Plastic jerry can for fuel tank

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

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  1. Aug 4, 2019 #21

    Tom H

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    I understand that the portable plastic gasoline containers (red color, in my experience) have some additive in the plastic that makes them slightly conductive to electricity. An effort to bleed off any static charge. This could be a consideration.
     
  2. Aug 5, 2019 #22

    Winginitt

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    Like SVSU said, the idea is to improve rather than settle for something of questionable quality or durability. It's not just about the can bursting although that's a major concern. The filler spouts have molded threads of doubtful quality that won't retain any cap under much duress. You have to find a way to adapt a fuel line and a vent line which means juryrigging some type of crap seal and fitting with no reinforcement at the tanks wall. A simple leak from an exposed tank is more than enough to turn an ultralight into a flying torch. You need solid and secure connections and a tank you can fasten them to. Anyone (probably everyone) who has ever used any gasoline to ignite a fire should comprehend just how dangerous gasoline is. My nieces husband just spent the last year wearing special gloves and rehabilitating his hands because he used the old "pour a little gas in the carb and crank the engine over" trick. Using an Ill conceived fuel system in an airplane can be a lot more devastating than that. Why use something that's very questionable when much better alternatives are available for a reasonable cost ? Can't say it any better than this, "Don't be fuelish.....just because it's cheap"
     
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  3. Aug 5, 2019 #23

    pictsidhe

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    But they aren't of questionable quality or durability! In fact, I strongy suspect that the basic can is far less prone to leaks than fabricated tanks.

    Yes, getting fuel lines in and out will take a little head scratching. If I do it, I'll use the standard tubular nut, throw the spout away and make a new bung that takes lines and the stock tubular nut. No tank mods at all, I'd like to be able to screw a blank cap on and use it as a gas can...
    If you do put lines through the side, weld a bung on and use threaded fittings. Simple. You won't even need pipe sealant.
    They DO have an issue with sunlight exposure. That isn't an uncommon issue on aircraft. The solution is often called 'paint'.

    If you can't repurpose a gas can safely, use a different construction that you CAN master. That idea does not just apply to gas tanks... Nobody seems to advocate not using other materials because somebody did a lousy job and killed themselves.
    The problem seems to be: "Oh, it' plastic, it must be awful." If so, why are jst about all car gas tanks now plastic?
     
  4. Aug 5, 2019 #24

    litespeed

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    True Cars are mainly plastic tanks.

    However that is where the similarity normally ends.

    They use a very high grade rotational molded fuel proof plastic.
    They are always in one of the most protected positions in the vehicle- ie under seat or front of boot (trunk) and thus very unlikely to rupture in a survivable accident.

    If you were comparing it to a rotomoulded race tank then that is a far comparison as long as it is mounted and plumbed correctly.

    Car tanks are not subject to UV damage- unless they turn turtle, and that is a much bigger issue than UV.

    Why put a tank in your aircraft that is a known risk from UV and thus a short term solution. And has to be modified to take lines and sender?

    Yes you can paint it- but now you can't inspect the integrity of the plastic and any crazing it has. Your cheap gas cans do not like vibration long term either.


    Would you put anything else in your aircraft that needs to be replaced often for safety? Will you religiously replace it say every 2 years and much more regular if kept in the sun?

    I would rather do it right once and know I and subsequent owners are safe and not relying on a substandard part and install.

    If you love plastic fine- buy a proper race tank and provide a cover when not in use.

    Or go metal or composite..
     
  5. Aug 5, 2019 #25

    103

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    Ultralight means 5 gallon limit
    Look at
    One without "fuel worthy certs"
    https://www.usplastic.com/catalog/item.aspx?itemid=104058

    and the same can with a sticker for California and a vent on the neck.
    https://www.usplastic.com/catalog/item.aspx?itemid=104086
    https://www.usplastic.com/catalog/files/drawings/13888 103114.pdf

    These race fuel cans could be coached into service but they are heavier than the flambeau stuff.
    https://www.amazon.com/s?k=5+gallon+race+jug&ref=nb_sb_noss_2
    over 6lbs each but the flambeau 5 is under 4lbs.

    If your consumption profile is say 1.5 gallons per hour consider a 3 or 4 gallon form factor
    https://www.usplastic.com/catalog/item.aspx?itemid=23334&catid=934

    US plastics seems to be the place to get these in low volume. If you speak to them refrain from saying airplane or ultralight. Report back your experience if you buy one to evaluate as the mechanic in charge.

    The clear 5 https://www.usplastic.com/catalog/item.aspx?itemid=104058&catid=934

    also has accessory straps available https://www.usplastic.com/catalog/item.aspx?itemid=104064&catid=934

    and permits a visual track of the fuel.

    Be sure to buy the correct vented cap or two they are inexpensive when shipping the tank.

    Fuel tank set up parts
    https://www.usplastic.com/catalog/item.aspx?itemid=104163&catid=578

    No I do not work for US PLastics or Flambeau and do not recommend you use these without making your own evaluation.

    Matt
     
    Last edited: Aug 5, 2019
  6. Aug 5, 2019 #26

    spaschke

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    have you got one of these lying around? Probably fuel compatible.
    [​IMG]
     
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  7. Aug 5, 2019 #27

    Winginitt

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    Ho Ho Ho !:)


    This looks like a reasonably priced and more durable option. Non slosh foam and AN fittings and even has the filler cap. Has a fuel level sender. Of course its always up to the builder to perform safety tests and verify suitability. Its also apparently not harmed by UV rays. 12" x12" x8" $61

    https://www.ebay.com/itm/5-Gallon-C...=ispr=1&hash=item3faf07ccb2:g:JEoAAOSw0lNcjKv

    TANK.jpg
     
  8. Aug 5, 2019 #28

    pictsidhe

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    Would I use a safety critical component that will rapidly rot when exposed to the elements?

    Like, say, polyester fabric?
    Well yes...

    I fail to understand the issue. Gas cans are designed to hold gas. They are designed to take 5psi. Which I believe is higher than the FAA thinks aircraft tanks should withstand? Now, if you can't use one safely, thats because you are doing something dumb. Such as letting the sun rot it, or leaky connections. It is almost never the fault of the can. A bad workman blames his tools...

    There are 'proper' gas can seats, which seem ideal for those seeking a Darwin award.
     
  9. Aug 5, 2019 #29

    SVSUSteve

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    I'm just going to point out that if you're making a flimsy tank out of thin fiberglass, you're going to wind up with **** poor performance. That's no different than not doing the stress analysis on an aircraft and wondering why the landing gear collapsed the first time you climb into the cockpit. By the way, the ban on fiberglass (GRP) tanks in the UK came about mostly because of people building their own to reduce weight for racing without consideration for what happens in the impact not due to the complete unsuitability of the material.

    A high percentage of the fuel tanks that meet the military crash survivability standards (and auto racing safety standards in many instances) are made out of composites to a large degree. One tank (a nylon/rubber composite lining backing up a fiberglass shell) described in the safety literature was about six times as tough as aluminum sheeting in tear resistance. Tearing failure (and the related issue of sheering) is the primary failure modes for fuel tanks especially if rivets are used (*shudder*) and where drains, lines, etc are connected. You also run into it when someone designs the tank attachments to be stronger than the rest of the tank wall. I have seen quite a few cases where the tank came loose but the attachment stayed in place keeping a piece of the wall with it. In preventing fuel spills in crashes, frangible tank attachments are generally your friend.

    That's the difference between making a tank simply to be "fuel tight" and actually designing the wall to withstand the forces at play. Contrary to what a lot of people think, tin non-integral tanks (read as: "every besides wet wings"), it's just as common for current fuel tanks to failure from hydraulic blowout or from the lines, drains, etc pulling out as it is for them to be penetrate by the primary impact. One of the easiest ways to almost guarantee a fuel tank hydraulic failure is the "classic" riveted aluminum tank often described by the "founding fathers" of homebuilding.

    I will also point out that designs other than rectangular or cylindrical (such as a "jerry" can with a handle through which fuel can shift) or anything with corners that are not gently rounded are generally considered more prone to hydraulic rupture because these confined areas act as stress risers. A "killing two birds with one stone" fix for hydraulic rupture is the inclusion of baffles in the tank which can also help prevent fuel starvation due to fuel sloshing away from the fuel line port during turns etc.

    Then there's the issue with wide variation of thickness in most plastic manufacturing that BMCJ brought up.

    Having made several small test tanks over the past several years to evaluate design options for my design, I'm just going to point out that one of my favorite ways to torture test them is to take them out and see how they react to gunfire etc. You'd be amazed how many relatively thin walls can stop a .40 S&W hollow point round at close range (usually about 10 yards).

    We (one of my wife's cousins works for Bear Archery...we get to play with a lot of fun stuff LOL) have also tested them with broadhead arrows fired from a bow with 60+ draw and, about half the time, the tip of the arrow (before the blades) does not or just barely penetrates the thickness of the wall sample. For comparison, a broadhead will usually will go completely through the "soft" aluminum often used in fuel tanks (2024 or 3003) just like the rivets will pull through under deceleration combined with hydraulic loading from the tank being compressed as happens if it's forward of the spar.

    One of the military standards is taking a test tank, soaking the entire thing in fuel (inside and out) for 30 days then drop a 5 lb chisel from 15 feet onto it in various orientations across the fabric weave; yes, it specifically mentions "fabric" and "weave orientation" in military crash resistant and ballistic resistant tank design standards. Then they take the thing, pressurized it to 5 PSI with air and it cannot have ANY leaks.

    Oddly enough, one of the best things you can cover the outside of a tank with is nylon felt (preferably ballistic nylon) impregnated with polyurethane (or epoxy). This (the polyurethane version) is actually recommended for covering hydraulic reservoirs, etc in the Aircraft Crash Survival Design Guide (see Volume 5). Ballistic nylon felt is not as available as industrial wool felt and I see little reason to not substitute it. Plus, the ignition temperature of wool is about 2-3x that at which nylon melts.
     
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  10. Aug 5, 2019 #30

    SVSUSteve

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    *facial tic*

    It's 1436 and apparently time to start drinking.
     
  11. Aug 5, 2019 #31

    SVSUSteve

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    The amount of structural reinforcement that makes them being compressed unlikely probably has a lot to do it. You're arguing a false equivalency with that comparison.

    Plus, the design criteria load for pressurization is 50 PSI and they literally place the thing in fire to test that the fuel vent system won't allow the internal pressure to exceed 50 PSI in an inverted position (49 CFR § 393.67 subsection C 5(d)(i)); if the tank is over 25 gallons, it has to be rated to withstand 150% of the maximum permissible pressure previously mention (IOW 75 PSI).

    EDIT: Sorry Litespeed....didn't see that you basically covered this.
     
    Last edited: Aug 5, 2019
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  12. Aug 5, 2019 #32

    SVSUSteve

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    Part 23 doesn't specify a pressure rating to my knowledge but I seem to recall that the standard for metallic tanks under Part 27 (helicopters) is 5 PSI and non-metallic is 3 PSI. For larger fixed-wing aircraft, 25.965 spells out of a bunch of requirements with the most applicable one being (a) (3): "Fluid pressures developed during maximum limit accelerations, and deflections, of the airplane with a full tank" which might well be greater than the 3.5 PSI stipulated in (a) (1).

    You also might want to check out the other requirements accompanying that Part 27 standard, specifically § 27.952.
     
  13. Aug 5, 2019 #33

    SVSUSteve

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    On this we agree 100%. That's a lose/lose situation. If you crash, having a solidly built seat with no vertical stroke (a rugged fuel tank under it for example), you're increasing the likelihood of spinal, pelvic, and aortic injuries. If the seat does stroke (flimsy tank), you're going to spray fuel all over yourself and everything around you so there's a good chance you'll be getting identified by your dental records.

    As a former Part 103 pilot myself, there are a lot of things that are "completely acceptable" to a lot of folks who should know better. Ultralights are, in many ways as a result of the reckless and feckless behavior of an uncomfortably high percentage of pilots and designers, fertile ground for espousing the sound advice "Just because you can does not mean you should".
     
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  14. Aug 5, 2019 #34

    Hot Wings

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    LSA ASTM is 3.55 PSI. I remember when we developed this standard we used part 23 as a guide - so IIRC part 23 does have a PSI specification. I'm just too lazy to look for it right now:p
     
  15. Aug 6, 2019 #35

    bmcj

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    I don’t see a weight given. Did you see one?
     
  16. Aug 6, 2019 #36

    Mad MAC

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    Last time I did a Part 23 fuel tank (can't remember the applicable rule) the test pressure was the equivalent maximum hydrostatic pressure caused by the emergency landing loads, which works about 5.5 psi per foot of fuel tank at 18G (its still far to low).

    SUVSteve have you seen any tests of friction stir welded aluminum fuel tanks, just asking as by design allowibles one should see something like 5 fold increase in joint strength.
     
  17. Aug 6, 2019 #37

    litespeed

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    Thanks Steve,

    That helps a lot to further our understanding.

    Could you give us more detail on your tank designs?

    I remember you tested by dropping off buildings if memory serves.

    Phil
     
  18. Aug 6, 2019 #38

    Winginitt

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    No, I didn't see a weight given. I suspect with the features given its probably 10-12 lbs. If you have ever watched the videos for Linex bed liner, they are impressive. I've always thought that a tank coated with linex would be virtually indestructable, but I don't know how much the Linex weighs either.





    Go to 4:10 mark

    We'll just call this last video "Fun with fuel"



    Seriously everyone, the point here is not what can be used but what is the best thing to use. Please don't just think "everything will be okay", because once something does go wrong its instantaneously devastating.
     
    Last edited: Aug 6, 2019
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  19. Aug 6, 2019 #39

    Charles_says

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    HAHA! I call BS! Sumo wrestler "stomps" uncoated cups with heels. but treads easily on the balls of his feet with his weight supported by two "helpers" Where were the helpers when he stomped the cups?
     
  20. Aug 6, 2019 #40

    SVSUSteve

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    I don't recall seeing any but since I am not planning on using friction stir welding (since, like most homebuilders, I cannot afford that sort of technology), I have to admit that I have not really paid much attention to it.
     

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