Wing Fuel Sumps

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6643
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Re: Wing Fuel Sumps

Post by 6643 » Fri Dec 07, 2018 7:12 am

That's nasty...

Looks like it may be leaking from the threads, or the tank fitting.

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Re: Wing Fuel Sumps

Post by 8359 » Fri Dec 07, 2018 10:27 am

It wasn’t leaking until I tried to use it, so hopefully replacing it with some good thread sealer and I’ll be good to go.

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Re: Wing Fuel Sumps

Post by 6863 » Fri Dec 07, 2018 10:32 am

Thanks John. Your valve looks like mine. I'll look for the safety wire provision.
John Kliewer

"Make things as simple as possible but no simpler." Albert Einstiein

"Wheels move the body. Wings move the soul."

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Re: Wing Fuel Sumps

Post by 6643 » Fri Dec 07, 2018 4:15 pm

If it's a straight thread there is an o-ring under the flats that seals the valve to the tank. If it's tapered threads you need to use Fuel-lub (now E-Z turn) to seal the threads.

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Re: Wing Fuel Sumps

Post by 6896 » Sat Dec 08, 2018 10:36 am

My C140 project came with fuel cells that were machined for the 7/16-20 SAE-Aerospace MS-33649 style straight thread female port with O-ring, but the prior owner had adapted 1/8 NPT thread fuel drain valves to the cells and even used epoxy or something like it to seal the threads. It was a bit of a mess for me to correct. I wanted to reuse the fuel cells obviously, but I needed to clean up the female ports and threads before going further. After re-dressing the threads with a tap, I ordered a rather expensive IRP-4 port tool with a TP-4 pilot from Tosco Specialty Tool that would pilot off of the 7/16-20 threads to correctly re-cut the spot face and tapered surface where the O-ring sits. See photo of tool. The carbide tool has all of the features of the MS-33649 port above the 7/16-20 thread and is used for mass production cutting of ports. I just needed it for two ports. It solved my problem. We then opted to go with a 6-32 Rivnut in the doubler plate for the the sheet metal skin below the tank for a fillister head screw drilled for safety wire to secure the fuel drain. I don't know if anyone else has this problem, but the way my fuel tank mounting rails are set up with the Neoprene bumpers (instead of wool felt) cause the tank port to be pretty deep inside of the wing. It almost seems as if my threaded port on the tank is not long enough, which may explain why the former owner did the improvising with the 1/8 NPT fuel drains. We machined some extensions to accommodate this issue so the safety wire does not drag along the aluminum skin to avoid cutting the skin. See preliminary photos of our installation.
Attachments
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DSCN0613.jpg
DSCN0613.jpg (28.49 KiB) Viewed 58 times
DSCN0608.jpg
DSCN0608.jpg (55.18 KiB) Viewed 58 times

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Re: Wing Fuel Sumps

Post by 6896 » Sat Dec 08, 2018 10:38 am

Remaining photos showing Tosco tool and safetying of 7/16-20 port fuel drain. The safetying of the drain is without the port extension we made so you can see how the safety wire is dragging across the aluminum skin, which is not something I want to be in the final installation.
Attachments
S5005208.jpg
S5005208.jpg (27.81 KiB) Viewed 58 times
S5003226.jpg
S5003226.jpg (43.18 KiB) Viewed 58 times

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Re: Wing Fuel Sumps

Post by 6643 » Mon Dec 10, 2018 9:22 am

6896 wrote:
Sat Dec 08, 2018 10:36 am
It almost seems as if my threaded port on the tank is not long enough, which may explain why the former owner did the improvising with the 1/8 NPT fuel drains. We machined some extensions to accommodate this issue so the safety wire does not drag along the aluminum skin to avoid cutting the skin. See preliminary photos of our installation.

Image
Is it just me, or is the bottom of that tank pushed in?

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Re: Wing Fuel Sumps

Post by 6896 » Mon Dec 10, 2018 7:18 pm

The photo commented on is for the left fuel cell, and it might appear that the drain port weldment is "pushed in" because of the shadow underneath the fuel cell and the angle of the camera. I don't have a much better photo, but I do include a direct shot onto the bottom of the left tank hanging from a clothesline after priming with white EP-420 primer, and there is no apparent push in.

Both my tanks have similar appearances and when I filled them up with water the contain about 12.2 gals to the bottom of the filler caps. I attach photos of both fuel cells after installation in both the right and left wings, and you can see that the drain ports are both recessed inside the wings about the same distance.

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Re: Wing Fuel Sumps

Post by 6896 » Mon Dec 10, 2018 7:30 pm

Forum isn't allowing photos to be attached right now to compare the right and left fuel cells when removed from aircraft, but if you look at previously posted photos DSCN0627 and DSCN0613, you can see that both fuel drains for both fuel cells are recessed into the wings by about the same amount. This leads me to believe that both thanks are very similar without one being collapsed due to deformation on the bottom and both have the same volume of 12+ gallons to the filler caps. Not sure why this is the case, but I suspect something about the length of the weldment for the drain valve.

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Re: Wing Fuel Sumps

Post by 6643 » Tue Dec 11, 2018 6:54 am

When you install the drain, is it up inside the wing, or does it protrude? IIRC, mine don't stick out more than 1/4" or so. And, I have one of each thread type.

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