28 September 2013

Wings: Flaps. Top skins on.

Left and right flaps have their top skins on, save just a few rivets each.

Below are the left rod end subassemblies.  Yes, on the inboard one I foolishly match-drilled and countersunk for a non-existent nutplate.  Consider them lightening holes.


It's not easy to squeeze some of the ribs onto the spar since other immediately adjacent ribs impede access.  Below is my suggested sequence and method of setting the rivets on those ribs that are crowded out a bit.

Left inboard hinge pair subassemblies.  The main rib's rivets were bucked.

Unfortunately, I initially tried to squeeze the outboard rib's rivets.  The middle rivet was easy, but the flanges separated slightly around the rivet shaft.  In order to access the upper and lower rivets I had to bend the main rib quit a bit.  Though the plans mention that such an approach is acceptable, you have to consider that the flange will be pulled from being flush against the spar.  This means a potential space between the spar and rib flange opens up and becomes an actual space for your rivet shank to have a party in and fill.  The left image is how that comes out.  Look at the left and right rivets - no narrative necessary.  The right side is what it looks like after I pulled out the rivet on the left (which is the bottom of the spar) and instead bucked it.  You can see that the removal process (a challenging affair given the limited access) elongated the hole so the replacement rivet doesn't sit in there nicely:  The shop end is short and now the spar is slightly deformed. 

I deemed that unacceptable.  Now, removing those left and right rivets wasn't going to be easy a second time.  The holes got even worse.  Here are the holes with a AN470AD4-5 (plans call for a -4) rivet placed in them.

An AN470AD5 nearly fit in them.  I didn't want to put that large of a rivet in there since I only have a 2x gun, don't have a rivet set for it and the flanges didn't need the additional stress from trying to buck such a rivet.  So for each side, I took an AN470AD4-5 (again, the plans call for a -4) and pre-squeezed to fit just snug in the hole.  Below are two pics showing, right-to-left, an AN470AD5-5, my pre-squeezed AN470AD4-5 and an AN470AD4-4.  This gives a good indication of how large I made that hole.

Here is the left side with the pre-squeezed rivet place in the hole.  It's a better fit, but isn't perfect.

I could then bend the spar back and get a better fit with all the flanges together.  The left image is from the left flap after (the now second) replacement with the pre-squeezed rivets.  The right image is the right flap in same place showing what things look like when you get it correct the first time.  Given the three layers coming together, looks like I should just have bucked them all on the right side.  That middle squeezed rivet separates out the flanges.

I'm pretty sure I'll be removing the two left flap rivets and just drilling up to an AD5.  I don't like how it all sits.  The right looks okay, save for that middle rivet which I can straighten up.

The hinge pair subassemblies call for the rivets along the joggled end to be riveted double flush.  I initially tried to buck these double flush rivets but because it's very hard to keep the subassembly flush against the backing plate, they didn't sit nice and it was too easy to injure the part with the rivet set.  So, after sanding out the damage I caused, I decided to squeeze all of the double flush rivets on the joggles.  Having never done that before, I was pleased with the outcome.  Unless you look really close, you might have a hard time distinguishing the factory (left) and shop (right) heads.  Tip:  If you screwed up a machine countersink on one side of the joggle, just put the shop end in that countersink.  Problem solved! 


Left and right flap skeletons ready for skins.

Here the left flap sits with the top skin cleco'd, ready for riveting.

Right flap with most of top skin riveted.  The inner AN426AD3-4.5 rivets have yet to be bucked.  I decided I wanted a bucking partner for those.  Too easy to damage the factory heads on the main rib rivets when going solo.  Also the aft two-most rib rivets need to be back-riveted.

Left flap in same state parked in the (nearly empty!) wing crate next to a bottom flap skin and aileron skins.

And just to be complete, here are the backsides of the right and left flaps.

17 September 2013

Wings: Fuel tanks. Left 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.

Capacitive probes on left tank are installed.  I had to replace a screw from last week since it got stripped going into the nutplate.  Thankfully the nutplate wasn't damaged.  The work for the left tank was identical to the right tank, so I won't go into as much detail here.

I put the masking tape just over the skin's baffle rivet holes this time.  Turns out it wasn't as useful as I had anticipated:  When the tape is removed, it just takes the sealant bead with it since the bead just fell aft onto the tape.  Here is the sealant on the skin ready for baffle install.  You can see the capacitive probe wire in the image.

As with the right tank I put a very thin layer of sealant on the baffle flanges (shown below) and aft rib flanges.

Here is an image looking aft through the filler flange to see the sealant along the baffle-skin joint.

And here are the "shop heads" of the AD-42H blind rivets along the rib flanges as seen through the filler flange.

I had to remove a AN470AD4-4 rivet I put on the outboard attach zee (it needs a -5).  With all the wet sealant, I realized a "chip catcher" was necessary.

And here is the left tank, inverted for curing.


I also countersunk for and placed the final baffle rivets on the right tank.  After it cures, it will be test time.  Once the left cures I will go through the same process.

14 September 2013

Wings: Flaps. Parts primed.

Nothing too exciting today.  Just primed up the flap constituents and some other extraneous parts (e.g., replacements and modifications).

General update:  Right fuel tank continues to cure after baffle install.  Waiting on a screw for the capacitive plate on the left tank (original got stripped) prior to its baffle install.  Still need to machine countersink the AEX wedges for the flaps.  I did get some of the connectors I need to finish up the wiring for the heated AOA/pitot.

And today is the 400 hours mark.

11 September 2013

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, 2) priming of the baffle and outside rib faces then 3) hanging of the tank.

09 September 2013

Wings: Fuel tanks. Some fuel tank sealing and initial leak testing.

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

Prior to the initial leak test, I went through the tanks with more sealant.  This encompassed slathering sealant under the curved surfaces of the J-stiffener and tank attach assembly brackets.  Because these areas are hidden from view, I used the "mirror-on-a-stick" approach to verify the slather.

The various fittings and the low fuel level optical sensors were installed and sealed.

The tanks were then dressed with toilet paper to preserve the evidence of any leaks (odd flashback of my youth notwithstanding).  With the tanks water-filled and a full tube of food coloring dye on board (not sure of the origin of this idea, but Mouser turned me on to it), they each sat for while soaking up life.

The right tank has three leaks:
  1. At the junction of the skin, tank attach assembly and inboard forward nose rib on the forward side.
  2. Filler cap left side at the cap's o-ring.
  3. Filler cap right side also at the cap's o-ring.
A liberal amount of sealant can fix the first one.  The last two will require some investigation.  They might actually be at the filler flange.  I would consider it a free vent, but I don't water to creep into the tank.  Incidentally, I tried with both the locking caps and the stock caps.  Both leaked (bot albeit, slightly different parts of the o-ring).

Right tank filled with water.  Leakage puddle visible on inboard side.  But no other rivet or seam leaks.

Internal bleeding?  No, just food coloring to stain the professional toilet paper detector.  Luckily the neighbors weren't curious about all the red water and associated stains on my clothes.

Left image:  Source of inboard leak.  Right image:  Two o-ring leaks on the cap.

The left tank has no apparent leaks.


No, not a fuel tank hematoma.  Just food coloring.

After fixing the leaks identified on the right and letting the tanks dry, it'll be time to install the capacitance probes and baffles, wait for curing and do the final leak test.