REFLECTOR: Vent Check Valve No-Yes

[Douglas Holub]

Good idea. Ain't the reflector great? Thanks Brian!

Doug
----- Original Message ----- 
From: "Glenn Babcock" <glennbabcock at roadrunner.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Sunday, March 13, 2011 5:40 PM
Subject: Re: REFLECTOR: Vent Check Valve No-Yes


> The check valve goes on the alternate vent inside the cabin.  You put a 
> T-fitting In the vent line and run one side out of the cabin, the other 
> side in the cabin with the check valve.  It's a backup in case the 
> exterior vent is clogged. I have this setup, works great.
>
> Regards,
>
> Glenn
>
>
> On Mar 13, 2011, at 3:59 PM, Scott Derrick <scott at tnstaafl.net> wrote:
>
>> Of course not!  Do you smell fuel in a Cessna, Piper, Beechcraft, etc... 
>> Their fuel vents don't have one way valves.
>>
>> If you smell fuel in the cabin you have a leak!  Nothing to do with that 
>> one way valve.
>>
>> Scott
>> -------- Original Message --------
>> Subject: Re: REFLECTOR: Vent Check Valve No-Yes
>> From: Mike Dawson <medawson250 at yahoo.com>
>> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>> Date: 03/13/2011 01:42 PM
>>
>>> Without the check valve in the vent line don't you get that fuel smell 
>>> permeated in the interior. That is what it is for, let the air in , keep 
>>> the gas out!
>>>
>>> --- On Sun, 3/13/11, Scott Derrick<scott at tnstaafl.net>  wrote:
>>>
>>>> From: Scott Derrick<scott at tnstaafl.net>
>>>> Subject: REFLECTOR: Vent Check Valve No-Yes
>>>> To: "Velocity Aircraft Owners and Builders list"<reflector at tvbf.org>
>>>> Date: Sunday, March 13, 2011, 11:42 AM
>>>> I'm not too sure about the vent check
>>>> valve that has been added to the kit.
>>>>
>>>> The general description of the vent system is to plumb all
>>>> vents, L&R tanks and sump into a block high on the cabin
>>>> side of the fire wall.  A feed line is plumbed into the
>>>> same block that travels down to the bottom of the fuselage
>>>> and is  positioned or set up to apply positive pressure
>>>> to the vent system in flight.  Mime is plumbed to a
>>>> little NACA scoop on the bottom of the fuselage.
>>>>
>>>> At some time after 2000,  a one way valve was added to
>>>> the feed line to only allow air into the system. Why?
>>>> I'm assuming it was to prevent fuel from leaking out of the
>>>> vent system in case of an accident or something?  Or
>>>> was there a different reason?
>>>>
>>>> I bought a valve recently and have yet to add it as I've
>>>> flown the plane for 600 hours with nary a problem with the
>>>> fuel system.
>>>>
>>>> The problem with adding this valve is it prevents pressure
>>>> from escaping the system.  Fuel tanks are vented to
>>>> allow air in and to allow vapor out when the fuel expands
>>>> from heat. We've all filled up an airplane, parked it on the
>>>> ramp, only to discover it puked a puddle of fuel onto the
>>>> ramp as the cool fuel heated up in the sun.
>>>>
>>>> Now that valve won't let that happen, and if your system is
>>>> tight you will be pressuring it as the fuel heats up. Is
>>>> that a problem?  I don't know..  A couple of
>>>> months ago I calibrated my fuel tank sensors, adding fuel
>>>> into each tank in 5 gallon increments until full. I had
>>>> planed on flying immediately after words but something came
>>>> up.  I pushed the plane back into the hanger but the
>>>> sun was shining in on the plane. I was futzing with
>>>> something on my workbench when I heard dripping.  I
>>>> looked arouns and saw a stream of fuel dripping from the
>>>> bottom of the fuselage!   Just like I've seen
>>>> from Bonanzas, Cessnas, etc..  I got all excited and
>>>> looked into the cabin thinking I would find a cabin full of
>>>> fuel, nothing.  I looked under the fuselage and could
>>>> then see it was coming out of the vent  It then
>>>> stopped.  I popped a fuel cap and left it un compressed
>>>> so anymore pressure wouldn't build up while the tanks were
>>>> completely full!  Now if I had that vent in there, the
>>>> pressure would have built up, and up?
>>>>
>>>> How high, I don't know.
>>>>
>>>>
>>>> Scott
>>>>
>>>> --
>>>> Stand porter at the door of thought.
>>>> Mary Baker Eddy
>>>>
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>>>
>>>
>>>
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>>
>> -- 
>> No pessimist ever discovered the secret of the stars or sailed an 
>> uncharted land, or opened a new doorway for the human spirit.
>> Helen Keller
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> _______________________________________________
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