Fuel vent alignment

[Maverick]

I started this message after reading some responses in a builder's log. I have four fuel caps. All of them have the vent pointing in an angle to the relative wind. In some of the other message replies there were mentioned a twisting of these vents until they are in the right direction. My question is what is the right direction. I've been flying for 60 hours and have had absolutely no problems with fuel flow so I'm assuming the fuel vents are doing a satisfactory job but, I have also wondered why the vents were not made to point directly into the relative wind rather than at an angle. I wonder if they are at an angle so as not to over-pressurize the tanks. Anybody know what the scoop is on this?
Fred

[jrevens]

Kitfox could answer this definitively, but I’ll give my opinion. The vent tubes should be pointed directly forward, perpendicular to the leading edge of the wing. There is no way they can “over-pressurize” the tanks. As far as the original misalignment goes, I believe there are probably very minor variances in how the filler neck gets installed when the tank is manufactured, and possibly also in the installation of the vent tubes on the caps. It really is extremely easy to “adjust” them.

[Maverick]

Thanks, John.

[taff]

I am trying to understand how all 4 fuel caps are pointing in the wrong direction.
Could it be that the receiver was laminated in the fuel tank incorrectly? We will never know!

You need to apply pressure, you don't need to have a syphoning effect of fuel or air.
Fuel delivery is vital.

[Delta Whisky]

How close to straight forward are they?

[Maverick]

I'm guessing that they deviate 20 degrees at most to the right when looking back from the leading edge. And I have no fuel flow issues so I don't know how necessary it is to twist them. There is no siphoning because of it. You would have to have a negative pressure to pull fuel out of the tank and that would require the tube pointing backwards rather than forward. Even with a small angle the relative wind is from a forward direction. And, since these are just vents, plus that I have four of them all the same, I have to wonder, as they say, if there isn't more to the story? Two of them came from a 1994 kit. I bought new fuel tanks from John & Debra in 2018 and so two caps came with these new tanks and the caps are the same as those from 1994. I'll get a pic next time I go out to the airport.

[jrevens]

Maverick,

Everything I have came from my 2009 kit, and they were pretty much just as you describe yours, until I adjusted them. Many other (maybe most) builders have found the very same thing... as far as I know, yours are not unique by any means. I think that there is a possibility that they are manufactured that way, as I've said before, because there can be small differences in the angles of everything when put together, and they are very easily adjusted to the correct position. While I'm no expert, every one that I have seen has been misaligned in the same direction (again, possibly on purpose) so that they need to be twisted in the direction that tightens the cap, making it simple to install the cap and bend the tube to exactly the right angle. It may not create suction, but it certainly may decrease the amount of air pressure when misaligned. The maximum amount that these tubes can produce is good. You're smart to take advantage of that. One other personal thought is that the tubes just don't "look" right (because they aren't "right") when they're not pointing directly forward, at least to me. You should put one on a tank, grab it as close to the base as you can, and slowly twist it to the correct position. when they are welded or silver-soldered to the caps the SS is annealed in that area. I don't see any visible distortion, "twisting" or surface cracks at all on either of mine. That's about all I can say.

[taff]

Syphoning effect could happen if the tube is a 90 degree angle to the oncoming wind.
Like a syphon feed spray gun, wind passes over the top of the tube that's in the cup and draws the paint up and out.
Of course, that is if the wind is above 16 lbs per square inch (PSI) and the spray up is vented

Your tube is slightly off foreword. Shouldn't be an issue even when your crabbing to get down to final.