Wings: Sheet Metal: LE Wrap Installation

Following are pics of installation of the Leading Edge (LE) Wrap, which was completed nearly a month ago. First pic shows use of Dremel drill with sanding flapper wheel (80 grit) removing the anodization from the spar at bonding area. This is important so that the epoxy bonds the wrap and spar well. The bonding areas also need to be roughed up for bonding with 80 grit sandpaper. Masking tape was used to control alignment of sanding ops on the spar.


Below is LE wrap being bonded to the spar. I used quick clamps at nearly every rib location to distribute pressure on a 1x2 oak strip which then distributed pressure to the LE wrap/spar. Waxed paper was placed under the strip so that it would not stick when removed. The epoxy used was DP-460 (Dow product?) which was applied using a helical mixing tip that mixes resin and hardener automatically so that an even bead can be applied.

Here is the finished leading edge after masking tape was removed and excess glue was removed with an exacto knife.

In a similar manner the trailing edges of the upper and lower root skins were bonded with epoxy (not shown). Next step is to fill-in area forward of LE wrap with bondo filler and then sand to get a nice smooth contour between spar and wrap.

Wings: Sheet Metal: LE Tip Wrap and Root Skins

I'm currently installing pieces of aluminum sheet metal to select areas on the wings. I have installed the leading edge tip wrap (not shown), which is a transition piece used to taper from the tip rib to the next inboard rib. Currently I'm working on fitting up the top and bottom root skins which are installed above and below the fuel tanks. Below are shots of the upper root skin being installed. The hole for the fuel cap and scupper was precut. I'm using a combination of clecos and hand clamps to keep the metal in place on the ribs while I transfer drill through the sheet metal into the ribs. The root skins will get riveted to the ribs.

The long aluminum sheet metal piece shown below is the leading edge wrap. This will get epoxied and riveted to the leading edge spar and ribs, following root skin installation.

Wings: Fuel Vent Lines, Pitot tubes and Flap Cables; Rib Final Install

The flap cables and pitot lines were installed in the wings prior to covering. These lines are routed to the aft root end of the wing where they will be hooked up when the wings are attached.
I installed the aluminum fuel vent lines that extend from the top tee on each fuel tank and routes through the wing through rubber grommets mounted on the ribs to daylight at the bottom of the wing. A section of line also extends from the tee to the wing root.


I zip-tied the flap cable (black) to the compression/diagonal tubes. The flap cable end on the wing will be retrieved from inside the wing following covering. The flap cable end and remaining cable from the wing root side was pushed and stored inside the leading edge spar.

The static/pitot lines (white plastic) were installed in the left wing through brackets riveted to 6 outboard ribs and zip-tied to the diagonal tube leading to the aft wing root. The pitot tube was temporarily installed to fitup the plastic lines. The Pitot tube (not shown, will install following covering) projects into the air from the LE spar and measures differential air pressure in the tubes. One tube is an indication of ram air which varies with velocity and the other measures ambient air pressure. The difference in pressures can be used to determine air speed.

I also was finally able to rivet and final install all of the ribs to the wing frames. Due to clearance problems, I needed to obtain a close-quarters angle drill and a 16" #30 drill bit. The long bit has proven very useful as it can be deflected around obstructions to drill holes. Therefore, the entire wing frame structure is complete.

My next step will be to bond sheet metal to the LE spars. I'm not looking forward to this phase as it will involve the use of liquid adhesives and clamps.

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.