwkSport2, when you leave fuel in you tank all the time, does your silicone clunk line tend to get soft and mushy on you? Mine sure does inside of the fuel jug. For the original question about water getting in your fuel. You said the DuBro jug system might not be sealing well enough. Usually they have an o-ring on the probe that has to be in good shape. When you store your jug and it gets cold at night or the next week, do the sides of the jug tend to suck in a bit? If so it is sealing very well. I use the Sullivan (or is it Slimline?) cap and probe system with a tiny o-ring and it seals remarkably well. An extra o-ring came with it but after about 5 years it is still sealing well. If there is a small amount of fuel in the jug it works great the following summer.
    The fuel line changes color, but doesn't get soft and mooshy, no. I use Dubro Medium blue tubing, I get a 50ft spool every other year or so. I have the Dubro system in use and it works fine. I had sealing problems between the cap and the jug. Needed to cut a new gasket for the cap. I o-ringed the in/out fittings for the fuel pump but until I changed the jug gasket under the cap I did re-cap the jug at the end of the day as a precaution.
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  21. #21

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    I run the fuel out of the jug down to the last drop, my current fuel jug is more than 2 years old, it was stored 1/4 full, and runs fine. a nitrogen blanket is often used in storage of methanol in large quantities, but it's not to protect the methanol, it is generally used as a safety feature, nitrogen is chemically inert and is heavier than both oxygen and methanol vapor.

    Usually the problem with our fuel is that it has absorbed too much water from the atmosphere, the water vapor absorption properties of methanol is so great that it is safe to say; if it's exposed to atmosphere, it's absorbing water. Evaporation can be an issue also, but Methyl alcohol has the slowest rate of evaporation of all the alcohols.

    I would note a few precautions I take to prolong the storage life of my fuel. 1) I always put the unmodified filler cap back on the jug when I'm not fueling, it only takes a few seconds to switch caps. 2)I Keep the fuel container out of direct sunlight. 3) I keep the fuel containers stored in a cool dry place when not in use, not in a hot garage, but a cool dry place.
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