(page 29A-02 + page 54-01) Upper firewall + stiffener kit

The upper firewall fabrication involves lots of nut plate installation and match drilling of piano hinges.  Much of the drilling is through the stainless steel firewall itself, a bit harder than the usual aluminum.  A drop of BoeLube on the bit helps with this.  I included the

"optional" stiffener kit installation with the firewall since they connect.  As might be imagined, the stiffener kit is much easier to install at this point in the build.  The instructions are written as if it's a retrofit, so all of the rivet removal described was avoided.  The kit does involve drilling 40 or so holes in the side skin, some from the inside out and some from the outside in.  At this stage in the build, I approach the drilling of holes in the skin with fear and trepidation.  Screwing the skin up would be unimaginably bad.

Oshkosh is finally here!

I accomplished nothing on the build today, devoting the entire day to getting ready to leave tomorrow morning at the butt crack of dawn for a week at Oshkosh.  As we did last year, we're having a get-together of RV-12 builders.  At last count, 42 people are scheduled to meet on Tuesday.  I'll get a group picture and post it.  I've been listening on the web to ATC for KOSH (tower for 18-36) and I'm pumped from hearing all the planes land.  Tomorrow afternoon, I'll be sitting in the grass beside the runway with radio in hand, witnessing it in person. Can't wait.

(page 24-05) Less like a boat, more like an airplane

I had been looking forward to attaching the rollover assembly primarily so it would start looking more like an airplane, and with the addition of the rear bulkhead the effect was even more pronounced.  The look really

got me fired up.  The machined aluminum pieces which bolt to the lower fuselage and are supposed to slide into the rollover structure didn't fit and required a bit of work on the belt sander followed by the ScotchBrite wheel.  The rule of thumb on this kit is supposed to be "if it doesn't fit, you did something wrong."  Not here.  Considering how the roll bar is constructed, I was not particularly surprised.  I probably had to take ten thou off the width of the machined pieces.  Fits great now.

The only other anomaly encountered was the channels which get riveted to the bulkheads.  The build manual shows three snap bushings being inserted into the channels, but my channels had only two holes.  I contacted the Mother Ship and was told to break out the step drill and make a new hole.  This would have been easy had I not already riveted everything together, as called for in the build manual.  Once again, the Tight Fit Drill Kit to the rescue.  I was able to drill a quarter-inch hole and then expand it to the proper diameter with a cutter (attached to the Tight Fit).  All is well.

The build manual calls for attachment of the tail cone soon, but, as many builders do, I'm postponing it.  With the tail cone attached, the thing becomes quite unwieldy. I'll continue with the upper fuselage construction, followed by the wings.  I can't imagine where I'll put them when they're done.  Space is a problem.

(page 24-02) Roll-over structure

The two curved channels and two straps that connect them arrive pre-punched to #40 and must be drilled to #30.  The four parts must be clecoed together with

the silver clecos, severely straining my supply.  The Isham tool kit which I bought at the start of this project had up to this point had the right amount of everything, and I initially feared the kit was actually lacking in this regard.  Not so.  Doing half of the structure at a time worked fine.  I clecoed every other hole, inside and out, with silver (#40), drilled the exposed holes #30 and clecoed with copper.  This pulled the straps in tight against the curvature.  Also shown in the first picture is my one-handed cleco-pickup tool (a board with holes drilled in it).  There are many times when you're holding something with one hand but need to insert a cleco with the other.

An air drill is an absolute must for this much drilling.  I use the air drill for anything that doesn't require speed control, such as drilling out rivets or counter sinking.

Speaking of which, the entire outer surface, a double row all the way around, must be countersunk.  Since the Lexan canopy will lie underneath these flush rivets (or "lay" underneath as stated in the build manual.  Perhaps they will be producing eggs since they will be "laying."  Van's should be embarrassed by having their grammar corrected by an engineer).

In the jargon of airplane builders a rivet or other item which protrudes slightly above a surface is described as being "proud" of the surface.  I love this descriptive terminology.  Along those lines I am hereby introducing a new term.  A rivet or other item which ends up slightly below a surface will hereafter be described as "ashamed" of the surface.  Since the canopy will lie against these rivets, I counter-sank them a bit more than normal, causing them to end up a bit ashamed of the surface and thereby unable to scratch the Lexan.

(page 23-08) Piano hinge cowling attachment

Anything involving match drilling piano hinges (anti-servo tabs, seat backs, cowling attachment) usually gives me heartburn in one way or another.  These two were no different.  The match drilling is done using the holes

in the side skins as a guide.  The holes go through existing holes in the side skin and stainless steel fire wall tabs, and the new holes go in the piano hinges and an aluminum spacer.  The problem is that once the clecos holding the fire wall tabs to the skins are removed, those two parts are no longer aligned fore and aft, making the match drilling impossible.  To overcome this, I left as many clecos in as were required for alignment during the drilling.  The protruding nubs of the clecos made it impossible for the piano hinge plus spacer to lie flat against the curve, but, starting at the uppermost hole, I removed the minimum number or clecos which would allow me to clamp (see the clamp at the bottom) the hinge plus spacer flat against the curve.  I then drilled and clecoed that hole and moved down to the next hole, repeating the process.  It worked reasonably well, still producing minor heartburn.  The major heartburn came when I managed to drill an unwanted #30 hole in the side skin near the (wanted) bottom-most hole.  The two are very close together.  My first thought was to put a rivet in it, but that would look a bit strange.  Alternatively, I could fill it with epoxy and it would be invisible when the airplane is painted.  I had to invent several new curse words when I discovered what I had done.  None that I knew seemed adequate.

(page 23-06 still) Side skins riveted!

We're drawing ever closer to that milestone in the build of every airplane: the first time the builder can sit in the cockpit and make airplane noises!  I may go ahead and install the seat backs (already completed) just to hasten that day.

Installing those hundreds of rivets in the side skins went mostly without a hitch, although my beloved pneumatic rivet puller did have an uncharacteristic hiccup.  After the first 50 or so rivets it quit releasing the steel arbor after breaking it off the rivet.  I disassembled, cleaned, lubed, and re-assembled the puller head several times to no avail.  Finally, for no discernible reason, it started working again.  The aviation division of Harbor Freight sells a cheapo puller (~$35) which some builders swear by (although it will probably rust before you get it home from the store).  I may get one of these as a backup before I start on the wings, which involve a sea of rivets.  The stiffeners required by the landing gear service bulletin require some CherryMax rivets which none of my regular pullers, manual or pneumatic, would set.  The manual puller made by Cherry (discussed in a previous post) again worked well.  Between those and all the Cleco installation and removal, by forearms got a workout.

Pulled rivet removal technique.  Van's writings on the subject insist that when drilling out a pulled rivet, the steel pin (arbor) in the center should be driven out using a pin punch inserted into the manufactured head, followed by drilling out the aluminum rivet itself.  The thinking is that if the drilling is done with the arbor in place, once the bit hits the steel it will go to one side, making the hole oblong.  Of the thousands of LP4-3 rivets I've pulled, I've had to, for one reason or another, drill out maybe 50.  I've always done it like this:  Using a #30 bit with very slow drill speed and light pressure, drill the manufactured head until the head spins under the bit.  At this point, what remains of the rivet (arbor and shop head) can be pushed out with very little  force.  No pounding involved and no chance of denting the thin aluminum.  I've not had a single problem with this method.

(page 23-06) Return of the porcupine

                                    
This can mean only one thing: My favorite tool, the pneumatic rivet puller, is about to see heavy use.  The skins have to be clecoed in place, including the stiffeners from the landing gear service bulletin, and hundreds of holes must be match drilled through the skins (easy) and through the longerons (pita).

The goodness (or lack thereof) of the longeron bends now becomes obvious.  I had worried about this, but I see now that the longerons can be easily tweaked to fit as the match drilling progresses.

Once the drilling is done, everything has to be taken apart, deburred and mating surfaces must be primed.  I'm still conflicted about priming
and painting the visible interior surfaces.  I can't find the dark grey enamel color I want, and since I'm going with a full interior much of it will be hidden anyway.  The color choice with rattle cans seems to be quite limited.