Tonight I was going to fly to the local EAA Chapter 80 meeting in Omaha, but I got a wild hair to knock out another session with tank sealant.  Since when is sealing fuel tanks more fun that going flying and talking about airplanes????  I must be breathing to many MEK vapors.

Now that I have my fuel pick-up fitting and anti-rotation bracket mounted to the inspection cover, I installed my newly fabricated fuel pick-up tube.  It fit better than Van's original pick-up tube, BUT....  I still am not super happy with the clearance between the tubing and the nutplate.  They don't touch each other, but that can't be more than the thickness of a couple of sheets of paper between the two.

I think that I am going to fabricate yet another fuel pick-up tube.  As you can see there is plenty of clearance between the stiffener and the tubing, but I had to work hard to see that the tubing and the nutplate don't touch.

Otherwise, I am really happy with how the fuel pick-up sits in the fuel tank.

The fuel pick-up sits nicely along the end rib and clear of the tank drain.  I guess this is a good example of why it is a good idea to sump your tank before flight.  If there is any water in the tank, the fuel pick-up sits very near what would be the lowest point in the tank when on the ground.

Anyway, I had enough tubing to attempt two new fuel pick-up fabrications.  I had one absolutely perfect so that the fuel pick-up was nearly centered in the clearance between the fuel tank stiffener and the pesky nutplate.  However, YOU MUST REMEMBER that when working with tubing, you must put the AN sleeve on AFTER you make the bend in this tube and BEFORE you flare the end.  I made that same mistake X2!!!!!!! Dam-it....  It only cost me about 2 foot of tubing (a whole $1.38), but it was the last 3/8" tubing I had.  Okay, time to surf Wicks Aircraft Supply.

Okay, now that my fuel pick-up is not a done deal yet, I decided to move onto prepping and sealing the fuel tank filler flange and vent tubing clip.  I had everything ready on the fuel filler flange, so all I had to do before sealing was to finish fabricating the vent line clip.

I made this clip a fair amount shorter (less than 3/4", but noticeably shorter than the right tank).

When I clecoed the vent clip to the filler flange, I looked down the tank and it lined up almost perfectly with the tooling hole for the vent line.  In the background, you can see my vent and fuel return fittings on the inboard rib.

Where the vent clip butted up against the neck of the fuel filler flange, I radiused it slightly.  My thought here was to allow it to "hug" the neck of the filler flange which would keep it from twisting.  The vent clip is only held by one rivet and it doesn't take to much effort to twist it.  It is kind of a mute point after you put the vent line through it.  It becomes pretty immobilized after that.

Pretty happy how this is looking so far.  Alright, where's the tank sealant?

Let the sealing fun begin....  I am rather generous when I put on tank sealant.  I have seen builders who have really small fillets and sealant lines that look like a work of art (which is very difficult if you have ever worked with this messy, sticky stuff).  Then they go to leak test their tanks and sure enough, they leak.  My approach has been to fully encapsulate rivet heads and flanges.  What I work hard to stay away from is to have "stringy" messes all over the inside of the fuel tank.  Those little chunks of sealant that can become dislodged and make their way to the fuel pick-up.

I got the fuel filler neck riveted and sealed.  Then I spent about as much time again cleaning the area so I had none of those small, stingy, blobs of sealant I was talking about.

Nothing is fun about riveting this flange in.  Van's calls out AN426AD3-4 rivets for this fuel flange (when you are using the kits standard, non-locking flange).  The problem is that I upgraded my fuel cap to the locking style which has a different flange.  It is thicker on the sides and thinner on the forward and aft sides of the flange.  I reviewed my log entries for the right fuel tank and I didn't make any mention of trouble with rivet length.  It was clear that the rivets Van's called out were going to be to short in some of the areas around the flange (see my rivet call out below).

I saved the forward rivet that holds the vent clip until last.  This rivet gave me a hard time on the last tank and on this tank, I didn't have any problems.  As I detail in my right tank, the best solution I could come up with for riveting the forward rivet that holds the vent clip was to use the rivet hammer with the back rivet attachment on the shop head side of the rivet.  I used the bucking bar on the skin side of the rivet.  The reason I saved this rivet until last, was that in order to get the rivet hammer on the inside of the tank, you have remove the fuel tank from the cradle and set the skins on the table.  The tank skins open up enough to get the rivet hammer on the inside.

Here is my unofficial rivet call out I used for my fuel filler flange.  The 3-5 rivets were a little long, but the 3-4.5 rivets were a little short.  Why does it have to be so complicated?  I ended up bending over one of the 3-5 rivets, so I did have to drill one rivet out.  That was better than last time, when I drilled the same rivet out 3 or so times.

I should have went up to the EAA meeting.....  I feel pretty good about having the fuel filler flange riveted and sealed.  One more tank sealant session behind me...  WooHoo...

We are getting ready to head to Airventure for a couple of days this week so today's goal was to get all the miscellaneous tank prep work done so that when we come back, we could start sealing this darn thing up.  I will be so glad when I have the fuel tanks behind me.

This morning, I started by match drilling all the holes.  Using the sharpie marker to track which holes have been drilled has worked so well for my absent mind, I continued to use it when drilling the fuel tank.  You quickly forget how many holes are in this tank until you have to drill and debur them.

In the picture below, I placed a 2 x 4 scrap behind the screw attach holes and then drilled them out to size #19.  The 2 x 4 worked well to hold the skin and prevent it from chattering.

Next, I clecoed the stiffeners to the tank and labeled them with the same labeling convention I used on the right wing.  'A' = forwards, 'B' = aft and 1-6 from inboard to outboard.  Then I match drilled all the stiffeners.
Are you starting to see a recurring theme with this prep work????

On to the fuel drain.  When I had it positioned where I wanted it, I used a set of vise clamps to hold it in place.  I lined up the drain flange so that the forward and aft rivet holes were equally spaced from the edge of the skin.  It doesn't really matter, I just like a little symmetry and this is how I lined up the right tank drain.

Looks pretty good from this picture.

Next it was onto the fuel cap.  Since these are locking caps, the flange has a definite orientation (one because the filler neck is curved to line up with the skin and TWO, the locking cap has to be oriented in a specific location so the filler cap sits in the flange correctly.  See my right fuel tank log entries for more detail).

Drilling this flange kind of made me nervous as these fuel filler caps are not all that cheap.  $90 a piece.  All I need to do is mis-drill this filler flange to piss me off.  Everything has gone great since starting this right wing.  I didn't want to make my first mistake on the wing here.

Can't forget to machine countersink the filler neck flange.  I used my test coupon with the tank dimple die to set the countersink to the proper depth.

Then it was onto countersinking the tank skin where it is riveted to the rear baffle.  Just cleco the rear baffle in place to give the countersink pilot a guide point.

I countersunk the rivet holes a couple of thousandths of a inch here to allow for tank sealant between the tank skin and the factory rivet head.

Just a staged photograph what I worked on today.  I got so busy, I forgot to take pictures as I went along.  It is kind of boring anyway....  You know the routine: drill, debur, dimple, repeat....

Things yet to do before sealing:

1. Debur outside of skin
2. Dimple ribs
3. Dimple Skin
4. Dimple stiffeners
5. Drill ribs for capacitance senders
6. Fabricate vent clip (make 2 in case I screw up the first one while riveting)

Today, I set out to get more tank sealing done so that I could knock out sealing tank ribs next week.  I didn't think today's sealing efforts would take but a couple of hours and then I could get some work around the house done.  WRONG!!!  Tami and I riveted the leading edge together in about 2 hours.  Tank sealing is turning out to take me a WHOLE LOT of time.  Over 20 hrs of riveting and sealing and I haven't started on the ribs yet.

Below, I riveted in the anti-hangup bracket for the root rib inspection hole.  I fully encapsulated the bracket and rivets.  Most builders do not do any sealing on this inspection hole as it is sealed by either the inspection cover gasket (if you use it) or the inspection cover plate is sealed with tank sealant to the outside of the root rib.  I have opted to use some after market sealed (floating) plate nuts.  I am hoping that sealing this reinforcement ring and other hardware, that I am able to use the gasket that is supplied with the kit.  If I need access to the tank or the gasket ever needs changing, no problem as my leakage paths here at the root rib are only through the "Big Hole" and not around every plate nut rivet and plate nut screw....

The next component sealed was the drain flange.  The drain flange was machine countersunk at the factory and the factory rivet heads are almost perfectly flush.  I frosted up the back side of the drain flange and slapped it on the skin and threw a couple of cleco's to hold it in place.  I was able to squeeze all of these rivets with the pneumatic squeezer.

Just another angle of the drain flange.

This is the back side of the drain flange.  As with all of my sealing to date, I fully encapsulate my rivet shop heads.  I tried to keep the skin between the rivets clear of tank sealant.  I didn't want any condensation in the tank from being impeded in its flow toward this drain flange.

This is a picture of my outboard rib tooling hole.  I cut a triangular shaped piece of aluminum and riveted it over the tooling hole.  The only trouble with this I had is that I didn't have any solid rivets short enough.  I did have some CherryMax universal blind rivets that were short enough.  The CherryMax universal rivet had a larger shop end.  The CherryMax rivet is really a pretty sophisticated rivet when you read through Textron's technical bulletin.  Link To:  CherryMax Rivets Info

I just placed copious amounts of tank sealant over everything.  This sucka is not going to leak.

This is the outboard side of the rib.  Again, plenty of tank sealant over the hole and the factory heads of the CherryMax universal rivet.

The last three sealing operations were not to bad.  Okay, now it is on to the problem child of today's efforts.  The fuel filler flange....  What a pain in the arse.  I started by clecoing the ribs in on both sides of the filler flange to hole the tank skin in its basic arc.  Then with all tank sealing efforts, I frosted up the filler flange to skin surface and cleco'd in place.  I got Tami to help me with this as I was not going to be able to reach every rivet with the pneumatic squeezer so I decided to buck these rivets.  They were all fairly straight forward with the exception of one rivet (read on).

After Tami and I got about 3/4 of the rivets set, we removed the ribs to gain access to the remaining rivets, including the difficult one...

Okay, can you guess which rivet on the filler flange is the problem child???  Hint:  It holds the vent line clip (T-714).  How am I going to set that rivet?

• Grind down end of bucking bar to get in between the filler flange and the clip.  NOPE>>>  Didn't work.  The end of the bucking bar that was flattened with the grinder does not allow enough surface area to properly form the shop head.  DRILL OUT RIVET start over.

• Use pneumatic squeezer.  NOPE>>>  Yokes are not long enough.
• Back rivet against bench back rivet plate.  NOPE>>>  Didn't work.  Factory rivet head set high, couldn't get skin to set up against back rivet plate.  DRILL OUT RIVET start over.
• Hold bucking bar on factory head and form shop head with rivet hammer and back rivet attachment.  YEP, GETTING CLOSE.  However, flattened out rivet shop head.  *&$%*%*$#@!*.   DRILL OUT RIVET AGAIN, Inspect T-714 clip find out clip mounting point is distorted....  Fabricate new vent line clip and start over.

On the 4th try, I did get a properly set rivet.  However, I will do this rivet slightly different on the next tank.

As you can sort of see in the picture, the factory head is not completely flush on all sides.  This is in part due to the fact that this is where the skin has the most curvature.

One the next tank here is what I am going to do for this troublesome rivet:

• Use the bucking bar on the factory head side.
• Use the rivet hammer back rivet attachment to get in between the filler flange and the vent line clip.
• Use a short burst (2-3 hammers at a lower pressure (approx 35 psi with my Sioux 2x rivet hammer).
• Rotate (rock) the bucking bar a couple of degrees forward to attempt to keep the factory head flush with the curvature of the skin.
• Use a short burst (2-3 more hammers).
• Check shop head for proper dimensions.

After all of this, I was sticking to everything.  I spent the rest of the night cleaning up.  WooHoo....  Am I done with this tank yet?

Tonight's goal was to put a couple of hours on the plane without having to think too much...  For my fuel tank cap, I went with Van's deluxe locking fuel cap.  These fuel caps are very nice (and spendy).  These use a different filler flange than Van's stock fuel caps that are shipped with the wing kit so these deluxe caps have to be installed at the time of tank construction.

Because they are lockable, the fuel cap is oriented in definite locations (it can be locked down every 90 degrees).  So the idea here was to get the cap centered in Van's pre-punched hole and to have it oriented so that the latch is pointing straight aft (or forward) and not at some screwball odd angle.  The filler flange is angled so that it follows the curvature of the tank.  So orienting the flange is not to difficult.  If you are rotated out of position a couple of degrees, you can tell as it doesn't feel like it fits correctly up against the skin.

It should be noted at this stage, my fuel tank is clecoed together, but I have removed the inboard rib (T-703) so that I could use some simple clamps to hold the flange in place until I got a couple of holes with clecoes in them.

Below, is a far off shot showing the alignment of the fuel cap position .  I even had Tami come out if do some quality control for alignment in case my eyes were on crooked today.  To double check our eyeballs, I took a straight edge and ran it centerline from the forward to aft rivet holes and verified that the straight edge intersected the center of the latch rod and the little finger lip on the latch.

I just took it slow, drilled a hole, clecoed it, and made sure the hole I drilled was in the center of the fuel filler flange.  Went to the next hole (180 degrees out) did the same thing.  As I added clecoes, I took off my other clamps.  So far so good.

If you look at the filler flange, you can see the notches in the flange every 90 degrees.

After I got all the all the holes drilled, I inserted the fuel cap to make sure that the tank skin didn't interfere with the cap.  In the picture, it looks like it is not perfectly centered.  It must be the angle I shot these pictures because when I was putzing with this, it was perfect (thank goodness).  In the picture, the fuel cap is unlatched and you can see the keyhole.  Van's has put a little forethought when shipping these locking caps as they sent me two that were keyed alike.  Yes, you have to buy them individually.

Pictured below, you see the cap is latched and the latch is bent down (in-flight mode>>>   SOMEDAY).

While I was at it, I decided to countersink the fuel filler flange holes.  I made a test coupon out of some scrap aluminum.  However, for this coupon, I used my tank dimple dies (Cleaveland Tool Part #: DIE4263T) as I wanted a slightly deeper countersink to account for use of tank sealant.  The tank dimple die is supposedly .001" or .002" deeper than the standard 3/32" dimple die.

I don't particularly like countersinking as I have a difficult time getting consistent results with micro-stops.  Tonight, all holes looked really good...  I couldn't be happier.

Just a little anatomy lesson on these locking fuel caps.

Do I really need to go into more detail here???

I had a little time left before I wanted to quit for the night so I decided to cut out the tank access plate.  The first thing I was challenged to do was to determine the center of the hole being cut.  I tried to apply a little Geometry 101 here.  What I did was take two measurements 90 degrees apart with a machinists ruler.  I fixed one end of the ruler (with my finger) and then pivoted the opposite end.  At the maximum diameter, the ruler would intersect the center of the circle.  Do that again displaced by 90 degrees and viola, you have the center of the circle.

Okay, the center of the cutout has been determined...  Next, I had to adjust the cutter radius to get the proper diameter cutout.  I measured the INTERNAL diameter of the T-407 reinforcement ring.  Van's gives you the external diameter of the ring and you could subtract to get the internal diameter, but my way was just as easy.

After about 30 seconds of shaking the table with a spinning circle cutter, the damage has been done.  I de-burred and took 400 grit wet/dry sandpaper to finish the edge of the hole.  It turned out GREAT....  WooHooo!!!!