Covering: Doors (Cont.)

I finally got the doors completed and ready for paint. It turns out the best glue application method is 3 parts U500 to 1 part MEK below the fabric and then 3 parts MEK to 1 part U500 over the fabric. In the following photos you can see patches and then 2" tape glued on the doors. The patches correspond to bushing locations and holes will be burned later with a heat knife to facilitate passage of fasteners (small holes were punched with an awl for easier location later). The tape serves to trim out glued seams. The whole process turns out to be extremely time consuming because, in addition to all of the multiple coats of gluing, you're also constantly removing extra glue with MEK and ironing tape, patches and fabric. Next I move to the control surfaces

Covering: doors

I finally have reached a major milestone and have begun the covering process. I decided to start with the doors since they are not control surfaces and look fairly simple. I'm using the Superflite product process which encompasses covering, adhesive, primer paint and topcoat paint. The adhesive is called U500 and needs to be thinned with methyl ethyl ketone (MEK). MEK is highly volatile compound which allows the glued areas to dry quickly. I have learned that the Rans fuselage is epoxy primed and remainder of painted parts are powder-coated. It turns out the MEK compound will quickly dissolve the powder coating so several coatings of straight U500 needs to applied first as a foundation. When the fabric is applied, thinned U500 (3 parts MEK to 1 part U500) is applied to the top of the fabric and the underlying basecoat is then dissolved and wicked up through the fabric. Outside of the wings and fuse, all of the parts to be covered are powder-coated and will follow this application regimen. Dacron fabric is the covering and an iron is used to taut the fabric at three temperature settings: 250, 300 and 350 degrees. Each temp setting results in a greater degree of fabric shrinkage so that at the final temp the dacron approaches a snare drum type quality. The iron also smooths out the surface of glued edges where any wrinkles might be present. Following is a pic of one side of the door covered and ironed to 250 degrees. I'm amazed at how uniform and tight the dacron got at 250 degrees. Need to apply each temp to alternate sides of surface stepwise to distribute shinkrage tension or piece could severely warp. It is important to have each fabric layer glued nearly completely around each structural member in order hold fast to the fabric shrinkage.

Fuselage Precovering Add-on: Ballistic Airframe Parachute

I opted for installing a Ballistic Recovery Systems (BRS) airframe parachute in order to provide insurance for the unthinkable and curry favor with my wife for letting me take the kids up someday. The parachute is deployed in a split second by means of a rocket assembly, which provides great utility when at low level altitudes. In my case, the entire skylight will be ripped off in a deployment. I opted for holding off on purchasing the rocket and chute since there are shelf life issues with those items. Instead I installed the minimum hardware needed before fuselage covering, which includes the kevlar parachute bridles and mounting hardware. I fit-up the whole assembly first with clamps and vise grips to find optimum location. I tried to keep as far forward as possible due to CG issues. I then burned slits through the fabric and installed the band fasteners around fuselage members and transfer drilled through the angle. I then transfer drilled holes through the white mount into the angle and bolted everything together. Triggers will be mounted left of each fore/aft seat. No sense doing that until I have fuze interior painted.

Here's a picture of the 1350 softpack chute with rocket I will be ordering later from the manufacturer. Total weight 29 lbs.

Wing Precovering Add-ons: LRI, Wing Tip Strobes

I purchased Aveo LED aviation lights for the wing tips. They provide strobe and navigation light functions. The setup is brighter, lighter, and more efficient than the conventional incandescent packages. I installed the wiring in the TE spar prior to covering.



I also purchased a lift reserve indicator (LRI) system. Similar to a pitot system, there is a probe mounted on the wing that measures differential air pressure and two air lines which run to an analog gauge in the cockpit. Based on wing angle of attack, the LRI displays how much lift the wing is generating and what is available for you to use at any given time. It becomes very useful in optimizing short field take-offs and landings. Check out at: http://www.liftreserve.com/. The owner was very helpful on followup technical assistance related to installation.

I installed the probe onto the right wing, prior to covering. The probe is mounted on the underside of the wing near the tip (to prevent air disturbance, such as from struts) and a distance of 15% to 30% of the wing chord aft of the LE. The probe pivots and is angled 50 degrees forward. A sheet metal spanner had to be fabricated and mounted between ribs to provide a stable platform for the LRI probe. The probe was then mounted on an aircraft inspection port and the port/probe assembly screwed to the spanner.








The wings are now complete and ready for covering.

Final Wing Precovering Assembly-LE Support Tubes, Misc

After a Summer hiatus, I'm finally back in production. I applied Bondo filler puddy and sanded it to create a smooth contour between leading edge wrap and front spar.

Next I cut 1/2" tubing and spaced between each rib 3-3/4" from trailing edge of LE wrap. Gussets were riveted to each rib at this location and then the tubing was riveted to the gussets. The reinforcing tubes will support the LE wrap during flight and prevent "oil-canning".

I assembled stands I borrowed from Rans and used one on each wing so that the wing can be rotated and braked for ease of work.

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.