Gas tank cover leaks air?

[Tripod]

I guess I get to thinking about picky little things sometimes, but I've long wondered if the opening that surrounds the gas cap leaks air into the low-pressure area of the top of the wing, thus spoiling a little lift. Would it be worth the trouble to seal the neck of the gas tank to the cover?

-dave

[JohnW]

It IS sealed. Piper p/n 80122-48 is supposed to be installed around each filler neck BEFORE laying the tank cover over the filler neck. I have seen thick foam toilet bowl-to-floor seals put under there (which closely approximated the original thing Piper put on the SuperCubs AND the ShortWings, but retired from service in favor of the above part number), but this can result in sealing the fuel cap vent inlets, and THAT is clearly a no-no. If air can't get IN, eventually fuel can't get OUT. That kind of jonnie-ring "ingenuity" takes "frugal" into the Twilight Zone (these rubber seals are really plenty cheap).

The only "issue", really, is potentially the necks/caps sticking up into the slipstream, but if you consider that wing rib stitching at HALF SPACING is required OUTBOARD of the fuel filler (first three ribs on the ShortWings), this might make a little more "don't bother" sense. However -just to prove the point- a friend on mine spent a STUPID amount of time quite a number or years ago putting flush caps on his TriPacer, with no apparent benefit except making the caps harder to put on or take off, AND it made it impossible to see if you forgot to put the fuel cap back on after fueling without getting a stepladder. Again. I've spoken to a few fellas with STCs on their airplanes that required putting forward-facing "ram tubes" on the caps (like the Vagabonds and Clippers had, with their fuselage tanks venting into the reduced pressure zone just ahead of the windshield base), and they don't see any difference with those extra probiscii sticking up off the wing, either.

My "one word answer" would be: "No, it isn't worth the trouble, and as is the case in MOST things like this... if it had any practical reason that would make it justifiable, how come Piper didn't DO IT?" We didn't live in a Price-Waterhouse environment until a little AFTER the last ShortWing (Colt) rolled of the line.