Plastic jerry can for fuel tank

Discussion in 'General Experimental Aviation Questions' started by jany77, Aug 3, 2019.

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  1. Aug 6, 2019 #41

    SVSUSteve

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    I am not familiar with the Part 23 one (or have it in my notes) since I am planning on using the military crashworthy fuel tank standards as a guide. :p
     
  2. Aug 6, 2019 #42

    SVSUSteve

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    I'm still working out the bugs and making sure they have long term durability to minimize maintenance issues so I don't want to get into the finer details. And we used a crane from a local construction company. It's amazing what people who like to smash things with their wrecking ball will do in exchange for pizza and drinks. LOL

    One of the things I tested (pretty successfully) was using Rhino Liner 9700 as the outer layer. My notes from that are in storage so I would have to go dig them out. If I recall, the density was something between 1-2 g/cm^3. For comparison, 7076-T61 is 2.84 gm/cm^3
     
    Last edited: Aug 6, 2019
  3. Aug 6, 2019 #43

    pictsidhe

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    I've abused numerous plastic gas cans over the years. I've even dropped a tree on one. The can did not burst, though it never sat upright again. I've seen a half full one fall off the back of a 60mph flatbed. As a good citizen, I removed it from the road and used it for several years. Now, do a search for 'fuel leak' in this very forum, and you may see why I like the idea of readily available, inexpensive and tree-resistant gas tanks rather than a 'proper' riveted or composite tank. A leaky tank can structurally destroy a styrofoam cored aircraft without it being obvious. That happens.
     
  4. Aug 7, 2019 #44

    litespeed

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    Thanks Steve,

    That helps us all.

    That Rhino liner and similar does seem like a good idea, easy to apply.



    AS far as the plastic cans go- why when above was a ad for a good looking alloy welded one for a very cheap price?

    OR use a plastic black race fuel cell?

    Why not do some tests, fill it to capacity. Include the lines and fittings with sealed hose ends.
    Drop it off a high point and test the g loads. The cost would be minimal. Make sure you do extreme G loads to test properly.

    Repeat to destruction. Then you can be sure the performance of that particular can. Other cans may be different.
     
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  5. Aug 7, 2019 #45

    SVSUSteve

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    Also remember to see what happens when you put a tensile load on the lines and fittings. You know..what would happen if the tank came loose in a crash or hard landing while the hoses etc were still hooked up.

    As one of my mentors once said, "There's a difference between being cocksure of something and being sure enough to bet your life on it". It's not really a concern in the ultralight community (which is both good and bad depending upon how you view it) but my way of looking at it is that my bigger concern is for the lives of those who are in the airplane with me.

    Honestly, if you asked around the racing community, I am willing you could find an "old" but serviceable fuel cell someone is willing to give you. Not an ideal solution but certainly a lot sturdier than any plastic gas can.
     
  6. Aug 7, 2019 #46

    pictsidhe

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    I don't know about other people, but a 20lb tank seems a bit heavy for an ultralight. I'm going lighter, and I'm going to skip the bulletproofing. 5psi and following Steve's mounting tips will be enough for me. FAR23 seems adequate. I have a weight limit ro meet.
     
  7. Aug 7, 2019 #47

    SVSUSteve

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    I believe they make smaller ones for certain types of race vehicles.

    Either way, at least you are willing to consider the issues at play. There are a lot of folks who can't or won't even do that. If I can be of assistance in any way, you let me know.
     
  8. Aug 8, 2019 #48

    Charles_says

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    Agreed! That 20 lbs could go to reinforcing the cabin area, so that engine and prop fold under in the event of contact with an immovable object ...

    I'm using two 2.5 gal wing mounted riveted aluminum tanks,
    plumbed together with a Wye to act as one tank.
    And since my wings fold, I'm using quick disconnects,
    where the lines enter the cabin area so if a wing is torn off, the disconnect will ( hopefully) separate, without losing fuel.

    Advantages= weight over the CG, no complex switching,
    in the event of a crash less chance of fuel bath., and better chance of losing less fuel to feed a fire.
    If the rivets should suffer enough force to shear, I won't
    have to worry about it ... ever!
     
  9. Aug 8, 2019 #49

    pictsidhe

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    I would like to use a pair of plastic gas cans in the wing roots. They will not be exposed to daylight. They will be removeable to add refuelling options. But, I may resort to aluminium. The plastic ones look much sturdier.

    Edit, can't trype
     
    Last edited: Aug 9, 2019
  10. Aug 8, 2019 #50

    SVSUSteve

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    Do me a favor (and yourself and your family): take a few of those disconnects out and hook them up to a "dummy" tank. Jerk the tank real hard to get them to disconnect. A lot of the folding or removable wing disconnects don't seal when you do that. I was surprised when I tried it myself while trying to find a cheaper and lighter option to a standard frangible valves.

    You'd be surprised how often that is not the case. I've seen a few autopsies of ultralight homebuilts with fuel tank ruptures (witnesses reporting a "ball of fire" immediately after impact usually implies this) and the pilot has soot deep in his airways implying that he survived the initial impact. We got hold of pictures taken during the build of several (usually from local homebuilders who were friends of the victim) revealed riveted fuel tanks.

    The critical value for this is that people forget that some aluminum has a tensile strength far less than the other values (3003 comes to mind where the tensile strength is 29000 PSI vs shear strength of 16000 psi). Also, the area across which it is being applied for each rivet is comparatively small.

    Also, it's not usually the rivets shearing as a failure mechanism. Usually they either fail in tension (the head pulls off) or the aluminum yields under tension (the head of the rivet pulls through) or shear (the tank material yields to the stronger rivet being pulled through material. This is why orientation of the seams makes a differences although what's referred to as a "reflected hydraulic blowout" or a "remote hydraulic blowout" is possible.

    The former is basically the mass of the fuel hitting the front of the tank, rebounding and then slamming off the back of the tank with sufficient force to part at least some of seams. The latter is where impact of the fuel against the front of the tank puts a tensile load on the wall and may pull the rivets through the seam at a point other than where the primary load is applied. Think of it as basically taking a rectangle and trying to make a parallelogram out of it.
     
  11. Aug 8, 2019 #51

    Hot Wings

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    By "quick disconnects" are we all using the same terminology? Dry break connections are part of my fuel system plan with the intent being if the engine separates, or moves enough, and takes part of the fuel line with it the well protected up stream fuel line with the remaining half of the dry break connection remains with the intact tank.

    If these connections do in fact leak when disconnected then their value is in question. Could this be a QC problem? The dry break connections I have experience with - in hydraulic systems - are dry* when disconnected.

    * at most a 1/10 ml of 'drip'.
     
  12. Aug 8, 2019 #52

    SVSUSteve

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    When I say "frangible", I am talking the ones used in racing or described in the military Aircraft Crash Survival Design Guide.

    When I say "quick disconnects" I am talking about these:
    https://www.aircraftspruce.com/catalog/cmpages/vbhightempdisc.php?clickkey=28961
    or
    https://www.aircraftspruce.com/catalog/appages/quickdisline.php?clickkey=28961
     
  13. Aug 8, 2019 #53

    Hot Wings

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    Clarified.
    Your frangible is = to my dry break.

    My example of the hydraulic coupling is a poor one. They are the quick disconnect type. Same internal mechanism as a dry break but differ in the dry break having a breakable mechanical link holding the bits together.

    A quick disconnect, like an air hose, is for a completely different purpose.
     
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  14. Aug 9, 2019 #54

    N804RV

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    I prefer the "utility can". They can't label it for sale as a gas can. But, that doesn't mean I can't use it as one. As far as I'm concerned, its safer than the "safety cans" everyone has, because you can get a solid stream of fuel with no glugs and you can control it. The "safety cans" don't vent fast enough, so fuel splashes. And the stream is too small, so you're holding the **** can up at an awkward angle for too **** long.

    [​IMG]
     
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  15. Aug 9, 2019 #55

    bmcj

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    I agree. That’s pretty much the same can as the racing water jug that I mentioned, except the one I have is translucent.
     
  16. Aug 9, 2019 #56

    Charles_says

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  17. Aug 9, 2019 #57

    Charles_says

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    (Re: 1) No family, but thanks anyway

    (Re: 2) Keyword there is autopsies. I still won't have to worry :)
     
  18. Aug 9, 2019 #58

    SVSUSteve

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    Key point in my statement was that they survived the crash and burned alive because of an inadequate fuel tank design. You still should be concerned.

    Everyone has someone to cares about them even if it's just the somewhat grumpy resident safety guy on HBA.
     
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  19. Aug 9, 2019 #59

    Charles_says

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    To clarify:
    You seem to be referring to this as a fuel transfer tank
    (which it is perfectly suited for) as opposed to a mounted to the airframe fuel tank, because as a fuel tank, the speed of emptying isn't an issue, nor are "glugs" And one wouldn't be: "holding the **** can up at an awkward angle for too **** long."

    However, this thread concerns airframe mounted fuel tanks.
    I originally had a red container...
    ( sold, as a gasoline storage can)
    as a fuel tank. gas can tank.jpeg
    I wasn't happy with the idea of 30 pounds of fuel, a few inches behind me in the event of a catastrophic event,
    perhaps losing its filler cap, and bathing me in fuel.
    or having the stainless steel mounting straps slice into the tank with the same result as losing the filler cap.
    Or the moment behind the CG it imposes. It may not burst as delivered, but when one starts drilling holes in it for fuel lines, and drains, it leaves room for doubt of its integrity.

    Therefore I switched mid build, removing this tank, and opting for the two 2.5 gal rectangular, baffled, riveted aluminum tanks mounted in the respective wing roots.
    I don't see 1.25 gals of fuel having the mass to rupture a riveted tank, which I calculate to be the tank volume divided by the baffles.
    Hence, the discussion about dry (quick) disconnects for my folding options.
     
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  20. Aug 9, 2019 #60

    N804RV

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    I missed the post where the OP (jany77) clarified that point.
     

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