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Thread: J3 float cork

  1. #1
    a3holerman's Avatar
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    J3 float cork

    Hi,

    My float cork had seen better days. It does float but needs to be replaced. Is there is supplier for just the cork? I also plan to replace the rusted wire indicator with stainless.

    Thanks for any help advice in advance....
    Tom
    Cape Cod

  2. #2

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    In the J-3 I fly, the cork has been replaced by a handmade brass float -- works great.The top and bottom are brass disks small enough to fit through the opening in the filler cap. They have holes drilled in the center for the indicator stem to pass through. The circumference is thin brass sheet wrapped around the disks, soldered top and bottom and along the vertical seam in the circumferential sheet. This float has been in service for about 35 years now and is still working OK. I can send dimensions if you wish.
    JimC

  3. #3

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    Tom,

    As with most everything J3 related, Univair does have new gas cap/float/wire available. The float is now the same black plastic/foam stuff used in car gas gauge sending units.

    They come fully assembled and this leads me to a question. With the original gauge, Pipers intent was that when the bend in the wire rested on the tube coming out of the cap, you were supposed to have 30 minutes of fuel. With the A-65 that was a little over 2 gallons.

    I flew a friends J3 recently that has a new Univair gas cap. Had a great time and landed with the bend in the wire just resting on the tube. Filled up the tank and was shocked to find that I had barely over 1 gallon left in the tank! I've talked with him about this and we plan to drain his tank, then put 2.5 gallons in and either mark or re-bend his wire.

    You can easily make a new cork and indicator. A length of welding rod (get something that won't rust) and some cork from the craft store (I have also seen people purchase a sending unit from NAPA with the approx size float to use). You may have to use two or three pieces of cork stacked to get the right dimenion. a washer soldered above and below the cork will keep it in place. coat the cork with several coats of fuel proof epoxy to keep it from getting saturated.

    As you cut the wire to length and bend it, I'd suggest leveling the fuselage and putting 30 minutes worth of fuel in your tank. (~2.25 gal for 65hp, 3 gal for 90hp). Install the wire through the cap and install the cap. Trim the wire so it is about 1 inch above the tube, then mark the wire at the tube (this removes the extra weight of the wire, giving a more accurate reading). Bend the wire 90* at the mark and trim if necessary. Now you have "calibrated" your gas gauge!

    Good luck!

    John Scott

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    Two things: 1. Never trust a fuel gauge completely, even one as bulletproof as the J-3. If you burn four gallons an hour, you have 2 1/2 hours of useful fuel, and a 30 minute period when you will mostly be sure you won't make the airport. That last 30 minutes is when the headwinds get really serious; 2. There is an outfit that has the correct cork, and I believe the source is in Cub Clues of a bit ago. I'll look.

    I used a pair of Mustang gas tank floats for years, until Len Buckel gave me a brand new cork. I kind of like the cork, and am indebted to Len for many acts of kindness over the last 20 years.

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    Guys, what's the reference source for the 30 minute reserve when the tab hits the cap? I've got about 1200 hours in various J-3's, and I don't think I've ever flown one that had more than about a gallon left when the tab bottomed out. Note that I'm not implying that you're wrong (I'm sure you're correct), I'd just like to be able to quote the reference.

    As an aside, in a J-3, my personal preference is that the tab bottom out and the engine get quiet at the same time. What I don't want is for the engine to get quiet before the tab bottoms out :-)
    Many thanks,
    JimC

  6. #6
    Crash, Jr.'s Avatar
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    Time to pull this thread back up to the top.

    My J3 seems to have the indicator bottom out with a full 4+ gallons still in the tank. I'm putting a new gas cap/float together and want to be able to more accurately know what's left in the tank.

    Does anyone know how much should be left in the tank when the fuel indicator bottoms? I feel like there should be a couple gallons at least to make sure you don't un-port the tank in a climb but I'd like to hear what others have done.

  7. #7
    cubdriver2's Avatar
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    Quote Originally Posted by Crash, Jr. View Post
    Time to pull this thread back up to the top.

    My J3 seems to have the indicator bottom out with a full 4+ gallons still in the tank. I'm putting a new gas cap/float together and want to be able to more accurately know what's left in the tank.

    Does anyone know how much should be left in the tank when the fuel indicator bottoms? I feel like there should be a couple gallons at least to make sure you don't un-port the tank in a climb but I'd like to hear what others have done.
    Every J3 is different. Only thing that's important is knowing how much is in it. Sounds like you do? If you don't, raise the tail to cruise attitude and add a gallon at a time and calibrate your wire. If you make a longer wire it wouldn't move above 50 mph when tank is above half full. I like the 4 gallons left when bottomed out. Means I have 30 minutes to land
    A timer is a better/safer fuel gauge

    Glenn
    Last edited by cubdriver2; 07-16-2021 at 10:18 PM.
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  8. #8
    skywagon8a's Avatar
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    The FAA is only interested that you know when the tank is empty.

    CAR 3

    3.672 Fuel quantity indicator. Means shall be provided to indicate to the flight personnel the quantity of fuel in each tank during flight. Tanks, the outlets and air spaces of which are interconnected, may be considered as one tank and need not be provided with separate indicators. Exposed sight gauges shall be so installed and guarded as to preclude the possibility of breakage or damage. Fuel quantity indicators shall be calibrated to read zero during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply as defined by § 3.437.

    3.437 Determination of unusable fuel supply and fuel system operation on low fuel. (a)The unusable fuel supply for each tank shall be established as not less than the quantity at which the first evidence of malfunctioning occurs under the conditions specified in this section.
    N1PA

  9. #9
    skywagon8a's Avatar
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    Quote Originally Posted by Crash, Jr. View Post
    Time to pull this thread back up to the top.

    My J3 seems to have the indicator bottom out with a full 4+ gallons still in the tank. I'm putting a new gas cap/float together and want to be able to more accurately know what's left in the tank.

    Does anyone know how much should be left in the tank when the fuel indicator bottoms? I feel like there should be a couple gallons at least to make sure you don't un-port the tank in a climb but I'd like to hear what others have done.
    If I were you, I would follow the FAA's requirements. THEN paint a band on the wire at your desired locations for your own information.
    N1PA

  10. #10
    cubdriver2's Avatar
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    Quote Originally Posted by skywagon8a View Post
    If I were you, I would follow the FAA's requirements. THEN paint a band on the wire at your desired locations for your own information.
    Doesn't last very long and the paint bump helps the wire get stuck. Always fun when you slow down and the wire drops a foot.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

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    Quote Originally Posted by skywagon8a View Post
    The FAA is only interested that you know when the tank is empty.
    According to CAR 3.672 FAA is actually only interested that you know when the only fuel left in the tank is the unusable fuel determined by CAR 3.437 (b). I doubt that is "empty" even for a fuel system as simple as the J3.

  12. #12

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    Quote Originally Posted by skywagon8a View Post
    The FAA is only interested that you know when the tank is empty.

    CAR 3

    3.672 Fuel quantity indicator. Means shall be provided to indicate to the flight personnel the quantity of fuel in each tank during flight. Tanks, the outlets and air spaces of which are interconnected, may be considered as one tank and need not be provided with separate indicators. Exposed sight gauges shall be so installed and guarded as to preclude the possibility of breakage or damage. Fuel quantity indicators shall be calibrated to read zero during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply as defined by § 3.437.

    3.437 Determination of unusable fuel supply and fuel system operation on low fuel. (a)The unusable fuel supply for each tank shall be established as not less than the quantity at which the first evidence of malfunctioning occurs under the conditions specified in this section.
    The J3 is a CAR 4 airplane, not a CAR 3 airplane. The appropriate regulation would be CAR 4.624. Similar wording, but not exact.


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  13. #13
    skywagon8a's Avatar
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    Quote Originally Posted by cubdriver2 View Post
    Doesn't last very long and the paint bump helps the wire get stuck. Always fun when you slow down and the wire drops a foot.

    Glenn
    How about magic marker?
    N1PA

  14. #14
    cubdriver2's Avatar
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    Quote Originally Posted by skywagon8a View Post
    How about magic marker?
    I had a couple dots on inside of windshield for reference for awhile.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

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    Quote Originally Posted by dgapilot View Post
    The J3 is a CAR 4 airplane, not a CAR 3 airplane. The appropriate regulation would be CAR 4.624. Similar wording, but not exact.

    CAR 3 specifies how unusable fuel is established but I can find no mention of "unusable fuel" in CAR 4a. What were the unusable fuel requirements for the J3? I couldn't find CAR 4.624 but CAR 4a.624 seems to refer to oil quantity not fuel quantity indication.

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    Quote Originally Posted by frequent_flyer View Post
    CAR 3 specifies how unusable fuel is established but I can find no mention of "unusable fuel" in CAR 4a. What were the unusable fuel requirements for the J3? I couldn't find CAR 4.624 but CAR 4a.624 seems to refer to oil quantity not fuel quantity indication.
    Eventually found a scan of CAR 4 and in that version 4.624 is fuel quantity gauging. Still found no mention of unusable fuel though.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	CAR 04.624.PNG 
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  17. #17
    skywagon8a's Avatar
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    Civil Aeronautics Board

    www.stacheair.com/data/At Work 9B Repair Station CD/Data Info/CAR's/CAR Part 4a/Word/CAR Part 04a As Amended to 4-7-50.doc

    § 4a.624 Gauge. A suitable means shall be provided to determine the amount of oil in the system during the filling operation. § 4a.625 Piping. Oil piping shall have an inside diameter not less than the inside diameter of the engine inlet or outlet and shall have no splices between connections.


    This link brings up CAR 4a



    § 4a.711 Check of fuel system. The operation of the fuel system shall be checked in flight to determine its effectiveness under low fuel conditions and after changing from one supply tank to another. (See § 4a.605.) For such tests low fuel is defined as approximately 15 minutes supply in each tank tested, at the maximum-except-take-off power certified.

    § 4a.605 Capacity and feed. The fuel capacity shall be at least 0.15 gallons per maximum (except take-off) horsepower for which the airplane is certificated. Air-pressure fuel systems shall not be used. Only straight gravity feed or mechanical pumping of fuel is permitted. The system shall be so arranged that the entire fuel supply may be utilized in the steepest climb and at the best gliding angle and so that the feed ports will not be uncovered during normal maneuvers involving moderate rolling or side slipping. The system shall also feed fuel promptly after one tank has run dry and another tank is turned on. If a mechanical pump is used, an emergency hand pump of equal capacity shall be installed and available for immediate use in case of a pump failure during take-off. Hand pumps of suitable capacity may also be used for pumping fuel from an auxiliary tank to a main fuel tank.
    N1PA
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  18. #18

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    J3 float cork

    Quote Originally Posted by frequent_flyer View Post
    CAR 3 specifies how unusable fuel is established but I can find no mention of "unusable fuel" in CAR 4a. What were the unusable fuel requirements for the J3? I couldn't find CAR 4.624 but CAR 4a.624 seems to refer to oil quantity not fuel quantity indication.
    There are no unusable fuel requirements in CAR4. The J3 was designed to meet the CAR 4 requirements. Within CAR 4 they mention that all fuel is to be available in each flight condition, and they specify that for evaluating loading conditions, the minimum amount of fuel would be 15 minutes at maximum non take off power. In short, there is no unusable fuel in a J3. Oil is part of the useful load, not part of the empty weight.

    Keep in mind that the J3 was certified in 1938. Car 4A wasn’t published until 1945, and CAR 3 shortly after that. The J3 certification basis is the 1937 version of CAR 4. More likely, the original design was AeroBulletin 7A as the early design work started a few years before certification, likely before the original version of CAR 4, but was likely updated to CAR 4 as the design progressed.


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    Last edited by dgapilot; 07-17-2021 at 07:12 PM.
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  19. #19
    55-PA18A's Avatar
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    ?? All this for someone who asked where to buy a friggin cork?
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  20. #20

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    I think Paul Smith (AOP on the J3 forum) sells J3 fuel gage rods with floats.


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    Quote Originally Posted by 55-PA18A View Post
    ?? All this for someone who asked where to buy a friggin cork?

    The question was "Does anyone know how much should be left in the tank when the fuel indicator bottoms? I feel like there should be a couple gallons at least to make sure you don't un-port the tank in a climb but I'd like to hear what others have done."



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    The only real regulatory requirement is that when the tank is empty, the gage has to read empty.


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  23. #23
    RaisedByWolves's Avatar
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    https://www.univair.com/piper/piper-...auge-assembly/


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    It is not just a climb that can un-port a tank early Cessna and stock cub right tanks can do it in a long nose down approach. I prefer to have empty to mean empty. It is up to me to understand my plane and know the outlying factors.
    DENNY
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  25. #25
    cubdriver2's Avatar
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    Out of all the gauges in all types of aircraft the simple J3 wire is the most accurate. But only if you calibrate it first.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  26. #26
    courierguy's Avatar
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    I had a float in my T-Craft, can't remember if it was brass or a cork, but will never forget the setup, simplicity at it's best! You guys do realize this discussion, for most pilots and especially non pilots, is like talking about the best and greatest buggy whip, or a new style of spats, pretty funny for most but dead serious for us.

  27. #27
    Doug Budd's Avatar
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    Wag aero sells floats. I bought kits for my pacer from them.


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  28. #28
    BC12D-4-85's Avatar
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    I always wondered why they didn't put an external tube gauge on the main like the wing tanks have. At least for the last 1/4 tank.

    Gary

  29. #29
    Doug Budd's Avatar
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    I saw a champ that had a plastic tube on top of the gas cap with the rod in the tube . It was marked so he knew what he had for gas


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  30. #30
    jackndiane
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    Quote Originally Posted by DENNY View Post
    I prefer to have empty to mean empty. It is up to me to understand my plane and know the outlying factors.
    DENNY
    Agreed and it isn't hard to replace the stock wire (bottom = 4 gallons remaining) with a longer one.

  31. #31
    cubdriver2's Avatar
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    Quote Originally Posted by jackndiane View Post
    Agreed and it isn't hard to replace the stock wire (bottom = 4 gallons remaining) with a longer one.
    I like that it has 4 gallons

    Glenn
    Last edited by cubdriver2; 07-18-2021 at 09:51 PM.
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  32. #32
    Crash, Jr.'s Avatar
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    Haha, you guys always do find the long way around a straight answer.

    I bought a new float/rod assembly from a guy on the J3 forum. Very reasonably priced for sure. Gotta love forum members helping other members.

    This weekend I drained the tank completely and slowly poured the fuel back in to check the stock float that's already there. Looks like 3.5 gallons remaining in level flight when the gauge stops reading.

    Still unsure how I'm going to calibrate the new float. It's nice to be able to see the thing bobbing around when you're low on a fuel as a reminder there's still gas in the tank but at the same time I'm getting used to having a 30 minute (4 gallon) buffer as an "oh $h!t I need to find somewhere to land" indicator when the rod hits the cap.

  33. #33
    jackndiane
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    Quote Originally Posted by cubdriver2 View Post
    I like that it has 4 gallons

    Glenn
    If you have a J-3 with an eight gallon aux tank it's perfect... Transfer at zero.

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