Author Topic: Fuel vent  (Read 5648 times)

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Offline wildbird

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Fuel vent
« on: September 09, 2010, 10:09:49 AM »
I had a strange event happen  yesterday. My Long-EZ was sitting parked nose down in the hanger with about 40 gallons of fuel in the left tank and 30 in the right. It was hot and getting hotter into the low 90s. All of a sudden I heard a gurgling sound and fuel shot out of the left vent and shot all the way to the front and hit my instrument panel and all over my interior. As soon as it started it stopped. My guess is with that much fuel in the tank and the nose down that the vent line must be under fuel and the pressure built up and shot the fuel all over the place. I've seen them drip a little but not shoot out like that. I wonder if the line was partially clogged with a mud wasp or something and it gave way under pressure and shot the fuel out. Maybe I should drill a tiny vent hole in the cap?

Bill N227EZ

Offline Rodney

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Re: Fuel vent
« Reply #1 on: September 09, 2010, 04:16:32 PM »
Mine does the same thing.  I got a nice blue streak in my paint job when it happened over a long hot weekend.  I try not to park with more than 10 on a side. 20 total.  Going to Oshkosh this year was challenging because fueling full for some of the longer legs the last thing I would do is put the caps.  Make sure you don't forget because it could ruin your day.  If you're clever you can add another vent to port the tank when your plane is parked nose down. 

Rodney
long ez 0-320 p51 scoop based at PAE

Offline Bill James

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Re: Fuel vent
« Reply #2 on: September 09, 2010, 08:02:27 PM »
For what its worth, a description of the left strake vent line, both are the same. It goes per VariEze plans starting at the strake high point about 5 inches out from the longeron, about midway between the headrest and the aft canopy corner. It goes under the longeron and up inside the near wall of the passenger head space. It goes up and over and down inside the headspace and down inside the fuselage wall along the front of the main spar, straight down and exits just in front of the right main gear strut, and curves out forward about two inches, about one inch from the surface. One piece of tubing per side. Benefits are that the vents don't pee on anythiing, and are in that area in front of the strut where the drag is hopefully insignificant.
Cheers y'all-
Bill James, Fort Worth VariEze N95BJ
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There was supposed to be anhedral?
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Offline GlennBob

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Re: Fuel vent
« Reply #3 on: September 09, 2010, 10:35:38 PM »
Now William, . . .that was a beautiful description of a wild goose chase ! !   Only this time, . .I think the goose got away ! !   Maybe we could get some GPS coordinates to locate the change in direction of the vent lines. (Just ribbin' ya buddy! !)  That's first, . .second, . .doesn't the gear leg exit the fuselage about a foot below the strake ?  If so, . .how could this be an insignificant drag area ?   I've heard stories of the vent line peeing on the passenger seat when parked, . .so I moved mine to the outboard area  about even with the GIB's ears. (On the side of the area directly behind the canopy).  My concern is that I've also heard about lack of vent pressure and engine ceasing as a result.  (That's not a very comforting sound).  I think that venting below the strake is a great idea, but I'm not sure about the path getting there and also the exact (gps) location of the point of penentration.   Venting below sounds like a great idea, so that peeing is not a problem. My wife had the cats in the car and on a hot day, . .it's intoxicating ! ! - side's that, . . I don't like it ! !   Come to think of it (venting that is )  Cessna has it's vents below the wing near the strut attach point too.  Did they get that from you ?   ;D
N600EZ  O-320-E2A,  Hertzler prop, Trio AP, Narco HSI, Custom headers, Oil heat.

Offline Juan Rivera

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Re: Fuel vent
« Reply #4 on: September 10, 2010, 01:48:12 PM »
I think their was a CP plans change that added a second vent line to each tank, so that each tank had a forward and aft vent.  I have the two vents per side and usually have no problem with fuel coming out the vents.

Offline Bill James

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Re: Fuel vent
« Reply #5 on: September 10, 2010, 10:30:53 PM »
At - -     http://v2.ez.org/feature/F0502-1/F0502-1.htm     - -the 8th image down, there is a picture of the rear cockpit with the fuel vent line going down in front of the spar in the fuselage corner. It goes down and exits an inch in front of the gear strut. This is very similar to many VariEze vent installations, except installed a little further forward.

Sorry, no coordinates  :)
Bill James, Fort Worth VariEze N95BJ
Downdraft Plenums, QuickCowls
There was supposed to be anhedral?
ATP, Society of Flight Test Engineers

Offline wildbird

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Re: Fuel vent
« Reply #6 on: September 13, 2010, 07:13:13 PM »
This is wildbird again just wanted to say thanks for the input. It also seems to me I could just vent the cap with a very small drill hole if this becomes a problem. I was told by a fellow EZ builder  that he used the caps that were called out for in the plans and it has about a .040 drill hole in the cap and he seems not to have any problem.

Offline GlennBob

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Re: Fuel vent
« Reply #7 on: September 14, 2010, 10:43:47 PM »
I'd be afraid of the " venturi "  effect of the low pressure whizzin' over the hole creating a vacuum and sucking fuel out of the tank.  The other issue . .though maybe minor would be the possibility of water getting in.  You don't want to go there ! !   GM
N600EZ  O-320-E2A,  Hertzler prop, Trio AP, Narco HSI, Custom headers, Oil heat.

Offline A. Bruce Hughes

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Re: Fuel vent
« Reply #8 on: October 02, 2010, 07:55:06 PM »
I think a hole in the cap would be a VERY bad idea; it would suck gas out.  :'(

I though everyone had 2 vent lines for each tank.  One is at the high point
when the nose is down, the other is at the high point when the aircraft is
horizontal.  Was in the CPs.

Bruce Hughes   :)