First Service Bulletin: SB 14-11-03

Announced recently by Van's Aircraft Company was a Service Bulletin, No. 14-11-03, requiring RV-12 owners to inspect certain wing rivets for signs of wear.  Apparently the demo plane at the factory in Oregon started showing signs that rivets were starting to wear in the wing root area, and so Van's decided that the safe course of action was for the whole RV-12 fleet to be inspected.  If signs of wear are found, then a skin-to-spar doubler is called for to beef up the area, and that's expected to take an hour and a half per wing to install by a qualified airframe mechanic.  Of course you don't have to install the doubler if there's no sign of wear; the plane will probably fly hundreds of hours just fine without showing any of the symptoms described in the SB, it's just that it's relatively easy to do now, cheap (~$20, w/shipping) and installing the doublers will likely prevent future rivet wear problems by making the wing stronger overall.  So I ordered the parts from Vans and got to work removing rivets where doubler plates are to be added at the wing root on the bottom side of the wing.

I didn't get any photos of yours truly removing rivets so I can't show any, but here's one of the bits and pieces of pop-rivets that were drilled out placed next to SB Figure 1, which shows the orientation and location of the doubler.

Step one in removing a pop-rivet is to knock out the leftover piece of mandrel through the bottom of the rivet with a suitably sized punch.  That's the little bits on the right side of the tray picture below.

Step two is to use a 1/8" drill bit to very lightly drill off just the manufactured head of the rivet.  That's the washer-looking thingys in the bottom of the red tray in the picture to the right.

Step three is to push out the shop-formed side of the rivet with a couple taps on a slightly larger punch, shown in the upper left of the tray.

There's 21 pop-rivets to drill out on each wing, and each piece, except the heads, had to be found and removed from inside the wing by reaching through the rib lightening holes and feeling around 'til I found it.  I got most of 'em but unfortunately a couple of the tiny mandrel pieces didn't want to be found.

Once the rivets are removed the SB calls for you to cleco on the doubler and match-drill 42 holes into the bottom wing skin using the doubler as a template, and enlarge 8 existing holes to accept the larger and stronger 5/32" pop-rivets.

As always, appreciation goes to my beautiful wife for taking photos for this blog, buddies who help move the wing from the ceiling to the workbench and back, and for every neighbor who steps up the driveway when the garage is open to ask "Howzitgoin?".

Appreciation also goes to Mr. B for the extended loan of his airplane building tools.  When he loaned me his tools two and a half years ago, included in one of the parts trays was a tiny little ziplock baggy of #30 high-speed "jobber" drill bits, the size used for LP4-3 pop rivet holes.  I almost can't believe they've lasted this long, but they're still cutting just fine so I keep using 'em.  Here's a couple pics of the drilled out holes:

After removing the doubler, clearing away chips and cuttings, deburring holes, and vacuuming out the inside of the wing, the SB has us "chamfer" the edges of the doubler.  I thought the word was "bevel", but what do I know?  Mr. B's belt sander (below) accomplished that task quite nicely.  I think the bevel angle is supposed to be about 45°, but I tried to aim for something closer to 60°, but lightly rounded at the edge.  You don't want a metal edge you can cut paper (or fingers) with.

With the prep work done all that's left is to rivet on the doubler, right?  There's just one little problem.  Can you see it in the picture?

        No?  How about now?

The rivet mandrel for the larger 5/32" rivets broke off above ("proud") of the rivet head.  Which means they had to be filed down flush with the top of the rivet head, which is not fun.  How did that happen?

I think what happened is Van's sent the wrong length of rivets.  SB Figure 6 calls for using "BSPQ-5-2" rivets (also known as "oops" rivets in certain unfortunate contexts), but Van's sent BSPQ-5-4 rivets, according to the parts list.

As you can see there are eight 5/32" rivets for each doubler (the rest are "regular" size)
.
Builders take note:  The way you want to do this (having learned the hard way) is, counting from inboard 1, 2, 3, ... 8, do rivet #8 first, before any other rivets.  If the mandrel sits proud of the head, file it down.  Then do #7, then #6, and so on, working your way back to the wing root end.  Take care not to scratch the doubler with the file while you're doing it.  That's the tricky part.

Or you could be smart and just get the correct 5-2 rivets to start with.

After filing down the 5/32" rivets the rest was easy.

Here's the doubler installed on the bottom of the left wing:

And here's the right wing hanging from the ceiling again so I could use the bench for the other wing.  My first SB!

Recall that I said that Van's SB says that installing the doubler should only take 1.5 hours per wing?  It took me about three times longer than that.

Garage Light Upgrade

In 2002 the company that built my house installed lighting fixtures unchanged from the 1920's, or perhaps Thomas Edison's time, to provide lighting in the garage.  They've worked reasonably well for our three-car garage, but it's always annoyed me, especially in the summer, that the bulbs actually produce about 90 watts of heat and only 10 watts of light.  In other words they are mini-heaters.  Light's just a by-product.  Since I'm storing the airplane wings by hanging them pretty close to the ceiling, and there's a good chance that the light bulbs will interfere with the hanging thereof, it was time for them to go the way of the horse and buggy.

So out they came.  For replacement I purchased new LED lights from Home Depot for $129 apiece, plus tax.  They install easily, don't flicker when you turn 'em on (although there is an annoying half-second delay), have a 50,000 hour life, and produce very little heat.  They're also low profile, protruding just 2-¾ inches, which allows me to hang the wings a little bit closer to the ceiling.

So here's how it looks installed with the diffuser lens on.  I put the lens on for this picture, but I'll actually be leaving it off, at least 'til the airplane's built. 

Then I moved the airplane wings around with help from good neighbor Mr. G and did the same for the other light.fixture.

Here's the right wing sitting on top of the rolling dresser/workbench and then re-hung from the ceiling again.  The lighting is now mostly indirect as the light reflects off the wing and back onto the ceiling (which is why I took the diffuser lens off - no need for it).  To aid reflection off the shiny aluminum wing skins, I removed the blue plastic where the LED lights shine directly onto the wing.

Finally I installed a remote-control light switch so I could turn on/off the garage lights from inside the car.  The ones on the garage door openers weren't cutting it.

Skinning Left Wing

This is a condensed repeat of my September 17 and October 17, 2014 posts (Right Wing Skins On and Big Hole, Small Wires) except that I skinned the left wing.  The three bottom skins are on, the three top skins are on, and the top wing-tip skin is on, so that should be close to about 2,000 rivets pulled.  2,000 seems to be about the number of pop-rivets that a $9 Harbor Freight hand rivet squeezer is good for before it breaks or wears out.  It's still a good deal though.  I'll just keep returning it when it wears out and exchange for a new one.  The lady at HF didn't even ask for the receipt.

Got some help from a buddy for an hour or so setting up and squeezing rivets Christmas eve.  Incidentally, Phil's the guy who built the tandem recumbent bicycle hanging in the background.
He's also a master kayak builder.  Those skills will be handy when it comes time for the fiberglass work on the wing tip lights and engine cowling.




Next on is the bottom wing tip skin.  Before I started prepping the skin for installation (by bending each of the tabs at various angles, and sanding smooth the edge of the skin), I cut out the Vans-prescribed hole for the navigation and strobe light wires.  A big hole for three small wires.  It's not easy cutting a hole like that, even with the pneumatic nibbler, but eventually I snipped enough away one small piece at a time to finish the hole with a two-inch sanding drum attachment on the drill.

I did the tab-bending work on the wingtip bottom skin in the kitchen so I could sit down.  It went much faster this time around, although still kinda tedious.  Perhaps because I wasn't as fussy about getting the bend angles exact like I did on the right wing.  To get the correct angle of bend I used a cheap protractor to cut business cards into triangles to use to check the bend angles on the tabs, which range from 16 to 116 degrees depending on its location.

RV-12 BUILDERS TAKE NOTE:  While at the work bench (which in my case was the family dinner table), I recommend not bending that last tab as instructed in the plans.  Instead, cleco the wing tip skin on and the tip closeout piece and mark where the bend line should be as shown in the picture to the right.  Then apply the bend. It's the only way to get the bend line exactly where it should be on the first try.

Voilà! Both wings are now skinned!  I should order the next kit before prices go up.  Or start my tax return.  Or both.

Sew What?

Now that the right wing is done (except for the nav-strobe light and fairing that goes on the wing tip), it was time to hang it out of the way.  In my opinion a wide strap near the outboard end is the way to go.  Luckily for my wallet an RV builder in Davis gave me about 50 feet of fire hose that he no longer needed that fit the need perfectly.  Are airplane builders the nicest people or what?  As an indoor-use hose the outer canvas cladding is surprisingly silky, so I don't have to worry about it scratching the aluminum wing skins.  But first I had to find something that could poke through four layers of lined canvas to sew on D-rings that I bought through berkeleypoint.com

After searching the internet I found what I needed:  The Speedy Stitch Sewing Awl. According to speedystitcher.com,

"The Speedy Stitcher Sewing Awl is a hand tool that can be used to sew any heavy material. It's a handy tool to have around the house, farm, workshop or any place where leather, canvas or vinyl has to be sewn or repaired.
Every Speedy Stitcher is Made in the USA and comes with our high-tensile waxed thread and custom-made diamond point needles. With a little practice, it sews a perfect lock stitch every time - just like a sewing machine.
Uses for the Speedy Stitcher include the assembly and repair of leather goods, canvas tarps, climbing and camping gear, saddlery and tack items, athletic equipment, even shoes and belts."

So I ordered one from Amazon for $12.  A week later I found the same thing at Harbor Freight (or Chinese knock-off, probably) for $8 that included a big bobbin of canvas thread.  Grrr.

Know what else I found at Harbor Freight Sewing and Toiletries Supply Store while shopping for removable chain links?  A cheap ear and nose hair trimmer.  Score!  I've been needing one of those for a while now.  Sorry, is that TMI?

After watching a couple YouTube videos on how to use the durn thing, I went to work.  With three rows of lock-stitching and high-strength thread I feel pretty good about the sewing job I did.  You could probably tow a car with it.  Heck, you could probably lift a car with it.  The wing that this thing will be holding up weighs less than a hundred pounds.  I figure the weakest link is the four-inch lag bolts screwed into the ceiling joists.  I'm not sure how you would estimate the strength on those, but I'm comfortable knowing that there are six lag bolts being deployed for each wing.

A few rows of stitches and the first D-ring was securely sewn on.

Once I double-checked the length needed I cut the hose, sewed a D-ring on the other end, and added a third D-ring in between.  Having three D-rings on the strap gives both low and high strap positions, as we'll see below.


















I also had these brass snap-swivel thingys hanging around the garage for the last 12 years and finally found a use for 'em.

Here's the low position D-ring being used to initially hang the end of the wing on the strap until the spar end can be lifted and hung:


























Here's the strap in the high position - closer to the ceiling and out of the way.  There's a wood block there to keep the strap from pressing on the upper skin, which extends past the aft wing spar a couple inches...






























...So I need to move this ceiling anchor to the left some (which will also put the wing a little closer to the ceiling) but that can wait 'til another day.

Here's the root end of the right wing hanging from a hitching ring mounted on the ceiling.  You can see the left wing skeleton is already back on the work table.  Thank you John-John and Griffin for helping me move the wings.

I removed the latch and filed notches into the inside-bottom of a carabiner so that it's flat against the brass wing spar bushing instead of concentrating weight on the edges of the bushing.






February 23, 2015 Update (aka back from the future):
Finally got around to moving the ceiling anchor d-ring so that the right wing hangs closer to where I wanted relative to all the other stuff in my getting-ever-more-crowded garage.  Here's the pic:

Big Hole, Small Wires

After riveting the main wing skins next up was to install several oddly-shaped skins and ribs that make up the wing tip.  The top ones went on and then it was time to turn the wing over (again, with assistance from neighbor Ken) and close it out with the bottom wing tip skin.

I'm also installing nav lights for night flying, so I needed to cut a hole in the bottom wing tip skin.  Since the wing-tip lights and landing light installation instructions were originally intended to be retrofitted onto a completed wing, Vans instructs builders to cut a fist-sized hole in the bottom skin to order to get a hand in there and fish through wires needed for the lights.  But cutting odd shapes like the one on the provided template into sheet metal ain't that easy.  Furthermore, the big hole is only needed if you are retrofitting the lights and need to get your arm in there to pull wires through.  If you're not doing a retrofit, and you haven't yet closed out (riveted on) the bottom tip skin, then a small drill hole, say 3/8", to pass lighting wires should be sufficient.  In my opinion Vans should have provided a small hole option for builders who are installing lights as they build and finish out the wing.  Alas they did not, and are not likely going to. Since deviation from the plans is not allowed under the ELSA airplane category, I'm stuck cutting a fairly large odd-shaped hole in the wingtip bottom skin whose purpose will be to simply pass three small wires to the wingtip strobe/nav light.

On the Vans Air Force RV-12 forum (thread link here), I posed the question on whether a small hole could be used instead of the big hole.  The answer I got from the unofficial factory rep who monitors forum postings was this:

The answer is really pretty simple... would the hole match what the plans say to do?  If not, then it is not per plans.  So it is obvious, the answer is no.

Would an inspector be able to see it wasn't?  Probably not.  Does that make it right?  You will have to decide that one for your self....

And that's the final word on that.  Scott (aka rvbuilder2002 on the forum) is right of course, so big hole it is.  Sigh.  But really, IMHO Vans should have provided optional/alternative plan instructions for a small hole.  Feel free to comment below if you disagree.  I'll get the flame suit on.  Who knows, maybe it'll help out the next builder who reads this.  Or help me feel better about cutting a 14 square inch hole just to pass three small wires.

    Now on to the pictures.  This is a pic with the top wing tip skins and tip rib riveted on.

     Here is the wing turned upside down (inverted) again.

    Here's the wing tip bottom skin with the hole that I wanted to use.

And here is the bottom wing tip skin with the Vans-supplied template sized hole.  I used a unibit, metal snips, drill with 2-inch sanding drum attachment, and of course the deburring tool.  Helps that the radii of the cutout corners are about 1 inch (same as the sanding drum).  I ended up spending way too much time sanding down to the marked line so for the left wing I'm definitely using the sheet metal nibbler that worked so well on the landing light hole.

The tabs at the top need to be bent down at specific angles in order to match the other tip skins.  A bending tool fabricated from plywood is used to make the bends.  Most of the bends are 30 degrees, some are more and some are less. 30 of the tabs are bent at 30°(nice symmetry eh?), 9 are 31°, 4 are 17°, 3 are 32°, 2 are 28°, and one bend each at 16°, 19°, 20°, 21°, 22°, 24°, 25°, 35°, 41°, 51°, 82°, and 116°, as we shall see a little further on.

Click to enlarge

Personally I think Van's draftsman was having too much fun with this plans page. One degree of bend angle on a half-inch tab is less than 1/100th of an inch -- barely measurable. If the bend is within +/- 5° it'll work. Some builders have some pretty fancy angle-measuring tools but I used my daughter's $2 protractor to mark and cut a bunch of business cards for checking the bend angles.

Bending, checking, and sometimes re-bending all those skin tabs was tedious and I kept putting it off but eventually I got 'em all done.  The result is that the bottom wing tip skin fit like a glove.  I wasn't sure about the location for the bend line for the last tab on the trailing end (and also remember reading something about it on the VAF forum), so I trial-fit the skin onto the wing to visualize how it should go before actually bending it with the tool.  I'm glad I did because the desired bend line is not where I initially thought it'd be.

Above right is a picture of the final aft-most tab without the bend, and the picture to the left shows the bend in the tab.

Finally it was time to cleco on the bottom tip skin for an hour-long session with the pop-rivet squeezer.  Can you tell which tab got the 116° bend?

Below is a pic with the bottom tip skin fully riveted on:

Three rivet holes are left open where a wing tip fairing for the nav-strobe light will be fastened.  The fiberglass fairing will also cover up the access hole.   The open rivet holes are marked No, No, & No, which is what I say to people who ask if the plane is almost done yet.

I saved the leftover rivet mandrels beginning from where I started riveting the first wing skin and then counted 'em up.  It takes 2,128 pop-rivets to skin a wing on the RV-12.