Life span of capacitive sending units

[Kahuna]

When you build the capacitive sending units into the tanks and close em up. Thats it. Game over. There is no repairing them without complete removal of the rear baffle. ARGH!

Im curious as to the life of the wire and plastic stand offs. I have no idea how long this stuff will last in fuel and fumes.

Are there other non-rv planes in the field that have used this material in the field where we might know the life span? RV'ers are not a good source for data as most are young relatively speaking.

Please no debate here on cap vs resistive units. Im only interested in field data on this material used in fuel tanks, aviation or otherwise.

Thanks

[chaskuss]

Mike,
I had the same concerns. That's why I substituted a quality [made in USA] Amphenol brand electrical bulkhead connector for the import unit supplied by Vans. I also substituted one piece spacers made from Delrin for the 3 piece nylon washers Vans supplies.
Regarding difficulty of repairing those units, you don't have to completely remove the rear baffle. You will have to cut two access holes [in the 2nd and 5th bays] to facilitate repairs. That will require fabrication of doubler rings and access covers, though.
Make sure you apply ProSeal to the wire which is wound around the vent tube. This will keep it secured to the tube. Having the wire loose in the tank is sure to cause problems.
Charlie Kuss

[Kahuna]

Charlie,
I had one of those Vans supplied bnc-ish connectors leak years ago in my RV-6. THe plastic insulator was dried and cracked. Lesson learned. Encapsulate the connector and wire to prevent fuel getting to it.

Building 4 tanks right now for a replacement set of wings for my 8 for greater range. ARGH!

[Paul Thomas]

How many gallons are you planning for?

[Kahuna]

In the wings 97 gallons.
In the fuse ~20

[JakeLewis22]

Originally Posted by Kahuna

In the wings 97 gallons.
In the fuse ~20

117 gallons! Are you installing a restroom also?

[longranger]

Originally Posted by JakeLewis22

117 gallons! Are you installing a restroom also?

Who says you gotta burn it all in one hop?

[Paul Thomas]

Cool. I'm currently converting the outboard leading edge into an extra set of fuel tanks. After the airplane is flying, I'll build a set of tip tanks. IIRC, you currently had 60 gallons so your range will be a bit more than double.

I think someone has made the outboard tank removable so you could, in theory, fix potential problems. I'm riveting mine on and put a float in. I'm not even sure you're required to have a sender in there. I believe the Cessna 340 doesn't in the nacelle tanks.

Going back to your original question, when I researched the subject, it wasn't as long as a float but long enough that it's not something to worry about. BMW decided to use capacitive senders in their vehicles which failed for other reasons. You may be able to find out how long it took for components to fail on their forums.

[Kahuna]

Originally Posted by chaskuss

Regarding difficulty of repairing those units, you don't have to completely remove the rear baffle. You will have to cut two access holes [in the 2nd and 5th bays] to facilitate repairs. That will require fabrication of doubler rings and access covers, though.
Make sure you apply ProSeal to the wire which is wound around the vent tube. This will keep it secured to the tube. Having the wire loose in the tank is sure to cause problems.
Charlie Kuss

I dont think you could replace the wire between bays 2&5 with only access to 2&5. With the wire prosealed in the snap rings to prevent movement and chaffing, the entire rear baffle, or access panels for bays 2-5 would be in order. No way to get the wire through the other center bays. Not fun.

[Paul Thomas]

You could always use a small fuel line as a conduit. You could then just use an access panel on each side; you wouldn't even have to remove the tank.