Water tight. Not air tight, but water tight.

 I bet y'all thought I had quit and walked away.   Nope.   Thought about it a bit, but nope.

Both tanks remain stubbornly not-air-tight.  I was extremely hopeful that the through-bolt locking mechanism in the cap was the culprit.  I tried sealing the caps with rubber gloves, but there aren't any more latex rubber gloves and nitrile gloves don't have that stretch that is needed to make a perfectly smooth sealing surface.  They tend to fold and bunch up and that makes them leak way more than the cap by itself.  Condoms, on the other hand, are perfectly round in cross section and can be made to fit over the cap.  It typically took 3 or 4 condoms getting torn to lock the caps in place without damaging the condom itself, but I got good at it.

Still, the damn tanks wouldn't hold pressure.  I gave up on the balloons as pressure gauges and got some clear plastic tubing and food coloring to use as a simple manometer.   15 inH2O is about 0.5 psi and so I used that difference in water height as my pressure gauge.  Pumping up the tanks to 15 inH2O resulted in a drift down to about 1 or 2 inH2O in half an hour.  This was fairly repeatable.    Despite being repeatable, I could not find where the air was leaking using the soapy bubble water trick.  (Which is messy, by the way.  At some point, I'm going to have to haul the wing assembly out to the drive way and hose it off.)

I posted my plight on the forum and, man, did I ignite a firestorm!  Two suggestions were worth merit: one was that I had not accounted for the heat of compression and that the declining pressure was actually the heated air cooling off.  The second was to use dish soap rather than kid's bubble soap for my leak detection.   Both of these have been filed for potential future use.

Several commentators had used the logic of "it's a fuel tank, not an air tank" and simply filed their tanks with 100LL fuel and looked for the tell-tale blue stain.  Other's commented that that takes too long to see the stain, and others said balderdash and basically it turned into a debate similar to the holy war of priming vs not priming.

I like the pragmatic approach exemplified by the "it's a fuel tank."   I did a full up water test over the previous weekend.  Literally.   Lada & I filled both tanks to the brim with water and then left for a 3 day weekend.  Upon my return, there was no damp or wet spot on any of the sides or the tops.  I couldn't check the bottoms because of the weight of the water itself, but if either tank develops a leak on the bottom, I can repair those even after the wings are mounted on the plane.

Last night I drained the water and fetched 29 gal of 100LL from the airport.  I didn't have the correct hoses to configure everything (I can't use the cheap PVC tubing with 100LL, so I have to go to the hardware store for the proper fuel hose.).  I'm going to fill each tank and watch for 24 hours.  If no leak, I will declare them airworthy and get back to actual assembly.   This final step will probably take another week or so.  Stay tuned.

still leaking.

 I finally ended up using a condom to seal the fuel cap on the Left tank, but alas, the tank still leaks.  I have this weekend off work and will spend the majority of my time searching for the remaining leaks.  The good news is that the fuel sender and access plates are air tight.  The bad news is that he fuel sender and access plates are air tight...  :-(

might not be so bad after all.

 I have to admit I was pretty bummed the other day.  I really thought that I had a decent chance at not having the fuel float assembly leak.   Maybe I'm still in the running.    I had to walk away for a day to get over my funk, then worked a 24 hr shift, so I didn't go out to the shop until last night.  The kids came over for Labor Day family get together.   Travis is my son-in-law who happens to be an HVAC technician.   As he puts it, "I chase leaks for a living" so he followed me out to the shop and we got to work.

I pumped up the tank to bout 15 cmH2O and the balloon ballooned.  (That's still so weird to watch Starling's Law in action!).   Travis spent about 30 seconds listening and immediately found two leaks. (I have presbycusis and even wearing hearing aids I couldn't hear a thing.)  I  One was the 6D nipple upon which I had attached the balloon. Although I had  applied thread sealant, that didn't work as well as I thought.  That got capped with the appropriate 6D cap and we repressurised.   It still started dropping, but not as fast.   Travis then noted that I had left the bicycle pump on the Schrader valve and pointed out that's just a friction fit and is a likely culprit, so that came off promptly.   Tried again;  still dropping but again dropping more slowly.

The fuel sender seal had no soap bubbles, so that made me hopeful.  I soaped up the fuel filler cap and found a nice leak at the shaft that goes through the cap from the latch to the nylon lock nut on the inside.  I put some thread sealant on it, but it still leaked.  We called it a night and I slept much better even though I haven't proved the L tank is pressure tight.

 

Tiny bubble in the center of the cap

Today, I'm at work and I just did some searching on VAF about this topic and found the following gem, which I'll try it tomorrow night when I get home from work!

 Old trick but for those have never heard it before: Put a rubber glove inside the fill port before installing the cap. That will seal and isolate the cap.

Well, damn.

 4th time was not the charm, either.   Last week we went on vacation. Before we left, I used an extra thick layer of sealant and specifically embedded the star washers and electrical lug in sealant and then covered the stack.  I had such high hopes.

After we got back on Tuesday, I got some clear 3/8" hose to use as a manometer and hooked that up to the Left tank.   I pressurized it to about 13 inH2O which is around 0.5 PSI.  That was the pressure at which the balloon inflated.   I left it overnight and was really disappointed the next morning as the balloon had deflated and the manometer showed only about 1 inH2O.

I haven't had the time nor the heart to try to find the leak yet.  I'm really hoping it's from the filler cap, as that is considered acceptable by Van's.    I really need to get the tanks sealed because I am essentially at a stand-still until they're done.     Alternatively, I might buy another table and start working on the tail surfaces while debugging the tanks.  Stay tuned.

Empennage kit unpacked & inventoried

 Lots of grunt work involved in unpacking Van's kits!  The other night I unpacked and inventoried the major items and was very happy that none were missing.  It took a little bit of creative engineering to find places to store everything in the garage / shop, but it's all on shelves or standing behind other shelves.  I will need some help taking down parts of the empennage kit to get to the R wing spar, but that's a solvable problem for another day.

Today I inventoried the "small stuff".   The shipping company didn't pay attention to the "UP" arrows on the crate and it was actually on its side on the first day they tried to deliver it.   As expected, a few of the small parts shifted in their parts bin and were in the wrong bins.   it only took about 30 min to sort everything out and I can't complain too much more than I already have.    

EMP Bin #1 -- lots of 'small stuff' !

I'm about $6 short in parts that weren't in the kit.  I'm not even going to 'claim' them, I just put them into my cart for my next purchase.

Cutting up the crate for disposal was by far the most difficult part of the process.

Cut up crate parts & a pile of sawdust

3rd time was not the charm 😤

 Well, I had high hopes.   As my flight partner, Ed, often comments: "Hope is not a strategy."   Despite pre-smearing the adhesive on the mating surfaces, both tanks continue to leak.   The good news is that both are leaking in exactly the same place -- the electrical connection at the top right of the fuel senders.

Bubbles, Bubbles, everywhere! 😩

Since both tanks leak at the same place, and that place is where there are 3 stacked components, I clearly need to up my game in that location.  On Tuesday, I will pull off the fuel senders and the inboard access ports (again; for the 3rd time).  On Thursday, I will make another valiant effort to get these damn things on and air tight!

This time (next time?  Anyway, on Thursday) I'm going to repeat the technique of pre-smearing sealant on both of the mating faces.  I will then insert the screw for alignment.  I will place the first star washer on the screw and coat it with sealant until it is completely 'submerged' in the goo.  Then goes the electrical lug which will again be 'submerged'. and finally the 2nd star washer and its immersion.    Finally, I will place an absurdly large bead of sealant on one of the faces and finally install it.  Hopefully, that will be the final time.  

§22-08 thru -11 Inboard Aileron Bracket Assy Right

 Somewhere along the way, I lost a W-15015A-001 and couldn't finish the remaining aileron bracket.  The part was reordered and arrived last week.  It was pretty straightforward to press the bearing into the bracket and then rivet together the rest of the pieces.   The finished subassembly went back onto the shelf to await its installation on the right wing.

I also received a bearing that I had ruined and was planning on finishing the push rod that was affected, but doing so requires access to the front of a spar for measurement.   Steve & I put the R spar up in storage in a place that isn't convenient or safe for a single person to remove it, and the L spar now has nose ribs attached.  No big deal (except for my OCD).   It's a 5 min job and I can do it when I get access to the spar again.

Cool Picture

This is a pretty cool picture.  I just like the effect of staring down the perfectly aligned holes in the ribs after they are attached to their spar.  Check out December 5, 2013 for a similar shot of the RV-12 wing being built.