Wings Fuel Tanks: Final Install

After successful pressure testing, the tanks were filled with unleaded fuel and allowed to set from 12/31/07 to 1/19/08. Again, Rans recommended at least two weeks to allow the tank material to interact with the gasoline which they claimed could result in an inch of tank elongation, obviously important to do before riveting the tank to the wing structure. A tank support tube was added to the wing frame and the tank was set in place with mounting brackets attached. Once the tank was clamped so that it lied uniformly along the compression tube and tank support tubes, the mounting brackets were drilled and riveted into the tubes. Below are the installation pics from one of the installed tanks.

Once I get the wing ribs riveted to the spars, I'll then install the fuel lines.

Wing Fuel Tanks (cont.) & Aileron Bell Cranks

The second fuel tank was air pressure tested for several days and held approximately 23" of water for a couple days. Again, I could not get this tank to hold greater than roughly 0.5 psi. Initial soap solution testing of both tanks and associated tank fittings revealed no evidence of leaks, however. Based on these results and consultation with Rans, I decided they were good enough. I have since filled them with unleaded automotive gas and will let them set for two weeks. I'm told they will potentially elongate up to 1" due to interaction/absorption of gas with plastic. Want to make sure this occurs before attempting to install the tanks on the wings. Another pic is shown below of second fuel tank being leak-tested with manometer.

As I'm waiting for tanks to cure, I decided to install the aileron bell cranks to the wing frame. I had initial difficulty getting the spindle flange to seat flush with the mounting bracket (could see daylight between seat area). Rans recommended chamfering corners of hole slightly to remove anodization coating and this worked successfully. After assembly and when mounting the assembly to the bell crank brace on the compression tube, the key here is to ensure the lower bell crank arm remains horizontal to the rear spar (check by positioning parallel to rear spar and looking from behind TE spar). Otherwise, later the nut holding the two arms of the bell crank could rub the fabric on the bottom of the wing during normal rotation of assembly. The type of vise grips shown aided greatly in clamping the assembly to the compression tube so the transfer drilling would be successful. Pic below.

Wing Fuel Tanks

I have drilled a total of five 1/2" diam. holes through each of the fuel tanks and installed associated tank fittings. A combination of Loctite and teflon thread sealant is used to ensure fittings remain tight and do not leak. Rans recommends leak-testing the tanks to 1 psi. To do this, I decided to pressure up the tank with air and adapt a home-made manometer. I adapted short lengths of tubing to 3 of the 5 fittings with bolts insert to plug holes. I adapted a ball valve and tubing to the fitting that I inputed air and hooked up a manometer to the fitting where air would output. My pressure source was a refillable compressed air reservoir with an inflator needle (like used for footballs, etc.) . My first attempt resulted in numerous air leaks at locations where the bolts were inserted to the tubing. This was solved by filling threads with thread sealant and tightening up the hose clamps. I pressured up the tank again to 2.3 feet of H20 (1 psi), as observed by the differential distance between water levels in the manometer. To date on the first tank, I'm only able to maintain about 20" of water over 48 hours. I've applied soapy water to all fittings and cannot identify any physical leaks. I will inquire with Rans....









As a side note, Christmas yesterday brought me a brand new Bose X headset from my wife! A complete surprise, apparently this headset is the best active noise reduction set on the market. This will give me a nudge to increase production on the project and get flying. I have tentative plans this Summer, however, to make a road trip to Rans in KS to obtain flight and instruction and get current in an S-7S. I have not flown in close to 5 years and fear I will lose acquired skills permanently. Perhaps I can demo the headset then....

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.