DaleB

DaleB

Well Known Member
I'm about to pull the leaky tank out of my -12. I'll be completing an SB or two, installing the mechanical gauge upgrade and sealing up whatever is leaking.

While I have it out, should I also install the tank vent? It doesn't look too labor intensive (famous last words, I know) but the one time I refueled I didn't notice any issues. How big of a difference does it make? What's the big deficiency with the drilled fuel cap?
 
Deficencies

DaleB said:
I'm about to pull the leaky tank out of my -12. I'll be completing an SB or two, installing the mechanical gauge upgrade and sealing up whatever is leaking.

While I have it out, should I also install the tank vent? It doesn't look too labor intensive (famous last words, I know) but the one time I refueled I didn't notice any issues. How big of a difference does it make? What's the big deficiency with the drilled fuel cap?
Click to expand...

Possible deficiencies:

1) If you are prone to getting every bit of gas in the tank, and include the filler tube as part of that fill, when things warm up and expand, you can have a nice spray of gas out of the filler cap, into your fuselage/rear window.

2) What goes out might come in: water could possibly come into the tank via the hole in the fuel cap.

3) the fuel cap hole is pretty small--if it got clogged for some reason, proper ventilation might not occur

Disadvantages of the new scheme:
1) As designed, the 3/8" tube hangs down from the rear bulkhead. I put another AN fitting through the rear bulkhead so that the tank-to-bulkhead tubing could be removed and not get in the way when the tank/upholstery is being removed/installed.
2) This adds another 3/8" hole for insects to enter/build mud over, if they don't mind the gas fumes.

I have a solution to 2), which I will post shortly in the modifications thread.
 
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So if I understand the diagram correctly, the 3/8 tubing is a vent/overflow line for the tank, and the small plastic air line is to prevent siphoning a bunch of gas in the case of overflow. Is that correct? It doesn't look like a big deal to add the vent system, and a fellow 12 pilot just finished telling me about how much fun it was to drain water from his tank after it rained at Oshkosh.

Another thing on my list, I guess. Along with an anti-rotation bracket on the return line nut. I just spent some time trying to wedge my giant Mickey Mouse oversized hands and two wrenches up through an inspection hole to get the return line fitting loose. I don't recall the last time I had that much fun.
 
I ordered the vent kit from Vans and after receiving it I wished I had not. The plastic tube inside of plastic tube is a little Mickey Mouse. This is something you can build yourself with left over fittings. If you can get the drawing for the mod from your friend take a look before ordering the kit.
 
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