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Screen over fuel vent

flightlogic

Well Known Member
Patron
Checking with builders to see what the consensus is on covering the small hole under the fuse where the fuel tank vents.
I have expoxied small metal screen there in the past, but it eventually gets knocked off.
Is there a history of them getting plugged? I know positive pressure from the tank as it warms would attempt to push out a blockage.
Any thoughts appreciated.
NC
 
This is what I did for vent lines on the RV-10 (first two photos). I did a similar setup in the RV-8 (third photo). Note the transition from 1/4” to 3/8” tubing. This provided a better surface area to JB Weld on a small piece of aluminum screen. After the JB Weld sets a light touch on the Scotch Brite wheel and good to go. The aluminum screen is to keep out the mud dabblers. The screens are firmly in place.

The black nylon thing is a vacuum breaker (Check Valve). It open on just a slight vacuum as in the vent gets clogged with ice and the fuel pump draws a vacuum on the tank. This eliminates the issue of having a collapsed tank. This vacuum breaker is very light. I got it from McMaster. There are two models, one for water and one for fuel. Get the fuel one.

Carl
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Warning! Anecdotal “Evidence” Ahead!!

Three RV’s, with a total of 7500 flight hours - stock Van’s vents with no screens or fancy things on them, and not a single evidence of blockage. Caveat - we don’t fly in ice! And yes, if you take that “golden BB” bug, you can plug a vent - but hopefully you’ve got the other tank to use (that is the design redundancy).

However, there is no harm in doing something else, and the fancy vents look pretty cool.... ;)
 
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I have a collapsed RV8 tank out back that occurred from a mud dobber plugged vent.
Actually the same aircraft had both vents get plugged, but we were able to repair the other tank.
Pilot almost lost the battle to keep it running till he found an airport....

If you live in TX I would definitely suggest some type of critter prevention.
 
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This is what I did for vent lines on the RV-10 (first two photos). I did a similar setup in the RV-8 (third photo). Note the transition from 1/4” to 3/8” tubing. This provided a better surface area to JB Weld on a small piece of aluminum screen. After the JB Weld sets a light touch on the Scotch Brite wheel and good to go. The aluminum screen is to keep out the mud dabblers. The screens are firmly in place.

The black nylon thing is a vacuum breaker (Check Valve). It open on just a slight vacuum as in the vent gets clogged with ice and the fuel pump draws a vacuum on the tank. This eliminates the issue of having a collapsed tank. This vacuum breaker is very light. I got it from McMaster. There are two models, one for water and one for fuel. Get the fuel one.

Carl
6-C57-F0-C6-4755-44-AD-A141-13-B71918-DDC5.jpg

66612-A1-A-1-BFE-4320-9248-37-D2707938-E3.jpg

87-E7-F6-E5-B797-434-B-B8-AF-356-DCD6396-F2.jpg

Carl that's pretty cool. Does the vacuum breaker ever leak fuel?
 
Carl that's pretty cool. Does the vacuum breaker ever leak fuel?
Nope - but to be fair there is not much exposure to fuel under normal circumstances as the air flow is into the tank. For those days where you fill up and the sun burps a little fuel out the vent there is fuel on it, but I never had a blue stain in the wing root where this is located.

155 hours on the new RV-8 so not enough experience with it to provide a hard answer.

Carl
 
Nope - but to be fair there is not much exposure to fuel under normal circumstances as the air flow is into the tank. For those days where you fill up and the sun burps a little fuel out the vent there is fuel on it, but I never had a blue stain in the wing root where this is located.

155 hours on the new RV-8 so not enough experience with it to provide a hard answer.

Carl

Awesome! I was wondering because after a top off on both tanks on my -7A the non used side will definitely put fuel in the vent and it stays there until I use it. I have taken my fuel cap off and the tank has a small amount of pressure on it if I didn't run the tank. Not a problem if I run it on that tank and its only been enough to make it on the ground out of the vent on one occasion. Also remedied by not filling up to the bottom of the neck but I travel to another airport 100% of the time to get my fuel. :)

Cool idea!
 
I have a collapsed RV8 tank out back that occurred from a mud dobber plugged vent.
Actually the same aircraft had both vents get plugged, but we were able to repair the other tank.
Pilot almost lost the battle to keep it running till he found an airport....

If you live in TX I would definitely suggest some type of critter prevention.

Mud Daubers a plenty here in the northeast, Pitot tubes, fuel vents & more.
 
Safety Wire

I used a trick I read about here on VAF: cut a 2" length of safety wire and double it over like a bobby pin. Push it into the vent fitting cut ends first. Leave a short bit sticking out so you can grab it with needle nose pliers if you ever need to take it out. It stays in with friction, and blocks enough of the opening to keep critters out.
 
I have a collapsed RV8 tank out back that occurred from a mud dobber plugged vent.
Actually the same aircraft had both vents get plugged, but we were able to repair the other tank.
Pilot almost lost the battle to keep it running till he found an airport....

If you live in TX I would definitely suggest some type of critter prevention.

In Mud Dauber country, we never park (including inside) without flagged vent covers. They come off in preflight, and back on after landing. I defy the little critters to build faster than that..... ;)
 
My big fear is mud daubers. I learned a neat trick. I used a bent paperclip inserted into the opening of the sawed off AN fitting. They are still there 800 hours later and it reduces the space enough that the daubers can't get into the tube.

Larry
 
My plane has spent a total of 10 nights outside of a hangar, none of those in the natural habitat of mud daubers (honestly I don't know that). What I do know is that my original screen covers were a royal pain, the first one was plugged from the tank sealant from day one and gave me fits (short fuel pressure dropouts) when flying with a full tank. When I tried reducing the amount of sealant, it would just fall off.

I replaced the metal faucet screens with screen door material secured with a zip tie. Looks goofy, but it has worked great for me.
 
My version of the “bent paper clip/safety wire” idea is to use a tie wrap that fits snugly into the vent line opening. Just shove it up into the vent line all the way up to the fat end, which is too big to go inside the vent. It blocks enough of the opening to keep critters out, and would still allow airflow if you forgot to remove it during pre-flight. I keep a few of them in my control lock/tie down bag that I carry with me.
 
I flew my -6 in Texas for over 25 years and never had a problem.....HOWEVER, having said that, part of my pre-flight is to stick a pipe cleaner up into the vents to check for obstructions.
 
bugs

I've been using this same set for the past 3 yrs. and going on my 4th season. pop them on in the Spring and remove in the Winter. these are for the standard RV angled vents. squeeze fore and aft to release them.

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I have a collapsed RV8 tank out back that occurred from a mud dobber plugged vent.
Actually the same aircraft had both vents get plugged, but we were able to repair the other tank.
Pilot almost lost the battle to keep it running till he found an airport....

If you live in TX I would definitely suggest some type of critter prevention.

I wonder if the 8 driver was running Moe gas , I used to run Moe gas on one tank and 100 LL on the other ,,,, always had dobber issues with the Moe gas tank ,along with others I know of , one had a tank collapse!
 
Mud dobbers

Anyone have a idea how to trap mud daubers. I keep my plane in a hanger but they are a pain.
 
Anecdotal, but I've had fine screen material formed over the vent tips since new, held in place with a loop of safety wire. I think highly of them.
 
Pipe cleaners

Pipe cleaners. They cost about 20 cents and go on/off with the other protectors/control locks at each pre/post flight inspection. Any fuel burps on hot days just dribble and drip down the pipe cleaner.
 
Warning! Anecdotal “Evidence” Ahead!!

Three RV’s, with a total of 7500 flight hours - stock Van’s vents with no screens or fancy things on them, and not a single evidence of blockage. Caveat - we don’t fly in ice! SNIP

I do not fly in known icing conditions. But, I have encountered ice, both times while coming down from altitude through a layer (IFR flight plan). Ice accumulated in just a few seconds. I got a good covering each time before breaking into the clear.

Carl
 
This is what I did mainly for ice protection but could work against critters also. It is a control cable fairing ACS PN 05-05750 riveted and punctured in back end with a number of #40 holes. I have encountered ice on few occasions. 150 hrs with no problem.
 

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Doppers

How big are these pests?
I don't live in Mud Dopper country & wonder if my technique is sufficient. I have been drilling my vents through at 60 degree angles, than inserting small lengths of safety wire to form an internal screen. I than peen the holes shut so the wire segments don't fall out. Seems to be effective so far (probably 1500 hrs on 4 planes) but my planes haven't really been in Mud Dopper areas to stand the Dopper test. So, effectively, how fine mesh does the screen have to be?

----

Also - plug those tank fittings while your wings & tanks are being stored!
I had a set of tanks brought to me to final seal (built somewhere in the US). Before I gave them back to the owner, I pressure checked them, applying air through the vent line - they both held air with NO caps on the fuel line fittings! I removed the access plates on both tanks to check things out, I thought they were prosealed shut, Doppers had plugged both fuel pick-ups.
The standard pick-up was fairly easy to clean out, but the flop tube had at least a 2" blockage in the rubber hose portion that was quite the chore to clean out.
 
Not an expert, but I am guessing that they barely fit into the 1/4" tubing, so the bent wire inserts create more than enough blockage to keep them out. I believe a mud dauber is about the size of a honey bee. However, like mice, they are good at squeezing into small spaces. Fortunately they do not heavily populate the upper midwest, but do survive up here.

I bought my 6A kit from a guy in Wichita and the stuff sat in his shed for a decade. I bet that I pulled 3-5 pounds of mud out of the internals of the completed wings and stabilizers. Quite the sight to see me and my two sons holding and shaking the 10' wings on the front lawn trying to get it all out via the lightening holes. Whatever enzyme those critters add to the mud should be used in modern adhesives. It really sticks and came out in chunks as hard as limestone.

How big are these pests?
I don't live in Mud Dopper country & wonder if my technique is sufficient. I have been drilling my vents through at 60 degree angles, than inserting small lengths of safety wire to form an internal screen. I than peen the holes shut so the wire segments don't fall out. Seems to be effective so far (probably 1500 hrs on 4 planes) but my planes haven't really been in Mud Dopper areas to stand the Dopper test. So, effectively, how fine mesh does the screen have to be?

----

Also - plug those tank fittings while your wings & tanks are being stored!
I had a set of tanks brought to me to final seal (built somewhere in the US). Before I gave them back to the owner, I pressure checked them, applying air through the vent line - they both held air with NO caps on the fuel line fittings! I removed the access plates on both tanks to check things out, I thought they were prosealed shut, Doppers had plugged both fuel pick-ups.
The standard pick-up was fairly easy to clean out, but the flop tube had at least a 2" blockage in the rubber hose portion that was quite the chore to clean out.
 
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There are many ways to make the vents bug proof... or nearly so.

I never liked the large fittings protruding from the belly, so I used simple aluminum tubing, with a 45 degree cut on the end. Use a rubber grommet in the hole through the skin to keep it tidy.

The opening can have a small piece of brass screen Prosealed on the opening if you like, but I didn't do that. I simply used the polyethylene tubing covers below to keep the bugs out. You can get the poly tubing at Home Depot if you don't have scraps of it around. Use a little RTV to plug the bottom end of the poly tubing, then attach some sort of RBF flag to it.

To prevent that golden BB bug splat from closing off the tiny opening on the end of the aluminum tubing, I simply drilled a small 1/16" hole in the back side of the tubing about 3/4" above the main opening.

BTW, don't hit your head on the air vents. Ouch.

N540VF%20bottom%20wing%20root.jpg


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I bought the JD vents based on this thread. Just got them - they look terrific!

Any suggestions for how to connect in an RV-10? I'm thinking I cut the stock aluminum tubing flush and square to the top of the included fitting and add a B-nut to attach, the same way the metal line is attached to the tank itself.

Any other / better approaches?
 
Jdair fuel vents

Has anyone retrofitted an RV8A with the fuel vents from JDAIR? After the floors have been riveted?
Does it require cutting inspection holes in top floors to get them installed?
 
E-vac tips

I used these dental evacuator tips. They plug right on the AN fitting. Only problem is they come in bags of 100!
Stewart Willoughby 6, final assembly
 

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it used to be you could take an old faucet head apart and use the screen inside.kind of hard to find now. a ''head shop'' have fine screens for pipes that can be cut to size . my vent exits the skin with an an flare fitting. it can be taken apart and 1/2'' piece of vent line holds the screen in place.
 
Rain bird screens.

Yard sprinklers use a wire screen that I rolled up and inserted in the vent of my Tiger. They looked like a small cigarette filter when rolled up. I am not sure if my -10 vent is a little smaller though and I may just use the V shaped safety wire.

I have flown my -10 through clouds that iced over the pitot with no issues from the fuel vent. YMMV
 
Yard sprinklers use a wire screen that I rolled up and inserted in the vent of my Tiger. They looked like a small cigarette filter when rolled up. I am not sure if my -10 vent is a little smaller though and I may just use the V shaped safety wire.

I have flown my -10 through clouds that iced over the pitot with no issues from the fuel vent. YMMV

I have use something similar (bug blades) for the past 4 years, but I usually take them off in the Winter because of icing concerns. I'm not sure if my concern is valid.
 
I came up with this solution to use on the RV9A I am working on now. Was simple to do and suprisingly doesn't restrict air flow any more than all the screen methods described above.
AN426 3-6A rivet, drill & countersink slightly shallow, squeeze only enough to set shop head, grind smooth with belt sander to finish.
 

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I came up with this solution to use on the RV9A I am working on now. Was simple to do and suprisingly doesn't restrict air flow any more than all the screen methods described above.
AN426 3-6A rivet, drill & countersink slightly shallow, squeeze only enough to set shop head, grind smooth with belt sander to finish.

I like it.
 
I used these dental evacuator tips. They plug right on the AN fitting. Only problem is they come in bags of 100!
Stewart Willoughby 6, final assembly

Any chance of getting a couple of these. I tried ordering and need a dental license and I’m done with schools.
 
Cut a piece of .032" safety wire about 2" long. Fold in half. With a pair of needle nose pliers turn the bend around into a small 3/16" loop. Split the "legs" and push them into the vent until the loop bottoms out against the end of the tube and the legs hold itself in. Adjust

The obstruction in the hole takes all the fun away from a hornet or wasp looking for a nice round hole to nest up in ...

Cheers
 
I just take a nylon tie-wrap that fits snugly into the vent line and push up into the line until the business end of it bottoms out against the vent opening. It stays put because it’s a tight fit even though the end is slightly open. If I forget to take it out it during preflight it doesn’t matter because the tank can still breathe.
 
Tiny mud daubers

I just take a nylon tie-wrap that fits snugly into the vent line and push up into the line until the business end of it bottoms out against the vent opening. It stays put because it’s a tight fit even though the end is slightly open. If I forget to take it out it during preflight it doesn’t matter because the tank can still breathe.

Me too. Also in pitot tube.

As for mud dauber sizes, I had my static ports clogged! (Standard Vans big pop rivets). They are less than 1/8", possibly 1/16"! Now I use thin wire with red tape in static ports when not flying. Had no idea that mud daubers could get into such small openings.

Finn
 
Bugs

Everyone is discussing fuel vents. Did you put a screen on the NACA vents and the intake side of the heater scat?
Them buggers can invade the inside of the airplane too!
I was swarmed by yellow jackets as a child. Must have been bad because I remember my parents throwing me into a tub of baking soda water. I dint remember much after that.
No way I want that while flying. Just sayin'
 
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