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fuel vents

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dlm46007(at)cox.net
Guest

Posted: Tue Jan 29, 2008 2:35 am Post subject: fuel vents

Are the fuel caps  vented? Looks like the fuel vents below the wing intersection fairing could be  impact iced. Just trying to make sure the fuel always  flows.

    [quote][b]

Tim Olson

Joined: 25 Jan 2007
Posts: 2879

Posted: Tue Jan 29, 2008 4:20 am Post subject: fuel vents

No.  Vic suggested to me once installing mini rudder fairings in front

of those lines to keep them clear, because yes indeed that's a place

where if ice formed you could be in a bad situation.  I haven't stuck

anything on there yet, but I haven't been flying around in ice

either, luckily.  You're right though, you may want to find a way to

deal with that area.



Tim Olson - RV-10 N104CD - Flying



David McNeill wrote:

 	  Quote: 	
		   Are the fuel caps vented? Looks like the fuel vents below the wing 

 intersection fairing could be impact iced. Just trying to make sure the 

 fuel always flows.

dlm46007(at)cox.net
Guest

Posted: Tue Jan 29, 2008 4:48 am Post subject: fuel vents

I think you want those vents pressurized with ram air to prevent fuel

flowing out during banked flight. I was thinking of some alternate vent

source. Cessna had a problem in the past with clogged vents which cutoff the

fuel flow and caused some fatal accidents; in some cases just caused

accidents by collapsing the internal tank. 



--

Tim Olson

Joined: 25 Jan 2007
Posts: 2879

Posted: Tue Jan 29, 2008 5:10 am Post subject: fuel vents

Agreed, at least that's what I thought, too.  You certainly

wouldn't want any ventury effect on them.  I can't remember

if Vic had ice on his, or he put the fairings on as a preemptive

measure, but he's been flying them for a long time and not

seen issues with fuel leaking.  Although, he also has tip

tanks and I don't know where the venting is done when you

add that into the equation....if they vent the mains,

and the tips, or what.  It wouldn't take much of a vent

to solve the problem....I wonder if a one-way valve with

almost zero opening pressure, set to open IN, would

be a way to prevent a tank vacuum.  It could be

mounted in the wing root fairing.  Might not be a good

idea....just thinking aloud.  That way though, if there

were a vacuum, it would suck air from the wing root, rather

than collapse a tank.  Also, the valve would stay closed with

RAM air in the vent from the outside.



Also, while the tank Orings are good, I do get fuel leakage

out of the caps on climbout with real full tanks.  So perhaps

it isn't a worry anyway. I don't think the caps are vented

at all, but they may not be totally airtight, which might be

a good thing in this case.



Tim Olson - RV-10 N104CD - Flying

do not archive

David McNeill wrote:

[quote] 

 

 I think you want those vents pressurized with ram air to prevent fuel

 flowing out during banked flight. I was thinking of some alternate vent

 source. Cessna had a problem in the past with clogged vents which cutoff the

 fuel flow and caused some fatal accidents; in some cases just caused

 accidents by collapsing the internal tank. 

 

 --

jesse(at)saintaviation.co
Guest

Posted: Tue Jan 29, 2008 6:29 am Post subject: fuel vents

N256H has been in inadvertent ice once or twice, enough to block the pitot and have a chunk frozen onto the wing tiedown ring, a little build-up on the leading edge (no noticeable change in flight characteristics) and a partially blocked windscreen, but has never had an issue with the vent.  I don't know how much pressure it created, but in coordinated banked flight the engine driven pump shouldn't need too much help.

do not archive



 Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com (jesse(at)saintaviation.com)

Cell: 352-427-0285

Fax: 815-377-3694



 



On Jan 29, 2008, at 5:16 AM, David McNeill wrote:

 	  Quote: 	
		    Are the fuel caps vented? Looks like the fuel vents below the wing intersection fairing could be impact iced. Just trying to make sure the fuel always flows.

  	  Quote: 	
		  

href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List

href="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/contribution



	


	


 [quote][b]

zackrv8

Joined: 14 Jan 2006
Posts: 133

Posted: Tue Jan 29, 2008 6:37 am Post subject: Re: fuel vents

Also, while the tank Orings are good, I do get fuel leakage

out of the caps on climbout with real full tanks. 

Tim Olson - RV-10 N104CD - Flying

do not archive



Tim,



  That shouldn't happen.  As you may already know, the fuel caps can be adjusted.  It's a little tricky, but the O ring can be tightened to a happy compromise between lifting the lever and no fuel leakage.



  After refueling, I let the drips from the fuel nozzle onto the O ring to lubricate it, especially in the winter.  Makes it much easier to install after that.



Zack

_________________
RV8 #80125
RV10 # 40512

Tim Olson

Joined: 25 Jan 2007
Posts: 2879

Posted: Tue Jan 29, 2008 7:06 am Post subject: fuel vents

It's not an issue with the pump being not strong enough, and needing

the pressurization on the vent.  It's the issue that if you pump

fuel out of a sealed vessel, you'll suddenly end up with a vacuum

and if you keep pumping the fuel out, you can collapse the tank, or

prevent fuel from flowing because of the vacuum.  That's the

big safety issue.



Tim Olson - RV-10 N104CD - Flying

do not archive

Jesse Saint wrote:

 	  Quote: 	
		   N256H has been in inadvertent ice once or twice, enough to block the 

 pitot and have a chunk frozen onto the wing tiedown ring, a little 

 build-up on the leading edge (no noticeable change in flight 

 characteristics) and a partially blocked windscreen, but has never had 

 an issue with the vent.  I don't know how much pressure it created, but 

 in coordinated banked flight the engine driven pump shouldn't need too 

 much help.

 

 do not archive

 

 Jesse Saint

 Saint Aviation, Inc.

 jesse(at)saintaviation.com <mailto:jesse(at)saintaviation.com>

 Cell: 352-427-0285

 Fax: 815-377-3694

 

 On Jan 29, 2008, at 5:16 AM, David McNeill wrote:

 

> Are the fuel caps vented? Looks like the fuel vents below the wing 

> intersection fairing could be impact iced. Just trying to make sure 

> the fuel always flows.

> *

> href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List

> href="http://forums.matronics.com">http://forums.matronics.com

> href="http://www.matronics.com/contribution">http://www.matronics.com/contribution

>

Tim Olson

Joined: 25 Jan 2007
Posts: 2879

Posted: Tue Jan 29, 2008 7:07 am Post subject: fuel vents

Yeah, it's not much fuel, but a little.  My caps are darn tight.

It takes a lot of wiggling and work to get them out, and I

have to pop the lever, which is also very stiff and let the

cap relax a minute before pulling them out.  The Orings are also

not super elastic....but rather stiff.  So it makes for a pretty

hard to get off gas cap.  I never tried lubricating it with

fuel for reinsertion....insertion isn't usually the issue, but

removal can be tough.  I doubt I'm losing more than a fuel-tester

full on a flight with real full tanks...but I do know that it's

not so sealed tight that it will keep air out.



Tim Olson - RV-10 N104CD - Flying

do not archive

zackrv8 wrote:

 	  Quote: 	
		   

 

 Also, while the tank Orings are good, I do get fuel leakage out of

 the caps on climbout with real full tanks. Tim Olson - RV-10 N104CD -

 Flying do not archive

 

 Tim,

 

 That shouldn't happen.  As you may already know, the fuel caps can be

 adjusted.  It's a little tricky, but the O ring can be tightened to a

 happy compromise between lifting the lever and no fuel leakage.

 

 After refueling, I let the drips from the fuel nozzle onto the O ring

 to lubricate it, especially in the winter.  Makes it much easier to

 install after that.

 

 Zack

 

 -------- RV8 #80125 RV10 # 40512

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=161058#161058

jesse(at)saintaviation.co
Guest

Posted: Tue Jan 29, 2008 7:37 am Post subject: fuel vents

We have seen this issue, but when you pull the lever up, if you push  

straight down on the lever, it will release the pressure on the o-ring  

and come right out.  Have you tried this?



do not archive



Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com

Cell: 352-427-0285

Fax: 815-377-3694



On Jan 29, 2008, at 10:01 AM, Tim Olson wrote:



 	  Quote: 	
		   



 Yeah, it's not much fuel, but a little.  My caps are darn tight.

 It takes a lot of wiggling and work to get them out, and I

 have to pop the lever, which is also very stiff and let the

 cap relax a minute before pulling them out.  The Orings are also

 not super elastic....but rather stiff.  So it makes for a pretty

 hard to get off gas cap.  I never tried lubricating it with

 fuel for reinsertion....insertion isn't usually the issue, but

 removal can be tough.  I doubt I'm losing more than a fuel-tester

 full on a flight with real full tanks...but I do know that it's

 not so sealed tight that it will keep air out.



 Tim Olson - RV-10 N104CD - Flying

 do not archive

 zackrv8 wrote:

> 

> Also, while the tank Orings are good, I do get fuel leakage out of

> the caps on climbout with real full tanks. Tim Olson - RV-10 N104CD -

> Flying do not archive

> Tim,

> That shouldn't happen.  As you may already know, the fuel caps can be

> adjusted.  It's a little tricky, but the O ring can be tightened to a

> happy compromise between lifting the lever and no fuel leakage.

> After refueling, I let the drips from the fuel nozzle onto the O ring

> to lubricate it, especially in the winter.  Makes it much easier to

> install after that.

> Zack

> -------- RV8 #80125 RV10 # 40512

> Read this topic online here:

> http://forums.matronics.com/viewtopic.php?p=161058#161058

davelammers(at)mchsi.com
Guest

Posted: Tue Jan 29, 2008 8:17 am Post subject: fuel vents

Tim, et al.,



The RV caps are not supposed to leak and are designed to be totally sealed.

You can adjust the pressure on the O-ring by tightening the nut on the 

bottom of the cap.

Re the icing issue.  I am planning a small hole (#50 or so) on the aft 

side of the exposed vent (above the front opening).

The loss in ram pressure due to the hole is insignificant (because of 

its size) yet the hole will serve as a vent in the event of a blocked 

vent tube.

A KISS solution to an alternate vent.



Dave Lammers

Finishing



Tim Olson wrote:



 	  Quote: 	
		  

 Also, while the tank Orings are good, I do get fuel leakage

 out of the caps on climbout with real full tanks.



 Tim Olson - RV-10 N104CD - Flying

 do not archive

daveleikam(at)wi.rr.com
Guest

Posted: Tue Jan 29, 2008 7:16 pm Post subject: fuel vents

Just a thought Tim,



If your vent became blocked, and the pump pulled harder than your caps 

allowed through, they could seal completely from vacuum pressure.  Just a 

thought.



Dave Leikam

40496

---

Tim Olson

Joined: 25 Jan 2007
Posts: 2879

Posted: Tue Jan 29, 2008 7:37 pm Post subject: fuel vents

True...the suction alone might seal them up.  I do like the idea of

the T in the vent line with a one-way valve, but also like the

idea of Dave's of a tiny pinhole on the back side of the vent.

It wouln't take much of a hole to keep it from icing up.  For those

wanting to spend some cash, I guess you could also add a heating pad. 



I don't want to give the impression about the fuel caps that they're

all leaky.  It's just that my levers are darn tight yet I still get some

fuel flowing back occasionally if my tanks are less than 1" from the top

of the cap when full.  I haven't tried Jesse's suggestion yet of pushing

down while flipping the lever on the cap, so that should be something

for me to check out.  The tough thing here is that when it's cold,

you have to give the o-ring time to relax and it takes a while when

you're trying to get the caps of.  But, that's what I get for living

in the tundra.  Tonight's wind chill will be -42F.



Tim Olson - RV-10 N104CD - Flying

do not archive

Dave Leikam wrote:

[quote] 

 

 Just a thought Tim,

 

 If your vent became blocked, and the pump pulled harder than your caps 

 allowed through, they could seal completely from vacuum pressure.  Just 

 a thought.

 

 Dave Leikam

 40496

 ---

dlm46007(at)cox.net
Guest

Posted: Tue Jan 29, 2008 8:01 pm Post subject: fuel vents

I checked with the PhD in mechanical engineering in the neighborhood

discussing vent tubing ID, fuel line ID and flow rates ; the size 40 hole in

the vent line in a protected area should not impact the ram air pressure

significantly and will provide enough pressure equalization if the external

vent ices. Its getting cold here also; Mesa Az will be 39F tonight. 



--

sam.marlow

Joined: 25 Feb 2006
Posts: 99

Posted: Tue Jan 29, 2008 11:49 pm Post subject: fuel vents

What is considered a protected area, inside the wing faring, or just behind the vent line on the back side in the breeze?

Sam Marlow

#40157

---- David McNeill <dlm46007(at)cox.net> wrote: 



=============




I checked with the PhD in mechanical engineering in the neighborhood

discussing vent tubing ID, fuel line ID and flow rates ; the size 40 hole in

the vent line in a protected area should not impact the ram air pressure

significantly and will provide enough pressure equalization if the external

vent ices. Its getting cold here also; Mesa Az will be 39F tonight. 



--

dlm46007(at)cox.net
Guest

Posted: Wed Jan 30, 2008 5:19 am Post subject: fuel vents

Mine will be inside the fairing; my Cardinal had automatic alternate engine

air inside the cowl. I have seen some weird shape on clear ice that freezes

when it strikes the airframe and I don't think that its certain that an

external hole on the aft side of the bent line will stay open.  



--

speckter(at)comcast.net
Guest

Posted: Wed Jan 30, 2008 5:39 am Post subject: fuel vents

One thing that concerns me is that if fuel is flowing out, water can flow

in.  I think that could ruin your day if it hasn't run all the way down to

the sump when you preflight it.



Gary

40274



--

sam.marlow

Joined: 25 Feb 2006
Posts: 99

Posted: Wed Jan 30, 2008 6:24 am Post subject: fuel vents

Sounds likke something I will try, has anyone else done this on an RV?



---- David McNeill <dlm46007(at)cox.net> wrote: 



=============




Mine will be inside the fairing; my Cardinal had automatic alternate engine

air inside the cowl. I have seen some weird shape on clear ice that freezes

when it strikes the airframe and I don't think that its certain that an

external hole on the aft side of the bent line will stay open.  



--

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