REFLECTOR: FUEL FEED

[KeithHallsten]

Chuck,
I don't have the reason from the original source, but a forward vent line would be difficult to run neatly so that it had a good, constant slope from the tank to the top of the firewall.  It would probably have to be run across the inside of the back window to have enough slope to positively drain towards the tank when the plane is in climb attitude.  Not too good.  If the line can't be properly routed, it would be blocked by the fuel "trapped" in the vent, so no advantage would be realized.

There are airplanes without forward vents that feed fuel from both strakes without difficulty.  This tends to suggest that a forward vent is not necessary.

All of this tends to emphasize how important the routing of fuel and vent lines can be.  The portion of the vent system which could be below the fuel surface elevation at any likely aircraft attitude needs to have enough slope so that it cannot act as a plumbing trap!

Keith
  
  ----- Original Message ----- 
  From: Chuck Jensen 
  To: Velocity Aircraft Owners and Builders list 
  Sent: Monday, February 21, 2005 8:30 AM
  Subject: RE: REFLECTOR: FUEL FEED


  John,

  The logic of your logic seems good, but the question I have is why the recommended location of the vent is at the rear of the tank (true?).  This vent area will always be covered up during climb with full tanks, potentially causing some, if only temporary, venting issues.  It would seem more appropriate to put the vent connection near the front of the tank, so it will be unported during climbs.  Later, during descent to land, the tank fuel level is lower and the AOA is near level, so a vent connection at the front of the tank is likely to stay unported.  With all that said, there must be a reason why the recommendation is to put it at the back of the tank.  Anyone know?

  Chuck


  -----Original Message-----
  From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On Behalf Of John Dibble
  Sent: Monday, February 21, 2005 11:07 AM
  To: Velocity Aircraft Owners and Builders list
  Subject: Re: REFLECTOR: FUEL FEED


  Jim, 
  I like your analysis of the vents getting flooded during a climb.  I think this explains why I only get uneven flow at high altitudes.  Because, I only fly high for long trips and I only have my tanks full for long trips.  I think my forward facing overflow vents provide enough pressure to flush out the vents once the fuel level goes down. 
  John 

  Jim Sower wrote: 

        
    Highest point in the tank varies considerably with airplane attitude.  Most vents are to aft inboard corner of strake.  In a climb, a point about a little aft of the forward most point of the strakes will be several inches higher than the aft corner.  That means several (3"?) of fuel in the vent line.  A LOT of chatter recently on the Cozy list.  Consensus was:  if you want acceptable venting at full fuel you need two separate vents for each tank - one at aft inboard corner, another a couple of feet further forward.  One or the other will be


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