Wings: Fuel tanks. Right tank capacitance probes and baffle install.

I decided to redo my fuel tanks.  See here for why.  The entries specific to the redone tanks are here.

For the installation of the capacitance probes, the RV-9 plans require you to cut a notch out of the vent line bushings to fit the wires.  Well, I had already installed the vent line, so that wasn't a viable option.  I didn't like the Van's method anyway since the wire could still fray up against the ribs with the notch removed.  Turns out there is a 7/16" hole at the top-aft of each rib which must serve the purpose of helping the fuel move around a bit or perhaps a tooling hole.  Since it's at the top of the tank, it wouldn't be a big deal to occlude it a skosh (effectively reducing its diameter) if I slipped in a bushing to carry the probe wires through.  So that's what I did, winding the wires around the vent line to help anchor them.

 

Capacitive probe on rib 6, inboard and outboard sides, prior to final sealing and tacking of wires.

 

Capacitive probe on rib 2, inboard and outboard sides, prior to final sealing and tacking of wires.  Note the fuel float.  I will be using both means of fuel measuring (one for EFIS, one for steam).  Also the low fuel level optical sensor is visible.

For installing the baffle, since it needs to be sealed on the inside, the plans call for the following sealant methodology.

After dropping in the baffle, using a more liberal interpretation of the above, here's what the sealant looked like prior to the baffle install.  This was done with two stripes of sealant using the manual syringe gun.  For the left tank, I'll integrate some of Mouser's approach to mine.

And here's what the sealant looked like against the baffle inside the tank (the below image was taken through the fuel filler hole).  The sealant bead at the top is the baffle-skin joint (i.e., ignore the arrows).  I also put a very thin layer of sealant (thin enough to prevent skin pillowing) on the inside of the baffle flanges.

And here are the baffle and attach zees cleco'd.  I decided to sand down the primer I originally put on the tank attach zees' flanges so the sealant could get a better grasp of the parts.  May not matter, but surely won't hurt, especially considering how ridiculously tenacious that EkoPoxy/EkoPrime is!

Where the baffle webbing attaches to the ribs, all of the rivets are AH-41/2H blind, except the out- and inboard ones which are bucked AN470AD4.  The latter are very easy to buck solo, just be careful not to let the rivets work-harden prior to getting a good shop head.  Also, there is one AN470AD4-5 rivet on that outboard side that requires a deliberate approach since there is a AN470AD6-5 filling a tooling hole impeding good bucking bar access.

The tank will sit inverted for a week or so to promote better sealing against the baffle.  Probably won't make a difference, but it surely won't hurt.  Every rib and baffle rivet head (shop and factory) and all mating surfaces were slathered with sealant, including a fillet at all joints.

After a full cure, the last baffle rivets will be installed following skin countersinking.  Then it will be 1) final leak testing of left and right tanks, 2) priming of the baffle and outside rib faces then 3) hanging of the left and right tanks.

Wings: Fuel tanks. Right tank ribs and stiffeners sealed.

I decided to redo my fuel tanks.  See here for why.  The entries specific to the redone tanks are here.

The right tank ribs and stiffeners are in, along with the capacitive probe connector.

I bought an extended double offset rivet set to hit the top-most AN470AD4-5 rivet joining the aft and fore inboard ribs to the tank attach assembly.  Turns out this thing is really difficult to use and just ends up work hardening the rivet.  So, in the end, that rivet isn't very pretty.

The plans would do well to have you not rivet the VA-146 Flange Bearing to the tank attach assembly until after you drive that rivet described above.

Both tanks are waiting to have their fuel level optical sensor installed, final sealing forward of the J-stiffeners and fuel float senders (yes, I'm using those with the capacitive sensors).  Then I can leak test prior to putting on the baffles.

What a mess.  I should clean that.

Wings: Fuel tanks. Prepping for sealant, capacitive probes fabricated and locking caps.

I decided to redo my fuel tanks.  See here for why.  The entries specific to the redone tanks are here.

Here are the tank stiffeners, J-stiffener and fuel cap flanges placed in the skins.  I'm tracing around these parts so I know to what extent I should scuff the interior of the skin for sealing.  I'll do the same for the ribs separately.  Since the interior of the tank skin should not be primed, I want to preserve as much of the alodine layer as possible.

Using my new nut plate jig for the capacitive probes I fabricated.

Match drilling the VA-141 Flange, Finger Strainer to the T-1003B-R Tank Inboard Rib - Aft.

Below is the Tank Inboard Rib - Aft showing the location of the optical fuel level sensor I'll be using as a redundant low fuel warner.  I placed it about 1.75" from the bottom of the tank at that location.  A quick, back-of-napkin, entirely inaccurate calculation suggests this will correspond to a bit more than 5 gallons, which ain't much (Update 10-May-18:  It ended up being about 1 gallon as I didn't consider dihedral).  If the warner goes off, it's either time to switch tanks to a hopefully fuller one and/or find a place to put down of my own choosing.

The T-1010 Anti-Rotation Plate is visible on the left.  Also, there is an additional hole at the top which is for the BNC connector that will be used to connect to the capacitive probes.  I've decided to use both the capacitive probes and the floats as redundant fuel level indicators.  This is for two reasons 1) in case one fails and 2) in case my capacitive probes end up being non-functional or not satisfactorily accurate.

 

And locking caps which fit the stock flanges (I verified this with Robin at Newton SPRL prior to purchasing).  Left image:  Locking cap with universal flange on left.  Right image:  Caps swapped.  I will be using the setup on the right.  And I guess I'll have surplus caps and flanges.

 

And why not get a "Remove Before Flight" keychain for the associated keys?

Wings: Fuel tanks. Match drilled, countersunk and low level fuel sensor.

I decided to redo my fuel tanks.  See here for why.  The entries specific to the redone tanks are here.

Work on the tanks continue.  With the leading edges 95% done, I have more space to work on the tanks.  Here are the cap flanges after countersinking them to fit the skin dimples.  I plan to get locking caps.

Tank skins after matching drilling the J-stiffener and now ready for countersinking along the baffle holes.  About 336 holes in fact.  Match drilled, deburred, straightened, dimpled and fluted tank ribs visible, as are my in-progress capacitive probe plates.

 

And, the original crates are starting to look empty.

Okay, so the flap and aileron ribs and other smaller associated parts are elsewhere, but seems a far cry from the first day with the full crates and all the hardware.

Today marks the 250 hour mark.  I will take a guess that I'm looking at 200 hours to go.  We'll see how this prediction holds up.  Update 10-May-18:  Bad prediction. The wings required 611 hours.

Also, I liked the idea of a redundant low fuel level warning light.  Aircraft Extras has a nice setup, however I could make my own, with the features I want for less, using the same liquid level sensor.  After some digging around, I determined that the Honeywell LLE102000 is similar to sensor used with Gopher Electronics having it for the lowest price.  I picked up two and will also grab two anti-rotation plates for the install.  The sensor is just a simple TTL-type.  Just need to ensure a regulated supply which is easy enough.  I'll be able to integrate the input into a simple microcontroller setup that I plan to have doing various things.

The bottom of the 26-Jul-13 post shows the install of the sensor.