Fuel Tank 101

I'm at the point of tank construction where the plans say to "install the capacitive senders if using them", which I am. I have started the sender construction but, something doesn't seem right. The sender instructions say to install the inboard ribs and I haven't even dimpled the skins or installed the stiffeners. It seems like I need to wait a little while and use the plan sequence with the capacitive stuff thrown in later........I'm also using a flop tube in the left tank so I have some inverted stuff to do also. What is the best sequence of construction/installation to use?

My sequence was something like this:

• Cleco / match drill everything
• Drill and test fit all holes for fittings, BNC connector, outboard and inboard rib nose doublers, trap door, anti-chafe strip / anti-hangup strip
• Disassemble / debur / dimple everything
• Rivet stiffeners
• Block off the 1 1/2 diameter hole in the rib where the flop tube goes
• Rivet on all rib accoutrements (doublers, trap doors, etc)
• Rivet all ribs
• Rivet filler neck
• Install vent line
• Install flop tube
• Install capacitive sender plates
• Run wires / install BNC connector
• Install baffle

Good luck,

Thanks a BUNCH!

This helps a lot........

Don't forget to check for NON-continuity between the center pin of the BNC connector and the outside of the tank skin. If it shows very low ohms, you've obviously got some part of the system touching the tank somewhere. Now would be the time to locate and fix before installing the rear baffle.

On a side note, with the uncertainty of the future fuel types, I'm not sure why we're putting in these cap sensors. I've got float AND cap sensors now. Not sure I will even connect the cap sensors to a guage.

Bevan

mcencula said:

My sequence was something like this:

• Cleco / match drill everything
• Drill and test fit all holes for fittings, BNC connector, outboard and inboard rib nose doublers, trap door, anti-chafe strip / anti-hangup strip
• Disassemble / debur / dimple everything
• Rivet stiffeners
• Block off the 1 1/2 diameter hole in the rib where the flop tube goes
• Rivet on all rib accoutrements (doublers, trap doors, etc)
• Rivet all ribs
• Rivet filler neck
• Install vent line
• Install flop tube
• Install capacitive sender plates
• Run wires / install BNC connector
• Install baffle

Good luck,

Click to expand...

Thanks again, got everything fabbed and dry fit today.........



Won't be long now.......

Thank you for posting this. Are there ever issues with the flop tube bouncing around in there? I'd never seen one before.

For some peace of mind, Tim....

....and others, before you close up the tanks, proseal the fittings to their threads so they'll likely never loosen. There was an RV that had the fuel pickup come off and he couldn't fly with less than half a tank or it would unport the fuel!

Best,

The one photograph would seem to indicate that only a flop tube pick-up is being installed, without the additional use of a rigid pick-up tube. Could someone please comment on how effecient the flop tube is at drawing the last little bit of fuel from the tank. I would think the flop tube would leave a fair amount of "unusable" fuel.

dwrichey said:

The one photograph would seem to indicate that only a flop tube pick-up is being installed, without the additional use of a rigid pick-up tube. Could someone please comment on how effecient the flop tube is at drawing the last little bit of fuel from the tank. I would think the flop tube would leave a fair amount of "unusable" fuel.

Click to expand...

I have a rigid tube on one side and the flop tube on the other. I have not run my tanks dry while flying but I did test them on the ground and the differences were very small.

pierre smith said:

....and others, before you close up the tanks, proseal the fittings to their threads so they'll likely never loosen. There was an RV that had the fuel pickup come off and he couldn't fly with less than half a tank or it would unport the fuel!

Best,

Click to expand...

Pierre,

Are you saying to use the proseal like a thread sealer even on the flare/compression fittings? I did notice the brass pickup fitting on the end of the flop tube was prosealed to the NPT side of the AN fitting but there didn't appear to be any type of thread sealant on the other side that attached to the metal flex. Do I need to disassemble the tube itself and pro-seal that along with the flared fitting side of the elbow at the other end.......? I have also noticed on another builder site where he blocked off the hole in the first inboard rib to make the first tank bay with the flop tube in it almost tight, except for the trap door and the smaller fuel runways. However, I haven't seen anything anywhere else about this.............I don't think????? I did notice what mencula said in the first reponse about blocking off the 1 1/2" hole but at the time, I assumed he was talking about the hole in the access cover for the fixed pick-up, which is taken care of now by the solid cover that comes with the flop tube...

Thanks for all the help!
Tim