Capacitive to float conversion

[Floog]

Re: RV-7

Repair or replace???
My right capacitive system started reading intermittently then quit completely. The center conductor of the co-ax cable is grounded inside the tank. I have heard the BNC connector can fail in this way due to fuel contamination.
I believe it would be possible to install (/replace) Van's Float Fuel Senders (IE F-385B/C) without removing the wings if I decide to scrap the capacitive system.
Any thoughts or guidance would be appreciated.

 

[rockwoodrv9]

Re: RV-7

Repair or replace???
My right capacitive system started reading intermittently then quit completely. The center conductor of the co-ax cable is grounded inside the tank. I have heard the BNC connector can fail in this way due to fuel contamination.
I believe it would be possible to install (/replace) Van's Float Fuel Senders (IE F-385B/C) without removing the wings if I decide to scrap the capacitive system.
Any thoughts or guidance would be appreciated.

I am interested in this too. My capacitive system is not accurate. My Red Cube is perfect. I would like to know how much of a pain it is to switch.

 

[Ralph Inkster]

I've heard here where some were able to get the float senders in without removing their tanks. I personally would chose to do this messy & awkward process with the tanks off...
Note - part of the sender installation is to adjust (bend) the float rod just right to get maximum swing between the bottom & top inner skins of the tank. This can only be done accurately with the tanks out, or you will forever have questionable fuel level readings.

 

[BH1166]

Ive done it in place. Awkward position to do it, but mess level the same either way. There is a template with sender in which to make the bends. Worked for me accurate both up and down.

 

[planenutz]

If the capacitive senders have been installed so that they encompass measurement of the entire tank rather than just the first bay, then they should be more useful to you than resistive float-type systems. For this reason I would repair them rather than replace them if I were given the chance to do so.

The typical resistance type usually read "full" until the tank is under about half full, then start to provide an indication... an indication that is relative but not really accurate to the actual quantity remaining... until you get to under 1/4 tank. A properly calibrated capacitance probe should be able to provide you with an accurate quantity throughout its entire range.

 

[rocketman1988]

If the capacitive senders have been installed so that they encompass measurement of the entire tank rather than just the first bay, then they should be more useful to you than resistive float-type systems. For this reason I would repair them rather than replace them if I were given the chance to do so.

The typical resistance type usually read "full" until the tank is under about half full, then start to provide an indication... an indication that is relative but not really accurate to the actual quantity remaing... until you get to under 1/4 tank. A properly calibrated capacitance prob should be able to provide you with an accurate quantity throughout its entire range.

Which in most cases is around half tank and below. There are a few older systems that will read all of it, and one that runs the capacitance probe all the way through the tank. The best one I have seen so far uses 4 Cies sensors, two in each tank.

My Princeton probes are very accurate below 17 gallons.

 

[planenutz]

There are a few older systems that will read all of it, and one that runs the capacitance probe all the way through the tank.

Yes, those probes which are mounted diagonally from the root to the top outer section of the tank should provide the best results. I don't really see the value in having one probe mounted in the inboard tank bay... that's no better than the resistance float type. In my mind the primary advantage to go to a capacitance system is so you can take full advantage of its ability to provide an accurate total - something the resistance float type can't really do without more than one sender unit per tank.

 

[rocketman1988]

Yes, those probes which are mounted diagonally from the root to the top outer section of the tank should provide the best results. I don't really see the value in having one probe mounted in the inboard tank bay... that's no better than the resistance float type. In my mind the primary advantage to go to a capacitance system is so you can take full advantage of its ability to provide an accurate total - something the resistance float type can't really do without more than one sender unit per tank.

The sensor that goes the full length is not a retrofit option; you'd have to open the tanks to make that happen. While it would be nice to read the total quantity, with an accurate totalizer, it isn't necessary. In a retrofit scenario, you have the choice of stock floats, capacitive probes, or Cies sensors, none of which will read the full quantity. My next build, I will probably use two Cies sensors per tank to give the total quantity.