Wings Continued: Ribs

After a long hiatus due to finishing of several rooms in the home addition, I'm finally making progress again on the plane. I've got all of the wings ribs constructed and in-place on the wing spars (see below). I still need to drill holes on the top and bottom of ribs for later installation of fabric. I decided to tackle this later, as I have obtained stands from Rans where I can attach wings and fuselage and turn in a rotisserie fashion for more comfortable orientation of surfaces for working on. Once I get the fuel tanks fit-up, I will rivet the wing ribs in-place.

Wing Construction: Frame and Ribs

It's been awhile since my last entry, as I've been busy designing/managing construction of a home addition, among other things. I've completed construction of the wing frames, which consists of spars, compression tubes, drag braces and fittings (e.g. strut attach plates, bellcrank braces). Following are pics of the completed wing frames. Everything is final installed, except the diagonal drag bracing tubes, which need to be removed later to facilitate installation of the ribs. I noticed some defects (originating from extrusion process) in the original aluminum spars from Rans; however, they were quick to rush a new set back to me. They were particularly concerned with defects in the areas 90 degrees from leading/trailing edges, as that is where the most deflection (stress) occurs in flight.

I just recently completed my first wing rib out of approximately 26. When installed between the spars, the ribs create the airfoil shape of the wing. It first involves fabricating a jig out of plywood which locks all of the parts together for easy riveting. Following are pics. It took me over an hour to complete just one , so hope I get more proficient at it!

Once the wing structures are complete, I won't be too far off from covering. I hope to attend EAA Airventure in Oshkosh, WI the end of July and sit in on some of the fabric covering seminars in order to get educated on the process.

Fuselage Fit-up: Floor Boards, Rudder Cable Assembly, Battery Access Door/Box, Baggage Compartment & ELT Mount

This past holiday vacation, I began to near completion of the fuselage pre-covering fit-up tasks. These are items you should complete before covering, since they would be cumbersome to accomplish when all closed off. These items included: drilling, sanding, staining and varnishing the front and rear floor boards, installing rudder cable assembly in aft fuselage, installing the battery access door and battery mount hardware, installing the rear baggage compartment, and installing the ELT mounting tray. In addition, I completed fitting up the torque tube, which serves as the control for ailerons via the aft horn. The torque tube will be removed and painted separately.

With the floorboards, main goals were to drill holes through where it will attach to fuselage tangs and where rudder pedals will attach. It was nice to actually do a little wood-working for a change. I think they will really dress-up and complete the cockpit. I strived for a maple look. I found for the wear plates, which were received scratched up, that a fine emery cloth cleaned them up fairly well. One note, the manual indicated that nut-plates (described below) were to be riveted to tangs where floorboards attach; however, Rans said it would be best to hold-off until after painting the interior. They claimed that since they can be installed easy later, it's best to wait so that the threads would not get buggered up with paint.

The battery access door and box assembly were simply riveted together and then to tangs on the plane. The door screws to the door frame via installed nut-plates (imagine a threaded nut riveted to something). The wire shown is a battery ground cable. You can also see rudder pulley cables and guides shown. Two rudder pulleys were also installed.

The baggage compartment has two metal straps that slide into separate pouches in the fabric on the sides and rear. Holes are drilled through the fabric and straps once wrapped over the fuselage tube and then riveted. Straps are also riveted to four points on the bottom of the fuselage and buckles are placed on the straps, which enables vertical tightening of the compartment.

The emergency locating trasmitter (ELT) is shown strapped to a mounting tray that is bolted to welded tangs. This unit senses sudden horizontal deceleration and will broadcast a signal on an emergency frequency. The unit utilizes simple D-cell batteries which is much more economical. The unit is also portable and can be taken away from a crash site for locating purposes.

Now that all installations are complete aft of the baggage compartment and things are fitup in the cockpit, the fuselage is ready for covering and the cockpit is ready for painting. Next, however, I will begin construction of wing structures.

Fuselage Fit-up: Main Gear (cont.) and Tailwheel

I decided to final install the main wheels and brakes to the gear legs. This will make it more convenient to move around in the garage. When time to cover I can remove the gear simply by pulling the bolts holding the leg assemblies in the sockets. I used sacrificial bolts for now so I would not screw up the threads on the permanent bolts. I checked wheel alignment by clamping straight sections of angle to the brake rotors and they were dead-nuts parallel. So apparently the jig fabricated in the previous post was successful and tire wear should be minimal in the taxi position. According to Rans, a slight toe-in of wheels should occur on "wheel landings" which will enhance stability by pulling gear together as opposed to spreading. All that remains to do to the gear is hookup brake hydraulics later.

I then attempted to fit-up the tailwheel assembly. The tailspring is attached to the fuselage at three bolt locations: one forward and two aft. The latter two connections through three pillow straps, sandwiching the tailspring, to welded bushings on the fuselage. Upon inspection, I observed that the distance between the center of the welded bushings is much less (1/8") than the distance between the center of the holes on each pillow strap. Therefore, the holes were misaligned between welded bushings and pillow straps and bolts would not go through. I contacted Rans and they confirmed this is a common problem. Apparently, during welding operations the bead will cool and draw the bushing inward, resulting in the above discrepancy.

I decided to oversize drill the holes in the pillow straps from 3/16" to 1/4" in order to get the bolts to fit.

Fuselage Fit-up: Main Gear

I'm currently working on getting the main gear leg "fitup". The legs are inserted into a tubular sockets welded on the fuselage. I found that the legs did not fit, so the manual recommends lightly sanding either the ID of the socket or the OD of the leg; I chose the latter. I was surprised to find how much material that I needed to remove in order to have the leg "bottom out" in the socket. It turns out after looking at the sockets that they appear not to be uniform linearly along the centerline and this resulted in the need to remove extra material in order to make the leg fit. I'm somewhat concerned that, on one leg, up to .030" of material was removed where the leg extends from the socket. This is obviously a high stress location and I'm concerned that upon a "hard landing" the leg might fail catastrophically. I will inquire with Rans on this issue.

I constructed a jig to align the axles mounted on the gear legs (see below). Once the apparatus was built, I marked the drill holes through the gear sockets and step drilled up to the end size for later installation. I was informed that it is critical to ensure that the fuselage is in it's taxi position when doing this operation (when most of the tire wear will occur). I was told to place the fuselage on the floor with the gear legs in, measure this angle and then duplicate the angle in an elevated position. I used a hand clinometer to reproduce the elevated taxi position angle. This worked slick.
Footnote: I decide to replace the troubled gear leg mentioned above, and installation was uneventful; now I own a $260 "club".

Fuselage Fit-up: Formers

This past week I finally started construction on the plane. I began by installing aluminum tubing formers on to the fuselage which shape the fuselage properly for later covering. They were installed on the top, bottom and sides of the fuselage. I learned how to drill holes properly with a drill press and fabricated V-block, how to use cleco pliers and cleco fasteners to hold two materials temporarily together via drilled holes, and how to pop-rivet. I also safety wired several connections.

Organize Shop/Parts and Inventory

This past weekend I began dismantling the "big box" which turned out to be quite a chore as Rans stapled everything together instead of using screws. The stapling also resulted in mangled plyood which was a bummer because the intent was to reuse this material to construct a workbench, etc. This pic shows the box contents following removal of several items within the cockpit area of the fuselage.

Once I got everything out of the box I constructed a 16' long work bench and hung two 4x8 sheets directly above it for stapling of numerically labeled & bagged items. I also constructed a large drawer on wheels which slides under my existing work bench. I put the majority of my larger parts in there.

The inventory of 800 plus parts was very time-consuming. Rans sends you a parts list with an assigned Priority Number to every part. On the supplied list, I verified that each corresponding part was present, note where each part was in the shop on the list, and check off that I received it. The small, bagged parts were stapled in chronological order on the wall for easy locating. Rans did a very good job packaging and marking contents on all of the parts. I found every item except one consisting of aluminum tubing.

Upon inspection of the fuselage I noted the vertical stabilizer was deflected somewhat to the port side. After verification with Rans, they indicated all of their inventory of cages have this problem and originated from a bad jig. The engineer claimed the vertical front tube on the vertical stabilizer is rotated to the left; however, the fin is still reasonably straight and should fly fine as their production models have the same problem; still disconcerting nonetheless.