Covering: Flaps

I completed covering both flaps this weekend, which began on New Years Eve. The process will be similar to the ailerons and involves gluing fabric to leading edge, then wrapping around trailing edge and gluing to leading edge. Fabric overlap on the ends is then folded over and glued. Once fabric is secured on all sides with glue, the fabric can then be ironed and tautened. A drain grommet is installed on the inner bottom lowest point of the control surface. A grommet is just a small plastic looking washer which is glued to the fabric. A 2" patch is glued over it and later a hole will be burned through the grommet with a heat knife. Several other patches were glued to the flap where fasteners will penetrate through holes in the flap. End patches were fabricated and glued on. Then 2" tape was glued on LE and TE. First pic below shows masking tape placed on sharp part of ribs. The forward and aft part of ribs were smashed down and then smoothed with a dremel wire brush bit. Important to either tape over or smooth out any sharp points which could tear fabric. First pic shows base coat of concentrated glue on metal, then application of dilute adhesive being brushed over fabric to dissolve underlying glue and pull up through fabric matrix. Talking with Rans, I've begun applying two coats of concentrated U500 instead of one heavy coat. Surface prep cleaning of metal consists of naptha and then scotchbrite. The latter helps scratch the metal and enhance glue bonding.

Below pic shows completed flaps finished with tape. I punched holes where appropriate with an awl now as finding them later following painting will be difficult. Straight MEK works well cleaning up any glue off fabric which I'm told will be visible following paint.

I've been breathing the vapors in a closed garage so far (hard to justify opening garage door when 10 degrees outside), but after a long day yesterday I've had a persistent headache. Will begin using a supplied-air setup which I had purchased for later painting.

I've thrown away the razor blades for trimming fabric, as I had to redo a door earlier after tearing finished surface. A good pair of small sewing sizers (like used for fly-tying) works will for trimming excess fabric on glue joint. I've also learned to forego using a sharpie to mark lines on fabric, as MEK will dissolve and bleed. Soft lead pencil works great. A black and decker electric shears works great for cutting large pieces of fabric off the roll.

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.