Canard Community Forum  

Go Back   Canard Community Forum > Firewall Backward and Forward > Fuel Systems
FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Display Modes
  #1  
Old 12-15-2006, 01:31 PM
Dust's Avatar
Dust Dust is offline
Super Moderator
 
Join Date: Apr 2004
Location: Troy, Michigan
Posts: 7,963
Default Gravity vrs pressure

when people look at our systems - they "think" that just gravity is at work, but the reality of it is that it is a pressurized system.

this pressure is created by turning the fuel vent into the air flow, which then pressurizes the system.

this is what can lead to unforeseen problems on systems that are interconnected. if the pressure decides to affect one tank more than another, one will empty while the other does not.

Some use this pressure to their benefit and require no fuel pump!

So, when designing your fuel system, remember that this can bite you
__________________
Enjoy the build,njut av byggandet, godere il costruire, nyd bygningen, geniesse den Bau, apolafse tin kataskevi, disfrute la construcción, curta a construção, Pidä hauskaa rakentamisen parissa, bouw lekker,uživaj grade?inaslajdaites postroikoi, geniet die bou
dust

maker of wood, fiberglass, foam dust, metal bits and one day a Cozy will pop out and swiftly whisk me from meeting old friends and family to adventures throughout the world
Reply With Quote
  #2  
Old 12-15-2006, 02:24 PM
SteveWrightNZ SteveWrightNZ is offline
builder wannabe
 
Join Date: Jun 2006
Location: Bay of Plenty, New Zealand
Posts: 771
Default

Quote:
Originally Posted by Dust View Post
Some use this pressure to their benefit and require no fuel pump!
this reminds me of the old Citroens, where they pressurized the windscreen washer bottle with the spare tire.. an equally stupid idea in my opinion.

S
__________________
A dolphin breaths through an asshole on the top of its head. (Billy age 8)
http://canardaviationwiki.dmt.net/wi...:SteveWrightNZ
Reply With Quote
  #3  
Old 12-15-2006, 02:30 PM
MarbleTurtle's Avatar
MarbleTurtle MarbleTurtle is offline
Member
 
Join Date: Apr 2004
Location: Dalton, GA.
Posts: 1,344
Default

T-d vents won't do that... also the "pressure" in one tank would need to be enough to hold back the weight of the fuel in the other... in theory.
__________________
Past performance is no guarantee of future results.
Reply With Quote
  #4  
Old 12-15-2006, 02:47 PM
Waiter's Avatar
Waiter Waiter is offline
LongEZ-RG
 
Join Date: Dec 2004
Location: Northwestern Ohio
Posts: 1,096
Default

I had an old VW bettle that did that (spare tire as pressure source for the washer fluid)

Anyway, there are many considerations when designing a fuel system. Vent location and tank interconnects are just two factors.

My recommendation: Unless you know what your doing, stick to the plans.

"Modified Fuel Systems" ranks high on the list as contributing factors in amateur built aircraft.

Waiter
Reply With Quote
  #5  
Old 12-15-2006, 03:27 PM
SteveWrightNZ SteveWrightNZ is offline
builder wannabe
 
Join Date: Jun 2006
Location: Bay of Plenty, New Zealand
Posts: 771
Default

Quote:
Originally Posted by Waiter View Post
I had an old VW bettle that did that (spare tire as pressure source for the washer fluid)
haha! did it catch you out ?

S
__________________
A dolphin breaths through an asshole on the top of its head. (Billy age 8)
http://canardaviationwiki.dmt.net/wi...:SteveWrightNZ
Reply With Quote
  #6  
Old 12-16-2006, 08:06 AM
Riseguy Riseguy is offline
Donald James Rise Jr
 
Join Date: Apr 2004
Location: Greenwood,IN
Posts: 246
Default

I have used the vent pressure on my Long-EZ since day one. The fuel selector is on inside of firewall below sump. It is a, Left, Right, Off. With a push pull lever up on left armrest. At no time is the Carb bowel higher than sump blister. Even when grazing. It has never stuttered.
I do not want anyone else to do this on their plane.
I love the responses of those who have no tried it with the hands covering the ears, mouth, eyes. going. NO,NO,NO. Hay it worked on, J3,High wing Cessna's, Luscombe's, etc, etc.
Merry Christmas, and Happy New Year. to all.
Reply With Quote
  #7  
Old 12-17-2006, 07:50 PM
Dust's Avatar
Dust Dust is offline
Super Moderator
 
Join Date: Apr 2004
Location: Troy, Michigan
Posts: 7,963
Default

Riseguy-i see you noticed that i mentioned your system.

I ponderred your set up for a long time and it finally made me realize how a high wing 172 with fuel selector set on both and flying wings level for hours could burn from just one tank.
__________________
Enjoy the build,njut av byggandet, godere il costruire, nyd bygningen, geniesse den Bau, apolafse tin kataskevi, disfrute la construcción, curta a construção, Pidä hauskaa rakentamisen parissa, bouw lekker,uživaj grade?inaslajdaites postroikoi, geniet die bou
dust

maker of wood, fiberglass, foam dust, metal bits and one day a Cozy will pop out and swiftly whisk me from meeting old friends and family to adventures throughout the world
Reply With Quote
  #8  
Old 12-18-2006, 07:44 AM
Riseguy Riseguy is offline
Donald James Rise Jr
 
Join Date: Apr 2004
Location: Greenwood,IN
Posts: 246
Default

Dust, you are right on the cessna fuel flow on both. My 172 and friends 182 do drain the left tank first on both. My Long only has, left, right, and off. for that reason. Piper high wings with two wing tanks use the left, right, and off valve I used on my long. I
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 10:40 PM.


Powered by vBulletin® Version 3.6.7
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.