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  #1  
Old 08-22-2022, 08:42 AM
BruceMe's Avatar
BruceMe BruceMe is offline
 
Join Date: Feb 2005
Location: Shawnee, Kansas
Posts: 849
Default RV3 header tank vent details

I recently purchased an older RV-3 with header tanks. There was some trouble with the vent, which appears to be non-standard. I was wondering if anyone could describe or take a picture of the vent system for the header tank.

They installed a pitot-like ram air vent. I think the issue is that it can't actually drain properly with full tanks and high climb angles, so if the tank is full, it overboard into that tube and causes a partial vacuum. There are no pumps and the vent tube is at the same height as (maybe even below) the carb and causes a back-siphon effect.

https://photos.app.goo.gl/dXaa8q2C2FpJNfRu9

The solution the previous owner did was to put a hole in the cap, which is prone to water fouling [fowling], I wanted to know how the header tank should be vented to work properly without a fuel pump.

Thanks,
-Bruce
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Own RV-3 863WL
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Last edited by BruceMe : 08-22-2022 at 01:37 PM.
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  #2  
Old 08-22-2022, 11:00 AM
Flyjon57 Flyjon57 is offline
 
Join Date: Nov 2016
Location: Lubbock
Posts: 36
Default RV-3 fuel vent

Bruce,

I will need to look at mine when I get home this evening.

As I recall on my restoration there is a vent fitting at the top front of the tank.
And a 90 degree fitting turns down with a length of tube that extends down through the bottom skin.

I will let you know.

Jon
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  #3  
Old 08-22-2022, 11:18 AM
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BruceMe BruceMe is offline
 
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Location: Shawnee, Kansas
Posts: 849
Default Vent

I just got access to the online plans, It's described in the manual section 8 page 9 and DWG 32 is the fuse fuel tank. It shows a vent which is just AN elbow fitting at the front of the tank. There's no tubing attached, it vents to the cabin in so far as I can tell. Let me know if you see otherwise?
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Last edited by BruceMe : 08-22-2022 at 11:22 AM.
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  #4  
Old 08-22-2022, 11:31 AM
Flyjon57 Flyjon57 is offline
 
Join Date: Nov 2016
Location: Lubbock
Posts: 36
Default fuel vent

I am not real keen on having an open fuel vent into the cabin. Overboard would be best.

I will let you know what I have on mine because the upper skin is not attached and the tank is loose.

Jon
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  #5  
Old 08-22-2022, 01:26 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,491
Default

Does the tank vent collect ducks or geese? If it collects one of the endangered species, you'd need to contact a suitable wildlife expert.

Here's the tank drawing from the plans. You can get a full size copy from Van's for a nominal fee.

Dave

Click image for larger version

Name:	Screen Shot 2022-08-22 at 12.21.15 PM.jpg
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  #6  
Old 08-22-2022, 01:36 PM
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BruceMe BruceMe is offline
 
Join Date: Feb 2005
Location: Shawnee, Kansas
Posts: 849
Default

Quote:
Originally Posted by David Paule View Post
Does the tank vent collect ducks or geese? If it collects one of the endangered species, you'd need to contact a suitable wildlife expert.

Here's the tank drawing from the plans. You can get a full size copy from Van's for a nominal fee.

Dave

Attachment 29835
There will be no fowl language!
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  #7  
Old 08-22-2022, 02:50 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
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Default

You can run a line from that AN fitting down to the belly.

Dave
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  #8  
Old 08-23-2022, 03:57 AM
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Lufthans Lufthans is offline
 
Join Date: Dec 2017
Location: Hilversum, The Netherlands
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Default

Quote:
Originally Posted by David Paule View Post
You can run a line from that AN fitting down to the belly.

Dave
And if you plan to do negative-G aerobatics, maybe run that line up and down the tank in loops once or twice before sending it out to the belly...
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  #9  
Old 08-24-2022, 11:15 PM
oaklandaviator oaklandaviator is offline
 
Join Date: Dec 2014
Location: Las Vegas, NV
Posts: 159
Default Vent

Ours runs straight down and out the belly as others have described. It vents fuel overboard with the tail up when totally full of fuel. I only fill it to about an inch below the top and none is lost.
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