Princeton capacitive probe, and ethanol?

[karmarepair]

I've asked the current marketer for the probes to clarify, response pends. I too, would like to run MoGas, and it's unavailable in California without Ethanol.

"Basically, ethanol attracts water, and water in the probe is no bueno."

I wish he'd been a little more specific.

IMHO, there is little chance of getting water in the fuel of a Sonex if you keep the tank full all the time. The tight cap is protected from the rain by the fuel door. You Do You, but I think the risk of calibrating using MoGas with Ethanol, and using MoGas operationally keeping the tank as full as possible all the time, falls into the Acceptable range.

Having said that, my airport has 100LL and Jet Fuel as the only choices, so I'm going to calibrate my Princeton Probe/Dynon Skyview using 100LL and use Decalin/TCP, for the near term.

[13brv3]

The tank is vented, and moisture in the air could potentially be absorbed by the alcohol in the fuel. I've absolutely seen corrosion in carbs on lawn equipment I've owned, and switching those to non-ethanol fuel 100% cured the problem. That's mostly why I've not run any ethanol gas in the Rotax yet. I'll probably just keep running the 93 non-ethanol I've been using, along with the very occasional tank of 100LL.

I did end up ordering a couple cheap non-contact sensors to play with.

Rusty

[karmarepair]

I've concluded that capacitive probes and ethanol are not a good mix. The ethanol content of the available MoGas varies, and due to the dielectric constants being much farther apart than I expected, accuracy will suck. Get any water in your ethanol and it gets worse.

I think a sight gauge is a manageable risk, for situations where Ethanol containing MoGas is the desired fuel. I haven't gone looking but I'm not aware of a resistance type gauge that will fit in the molded Sonex tank. Sensing fuel pressure AT THE TANK might work, but it will be dependent on speed, particularly if you have (like I do) a top vent.

Or this might work: https://milonetech.com/products/chemical-etape-assembly. You'd have to use a hot knife to cut a slit in the top of the tank, and then seal it up, but I think it might work.

The Legacy plans have an aluminum tank option depicted, and you could mod it to use whatever sender your want. Or make your tank out of riveted and two part Polysulfide (Thiokol, ProSeal, Flamemaster) sealed aluminum, same same, configure it howsoever.

[Bryan Cotton]

I think a sight gauge is a manageable risk, for situations where Ethanol containing MoGas is the desired fuel.

Or, a fuel camera:


Here is mine:

16 gallons.jpg (75.6 KiB) Viewed 1493 times

[13brv3]

That funny. I was joking with someone about using a camera :-)
Rusty

[Bryan Cotton]

That funny. I was joking with someone about using a camera :-)
Rusty

No joke! I just stole somebody's good idea and it works. I poured in 1 gallon at a time, and marked the tank for both the 3 point and level attitude. There is a short strip of LED lights taped to the underside of the tank.

If I was comfortable with clear fuel line in the cockpit, I would have gone with the sight tube. But I really wasn't.

[13brv3]

Can anyone find the dielectric constant for 10% ethanol gasoline? I know it can vary with octane, additives, etc, but even a ballpark would be interesting. Gasoline is listed as 2, and Ethanol is 24.3, but I'm not sure how that works when mixing the two. I'm guessing it won't be as easy as taking the average if you mixed them 50/50. Nothing related to chemistry is ever that easy.

Rusty (I hate chemistry)