Wing Tank Cap, Pressure Tube Dimensions

[Howard Wilson]

What are the dimensions of the pressure tube on the 6 gallon wing tank gas cap? ID, OD, height above cap, length of horizontal extension from 90' bend. Is it 90'? Is there some kind of screening or filter material in the tube, or is it straight thru? This is on a '39 BL model if it makes a difference. Thanks. Howard

[Robert Lees]

Howard:

Photos of wing fuel caps at

http://www.taylorcraft.org.uk/fuel-cap-wing1.jpg

http://www.taylorcraft.org.uk/fuel-cap-wing2.jpg

The links show two views of two wing caps I have. Ignore the colours of the caps, one I have painted in white primer, the other is red as-found.

The dimensions are shown on one of the photos. Neither are quite at 90 degrees, and one is 1/2" above the flat top of the cap, the other is 3/4".

Both caps have "6 GAL" and "GAS" on the wing handles, so they are quite properly the Taylorcraft caps. My guess is that the differences were related to who made tham and/or what year they are from.

Whatever, they both work just fine on my 46 and my 45 BC12D, so take your pick.

Hope this helps.

[Ron Greene]

Wing Tank Cap

Here is the factory drawing, hope this attachment works. If this works I will send another drawing with the vent tube on it.
Ron Greene

[Ron Greene]

WING TANK CAP

Due to file size limitations, the drawing isn't very readable. Will e-mail full size drawing directly to anyone, just ask. The drawing for the vent tube shows copper tube 3/16 OD.
Ron Greene

[Robert Lees]

That's interesting...how does the vent (with the opening across an airflow (and a low-pressure airflow at that)) introduce high pressure into the tank? Or is that not the intention?

[Dick Huish]

The vent tube is shaped like that so that you can't inhale bugs whil in flight.

[Howard Wilson]

wing tank cap, pressure tube dimensions

Wow! Rob, Rons, and Dick, thanks for the quick response and obvious time and effort spent checking this. I've only ever seen in the field tubes like Rob is showing. I saw a stand off picture of the hooked ones somewhere but couldn't figure out what the heck their function was. Thought it was some way to pick the plane up to put floats on it or something. So theoretically speaking; if there is no ram air function and the end of the tube is sticking down into the low pressure area of the airflow there could be a negative pressure being developed in the tank. But not enough to create a vacuum and stop the flow? I guess the Talorcraft drawing would have to be the final word..........

Ron could you send a copy to me? I'll be happy to reimburse your expenses. Howard Wilson box 102 New Market, MD 21774

Might have to go over to Cap'n Jon's site and look at some pictures. Thanks again guys

[dennispip]

The air vent tube for the fuel system on my F21-B tank does not exit from the cap, but from a separate site above the left tank only. This model has two 21 gallon wing tanks only with no other tanks and both drain simultaneously through one on/off valve. The vent sticks up about 5 inches and curves forward with the opening facing forward. This would allow a bug or even some rain water in, but that is the way it is set up. I assume this has not presented much of a problem, but I did wonder about it. The tanks are interconnected, so only one vent is needed. This set up would seemingly pressurize the tanks to some extent during flight. I am reading about leaking fuel tanks in the F21s and maybe that is a contributing factor??? A previous owner did have to repair a leak in one of my tanks.

Perhaps the set up described in the earlier models pictured above still permits an air pressure higher than what is in the tanks and that permits the fuel system to function well in the models that use it. Don't those tanks then refill the main fuel tank and not directly to the carb, so maybe it is not as critical. It seems to have worked for a long time without any difficulty.

[stormman]

Gas cap

The Harer stc has drawings for pressure gas caps that u can make out of boats outboard motor fuel tank gas caps.

[Ron Greene]

GAS CAP

I can e-mail these drawings to anyone that would like them. Each drawing is about 1 meg in size. Great quality. Let me know.
Ron Greene

[TimHicks]

Vent tube direction

One day I was planning to fly formation to Dauphin Island, Alabama from our grass strip in Robert, Louisiana. This was my first flight with the eager right seat. He was very interested in learing as much as possible about the airplane (BC-12D). So I tasked him with checking the fuel level in the wing tank. We'd need all of it.
About an hour into the flight and in formation, I opened the fuel valve and waited for the main tank indicator to rise. I always get nervous at how slowly it seems to react. After watching it sink for another 1/2 hour, I called my wingman and told him I needed to divert to Slidell to check this out. I did a straight in approach to Slidell and landed with 2 gallons of gas in the main tank. The wing tank was full, but the cap was on with the vent facing backward. My right seat apologized effusively saying that he thought it would be more aerodynamic that way. I told him that these things are totally my responsibility and that he shouldn't concern himself about this. So we took on more fuel in Slidel and continued along for a nice lunch on Dauphin Island. My right seat later went on to become a millionaire in the dot com boom, bought a nice Maule, and became a pilot (in that order)

[TimHicks]

continued

I forgot to mention my point. Which is that I'm sure, for my airplane, that my wing tanks won't flow in flight with the vents facing backward.