The Independence Project: Winging It

In this new series on building a Vans RV-12, the first subkit is completed as we are reintroduced to the design.

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An organizational meeting got the building project underway.

 

Proximity matters. I live 150 feet from a hangar belonging to one of the most active airplane-building chapters of the Experimental Aircraft Association. For example, several years ago, Chapter 292 members built 14 Graham Lee

Nieuport 11s simultaneously. The chapter is located on Independence, Oregons state airport, which is less than 40 air miles from the Vans Aircraft plant in Aurora, Oregon. A residential airpark sits on the east side of the airport, and more than 40 kitbuilt Vans RVs of various sizes plus several offshoots (Harmon Rockets) currently taxi from their private hangars to the state-owned runway. Recently, five airpark families formed a group to build a high-end, four-seat RV-10.

With all of this RV building and flying activity, its not surprising that EAA chapter members began discussing the new Vans RV-12 Light Sport Aircraft (LSA) kit as a possible chapter project more than two years ago, long before the first RV-12 flew. Also logical was that RV-12 chief project engineer Ken

Airshow coverage sponsor:

Krueger committed to show off the RV-12 proof-of-concept prototype in its first public appearance at a regular Chapter 292 Saturday meeting.

That happened in February 2007, and it resulted in my review of the design in the November 2007 issue of KITPLANES. At the end of the article I signed off with what I consider to be my greatest and least-used compliment: I want one.

A Chapter Project

The winter of 2007-2008 was unusually cold in our part of Oregon, and my wife and I decided that the limited usefulness of our open-cockpit airplane needed some attention. We committed to buy an early RV-12 kit, and our EAA chapter agreed to host the project in unused space at the chapter building, solving concerns about adequate room in our small hangar. This would also allow chapter members to participate in the project, which was the initial motivation anyway. Twelve members signed up to help.

On the Sunday after taking delivery of the first RV-12 kit segment-the wings and flaperons-at the Vans factory, I invited the 12 volunteers to a meeting, and everyone showed up! We discussed how and when we would begin building, and copies of guidance on installing pulled rivets were provided.

At the meeting, I had the factory-built wingspars and a few rib brackets that could be pull-riveted to the spar. For a few minutes afterward, the volunteers watched a demonstration using my pneumatic rivet puller, and folks who hadnt done so pulled their first flightworthy rivets. We discussed schedules, and that night I emailed a week of office hours, my planned times to be present for building sessions. I listed times during the day plus some evening and weekend hours in hopes of accommodating everyone.

It worked. For the next three weeks, at least one other person was present during each office-hours period. A few times, as many as five of us were working together. For these groups, we had two riveting teams working to attach big pieces like wingskins. For a week, my wife and I left the project behind to visit our newborn granddaughter in San Francisco, but several volunteers continued to work in our absence.

Bob Schwarzler stuffs more rivets in holes between the Clecoes.

The Kit

A neighbor who brought home his Lancair IV-P kit in a large rented panel truck had volunteered to pick up the RV-12 wing and flaperon kit at Aurora. I took along furniture blankets to protect everything, especially the large, flat sheet metal parts such as wingskins. Except for the manufactured wingspars (nearly 16 feet long), the truck bed seemed almost empty on the return trip. All of the eighth-inch aviation-quality pulled rivets anticipated for the entire project, some 10,000 of them, are sold with the first kit segment and cost $250. (Vans later supplied 2500 more LP4-3 rivets; 10,000 werent enough.)

Especially for a first-time builder, instructions are critical. The RV-12 plans come on 11×17-inch sheets, and the first several sections are general instructions such as design philosophy, required tools and workspace, and construction methods such as edge finishing, riveting and identifying fasteners.

Experienced RV builders-and there are more than 40 of them in my neighborhood-note that the RV-12 plans are different from previous RV plansets. Most say these plans are better. There is little text in the actual building sections. Instructions consist mostly of engineering-quality perspective drawings showing every detail plus brief numbered text blocks. As I did years ago with many Heathkit electronic projects, I checked off and dated each step as it was completed. But the same instructions (with a few exceptions) are used on both wings, so I ended up with two checkmarks on many steps.

Still, it is possible to misread or simply miss critical steps. That happened a few times, resulting in some drilled-out rivets. I read the entire plans several times before the actual building began but still managed to overlook a few details. On the next kit segment, I will read the plans more than twice and highlight variations in yellow. Here is an example for my fellow builders. Small L-shaped brackets are used to attach some wingribs to the spar, and despite clear drawings and written descriptions, we positioned a few of these incorrectly. Fortunately, we discovered the error, drilled out a few pulled rivets, and reversed the brackets before the mistake caused major trouble. Even so, we were making sure all wingskin holes mated with rib holes before skinning, so the error would have been caught later.

An especially important consideration with the RV-12 is that the two wings are not identical. The beautifully built, clear-anodized, laminated spars (nearly 1 inch thick at the roots) overlap in the fuselage, and the right spar is almost an inch forward of the left spar, meaning that rib preparation is different for the two wings. In addition, most but not all of the rib parts designated with an L suffix (such as W-1208-L) are actually used in the right wing, not the left. The -L and -R designations are the direction of the rib flange from the rib blank, not the wing designation. The drawings and text are correct, and nobody erred, but theres no warning about this.

Making Usable Parts

Each sheet metal part blank requires builder preparation before assembly. The process is to remove the anti-scratch blue vinyl coating and deburr sharp holes and edges, usually on only one side-the exit side of the punched rivet holes. Files are used on edges and deburring tools on the holes. Large sheets such as wingskins may take more than 10 minutes to prepare.

The wingribs consist of noseribs and mainribs. Each of the 54 wingrib part blanks requires deburring plus a few minutes with a fluting tool on the rib flanges to flatten them. Thats because wing camber causes the rib blanks to come out of the stamping press curved a bit like a potato chip. Proper use of a handheld fluting tool, which resembles large pliers, gathers aluminum flange material and-done right-flattens the part. It takes a little practice to get good at it.

As recommended in the plans, I made a steel tool that allows the nose of the rivet puller to grab the rivets mandrel (which pulls and expands the end of the rivet and then breaks off) at an angle. The tool was used to pull rivets in tight corners such as where ribs fasten to the spar web or a bracket.

The builder makes a few parts from supplied stock material. One of our volunteers is a retired machinist, and he used the three-view drawings and extruded aluminum stock to turn out flaperon actuation tabs and attach fittings. His work is beautiful.

Some parts blanks are made from a single sheet of metal and need to be separated and otherwise prepared for assembly. A few small assemblies are made entirely by the builder. An example is the angle-of-attack (stall warning) sensor that is installed in the leading edge of the left wing. It consists of a MicroSwitch and various small parts including nuts, bolts and stacks of washers. Wire assemblies are made up, attached and routed through the leading edge of the left wing before riveting the leading edge in place.

Assembly Line

The RV-12 is the first Vans kit to punch holes to rivet size, eliminating the need to drill every hole to size. In other RVs (all of which use mostly solid driven rivets instead of pulled rivets) and in most other sheet-metal aircraft kits, the process is to temporarily fasten metal parts together with Clecoes, leaving some holes open for drilling the factory-punched pilot holes to the final rivet size. The Clecoes are then moved so that all pilot holes are drilled to size. Cleco fasteners are removed, the two parts are separated, and four surfaces (both sides of two sheets) are deburred. The parts are Clecoed together again, and solid riveting begins with either a pneumatic gun and a bucking bar or a rivet squeezer. If flush riveting is called for, both sheets are dimpled to accommodate the cone-shape rivet head.

Not for us. The RV-12 pulled-rivet process reduces the method by about two-thirds. Deburring occurs before the sheets are Clecoed together. The factory CNC hole placement process is so accurate that lap joint metal sheets line up for easy Cleco installation in every other hole or so. Rib parts often don’t align perfectly with the skin holes, because the rib is slightly out of position left or right. But using an ice pick or an awl easily moves the rib into position for capturing its flange holes with the Clecoes.

Most often, empty holes between Clecoes are easily stuffed with pulled rivets. A wing surface with close to 100 Clecoes and about the same number of pulled-rivet mandrels exposed is a fascinating sight. In this phase of wing construction with five people working together, we operated two overlapping teams. Some of us installed Clecoes, while others poked rivets in the open holes. Two pneumatic riveters pulled rivets, starting at the center of a panel and working in both directions to eliminate the problem of metal stretch, which tends to buckle the skin. Someone pulled the remaining Clecoes in the riveted area, and another person stuffed the remaining rivets, followed by a new round of pneumatic rivet pulling. Its quite an operation. Part of the process each day was to collect the mandrels scattered everywhere. The wings and flaperons may have absorbed more than 5000 rivets.

A Tip For You

One of Vans goals for the RV-12 was to minimize fiberglass parts to save weight and cost, and wingtip design using only sheet metal proved an impressive test of the concept. A casual look at the two RV-12s completed at the factory might lead you to think the underside of the wingtip must include a compound curve. But the lower wingtip is-like everything else-cut and punched from a sheet of Alclad aluminum.

Before the bottom wingtip skin is attached, a handhold bent and folded from a single piece of aluminum sheet is riveted to the spar end. The large lower wingtip sheet Clecoes easily to the upper skin, spar, handhold edges, and a bent and punched strip formed partly by hand to match the curve. The design results in a graceful twist in the lower wingtip skin. And better yet: All the holes line up without drilling. Amazing!

Flaperons

One of the many RV-12 features unique among Vans Aircraft designs is the use of flaperons instead of ailerons and flaps. They ease the design and function of the plug-in wings and their automatic hookup with controls.

The thick tube inside the outboard flaperon leading edge provides static balance.

The full-span flaperons are actuated from the root end, so they need to be rigid, resulting in a fairly complex design. Each one consists of 31 parts including bent leading- and trailing-edge skins, a full-length spar with lightening holes, a heavy wingtip leading-edge tube counterbalance plus many pulled and a few solid rivets.

One of our few mistakes was use of the wrong rivets in the first flaperon at the critical root end. Some time was spent devising a way to replace the wrong rivets without drilling out a large number of pulled skin rivets. Pulled instead of the required solid rivets were used to fasten the flaperon actuating tab. At first I thought we would have to unskin the whole flaperon to fix this, but after a few moments, I realized that an angle drill (to remove the wrong rivets) and unriveting the most inboard flaperon rib would allow getting inside to squeeze the replacement solid rivets. With the plan in mind, I fixed this in about 15 minutes. I should emphasize that although subsequent kit segments contained actual errors, the wing kit instructions-both written and shown in the drawings-were accurate.

The Registration Decision

As this project began, we expected to have a choice of registration as either an Experimental/Amateur-Built (E-AB), which would require an accurate builders log, or as an Experimental Light Sport (ELSA), based on Vans receiving Special LSA registration on the kit production prototype (the red airplane). Therefore, I kept track of who was present and for how long and took photos as we worked. At the end of the day I put hand-written notes in my building log, and will continue this documentation throughout the project. But our thinking now is to take advantage of the ELSA registration option for a number of reasons.

First, it is possible that the FAAs proposed redefinition of the major-portion (51%) rule for Experimental/Amateur-Built aircraft will preclude the RV-12 kit from being eligible for E-AB status because of factory operations such as holes punched to rivet size. This would be a ludicrous outcome, considering that the 200 or so aircraft types already on the FAAs approved kit list are grandfathered even though many of them come with large factory-built assemblies. But the RV-12 is too new to be on the approved list, so it will be judged under the new major-portion rule interpretation. (As this is written, well before Oshkosh/AirVenture 2009, the nature of the rule changes remains quite murky.)

Second, there are advantages and disadvantages to E-AB registration. In the former category are that the homebuilder may make minor changes without further FAA involvement, and the primary builder may get a repairman certificate for the aircraft after completing the test phase. That document allows the registered builder to complete the annual condition inspection on that one aircraft. However, the repairman certificate is not transferable. Any subsequent owner must get an A&P mechanic to sign the annual condition inspection.

Licensing as an ELSA is almost the reverse situation, which may be a resale advantage. [We have heard claims that an ELSA carries a substantial resale advantage over an Experimental/Amateur-Built, but have yet to see a lick of proof.-Ed.] Any owner-first or subsequent-may take the 16-hour LSA inspection course and, after passing a written test, complete the annual condition inspection on the ELSA. The disadvantage is that the ELSA must initially conform completely to the factory-built SLSA on which the kit is based. No owner may change anything without written approval from the manufacturer. The implication is that the factory tested the change and found it satisfactory. Once licensed, changes can be made.

Wrapping Up for Now

At the end of this first kit element, we had just over 200 total work hours in the completed wings and flaperons. Compared with working alone, the team method is probably less efficient except in a few operations. But this is a group project, and getting it together really fast is not an objective. Even so, the wings and flaperons required less than three weeks of fairly leisurely fun to finish. They sat in my hangar for four months awaiting the next kit element, the forward fuselage. Next month well press on with more on one of the first RV-12 projects to be built. Subsequent kit segments are expected in short order. J

For more information, call 503/678-6545 or visit www.vansaircraft.com.

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