Fuel Vent Issue

[rizzz]

That is a good point.
I might have to reconsider this option.

[wlarson861]

If you go inverted in negative G you won't be flying under power long enough to drain fuel through the vent.

[planeolbob]

Fuel Vents are always a good subject......
Here is what I did. This is a variation on what Tony, David and Gus did.
For this to work correct you do need to install the fuel area with a block off plate.

Mark 1 Design
https://www.flickr.com/photos/22138162@ ... 206891441/

Mark 2 Design (in the middle of the set)
https://www.flickr.com/photos/32288421@ ... 998890631/

Features:
1. Allows a full 17 gal in my tank.
2. Gives you a horizon reference.
3. Shields opening from air born clogging.
4. No chance of fuel spray on wind screen due to negative G as the fuel dumps into a void under high pressure.

250 hours, no problems.

Bob Mika

[dtwolcott]

If you thought you were going to be doing any inverted flying you might want to find a small check valve to put in line on the vent. That way when you are upside down the fuel could not run out. Of course you wouldn't want to be upside down very long because your fuel vent would be blocked by the check valve.

[mike.smith]

Fuel Vents are always a good subject......
Here is what I did. This is a variation on what Tony, David and Gus did.
For this to work correct you do need to install the fuel area with a block off plate.

Mark 1 Design
https://www.flickr.com/photos/22138162@ ... 206891441/

Mark 2 Design (in the middle of the set)
https://www.flickr.com/photos/32288421@ ... 998890631/

Features:
1. Allows a full 17 gal in my tank.
2. Gives you a horizon reference.
3. Shields opening from air born clogging.
4. No chance of fuel spray on wind screen due to negative G as the fuel dumps into a void under high pressure.

250 hours, no problems.

Bob Mika

I did this same thing. Seems to work great. My fuel flow numbers would choke a camel, so the vent size called for in the plans is more than adequate.

Mike

[fastj22]

If you go inverted in negative G you won't be flying under power long enough to drain fuel through the vent.

A poorly executed roll will momentarily slosh some fuel out the vent if you have more than half a tank. You don't have to be hanging from the seat belts. I can smell it in my plane and it vents out the bottom.
I wouldn't vent out the top like that.

[aganjoo]

Hi Folks

I apologize for the delay but I have been on the road the past few days so want able to update you all on the status. (work and then T-Flight training at Sonex)

I checked the vent pipe(compressed air & safety wire) and there was no blockage but the airflow was still restricted. The way I routed the vent pipe down, there were quite a few turns to work around the stuff hanging on the firewall which I believe may have been restricting the flow. I also confirmed with other folks using the same engine combination as me and they were using a 1/4" vent pipe. So I went ahead and replaced my vent pipe with a 1/4 " one and routed it straight down as much as possible without bends and all is well now and engine is running smoothly. I also bend the vent pipe forward at a 45 degrees angle to have some positive air flow.

Since them I have gone ahead and done some taxi testing and so far so good

Cheers

Amit

[Skygeezer]

I have a forward-facing fuel vent above the cowling, but it is only about 3 inches high. I am not the original builder of the plane, and this may have been the height originally specified. The plane is a tail dragger and I filled the tank to the bottom of the tank opening. I took off to practice landings, so remained in the pattern. All was well until I was on short final and reduced the engine speed to idle. Fuel suddenly shot from the fuel vent and sprayed over the windshield. Simultaneously, my Lexan windshield developed a spider web of cracks originating at all of the stress points where it was bolted to the airframe. I continued the landing, taxied to the first ramp, stopped the plane, got out and immediately wiped the windshield, but the damage was already done.

As I replaced the windshield, I took a piece of scrap Lexan and tried to break it. I was unable to do so, even though I bent a 6 inch long piece double. I then took a second piece, dipped it in gasoline, and again tried to break it. It snapped immediately, long before it had been bent double.

I am now replacing the original vent with one that will extend below the cowling and has a bend so that the outlet faces forward. I will not put an elbow directly into the tank, but will bring the line up as high as possible under cowling before bringing it downward. I will also put a screen over it to keep out wasps and check it before each flight.

[DCASonex]

This geezer made a rather unique assembly for this that is anti-splash back and anti-siphon. drawings and photos can be found on the Yahoo Sonexbuilders forum in files section under modifications to Sonex #1327, or e-mail me with your address and will send direct. Have topped up tank in my tail dragger often and no problems to date.

David A.

[peter anson]

If you vent like that from the top, and you ever go inverted, you will spray fuel over your windscreen.

Here's a valve I made to prevent fuel leaking out the vent if inverted.
http://sonexaus.wikispaces.com/Safety+valve+for+top-vented+fuel+tanks
It's not effective for gentle manoeuvres like steep descents with a full fuel tank, but works OK for a sharp nose-over so I think will work for inverted flight. The top vent allows a bit better fill and is easy to check for wasps nests.

Peter Anson
Sonex 894
190 hours