§27 R, $28 R, §29-5—7 R

 Another really productive day.  It wasn't all roses, but it was very productive and enjoyable.   Bottom line—the two wings are essentially at an equal state of assembly! 

For the record:  §27-05, -06, §27-08, -09, -10, §28-13, -18, -19, -20, §29-05, -06, -07

Section 27 was started the day before yesterday (I played hooky yesterday and went flying.  More about that below) and really is just riveting the flap mixer to the rear spar/tank.  This is where the famously expensive Cherry Max rivets are used.  These puppies can be used in lieu of driving AD470's in almost all locations, but Van's cheerfully lets you ensure you find the correct length and you must source them yourself.  Apparently there was a fire at the factory that made them and now they sell for ~$2 a pop! Ouch!   As much as I'm tempted in a few places, I'll pass for those prices.

I jumped ahead (§29) and attached the front spar to the tank and clecoed it to all of the loose ribs that would otherwise be hanging in the breeze.  This gives the assembly a significant increase in rigidity and makes me feel better about picking it up and moving it, etc.   Prepping the front spar involved riveting an extension to it using a doubler.  Those were all driven 470 rivets and, because access was easy, it was actually fun.

Front Spar clecoed in place

Section 28 involved finishing up the push rod that I had to set aside a few months ago when I spilled some loctite onto a bearing and decided I didn't want to use it.   When I went to find the replacement, I spent 5 panicky minutes searching before I realized that the smart place to have put it was in the parts bin supplied by Vans.  Yep, there it was.   The rest of that chapter was taking the previously manufactured bell cranks and figuring out which way was which and getting them installed.  Rather than last time, when I wished for a trained capuchin monkey, I discovered I could attach a push rod to a bell crank out in the open, then insert the bell crank through an access hole and into position. Much easier!

top view of the R outboard (aileron) mixer

Looking inboard, under the fuel tank top skin, 

at the inboard aileron  pushrod 

At this point, I could sort out the D-cell nose ribs and cleco them to the front, but I can only attach 11 of the 15 as I am waiting on LP4-4 rivets from Vans.  I'm also waiting on the plastic clips for attaching the wiring harness.   Essentially, the wings are at the same place and both stuck.

Steve Brown will return on Sunday to help me drive the awkward rivets for one of the nose ribs, and I'll attach what I can.  I have enough saw horses and work stands that I can actually move both wing skeletons off of the work bench.  That will give me room to start prep work on the skins so that when the errant parts arrive from Vans I can get right to work installing the skins.  That's going to be 2 or 3 days of long, tedious but FUN work!

(I played hooky yesterday because the weather was just too good to pass up.  I managed to get out to Marysville and fly the Citabria in moderate winds from about 45° off the runway.  I'm nowhere near feeling comfortable landing that plane and it was a good workout.  Surprisingly, I made 4 very good landings on the grass.  My technique wasn't really 'full stall' nor 'tailwheel'.  I was too busy not loosing control to think about classifying them.  I flew the Cirrus and did a set of engine verification procedures.  For the curious, they are called "GAMI spread determination" and "LOP mag checks."  Both went well.  Finally, I took up the RV-12 just to say I flew all 3 aircraft for which I am current.  I didn't fly the CAF PT-26 because (1) I'm not current, and (2) it has a bad mag and is grounded.)

§22R, § 24R& §26R !

 Wow!  Today was a very productive day.  It didn't start out that way.   My work/sleep schedule is truly chaotic.   I didn't feel much more tired than usual when we went to bed last night but I slept 12 solid hours and had no bouts of tossing & turning.  I woke up around 1pm, but puttered around the house and didn't even get dressed until almost 5pm.  (I might have been a touch hung over, but we won't talk about that, will we?)

In my last post, I was undecided about how to proceed.  I decided to build up the skeleton of the right wing in parallel and will then proceed with applying skins to both wings.  This way I have the open, accessible L wing to use as a reference for the R since there aren't any drawings of the R wing.  I had already purchased two portable work stands from Home Depot and Lada helped me move the L wing skeleton to those to get it out of the way and make room for the work on the R wing.

Despite not getting started until 5pm, I managed to finish 3 chapters for the Right wing!   Much of that speed was due to having already built up the mixer boxes and aileron brackets for the right wing a couple of months ago.  Today, I attached all of the main ribs to the rear spar, attached the outboard mixer box to the rear spar, and fastened the rear spar to the fuel tank.   In detail, I completed the following pages: §22-04, -05, -06,  -12, -13, -14, -15, -17, -22, -23, -24, -25, §24-05, -06, -07, -08, -09, §26-05 & -06.

Foreground: Right wing rear spar assy

Background Left wing assy

Right wing rear spar assy

I have tomorrow & the next day off.  I expect that I will be able to install the inboard mixer, finish the pushrod and install it, and then attach the main spar & D-cell nose ribs.   That will bring me to par with progress on the Left wing.  I'm waiting for parts from Van's to finish the D-cell Nose Ribs, so I might end up in a work-stoppage until those parts arrive.

§29-08, 10, 12-15, 17 Left

 Argh.  I was really hoping to finish off this section.  It's all about attaching the grommets and tie-wrap clips to the D ribs and riveting the ribs to the spar.  Surprisingly, it was the riveting of the plastic tie-wrap clips that was problematic.    5 of the 15 clips didn't hold up to the pressure exerted by pulling the pop-rivets and they ended up getting ruined.   While I could have stolen from the supply designated for the Right wing, the rivets that are called out are LP4-4's, not -3's.   I literally have thousands of -3's, but the supply of -4's is actually only half of what is needed and there aren't any surplus to borrow from.  As a result, I'll have to wait until replacements arrive from Van's before I finish out this chapter and move on to installing the wiring harness.

Ruined tie-wrap clips and LP4-4 rivets

I'm getting close to making a major decision.  Should I continue on the left wing alone, set it aside and then do the right wing, OR should I set the left wing on saw horses to use as a reference and build up the right wing skeleton, and then proceed to put skins on both of them?   I need to decide in a week or so.  Keep reading.

§21 addendum complete, Left & Right

 After 6 weeks of being stuck in the doldrums of sealing the tanks, I have resumed actual construction.  Van's issued an addendum to chapter 21 instructing me to install a bunch of nut plates on the tanks.  Since this had nothing to do with their fuel integrity, it didn't cause much headache.   One set of nut plates is around an access hole on the bottom of the skins.  That took some gentle skill because I had to mildly contort myself in order to see what I was doing and I needed to balance a 426 rivet on one die of the rivet squeezer, then thread the rivet through an upside down hole and finally squeeze it in place.  I only dropped 4 of the 48 rivets that were set that way.

Access hole being equipped with nut plates

The image above probably needs some explanation.   The bulges at the top of the image are the outboard skin of the Left fuel tank.   There's about 18" of skin both above and below the tank and we're looking at the bottom skin with its access hole.  In the foreground, you can see nut plates and set rivets.  in the background are the clecos securing nut plates that have yet to be riveted in place.   This is where I was having to balance the rivet on the squeezer and gently raise it into the open hole.  It was actually a lot of fun.

Airworthy fuel tanks, finally! §21 complete for L and R

(Mea culpa:  I wrote this 4 days ago and never hit the "Publish" button.  Doh!)

The fuel tanks are officially "done."   While I never was able to get them air tight, as some VAF members have been able to do, I have been successful in demonstrating that they would hold water and as of yesterday, that they could hold 100LL.

(recap) As you may recall, I spent nearly a month trying to get the fuel tank sensors installed correctly and without leaks.  The first few attempts were definitely learning experiences for me because it was obvious that I had done a poor job.  Each one got better (e.g., the residual leaks were smaller & slower).  I finally got the obvious leaks sealed and then proceeded to pressure testing.  There were some dumb leaks that were easily corrected, but then I really got serious about trying to make them airtight.   

I gave up on Van's idea of using a kid's balloon because there were some very thoughtful and data supported comments from VAF that it's an exceedingly poor gauge and should best be thought of as a pressure 'fuse' that will blow if you end up putting too much pressure into the tank.  Instead, I bought some clear plastic tubing, added colored water and used that as a simple manometer.   15 inH2O = ~0.5 PSI and is roughly double the pressure of a full tank of fuel, so I figured that would be a good value to use.  Unfortunately, despite everything I could think of, I could never get the tanks to hold pressure for more than 30 min.

I suspect it's the fuel caps that are leaking.  I couldn't prove it, but I just don't like their design.   I even tried sealing them with condoms, but could never find a leak nor maintain pressure.

Lada & I filled them with with water and left them to soak for a long weekend.  No leaks!    100LL is half the viscosity of water, so there might be a hole too small for water to leak through, but might pass avgas.  I drained all of the water and borrowed 29 gal* of 100LL from the Cirrus and tried it again in the Left tank.   Success!  I managed to salvage about 28 gal and put it in the Right tank.  Another success!  Neither tank had any visible moisture after 24 hr of containing 100 LL.

This officially completes section 21, as it was published on the day I received the wing kit.  More about that later!

*I have 3 jugs of 8 gal each that I use to buy premium auto gas and pump into the RV-12.  I also have a 5 gal container.  Together, they are 29 gal. The fuel tanks are 30 gals, so "close enough."  If there's a leak at the very top, it will not be operationally important because fuel won't leak up against gravity.  In addition, aircraft tanks are rarely stored in a completely full state.  I will take pains to ensure that the plane is not parked outside during rain, or will find a way to cover the fuel caps if needed.

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.

Empennage kit delivered

 Van's shipped my empennage kit (vertical & horizontal stabilizers, rudder & elevator) on the 5th.   It arrived in Columbus last Monday and I made an appointment for its delivery on Weds 12th.  When it showed up the driver spent about 10 min in the back of his panel truck, then came over to tell me he couldn't deliver it because it needed a fork lift and he didn't have one.   That's exactly what happened on May 9th when the first crates of the wing arrived!   That day, I enlisted my neighbor & his friend and the 4 of us manhandled the crates to the ground.  This time, I stood my ground and insisted that they re-deliver it.  Then I looked at the crate:

You'll notice something odd about this arrangement.  See the arrow?  Typically, that means "this side up", but the crate is on its side, not right side up.   

Yesterday, they arrived with a flat bed and attached parasite forklift. 

He got the crate off the truck and into my driveway and I pulled it into the garage. 

There was some minor damage to the wood and the paperwork is partially outside of the box.  I signed the e-receipt stating 'accepted with damage noted and not inspected'.  The driver/delivery guy was totally cool with that.  I'll file a claim with them if there are any damaged pieces when I get around to inventorying it next Thursday.

3rd time might be the charm ?

 Well, here's to hoping that I am capable of learning.  Specifically, this is the 3rd time I've sealed the fuel level senders & inboard access plate.   I have learned one thing -- I neither like nor am skilled with working with Proseal.  (BTW, Proseal is a brand name and I'm using generic products but will continue to abuse the name because I'm lazy.)

I'm pretty sure the access plates are not an issue because they are horizontal and straightforward.  The fuel senders are oriented vertically, so gravity is not my friend.  They also have a wrinkle in the installation:  one screw is fitted with an internal tooth washer, an electrical spade and a second internal tooth washer.  This stack-up is designed to have the angled teeth of the washers cut through the layer of sealant and ensure a good electrical connection from the tank itself to the electrical spade that will later be used to measure the fuel level.

On the previous installations, I had a lot of trouble holding the spade such that it didn't fall into the goop and I ended up making & breaking the connection of the sender's plate and the tank.  I suspect that didn't help the smooth, careful and uniform distribution of the sealant.

Rubber band as 3rd hand

I used a small rubber band to hold tension on the spade connector and trusted that the 'top' washer wouldn't go anywhere if I treated the arrangement with any delicacy.   In this photo, the connector is on backwards and would have dug into the side of the tank, but I installed it correctly after this dry run.

Sealant under electrical hardware

I smeared a small dab of sealant under the location of the hardware, then inserted everything and held it with the rubber band.

Smeared Sealant prior to installation

I then applied a bead around both the tank and the sender and smeared the beads into a relatively uniform bed.   Finally, I used one of my favorite tricks of inserting awls through two of the holes in the mounting plate and then into the corresponding holes in the tank and sliding the fuel gauge sender along the awls and into position.  I had a screwdriver at the ready to manipulate the screw (that was holding still because it was held by the rubber band) into its nut plate, then quickly inserted another screw into its nut plate. With two screws to hold orientation, the awls came out and the remaining screws were started, then evenly tightened.

Mounted Fuel Level Sender

As you can see in the final picture, there's a nice bead of sealant oozing out around the entire circumference.   It's a little thin at 12:30, but there is visible sealant. :)    BTW, I did both tanks at the same time, but only published pictures of one side.

I think the next time I'll have time to do a leak check is next Thursday, the 20th.   Fingers crossed!

§29-11 L, Nose Ribs to fuel tank

 Recall from a recent post that the Wiki community mentioned that getting the 6th rib attached requires two people because of the skins that are already attached to the tank making it impossible to hold the bucking bar and the rivet gun at the same time.  Steve B is a fellow RV builder and also an A&P.  In fact, he is the lender of the rivet gun I'm using to do this build.   He came over yesterday and used the gun while I assumed a very awkward position and held the W bucking bar.  Steve also noted that the FAA likes to see pictures of the builder and not just of the work done, so he offered to snap this:

Getting my head into the game!

Here's the photo of the rivets in question.  Even with the highlight, they're hard to see.  Imagine how hard it was to hold the bucking bar.   While I was in position, I had Steve hand me the go/no-go gauge and I discovered the top rivet needed a few more hits to meet spec and all the others were good.  I was really pleased! 

AN470AD4-12 shop heads

This completes page 29-11.

Busy & Productive Day!

Yesterday was a busy & productive day.  I got a descent amount of sleep after I got home at 8:30 AM.   In addition to the RV-15 stuff shown below, I also cleaned up the kitchen, trimmed all of the grass around the house where the lawn robot can't reach and installed the wall mount for a monitor in my wife's dance room.

• Got help & installed 6th nose rib
• resealed the tanks (again)
• received the empennage kit
• completed Right inboard aileron bracket

Rather than cramming all of that into one post, I'll make a separate post for each item.  Keep reading!

§29-06 thru -09 Left

Page 6 calls for making the spar even longer.  There is a doubler plate that connects a ~2 foot Spar Extension to the outboard edge.  I clecoed that up a few days ago and was very pleased with myself when 6 clecos went together nicely.  On Sunday I played Grandpa and gave Layne (an 8 year old) his 2nd lesson in riveting.  He did a good job of wearing ear & eye protective gear, too.   I shot my first 470AD4-6 rivet, but couldn't get the next one to insert.  Upon closer inspection I discovered that the doubler is not symmetric about the longitudinal axis and I had in fact installed it upside down.

Layne got another lesson; how to drill out a rivet.  It didn't take too long and I happened to have some spare 4-6's from the RV-12 kit so I won't be short at the end.

Wing Spar (gold) & Extension (silver)

I'm not able to re-seal the tanks (3rd time!) until I get some parts from Van's.  Specifically, I ordered replacement screws since the Phillips heads are getting stripped from so many insertion/removal cycles.  That left me with either the option of waiting around and wasting another day or starting another major component.   If there's a leak on the forward edge of the tank, I'm going to be very pissed at Past Me!

Attaching the main spar to the forward edge of the tank was very easy -- just my favorite LP4-3 blind rivets.   Attaching the inboard D-rib was pretty easy even with the ridiculously long 470AD4-12 rivets that were conveniently accessible from the root side of the wing. The next four D-ribs were another piece of cake as they, too, just attach with LP4-3's.    

On page 11, I came to a complete halt on the 6th rib.   To quote from the Wiki page: 6th rib from root: rivet gun + long-armed bucker through the lightning hole required. Plan for a helper or an unconventional body position.  That is an understatement.  I think even with a helper, it's going to be a bear.   I'm waiting for a confirmation that Steve B (he who lent me the rivet gun) will be able to swing by and give me a hand on Friday the 14th to finish that rib.   

The remaining 9 or so ribs will be attached with driven 470AD4-4's, which are not my favorite but will be easy to access.

inboard D-rib

§28-18 thru -21 Left Pushrod installation

 It's been a while since I last updated this.   Work is sucking up so much of my time, but that's how I keep up the cash flow to pay for this insane hobby.    Last week I finished up the pushrod installation on the Left wing.  It was fairly straightforward and kind of interesting to see how the system will work.  Basically, there is a pushrod extending from the root of the wing that will eventually connect to something inside the fuselage.  When that rod is moved outboard, it actuates a bell crank that moves the outer pushrod inboard.  This, in turn, pulls the small pushrod forward which will cause the aileron to deflect upward, thus banking the plane to the left.  It is left as an exercise for the reader to fill in the blanks regarding motion in the opposite directions.

Large pushrod at wing root.

Small pushrod at aileron attach point

Really getting a good look at the aileron pushrod system has done nothing to allay my concerns about how the flaps are going to be activated.  I identified a bracket that will hold a pulley for flap cables and can sort of visualize where something might fit in the inboard mixer box, but for the life of me I can't see how it's going to be retained in there since there are no nut plates or anything.   I'm guessing that there will be two cables in opposition connected to bell crank and one end of the bell crank will have yet another pushrod.  Why those components weren't included in the wing kit so they could be installed before buttoning up the skins is something that baffles me.   Regardless, I will trust the process and will complete the wing skins as directed by the instructions.

Finally, I have to report that the damn tanks are still leaking. It's a much slower leak now, and it's in the same place on both tanks -- at the ground lug that is behind the fuel sender plate.   I also learned that the soap bubble trick only works on really slow leaks and it did a great job of letting me see where the air was escaping.   On an academic note, there is a phenomenon known as Starling's Law that is really important in cardiology. Basically, the amount of stretch that you get out of a given pressure is highly dependent upon the radius (size) of the thing being stretched.   When you pump up the balloon with the hand pump, the balloon gets sort of inflated and does nothing for several pumps, then abruptly grows quite large without any further pumping.   Human hearts tend to do the same thing when they fail due to fighting high blood pressure for a long time.  It was really cool to see it in action rather than just imagining it as an academic factoid.

Today (well, yesterday) I spent two hours removing & cleaning the fuel sender units and the inboard access plates of both wings.  Man, I hate working with Proseal!   I'm going to use all new screws and lock washers for this 3rd attempt at sealing the tanks.   I've done some cruising through VAF and found several techniques that I will try to integrate into this next attempt.   Fingers crossed.

Finally, the tail kit is en route and should arrive some time this week.

§ 28 -6 thru 13 -- push rods

 Van's is famous for the smoothness of the control feel of their airplanes.  I think one of the contributing factors is that they use bearings and pushrods whenever possible when designing their flight control linkages.  I had already assembled the rotational bearings in bell cranks.  This post documents building the push rods that attach to them.

I also like a really nice technique they employed for establishing the exact length of the push rods.  When you build one, you can turn the stem of the spherical bearing to move the length in or out by 1/48" at a time.  When I built the RV-12, I remember trying to very precise about my measurement.  In the RV-15, they have you assemble the push rod and then use temporary bolts to insert into holes provided in the main spar.  In other words, the main spar has a jig built in to it.   Very easy to twist the bearings to get a perfect fit -- no tape measure required!

I used blue locktite as a safety feature for the jam nuts and ruined one of the spherical bearings when the locktite dripped on the bearing itself.  Although it felt like it was still moving freely in its race, I expect that it will not remain in good condition for very long.  I tossed it in the junk bucket and ordered another one ($26!) from Van's.

Aileron Push Rods

Push rods, prior to riveting and installation of bearings

I started the final assembly of this chapter where the bellcranks get installed in the mixer and the pushrods get attached to the bellcranks.   Even without the skins on the wing, it's definitely challenging!   I'd like to have a trained capuchin monkey w/ tiny hands to help out.    I am absolutely dreading / afraid of trying to install the flap control mechanism after the wing is closed up!

§27 L; IB Mixer - Rear Spar

 This was also a pretty straightforward chapter.  The Inboard Mixer was nestled into the space just next to the tank and directly in front of the spar attachment area.  The holes that were left open for the rear spar attachment were then used to rivet the mixer to the spar.  Here's where the infamous Cherry Max Rivets got used -- all 39 of them.  These are pull rivets ("pop rivets", although that's actually another brand name) but they are stronger than the typical LP3-4's used nearly everywhere else in the plane.   The book says to be sure to pull exactly in line with the stem, but that's not possible with a few of the rivets because there is a flange immediately in the way.  I bent the flanges as much as I could and did the best job possible.

IB Mixer, as viewed from the front of the wing assembly

For some reason, they decided to have the flap tracks installed in this chapter rather than give them their own chapter.   The flap tracks are interesting; they are jet black and I'm not sure if they're aluminum or something else.  I am getting better at riveting.  There were two rivets that couldn't be bucked with my titanium bar.  I used a flat plate of steel and got creative.  Worked great!

 

Flap Tracks

§26 L; Rear Spar - Tank

 I got a lot accomplished in the last week, but one thing I didn't have time to do was document it.  I typically have slow times between patients at night, but not recently.  Sorry for the delay.   I'll publish several updates in a row so i don't overwhelm you with a really long post.

Attaching the rear spar to the tank assembly wasn't too bad.  It was literally a one pager that consisted of bucking 33 rivets. The only challenging part was ensuring that I only riveted the holes called out in the KAI, as many holes were left open for the next chapter.

I'm starting to get a feel for when a bucked rivet will look good or look like a mess.  I think the key technique is to maintain pretty firm pressure with the rivet gun, but not much pressure on the bucking bar.  Time will tell.

Again, no picture as it really doesn't look any different.

flying instead of building

Well, didn't get out to the shop to do any building because I went flying instead.  I don't want to let my flying skills deteriorate due to spending all my free time building the new plane.  I was getting close to loosing my currency for IFR flights, so yesterday Ed & I took the Cirrus up for a good workout.

The weather was perfect for an IFR training flight.  There was a nice big low pressure system (29.69 inHg) sitting over Ohio yesterday and that gave us a cloud layer from about 1000' to 4000' above the ground.  I flew and Ed observed/coached/critiqued from the right seat.  I flew to Dayton, did a hold and shot the RNAV 24L approach there, all using the autopilot.  In other words, I programmed & observed while the plane flew itself.   That's the Standard Operating Procedure for an actual mission.   Then I disconnected the autopilot but left the flight director engaged and flew the same approach by hand.  The flight director essentially is a display driven by the autopilot that says, "if I still had control, this is what I would do."  Basically, it's a video game -- the A/P moves the cueing display and I fly the airplane to match the cue.  Then I turned off the flight director and flew using just the displayed location data.  I flew all the way back to Delaware by hand, went to the far side of the airport to get aligned with the wind and few the RNAV 28 approach back home.

Overall, 2 hours of a good workout and I feel better about being a competent pilot.

Back to building when I get home tomorrow.

§26 Left -- Rear Spar to Tank

Well, I took a deep breath yesterday and committed to joining the rear spar to the tank.  The section is a whopping 2 pages of actual instructions -- 1 page says to cleco everything together, the other says to rivet it.  All 33 rivets are 470AD4-4 that needed to be bucked since there was no way to get a squeezer anywhere near both sides.  

I am still quite leary of my skills in bucking rivets, hence the trepidation in this step.   Having said that, I'm actually quite pleased with how it turned out.   I am starting to get the feel of how much force to use with the bucking bar.  Counterintuitively, holding it with too much pressure simply causes a lot of noise and not much deformation of the rivet tail.  Obviously, not enough pressure and it simply bounces away.  If you use just the right amount of pressure, the tail of the rivet sets in only 8-10 impacts.

Some of the rivets were in a place that I could only see the shop head and had to hold the bucking bar blindly.   I'm quite surprised that it went well.  I did use the guage to ensure that the shop heads were within spec. 

Tomorrow, I'll finish riveting the spar, tank and inboard mixer box together.  Those use the famous Cherry rivets that are stronger than the regular LP3-4's but are harder to pull correctly.   The sealant should arrive tomorrow or Wednesday and I'll re-seal the Left tank.  They say 3rd time's the charm.  Stay tuned.

§28-14, -16 L&R Aileron bellcranks

 Two steps forward, one step back.    The right tank now holds pressure.  Sort of.   The left tank still has a definite leak at the fuel sender.  I used a cartridge of sealant from Aircraft Spruce, but the gun I bought (that morning) from Home Depot is much too large for the cartridge so I ended up just shoving the base with a spark plug socket as a make-shift plunger.  That made it barely possible to squeeze out the bead of sealant, with the resulting poor performance.   Since then, i've borrowed an appropriate sized gun and will give it another try when the next cartridge arrives from Aircraft Spruce.

I've been holding off attaching the spars to the tanks until they were sealed, but I'm going to go ahead and resume major construction since the leaks are at the other side and can be dealt with in parallel.

I built up the aileron bell cranks.  Took just a day and was a nice, straightforward project.

underexposed picture of the bellcranks

The aileron push rods have specific instructions to be primed.  I learned that just putting them on butcher paper and spraying them with primer, then leaving them overnight to get wet, results in paper that is well glued to the aluminum.  I sanded much of it off, but not all.   I stood the push rods using wooden dowels in the ground and sprayed them again while vertical.   I now have nice camo'ed push rods!

Aileron pushrods drying in the sun

 

§22-19 thru -26 Left

 Well, it's been a minute since I last posted anything here.  In addition to the usual 4-letter word ("work") that always is in the way, I had two very pleasant reasons to take a break from building.  

My eldest daughter came up from Louisiana with her family to visit for a few days.   Here are her 3 daughters and my middle daughter's son & daughter for a total of 5 grandkids.   It was a great, but short, visit.

One of the reasons it was a little short was that her visit overlapped with Thunder Over Michigan, an airshow held just west of Detroit.  My wife recently announced that she wanted to have a helicopter ride, preferably in a UH-1 "Huey", and of the attractions of the show was such a Huey.  Christie went to go stay w/ her sister and we drove up to Michigan and we got the ride she had hoped for!

Finally, back to building!  During the week, I received the extra parts from Van's that I had lost somewhere in the garage.  I finished building up the L outboard aileron attach bracket and got it riveted to the rear spar.  This completes the Left Rear Spar subassembly.   Recall that I had already built up the R outboard aileron attach bracket because of the mislabelled KAI. I thought I might as well build up the R inboard bracket since the workflow was already set up.  I then found the missing ouboard bracket cleverly imitating one of hte pieces needed for the inboard bracket.  This means that I'm missing that piece instead of the one that I just purchased from Van's.   "One step forward, one step back."   Sigh.

Next project:  Clean, scuff and re-seal the tanks.  I bought a larger batch (3 oz) of Fuel Tank Sealant than I typically use, but it's a 2 hr cure time instead of 0.5 hr, and it was actually cheaper than the 1 oz stuff from Van's.   I'll let you know how it worked in the next posting.

Left outboard aileron attach bracket assembly

Removed Fuel Senders

 I can't sleep and it's too late to do anything else, so I'm updating the blog.

My daughter & her family are visiting, plus I'm still working, plus we're going to try to go the Thunder over Michigan airshow tomorrow so I haven't had much time to work on the plane.   I happened to have 30 min to myself before going to work yesterday so I pulled off the leaking fuel level senders from both tanks.

Mounting location of removed R fuel level sender

As you can see, this doesn't look very uniform.   From 10:00 to 14:30, the darker and somewhat smooth color is fuel tank sealant that never even touched the base of the sender.   No wonder it leaked!  The lighter area is where there was some adhesion to the two pieces of metal and I had cut through it. Next session, I will clean that all off down to bare metal before trying again.

Curiously, there was no adhesion to the brass colored metal of either fuel sender.   I will really scuff up those surfaces, too.

Of course, to clean the inside of the tank and remove the debris from this process meant that I had to remove the inboard fuel tank access panels, too.  Those had been sealed with fresh fuel tank sealant and the showed proper, evenly 'wetted' distribution of the sealant after I got them cut off.  That made me feel better that I can apply things evenly if I'm using fresh sealant.

Both tanks, with senders and access plates removed. 

Good night.

§25 -- inboard mixer boxes

Section 25 is the inboard mixer boxes.  These were almost as easy as the outboard ones, but there are a few differences; mostly just a few more parts.  That made it a bit more complicated to ensure that I had the correct orientation when I built the other side, as I have a somewhat difficult time with L/R spatial orientations.

One trick published in VAF was to mirror the PDF images from the KAI in software.  Several VAF members have gone so far as to print mirrored pages of the whole book, but that's overkill.  I did something that was fast & cheap and just took quick pictures w/ my phone of the relevant pages.   10 seconds of editing on each page to mirror each one and I was in business.  Having just built the left version, I didn't need to refer to the printed notes very much and I concentrated on the object I was holding and comparing it to the image on my phone.  In the future, I'll use my iPad instead because of the larger screen and its attached stand.

Remember the NAS1097 rivets I talked about the other day?  I said that there were only 4 in the whole kit.   Wrong.  There were only four of the AD3-4 and I totally overlooked the bin that held 36 of the AD3-3.5's.  Those were the size I was supposed to use earlier.  As a result, when today's kit called out for the 3-4's I had none.  I elected to use AN426AD3-4's to achieve the proper length and deal with the larger head by accepting the larger countersink needed to flush the larger head than the called out AN1097.  The primary advantage to the 1097 is the ability to be used in very thin material, but the piece that accepted the rivets in question is quiet thick-- 0.063", so I ended up with something stronger (not needed) and the correct length.

Inboard Mixer Boxes

BTW, I'm determined to provide my grandson an early introduction to the project.  He just turned 8 and has a very short attention span, but I did manage to show him 5 different rivet setting techniques before he timed out.  Baby steps! :)     I have 3 granddaughters visiting later this week.  One or two of them may be interested, too!

Layne, learning about squeezing rivets

§24 Left; OB Mixer-Rear Spar

Like building the outboard mixer box itself, installing it into the rear spar was relatively straightforward.  It involved being very careful about which rivets were installed into which holes, since the structures had multiple pieces of varying thicknesses.  There were a lot of rivets that had to be driven, including some where it is really difficult to get your hand in place with the bucking bar!  I'm very glad I spent the money on the tungsten bar -- its small size came in handy for just this occasion.   I suspect I will never need another bar that doesn't have a unique shape/size.  (There are bucking bars for sale specifically for doing some hard to reach rivets in the tail cone of the RV-14.)

I took a picture, but it's not worth publishing because it looks just like the last one of the rear spar & ribs.

§23 -- outboard mixer boxes

Section 23 is a very short, straight foward chapter that builds the Outboard Mixer Boxes.  It's literally just installing 1 nut plate and riveting 4 pieces together with 16 of the easy-peasy pull rivets.   It took me about 2 hrs to do both L and R sides.

I decided to do them both because I do have a lot of trouble with mentally mirroring the drawings.  I built up the Left in its entirety, then set up the parts for the R and used the physical structure as my mirror source.

I learned a little bit about rivets.  The kit calls out for a very specific rivet, NAS1097AD3-3.5 rather than the much more common AN426AD3-3.5.  In fact, the entire wing kit has just four of the NAS rivets.  They are to be used in shear loads only, as they have a very small head and won't resist much axial loading.    They are typically used in very thin material.   What's odd is that Van's almost always called out the AN426's for similar applications and the material in question was actually pretty thick, 0.050", so I have no idea why they went to the trouble of stocking these specifically.  Oh, well.

L & R Outboard Mixer Boxes

Leaks identified

While working on the R spar, Marc came over to help figure out the tank issues.  He's also an engineer and I wanted a fresh pair of eyes on the problem.  He agreed that there should be no leaks based on my procedure and his visual inspection.  Back to testing: we split up the tasks of one person pumping and the other spraying bubble soap, but never saw any bubbles.   We finally took the compressor and blew air into the tank.  We could feel a breeze on our fingers on the inboard edge (with all of the connections) but couldn't make any bubbles appear nor feel our way to the leak.

Rather than using expensive, toxic, smelly and flammable avgas I decided to do an old fashioned test.  We filled the tank with water from the hose.  Viola!  The Proseal around the fuel sender leaks like a sieve!  Water streamed from the entire circumference.  Mystery solved.

This also validated my gut feeling that it was a systemic issue.   Recall that I used left over Proseal that had been in the freezer.   While working with it, it was appropriately sticky and gummy and I thought it was OK, but apparently it was by then too viscous to actually flow when I tightened down the fuel sender plates.

I'll order some more Proseal (or B2 sealant as it is now known) and re-do the senders when it arrives.  I'm feeling much more optimistic that we'll get something that is water tight next time.

§ 22-4 thu -17 Left, -18 thru -21 R

Got lots of building done this weekend.   The rear spar is the topic of construction for the next 4 or 5 chapters.  § 22 is pretty straightforward, if somewhat long.  I was really hoping to be able to complete the entire L rear spar on Saturday, but ran into a minor glitch.    

If you notice the title, I suddenly switched from building the L rear spar onto building the R rear spar.  Curious, no?    Page 18 calls out starting with W-15016B-002.   That's odd.  a -002 part implies that you've probably come across the corresponding -001 already.  I proceeded until I came to the conclusion that I had indeed built the corresponding assembly (outboard aileron attach point) for the other side.

No problem, I thought to myself.  I went to the parts shelf but for the life of me, I couldn't find the expected -001 part.  My inventory sheet shows I had it in my hand at one point, but neither myself nor my wife could find it in the shop.

I'll order another one this weekend and will eventually get to finishing the L rear spar, but during the meantime, there's other stuff to be done so I'm not stuck.

most of the L rear spar

Quick update

Just a quick update so you know I'm still here.

I've laid out the parts for the next section and feel pretty good that it will come together quickly in the next day or so.   

I finally received the last few back ordered parts from Van's.  My wing kit is now officially complete.  

There is much gnashing of teeth on VAF regarding some misaligned holes on a few wing spars.   Those spars are apparently ~$3K each!   I dug mine out and clecoed together the areas of question and the holes are well aligned, so I don't have to deal with getting Van's to replace them.   

Marc is a partner in the Cirrus and we're going to go flying tonight.  Tomorrow, he's going to swing by the house and I'll enlist him in helping me find the source of the leaks in the tanks.

Setback -- The Fuel Tanks Leak. A lot.

Well, I finally had an opportunity to work on the fuel tanks again.  I lost a day or so because I never read the manual on the little bicycle tire pump and I was putting it on incorrectly.  I thought it was defective and went to the aviation division of Walmart to find a pump with a different kind of connector.  There weren't any.  There was, however, one brand that thoughtfully provided an instruction card and I learned I had been trying to attach the pump while it was in the locked position.  Duh.

I got home, correctly attached the pump and tried to pressurize the left tank.  The balloon barely quivered with each stroke.   Damn.

Armed with my granddaughter's bubble soap, I put the tank on stands out on the driveway and liberally soaped up all of the seams, the access panels, the fuel sender, the supply lines, vent lines and balloon neck.   Nada.  I can't generate any bubbles at all.   I'm pretty bummed.   I washed off the soap and put the tank back on a solid table.   I rigged up the right tank and got equally nowhere, but I didn't bother to soap it up.

I've learned not to do anything when I get into a spot like this.  By doing nothing, I can't make it worse.  The fact that both tanks are completely incapable of holding any pressure at all implies that I'm missing something fundamental that will probably be obvious in retrospect once I find out what it is.

Tonight, I'm going to think about options.  I'll write to Van's and ask how they pressure tested the tanks without them being sealed and see if that sparks any intuition.  I'll look into acquiring a 4' x 6' x 1' plastic tub and might try to immerse the tanks under water and look for bubbles that way. (That's going to be 240 lb of buoyant force to deal with, so I'll need some brawn to help!)   I'll check w/ some RV builders at DLZ and invite them to come help me troubleshoot.   Something.

Tomorrow is a day off and I don't want to throw it away by doing nothing at all, so I'll start on the next section of constructing the aft spar and ribs.  As long as I don't attach anything to the tanks, I am maintaining their current state and not impairing my ability to troubleshoot later.

§21-11R, -13. Sealed access plates R tank, installed fuel drains

As expected, it wasn't difficult to apply B2 sealant to the access plates on the top of the right tank.  Overall, it took about an hour and about 3/4's of the jar of sealant.

As expected, it was much more difficult than it should have been to install the fuel drains.   The instructions on page 13 are deceptively simple -- Install (1) into (2), where (1) and (2) refer to the fuel drain and fuel tank, respectively.  It doesn't mention using anything to create a seal, but I know that those types of threads (NPT) aren't actually fluid tight and must have a sealant of some sort.   Basically, it boiled down to using B2, as is used everywhere else, or Loctite 565 which is called out in a different chapter but never mentioned in the actual instructions.  I posted a query on VAF and was told RTFM (section 5) where it generically calls out Loctite 565, so that's what I went with.

As mentioned a few posts ago, I had tried a simple trial fit by installing (finger tight only) those components, and somehow managed to strip threads.  I wasn't really sure if they were stripped inside the tank (horrible) or just on the $30 part (not too bad).   

I researched the drain and found that it was a 1/8" NPT.  I couldn't find any technical description of the threads for the part from Van's.  It appears that all 1/8" NPTs are 27 pitch but that was only because that was the only pitch number I ever encountered and it was rare to find it at all.  I bought a set of cheap taps & dies at Harbor Freight that included the desired NPT.  I've tapped internal threads before, but never cut or chased external threads.

Some scrap Al from the RV12 was used to make a test hole with the tap and I was able to thread the fuel drains into that.  This confirmed that they were indeed 1/8 NPT 27.  I debated chasing the external threads on the drains, but wasn't sure which side of the die was the starting side.  Since NPTs are tapered, doing it backwards would probably destroy the part, so I deferred.  In retrospect, I think running the drains through the test hole actually chased them a little anyway.

The tap was used to very gently chase the tank.  I only used finger pressure and no tools.  The drains got gooped up with 565 and I tried to install them.   Nope, the threads wouldn't engage.  I finally got them to engage and tighten by pushing up on the drain with my thumb to and apply a fair amount of axial load while gingerly rotating them with a closed 1/2" wrench.  Finally, success.  It only took an hour to install two bolts.

Right Fuel Drain

§21-07 thru -10, -11 L, -12. Installation of fuel senders, access ports, fuel caps

Two days ago I got a lot done and pretty much finished sealing up the Left tank.  I ran out of time, energy and sweat and didn't seal the access plates on the Right tank, but that is now one of those "just get 'er done" things since I've gone through the process and know what / how to do. 

To explain; we left off with both tanks inspected and rinsed w/ 100LL avgas.  There was no debris and we found nothing in the rinse process.  The tanks had a few days to dry before I got to work on Monday.  The plans call for bending the float attach arms for the two fuel senders and give some engineering drawings to show how to do it.  I did both of them backwards.  Luckily, it turns out that that configuration is perfectly acceptable.  The only variation is that the float arms are 'pointing' in the direction opposite of the drawing, but this is on an axis that is parallel to the actual pivoting, so it makes no difference.  (sin 0° = sin 180°).

The R fuel float was very stiff and would actually stay in whatever position I put it. This is not going to give an accurate fuel level measurement since the goal is for the float to fall by gravity and float by buoyancy in the fuel.   I actually didn't realize this until after I had applied the pro seal (or "B2", as Van's now calls it) and was in the middle of trying not to make a thorough mess.  I was able to gently apply a little bend in the mechanism such that it no longer was binding and free falls properly.

Right Fuel Sender, Internal View

I got both fuel senders sealed in place with the left over B2 sealant from the second flap.   It definitely was harder to work with and was getting stringy towards the end, so I'm pretty sure that it only had a few minutes of shelf life with which to work, but it was still spreadable enough that I'm comfortable that I have good seals on the fuel senders.   We'll find out soon.

Right Fuel Sender, External View

The inspection ports on the Left tank weren't too bad, but I was surprised that I used up most of a jar of B2.  I have one left in the freezer to do the Right tank later today.

As mentioned last time, I stripped the threads from the L fuel drain.  I have the 1/8' NPT tap from Harbor Freight and will address that later today, too.  With that done, the R tank will be curing for 24-48 hours and I'll start pressure testing the Left.

Stay tuned.