Tami and I finished sealing the rear baffle plate on Monday.  So today (Saturday), I decided to pressure test the fuel tank to see if my tank sealant days were over.  As I did with the right tank, I set up a tygon tubing manometer to monitor the tanks ability to hold a slight air pressure.

The idea here is that when you pressurize the fuel tank with low pressure air, the air will push on the water in the tygon tube and in this case, push the water up the 4" x 4".

I just secured the tygon tubing to the 4" x 4" and jammed a funnel at the top so that I could pour in the food colored water.

Using a manual bicycle air pump connected to a schraeder valve in the tank drain fitting, I pumped air into the fuel tank until I had approximately 20" in difference in the 2 column heights of water.  I marked the height of the water, the time, and the temperature.   A one degree change in room temperature was resulting in a change of approximately 1" in the height of the column of water.

After I initially placed pressure on the tank, level was very slowly lowering.  Ooh GREAT, my worst nightmare has come true, a leak that will be a pain to fix.  However, before I get to negative about the whole thing, I decided to check the fuel tank cap since it is a pretty big hole.  I have the more expensive locking fuel caps and the first tank gave me no problems.  Anyway, I see that their is a nyloc nut on the inside of the cap that controls the amount of pressure exerted on the cap and flattening a rubber washer.  I decided to tighten that up just a hair (I ended up turning it about "1-flat" on the nyloc nut).  I re-installed the cap, re-pressurized the tank and voila.....  The manometer was holding steady ...

I just sat a thermometer near the tank so that I could keep an eye on the temperature vs. water column height.

UPDATE:  I checked on the fuel tank the next morning (20 hours +) under pressure and the manometer level only varied a inch or so and this morning, it was higher than when I marked it yesterday.  I am going to call the tank good...

After I decided the tank was sealed, I removed all the manometer hardware and installed the tank fuel drain.  I torqued the fuel tank drain to 60 in-ibs.  As soon as I get some other miscellaneous wing stuff done, the tank will be ready to install on the wing.

I opted for the deluxe locking fuel cap when I ordered my wings.  I am extremely happy with the quality of these filler caps.

Now that my tanks are more or less done, I can work on a ton of other miscellaneous wing stuff I need to complete so I can get started on the fuselage.

I was beginning to think that I was never going to finish the left fuel tank.  I was waiting to make a Van's order to order some Polypropylene tubing to finish my capacitance fuel sender installation.  After some SLIGHT procrastination, I ordered the polypropylene tubing I needed along with some other airplane things since Van's charges a "$5 handling charge".

One of the tasks I still had outstanding on the tank internals was to solder my BNC fitting to the capacitance fuel sender wiring (wire).  Not a great looking solder job (remember, I come from the occupation of "bigger the blob, better the job").  After soldering the BNC connector, I used a Fluke digital multimeter to verify the following:

• That I had electrical continuity between the center pin on the BNC connector and each of the capacitance sender plates.
• The I had NO ELECTRICAL CONTINUITY between any of the fuel tank ribs and the capacitance fuel sender plates.

Everything checked out fine after my highly skilled solder job.....

A pict of the inboard fuel sender capacitance plate.

The outboard fuel sender capacitance plate.

I reviewed the log entry I made for sealing the rear baffle on the right fuel tank and started to assemble all the tools and equipment I was going to need conduct my last (hopefully) sealing session.

Before putting on the rear baffle plate, I finished sealing the BNC connector.  I have heard of a couple of builders who have had leaks around the BNC connector.  I used copious amounts of tank sealant to seal around the BNC connector.  I also encapsulated the wire back a couple of inches so that I didn't get any "wicking" of fuel up the fuel sender wire.  I did this on the right tank as well and didn't have any problems with leaks in this area.

I also put dabs of sealant securing the sender wire(s) to the tank vent tube.

Earlier, I had encapsulated the fuel sender capacitance plate wire that is attached to each fuel sender plate.  This is the inboard rib.

Ditto for the outboard rib.

After putzing with the miscellaneous fuel sender tasks, I coaxed Tami to come out and begin the task of sealing up the rear baffle plate.  Sealing the baffle plate is a BIG JOB.  I didn't get any "in-process" pictures.  If you have done any tank sealing, you know that you stay busy and are usually pretty messy.

One thing that made me really nervous sealing the rear tank baffle is when it came time to mount the 'z-brackets' to the rear baffle plate.  It is really easy to get disorientated and mount these 180 degrees out.  If that happened, I would really be cussing when trying to mount the tank to the spar.  Anyway, I took a few extra minutes to double, TRIPLE, verify that I had the correct orientation for my z-brackets

Just an end shot of the outboard tank rib.

There are a ton of rivets on the rear baffle plate.  It took a ton of time just to do "touch ups" on the rivets, the flanges, etc.

A shot of my inboard rib.

Everything looks okay from the end.

A little messy on the inboard rib, but by this time, I really didn't care.  I was just beat and ready to call it a night.

I am thrilled, if everything on pressure testing goes well, that I am done sealing fuel tanks.  I did make the mistake to seal the rear baffle on a "school night".  I started around 6 pm and didn't finish up until around 1 am.  I didn't even bother cleaning up my mess.  Tami had already cleaned up my clecoes and tools so I didn't have to worry about them.

Not a very detailed log entry.  Check my log entry I made for the right tank baffle plate.  I had much more detail.

Sealing The Baffle Plate Log Entry

This log entry is just a cumulation of several shorter tank sessions.  I spent two separate nights sealing the inboard and outboard tank ribs and reinforcement plates.  Pretty straight forward, just really messy....

I ended up using the fuel pick-up tube that I fabricated a week ago or so.  It was long enough to clear the nutplates on the reinforcement ring.  It is not perfectly centered between the nutplate and stiffener.  What I was really demanding here is that the nothing touched and chaffed.  I tried twice to get a more centered fuel pick-up, but I wasn't any closer than this pick-up.  We are talking 1/16" difference here.  Precision tube bending....

Anyway, after I screwed on the inspection plate, I torqued the 6N fuel pick-up nut to 100 in-ibs.

I also torqued the vent line 4N fitting to 60 in-ibs. 

Notice that there are two wires on the inboard capacitive plate.  One connection goes to the outboard capacitive plate and the other connection goes to the BNC connector on the inboard tank rib.

Tank sealant for the inboard capacitive plate.

I applied sealant to the electrical hardware before I mounted the capacitive plate to the tank rib.  Made it a little easier to goop the tank sealant on and clean it up.

I fully encapsulated the outboard capacitive plate electrical hardware.

To attach the inspection plate, I used the cork gasket and "buttered" it with EZ-Turn lubricant and then placed it between the rib and the inspection plate.  I then attached the inspection plate with some 8-32 x 5/8" stainless steel socket head capscrews.  I wasn't able to torque them with a torque wrench, but I tried to tighten each screw equally by feel.

To finish off the fuel seal of the inspection plate, I topped the whole thing off with some tank sealant around the screws and the inspection plate.  Since I used EZ-Turn on the gasket, I removed all excessive lubricant as I doubt if the tank sealant would stick to it...   This is what I did with the right tank and I didn't have any sealing issues.

The only thing I have left on this tank is to get 1/2" of polypropylene tubing to insulate one of the capacitive plate mounting screws (long story), mount-solder-seal the BNC connector.  Then it is sealing the rear baffle plate and pressure testing.  Woo Hoo....

Well after a little sleep, work, and time to reflect on my vent line problem, I decided to see if I could rectify the vent clip problem today when I got home from work.  I fabricated a new vent line clip from aluminum sheeting that comes with the wing kit.  This is all pretty straight forward.  I liked how my last clip lined up with the vent line and held the vent line pretty high in the tank.  I strived to repeat that characteristic.

After repeated installing of the clip and some time on the scotchbrite wheel, I got a vent clip that sat pretty nice on the fuel filler flange.

My bigger problem was how was I going to set a solid rivet in this NARROW space.  Like I stated in earlier log entries, I used the rivet hammer and the back rivet attachment to form the shop head.  Well, that wasn't going to work here as I could no longer open the tank skin far enough to get the rivet hammer in there.  The only thing I could come up with was to remove my 3" yoke from my squeezer and use it for a bucking bar.  This worked pretty good (for doing 1 rivet).  I got a nicely formed shop head.  The vent clip and the filler flange looked good.  The hand holding the "bucking yoke" took a little hammering, but it was only one rivet.

It is a tight space and even as thin as the yoke is, it barely fit.

I mixed up a really small batch of tank sealant to encapsulate the filler flange, rivet, and vent clip.  I was pretty generous here as I certainly didn't want to have to try and fix a leak after the rear baffle was on.

While I was at it, I tried to push some tank sealant between the vent clip and the vent line to hold it in place and kind of work as an "anti-chafe" cushion.

It all looked good when I was done.  I decided to wait to rivet the outboard end rib until I am sure that this vent line is NOT BROKE, secured to the filler flange, and fully sealed.  I decided to call it an early night.

I don't have a lot of pictures to show for my efforts this weekend.  I started installing and sealing tank ribs which is a MESSY operation.  I have been dreading sealing my second AND last fuel tank.

I have been prepping my wife for a month or two about sealing the fuel tank as she doesn't like working on tanks either.  So the weekend arrived and I asked (I mean told her) that is was time to work on sealing the tank.  After a little groveling on HER part, she came out to the garage and grabbed the bucking bar.

No in-process pictures for the log.  Everything you touch (i mean look at) during a sealing session gets tank sealant all over it.  We were well on our way to finishing our second rib and Tami broke the relative silence of the garage air conditioner;

"You know, I hate to admit it, but sealing the fuel tank is more enjoyable than riveting the ailerons"   I shit you not!!!  That is what she said straight faced an all.  It was a good thing I was already sitting down on the garage floor when she said that.  I thought I was delirious and like a fool I asked her what she said and she repeated the statement over.  Maybe she is delirious.

Anyway, over the course of the weekend, I got 5 of the 7 tank ribs riveted and sealed.  So far, so good.  Tanks are an incredible amount of tedious work considering the brevity of this log entry.

Before I riveted the outboard end rib on and sealed it, I wanted to get my vent tube fabricated and routed through the tank.

WARNING:  An abbreviated version of tubing bending for dummies (me)...
I had ran the vent line through the tank (before I bent the offset) and measured the distance between the rib hole for the vent and where I drilled the hole in the inboard rib for the vent line ELL.  That distance (as best I could tell) was approximately 1 18/32".  Okay, now I need to bend the tubing such that it will actually line up with the Inboard rib ELL.  How did I do that on the last tank???  Ooh yeah, a little trigonometry.  One of the few times I have had to use what little math knowledge I have.  I figured that I would bend my tubing to provide a 60 degree offset.  Basically the tubing angle forms the hypotenuse of a right triangle and this is where it turns into a math problem.

Needing a finished offset distance of 1 18/32" (1.562"), I just took the cosine of angle 30 and solved for the hypotenuse (or actual tubing) length.  I came up with 1 26/32" (approximate is close enough).  So before I made any bends in the tubing, I made my first mark at the end of the vent line far enough away so that I could get my AN fitting on and make my tubing flare (Approx 3").  I then measured down the tubing 1 26/32" and made my second mark on the tubing.  This represents where the two bends will be started in the tubing to create my offset.

The two lines that were measured out on the tubing are where I started my bends.  I put the first line under the "0" on the tubing bender, bent to approx. 60 degrees.  Then move the tubing down to the second mark and place it under the "0".  It is important to properly orient the tubing here or end up with a shape that starts to approximate that of a STOP SIGN.

When I got done with my two bends for my offset, this is how it lined up.  Pretty darn good.....  If its not perfect, there is a little room to bend the tubing by hand over the width of the inboard bay.  By measuring out the bend, I didn't have to do any additional "tweaking".

I am really happy with my offset.  I couldn't have gotten it any closer if actually knew how to bend tubing.   Now I just need to put my AN fitting on the end and flare it.

Okay, what the heck is this?!?!??!?!?  Damn It !!!   I was routing my vent tube through the tank and as I fed the vent tube through the vent clip, I noticed that it moved fairly easy.  It isn't supposed to do that...  Uh oohh.  I briefly pondered whether or not to move the clip and just see how bad this was going to get.  Of course, I couldn't let something like this go.  It is easier to fix now than it will be to fix later.  I removed the vent tube and gave the clip a little tug.  It was clear that the only thing holding the vent clip in place was the tank sealant I gooped over it.  It was actually pretty tough to remove just being held in place by sealant.

I wonder how hard this will be to fix?

I used an x-acto knife to cut and remove tank sealant around the vent clip, drilled out the rivet and cleaned the area of tank sealant with the x-acto knife and a small rag soaked in MEK.  The clip area looks pretty good.  I should be able to re-apply tank sealant to the affected area, install a new vent clip, and have no problem getting a good seal.

The real trick, which I haven't figured out yet will be how to set a solid rivet in here.  My back rivet method isn't going to work as I can't open the tank skin enough to get the rivet hammer in here.  I am thinking that I may be able to use a 426 Cherrymax rivet here as they sit and look very close to the aesthetics of the solid rivet and the Cherrymax rivet is way overkill for this application.

To much to think about tonight.  I am going to take the rest of the night off, give this some thought, and fix it tomorrow.