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  #1  
Old 08-01-2017, 09:41 PM
Jake14 Jake14 is offline
 
Join Date: May 2014
Location: Seattle
Posts: 99
Default QB wing vent leak

Just started phase 1 and noticed a drip from the QB Wing left tank vent line whenever the tank's more than half full, ie. when the fuel level is up to the inboard rib vent connection. Checking the forum, looks like the only cause could be a bad vent line connection inside the tank at the inboard tank rib...grrrrrr....

Nobody at Van's to talk to during Oshkosh so nothing left to do but pull the tank, buy $63 worth of hole saw and mandrel at Home Club and open it up.

The nut was fairly tight, but the flare was very large and thin. The nut would not go over the flare without turning it like a screw. so that may have jammed things up somewhat, Also the close-up shows what looks like a crack in the flare..
I guess this is the one fitting in the tank which can't be leak checked easily


Not sure what a good fix would be, there's not much room to cut or flare in such close quarters, but maybe if I removed the fitting from the rib, there would be enough room to pull the entire vent tube out and replace it with a new one.

When Van's support gets back I'll see what they recommend. Since it's a quick-build, maybe they'll just give me a new tank :-)

Last edited by Jake14 : 08-01-2017 at 11:03 PM.
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  #2  
Old 08-02-2017, 05:27 AM
Tom023 Tom023 is offline
 
Join Date: Jul 2011
Location: Cypress, TX
Posts: 180
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Replacing the line would be best, especially since you have the tank off and open. Just for thought, Could another solution be to reconnect and encapsulate the fitting ends in proseal on the outside effectively blocking any leak path? More of a bandaid approach and probably not ideal.
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Last edited by Tom023 : 08-02-2017 at 05:41 AM.
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  #3  
Old 08-02-2017, 05:50 AM
Tom Martin Tom Martin is offline
 
Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,288
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I had a situation like this on my rocket, same symptoms. The EVO wing tank is a bit more difficult to remove and I decided to try something different.
I sourced some proseal that was a bit more"fluid" then we normally use. I disconnected the exterior vent line and added as short, one foot, piece of
aluminum line and fitting.
The next step was to reach into the fuel tank filler hole and slide a piece of plastic tubing over the end of the vent line, it is just outboard the tank filler opening, and secure it with a cable tie.
I then injected some of this proseal into added short line on the inboard vent line, enough to make its way to the offending fitting on the inboard rib of the tank, then capped this end of the line.
Now the important step, and all this has to be done relatively quickly, I used air pressure from my compresser and applied it directly to the vent line. This pressure forces the " liquid" proseal into the leak. After the brief time, seconds rather then minutes, I removed the plug from the inboard vent exit and added pressure to the vent line at the tank filler end to blow out remaining proseal.
I waited a couple of days, put some fuel in, and the problem was solved. 12 years and over a thousand hours later with no issue.
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  #4  
Old 08-02-2017, 03:09 PM
salto salto is offline
 
Join Date: Apr 2015
Location: Wee Waa Australia
Posts: 222
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Well your in there now and can get in there in the future if putting some proseal around flange and doing the nut back up doesn't work.
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  #5  
Old 08-02-2017, 11:06 PM
Jake14 Jake14 is offline
 
Join Date: May 2014
Location: Seattle
Posts: 99
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yep, that was the solution; just slop on the pro-seal and bolt it back on...
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