Fuel Sump

[GraemeSmith]

Yes- it's true - there is no uphill after my gascolator. However the bottom of the gascolator bowl IS below the inlet at the aeroinjector. And that ACS gascolator has a nice gauze in it that acts a bit like a Gats Jar - turning back the water while allowing the gasoline through. Haven't caught any water in it yet. I'm not tempting fate by putting water in the tank either! I fill my tank chock full after every flight to try and avoid condensation sweating in the tank when sitting in the thermal cycles we get at the airport. I have had crud in it - which was easily cleaned.

I don't disagree with your fuel flow test. Frankly I was just interested in making sure it was no worse with the gascolator than the filter. It wasn't. If it had been - I would have been doing some more work. And by having it down to only 5 galls in the tank - there wasn't much head pressure.

[mike.smith]

Just to play devil's advocate... There is about 2' of fuel line from the tank to the AeroInjector. That's not enough length to hold enough fuel to even taxi to the end of the runway. If there's water in the fuel line, or in the bottom of the tank, it's going to make it to the AeroInjector in less than a minute, and get coughed out. That's why so many Sonexes (a majority?) fly without a gascolator. 480 hours without one for me. Thousands of hours for others without one, too.

Make your own informed decision, but it's good to think through both sides of the topic.

[Sonex1517]

Art

Do you have any photos of the Red Cube installed in that location? I’d like to see it as I have considered the same.

[GraemeSmith]

Just to play devil's advocate... There is about 2' of fuel line from the tank to the AeroInjector. That's not enough length to hold enough fuel to even taxi to the end of the runway. If there's water in the fuel line, or in the bottom of the tank, it's going to make it to the AeroInjector in less than a minute, and get coughed out. That's why so many Sonexes (a majority?) fly without a gascolator. 480 hours without one for me. Thousands of hours for others without one, too.

Make your own informed decision, but it's good to think through both sides of the topic.

Mike - It's a valid point from a water standpoint. Though I know of an extreme instance where ice in a tank ultimately melted in flight and introduced an 'engine stopping' slug of water that overwhelmed a gascolator and filled a float carburetor bowl. That stopped the engine.

--

But if there is one thing the gascolator DOES do - it is much easier to open to inspect for crud - than decowl, remove insulation and wrench open an inline filter if you suspect bad fuel. And it provides a much longer period that the engine will still run on dirty fuel than a small inline filter.

[builderflyer]

Hi Robbie, I've attached a photo of the red cube installation on my Sonex. You'll note that other than the wires coming out the top, this location doesn't meet any of the "recommended" ways to add one of these things to a fuel system. It doesn't have 6" of straight hose in and out and the out hose doesn't slope upward. Also, the k factor that I've zeroed in on is far from the 68,000 starting point. It's currently at 61,275 but that's giving me real good numbers at fill up time. The last two fill ups were 0.0 and 0.1 different from actual so that's about as good as it gets. I'll get more data as time goes on.

Art,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,Jabiru 3300 #261

[GraemeSmith]

So here is my concern about the design of the tank to firewall fuel line.

There have been post crash fires in Sonex and EVEN IF the pilot secures the fuel tap prior to the crash - deformation of the firewall or the tank straps will load the tank fitting through the solid fuel line and potentially tear it out or punch it into the tank - causing a fuel leak.

So I think I LIKE this picture because after the cube it APPEARS there is a flexible braided line to the firewall. Am I correct in this supposition? Because it would seem to me that if there was firewall deformation or tank strap failure in a crash - that braided line could perform an important shock absorbing function and protect tank integrity.

[builderflyer]

So I think I LIKE this picture because after the cube it APPEARS there is a flexible braided line to the firewall. Am I correct in this supposition? Because it would seem to me that if there was firewall deformation or tank strap failure in a crash - that braided line could perform an important shock absorbing function and protect tank integrity.

You are correct, Graeme, there is a "flexible" line leading to a fitting on the firewall. But if you've had a short length of 3/8" fuel line with a stainless steel braided wrap on it in your hands, you'll note that it is not all that flexible, given the short distance to the firewall. Something I try not to think about too often while flying is having as much as 16 gallons of 100LL in the cockpit with me.

Art,,,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,Jabiru 3300 #261

[Sonex1517]

Thank you Art!

[BRS]

Thanks everyone for the great replies. Gives me more food for thought.

I didn't realize the fuel pickup was at the low point during level flight attitude - cool! With the tail on the ground though there is plenty of space for water/contaminant to sit until during takeoff and lifting the tail. So that is what I'll be concentrating on. I think I know what I'll be doing but will keep it a secret until I git er done.

As for using a Tube or hose between the firewall and tank. If there is an "S" turn or perhaps just a 90˚ bend in a tube then it will likely kink nicely w/o causing much impact to the tank bung. My personal preference is tube inside and hose outside. Needs to be nice and flexible to the engine.

Red Cube. I'm a fan of the fuel transducers. On a gyroplane I had with a MGL Extreme I used a fuel tank float for one tank and setup a second "calculated" fuel tank. If they didn't match then I knew I had better dip the tank.

Fuel tank vent suction. OK that is a trick term. I was noticing that my fuel tank tube, and I think it's the stock setup, drags the vent below the cowl. I got to thinking that if that vent line is facing aft it could draw a low pressure on the tank contributing to fuel flow issues in flight. On the Sportsman forum there was a discussion last week where a owner described fuel starvation because he had a fuel cap vent that had swiveled aft. It was an eye opener.

Stay safe.

[mike.smith]

Fuel tank vent suction. OK that is a trick term. I was noticing that my fuel tank tube, and I think it's the stock setup, drags the vent below the cowl. I got to thinking that if that vent line is facing aft it could draw a low pressure on the tank contributing to fuel flow issues in flight. On the Sportsman forum there was a discussion last week where a owner described fuel starvation because he had a fuel cap vent that had swiveled aft. It was an eye opener.

Mine comes out the bottom of the cowl, but is curved/angled and faces forward, to give some positive pressure.