REFLECTOR: Fwd: Re: Vent

[Richard J. Gentil]

John,

The first thing that went through my mind when I saw the pictures in this email was to contact the factory on this one. 

I do not believe any of this is standard and I would send them detailed pictures and go over it with them. 

Richard

Sent from my iPhone 4

On Jan 31, 2011, at 12:19 PM, <aminetech at bluefrog.com> wrote:

> Just realized this didn't get sent to everyone.
>  
> John
> OK.  I need to explain this better.  I have 2 lines (one feed, one vent) from each tank connected to the sump at the bottom and middle positions.  In addition I have overflow/vent lines in the wheel wells as shown in the attached pic.  Regarding my "manifold", the line on the copilot side goes to the top of the copilot tank.  The line on the pilot side goes to the top position on the pilot side of the sump.  Today I attached a plastic tubing to the copilot overflow vent, blew into it, and air came out the other vent on the pilot side wing, so the 2 tanks are vented to each other (through the sump).  As I stated before, I think the problem is that, in flight air flows in one overflow vent and out the other and that results in gas vapors getting in the cabin.  If I block the copilot overflow vent, I will still have 2 vents for each tank.  The copilot tank will have one vent from the middle position on the copilot side of the sump and one from the manifold.  The pilot tank will have the overflow vent and one from the middle position of the pilot side of the sump.  How's that sound?
> 
> --- johnt at comp-sol.com wrote:
> 
> From: John Tvedte <johnt at comp-sol.com>
> To: "aminetech at bluefrog.com" <aminetech at bluefrog.com>
> Subject: Vent
> Date: Mon, 31 Jan 2011 09:36:37 -0600
> 
> John,
> 
>  
> 
> You need to have two sources of venting at all time – for each tank + header tank.  The manifold keeps all vents at the same pressure.
> 
>  
> 
> From reading your last post to AL –
> 
>  
> 
> “Those are great comments.  With my 220 hp Franklin/IVO I can easily get 2000 fpm also.  Maybe the builder was addressing the same issues by using overflow lines.  I've noticed when filling the tanks completely full, if the pavement is not level, fuel comes out one of the overflow lines if either the nose is low, or the wings are not level.  If I have the wings level and the nose high I never see fuel coming out these vents.  Therefore I think that a high AOA should not be a problem.  I think my problem is that, in flight, the pressures at the 2 overflow vents are never perfectly in balance and that results in an air flow in one vent and out the other one.  Of course fuel vapor will be in that air and get into the cabin via the gear opening.  Maybe blocking one vent would fix this issue, assuming one vent is adequate.  I'll get some more pics today so you experts can get a better look at this unusual setup.”
> 
>  
> 
> The picture Andrew posted of his system – is very clean.   It’s still not what the factory does with the higher HP models.  What Al posted – is correct – I’ve seen it at the factory.
> 
>  
> 
> It looks like you may not have tank vents installed  - it appears that your tanks feed into the sump/header tank – and then on either side you have a line (your nomenclature is ‘overflow vents’).
> 
>  
> 
> Today, the main tanks would have the gravity feed for fuel and in addition a higher mounted vent line.  The size of the lines has also been changed  - to larger lines.
> 
>  
> 
> I’d like to see a picture of your system from the same basic angle as Andrew’s.
> 
>  
> 
> I would strongly suggest you email your pictures to Scott Swing -  and call him to discuss. scotts at velocityaircraft.com
> 
> <vent system 05.jpg>
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