The inevitable fuel spill disaster

[13brv3]

The Onex looks similar to the Sonex-B design.

So the B models have that same horrible through-the-windscreen fill hole? That's really sad to see, as it's the single worst thing about the Onex. The pan is about what I was thinking, but of course I already have a vent line close to the cap, which complicates things. I need to add another port for fuel return as well. Not sure what I'll do yet, still thinking.

[daleandee]

The Onex looks similar to the Sonex-B design.

So the B models have that same horrible through-the-windscreen fill hole? That's really sad to see, as it's the single worst thing about the Onex. The pan is about what I was thinking, but of course I already have a vent line close to the cap, which complicates things. I need to add another port for fuel return as well. Not sure what I'll do yet, still thinking.

You make me smile and hug my Model C (Cleanex i.e. Corvair powered model A) sonex airframe. The original models had concerns with the fittings possibly spinning if overrtightened but work arounds were found (don't overtighten the fittings). The fuel filler is still close to the windscreen but a small safety area exists. Having the fuel filler hole through the windscreen is something that would be very hard for me to deal with and I'd have to devise another method.

I do have a fuel cart with a shut off nozzle and it pumps fuel at a rate of about 5 gallons in less than a minute. When fueling at airports with full service I always ask the attendant to allow me to fuel the plane and I've never been refused that request. These airplanes are such great designs but there are a few things that could be improved upon IMHO. This is one of them ...

Dale
3.0 Corvair/Tailwheel

[WaiexB22]

As I was working tonight I was thinking about how much I don't want to deal with this and how much I agree that the fuel fill location just plain sucks. Here is what I was thinking:

I have been considering adding a 5-7 spun aluminum auxiliary fuel tank to the area right behind my seat. I'll be running mogas and having the capacity on a cross county would be great, but in reality most of my flying is for fun for an hour or two. I had pretty much talked myself out of it for weight and balance and unnecessary complexity; however, I have chosen a REALLY heavy propeller....so i was thinking....if I add a real fill port for the aux tank the on the turtle deck or aft sidewall I would have a really convenient fill location that would eliminate my possibly of destroying the windscreen. If I use a fast enough transfer pump I could feasibly transfer from my aux tank to my main while taxiing. The vent for my main tank is routed overboard and the aux tank would too. This would also reduced fuel vapor in the cockpit after refueling (those with flying planes chime in if this is actually a problem).

I have my tank out right now to install the new straps and work on the firewall. While the tank is out I can easily add a fill for the aux tank.

[BobDz]

As I was working tonight I was thinking about how much I don't want to deal with this and how much I agree that the fuel fill location just plain sucks.

Exactly what I was thinking. One concern I have is that adding more "stuff " reduces the usable weight. Lots to consider. I'm considering an aluminum tank. If I do an aluminum tank, a different fill site would be great. Also considering a heavier engine. Then a fuel tank in the aft fuselage makes sense. An aft fuel tank filling a header tank has the potential to make for interesting in-flight weight and balance calculations. Easy enough to determine prior to flight. Another reason to play with Excel.

This could be fun!

[13brv3]

When I first put all this together, I considered using one of the extra fittings on the gascolator as a fill port. I figured it could be run to a valve behind an access panel on the cowl, then use a 12V transfer pump to fill the tank. On the rare occasion that I'd fill the plane at another airport, you'd still have to use the normal fill port.

The biggest problem with this is being able to see how much fuel is in the tank when you're filling it. Fuel gauges aren't the best, and if your 3rd wheel is in it's natural location <g> that throws the readings off when you're on the ground. Removing the fuel cap sort of defeats the purpose. Of course eventually it will squirt out the vent, but that's certainly not the best method.

[Bryan Cotton]

If you are building an aluminum tank you can make a filler neck like the A model, and the stainless box that goes around it.

We generally read the fuel level on the ground and add a specific amount of gallons, rather than watching. Two up, we can't take full fuel. It also works if you want to go full fuel when flying solo.

[DCASonex]

The "A" series Sonex was much better in this regard, do not know what they were thinking when they put the filler through the canopy on the "B" series and Onex. Added an overfill catch and drain to my "A" series that does not need a positive seal to the tank.

The Sonex canopies (at least on the "A" series are curved on the sides then held straight by the aluminum frame. This leaves the material under stress on the inside right where the screw holes go. Mine cracked during the night following its installation. Replaced it with a Todd's Canopy (unfortunately no longer available) and bonded in place. 12 years no problems.

David A.

[BobDz]

David
Do you have a picture of your overfill catch?
Thanks

[Bryan Cotton]

David
Do you have a picture of your overfill catch?
Thanks

It probably looks a lot like the one in the "Waiex 191 fuel catch and drain" video I posted on page 1. I copied what others had done.

[Onex107]

A few years ago we did a fuel, windshield test. We took a piece of windshield and duncked it in fuel. No effect. Then bend the piece and put some stress on the surface and drip a few drops on the surface and you get cracks. I presume if our windshields were composed of flat plates we wouldn't have a problem. All the fuel is doing is relieving the stress of the bending.