Fuel Cap alignment with slipstream.

cfiatzph · Post by **cfiatzph** » Sun Dec 17, 2006 10:39 pm

Have some new tanks sitting her with new necks that need to be screwed on. Question is this though The cap when it closes is about 30 degrees off of center (slip stream) and there is just no way to bolt it so its not. Anybody have any experience with this? How are yours?

Thanks

Sun Dec 17, 2006 11:00 pm

I have one that lines up and one that doesn't. Doesn't seem to matter except everyone including myself thinks the cap is not secured.

I don't know what it would take to correct your situation but i'd spen some effort to do it. I plan to if I ever remove my tank or the filler neck.

Post by **GAHorn** » Sun Dec 17, 2006 11:52 pm

The filler neck is "screwed" (threaded) into the tank flange, and then sealed with pro-seal type sealant. In order to align the cap tabs with the slipstream, you will have to tighten or loosen the filler neck and reseal the threads. (The best way to seal the threads is to paint them with sealant before threading them into the tank flanges. If yours are already sealed then the problem will be to re-do the job. Some crazy people even went so far as to "stake" the necks into the flanges.

This will require some effort to move them, but is still possible.)
Be careful doing this if you have already had fuel in the tanks. Steel tools (like pipe wrenches/pliers/etc.) can cause sparks.

hilltop170 · Post by **hilltop170** » Mon Dec 18, 2006 2:44 am

My left cap lines up properly, the right cap angles about 30Â° to the right (clockwise) looking down on the wing. The caps are the new Cessna red metal caps with the vertical tabs and a vent.

Post by **GAHorn** » Mon Dec 18, 2006 2:55 am

Richard, if you can remove the moat, and get a "strap-wrench" onto the filler neck, you might be able to unscrew it, clean the threads and recoat them with pro-seal, then thread it back where you want it, and let the pro-seal set. If you get it to that point and you don't feel the neck is sufficiently tight into the flange, you'll have to thread it even further (sounds like about 150-degrees additional) before your cap will be aligned.

ron74887 · Post by **ron74887** » Mon Dec 18, 2006 6:51 pm

GUYS,

what in the hell are you talking about.

put your gas cap on tight and undo the screws and rotate the cap with the filler neck to the correct alignment and put the screws back in. I think I undid the inside screws and turned the cap but if the caps have been removed to change the gaskets you may have to undo the outside ring of screws to rotate the entire cap system on the tank. don't tighten anything with a wrench or strap wrench. They were right at some point by Cessna and it shouldn't require anything esle unless someone else tried to realign it with a wrench!! Ron

Post by **GAHorn** » Mon Dec 18, 2006 7:24 pm

Ron, the screws in the mount flange will only accomodate 45-degree angle adjustments. If original caps have been replaced with newer plastic-tab caps (and virtually all of the right-side have been, and many of both sides as well), then the tabs may not align with the slipstream in tanks that have undergone repairs. The only way to get some of those to align will be to adjust the filler necks by screwing them in or out.

cfiatzph · Post by **cfiatzph** » Tue Dec 19, 2006 12:03 am

Ok question. Big time feeling embarassed. The filler necks on these tanks are well say not maybe Cessna filler necks. Where do I get them?

Thanks

ron74887 · Post by **ron74887** » Tue Dec 19, 2006 1:09 am

George and guys, the filler neck is attached to the ring inside the tank and is adjustable by six screws if I aint thinking wrong which is 36 degrees per screw hole. the 8 screw flange is just a seperator between the tank and cover, which he will not remove or move. I know the parts manual shows it screwing into the top flange but that is not right

. Hold on to the chain and undo the 6 screws and let is rotate just as if you were changing the inside gasket. Right ? I may be wrong but after I changed my gaskets I had to realign one gas cap. Old Gar had a tank outside and I had to look and see where that 2nd gasket went inside the tank which slides around the filler neck and on top of the T looking deal in the tank--there are 2 gaskets with 6 holes, which I had to learn the hard way.

The 8 hole flange 45 degrees will not adjust anything with the cap. Keep up the good work it keeps us all on our toes.

Ron

ron74887 · Post by **ron74887** » Tue Dec 19, 2006 2:16 am

I told you I'd be wrong it's 60 degrees per hole and I used a calculator.

it kinda work like my typing

. if it's off 30 rotate it two holes and the opposite end should line up. that would be the 150 degrees to get it straight.

I'll get it right sooner or later.

duh Ron

hilltop170 · Post by **hilltop170** » Tue Dec 19, 2006 3:55 am

The tanks don't leak and the cap being off 30Â° doesn't make the plane pull to the right too bad so I think I'll just leave it like it is. With all this advanced geometry being discussed, I'm totally confused. I'm doing good to remember how to do a 180Â° turn when the weather gets bad, or was it a 360Â°?

Post by **GAHorn** » Tue Dec 19, 2006 6:44 am

Ron,... help me out here. If the inside circle of screws is six holes (60-degrees apart), and the outside circle of holes on the same flange is 8 holes (45 degrees apart)... how are you going to rotate it or or two holes/60 or 120 degrees to re-align the cap with the slipstream...and still get the 8 holes (which are at 45-degrees) in the flange to line up with the tank cover?

hilltop170 · Post by **hilltop170** » Tue Dec 19, 2006 8:43 am

See what I mean?

ron74887 · Post by **ron74887** » Tue Dec 19, 2006 2:42 pm

I went out this morning and looked at the plane. I told you I'd be wrong

You don't rotate the outside ring at all. The inside ring is 60 degrees and that's all you rotate so no 30 degrees. SORRY for all the math screw up. I don't remember but I don't think mine was off 60 degrees either and the only way is if the flange inside the tank which is attached and rotates with the filler neck has 30 degree spacing which would be 12 holes. I'm not taking mine off again, but if old GAR would go look inside his tank he could tell us. Also I installed the original style metal caps vented sold by Aircraft Spruce which the AI accepted without any problems -- not the crappy plastic ones any more. Ron

MeeksDigital · Post by **MeeksDigital** » Thu Dec 21, 2006 4:58 am

hilltop170 wrote:My left cap lines up properly, the right cap angles about 30Â° to the right (clockwise) looking down on the wing. The caps are the new Cessna red metal caps with the vertical tabs and a vent.

Mine too! Except the left one is an original C170 cap, and the right one is the red metal cap with the vertical tab.