Wing

September 16, 2014 Ordered all the foundational materials needed to cover the tail and wings. Not included in the screen cap at left is 30 feet of aluminum trailing edge (in 5' strips) and a quart of 3M Fastbond 30-NF water-based contact cement... the same blue-green stuff supplied to Stewart Systems who rebrands it as Ecobond and sells it for $15 more. All but the cement is coming from Aircraft Spruce. December 10, 2019 Because this plane has been flying safely and efficiently for four years now, I am more comfortable sharing the plans I've drawn up for this wing. No other file formats will be provided. You must convert as needed on your own. I DISCLAIM ANY AND ALL FORMS OF LIABILITY FOR HOW THEY ARE USED. Wing Plan Drawing 43012_Wing_Plan.pdf New Root LE Bracket Design Plans Weedhopper_NewLE_RootBracket.pdf Rib Outlines 43012_CutLayout_Plywood2_Ribs.eps Rib Webbing Cutouts 43012_CutLayout_Plywood2_Cutouts.eps

---

September 30, 2014: This is what my original wing trailing edge (TE) spars look like, a mismash of fixes on the ends to repair wallowed holes. The central outer reinforcement sleeve came with the plane when I bought it in 2001. It actually had a second sleeve over top of it that I removed in 2008 as part of my "Lighten The Bird" rebuild. Due to all of the above, I'm remaking the TEs.

Construction begins with four, 7-foot lengths of 1.5" OD x 0.058" wall 6061 T6 aluminum tubes, a 16" length of 1.375" OD tube (058 or 065, whatever I had on hand), and a box of 1/8" dia x 1/8" grip aluminum pop rivets. I measured out the spacing of four rows of rivets, 90 degrees apart, then drilled one hole through both the TE and its inner sleeve splice and popped a rivet to hold it in place. I then drilled the remaining 17 holes (5 rivets in rows 1 and 3 and four in rows 2 and 4).

With the splice securely attached to each half of the TE tube, the other halves were slipped on, aligned, drilled, and riveted.

---

October 24, 2014: Now begins the thrust/drag and compression strut rigging, but somehow I overlooked ordering saddle washers for 1.5" OD tube, which provide a wobble-free base. Not to worry, Scott McClure to the rescue with a rush order of 18 pieces, which arrived in two days via USPS mail (Thanks Scott!).  The brackets shown are made from 1 1/4" x 1/8" 6063 T52 aluminum C-channel (1" ID) and are attached to the wing TE and LE spars with 3/16" x 1/4" grip aluminum pop rivets.

---

March 24, 2015: I used a CNC router at a local university (where I had been previously employed for 10 years) to cut the 43012 airfoil ribs. The wing design was created to-scale in Lightwave 3D, exported to EPS, edited in Adobe Illustrator to separate the cut outs from the airfoil, and saved as AI, then imported into Vcarve Pro CNC software to create two cutting paths from the shapes. The first path is the webbing cut outs and the second path is the airfoil itself. Each wing has 13 ribs, which are cut from a 4 x 8 sheet of SurePly® 1/4" 3-ply underlayment. This material, made by Patriot Timber, sold by Lowes at $13/sheet (at this writing), has NO voids or knots, and has a very clear, straight grain in the veneer.

---

March 25, 2015:

Today I cut 1/4" wide x 1/8" deep slots in all the 1/2" x 3/8" Sitka Pine rib cap strips. I don't have a router, but I do have a friend's drill press in the hangar where I'm building the wings. So, I bought a 1/4" straight-cut router bit, set the drill press to maximum speed, and set the bit's cut depth with the press' table and clamp block. The results are not too shabby. I'm sure the cuts would be less frayed and rough if the bit were spinning at 10,000 rpm, but this will just give the Tightbond III glue more material to grip.

---

March 29, 2015: Gluing the cap strips to the ribs REALLY stiffens up the ribs and will prevent them from warping when the wing covering fabric is shrunk. Filling the 1/8" deep x 1/4" wide slot in the cap strips half full of Tightbond III glue. Laying the rib into the glue bed and clamping along the way. Why is the cap strip not going all the way to the front of the rib? Because I'll be using a sheet of vinyl roof flashing and foam blocks to form a D-cell, instead of adding false ribs in between the full ribs to prevent fabric scalloping when shrunk. Tooling the glue that oozes out. Not that it helps an awful lot, because the glue shrinks as it dries, forming breaks and gaps in the exposed bead. Because the spring clamps don't have enough force, I use C-clamps to hold the rib cap strips against the curve of the ribs. For the larger ribs, it takes ten spring clamps and two C-clamps to secure the top and bottom cap strips. Thus, I'm only able to make one rib per day. When the ribs get short enough, I'll be able to do two per day. Leading edge after 24 hours drying. The bottom cap strip will be filed down to make a smooth transition to the LE tube. Trailing edge cut and trimmed after 24 hours drying. An aluminum V will be added to create a sharp TE after all the ribs are glued to the wing tubes.

---

April 4 - 18, 2015: Here I dry fitted the left wing's 13 ribs, which weight 10 pounds. The internal compression and thrust-drag spar brackets were then installed and compression and thrust-drag spars cut and drilled according to my plan drawing. This is the 3-bolt LE bracket with the center bolt securing the forward lift strut attachment tang (versus the OEM's 2-bolt bracket). The TE bracket will use two bolts instead of the OEM's single bolt to anchor the aft lift strut tang. These two modifications will add life-extending strength to these two high-stress point on the wing.

Close up of the 1-1/2" diameter x 1/8" thick nylon-6 TE saddle washers. And the same on the LE, except the diameter is 1". Notice there are no bolts going through either spar tube, because the brackets are secured with 3/16" rivets, instead.

A better view of the "double N" compression/thrust-drag spars, made of 1" OD x 0.065" wall 6061 T6 aluminum tubes, anchored in 1-1/4" x 1/8" wall C-channel brackets, using AN3 bolts. Each bracket, except for the left-most LE and TE, are 2-3/4" long and are secured to the LE and TE with two 3/16" aluminum blind pop rivets, backed by 1/8" nylon saddle washers. The lift strut brackets for the LE and TE are 6" and 4" long, respectively and attached to the LE and TE with AN4 bolts.

Setting the 2.5 degree wing-tip washout. This is achieved by raising the center line of the TE, shown here, 1-1/4" higher than the LE. Why the extra 2" vertical block? Because the LE is sitting on a 2x4 block, making its center line 1-1/2" above the table top. To get the center line of the TE even with the LE it has to be raised up 1/2" more, so 2" total. Now that they're even, add 1-1/4" (a 1" thick horizontal block and a 1/4" piece of plywood)! For the wing tip spar, a 3/4" x 2" long slot is cut into the TE. The spar is a 3/4" OD x 0.058" aluminum tube, the same material OEM ribs are made of.

Dry fit of the wing-tip spar. A 3/4" square tube is used to provide a flat surface at the proper spacing to hammer the TE flat against it. Flip the wing over and repeat for the other side.

A 3/16" pop rivet top and bottom secures the wing-tip spar to the TE. The ends of the TE were hammered to roll them around the tip spar. 3/16" pop rivets secure the wing-tip spar to the LE.

Laying out the cut lines on a 2" thick sheet of construction/sheething foam to be used to form a "D" cell on the LE between each rib. Gluing the foam to the ribs every other space in order to leave empty space for hot-wire cutting off the extra using the ribs as the guides.

---

April 19 - 21, 2015: One 'D' cell of 12, glued and ready for hot wire cutting. I made a hot wire cutter about 10 years ago when I made foam core wing strut fairings (long since discarded). It's simply a 3' length of nichrome wire (higher resistance than ordinary stainless steel wire) anchored with #8 screws to a slightly shorter length of 1/2" pine furring to make a bow. It's powered by a 2 amp, 36 volt AC transformer salvaged from some sort of electronic equipment... maybe a 1980's era VHS deck. Using the ribs as guides, the wire is slowly and evenly moved through the foam. As you can see, the process doesn't have to be perfectly smooth, but do try to avoid really gouging it up (I got better towards the end).

Close up of a typical hot wire cut. After sanding smooth using a drywall sanding pad. Again, doesn't have to be perfect as it's only for providing a solid base on which vinyl roof flashing will lay over. The flashing is what provides the smooth surface for the polyester fabric.

Before. After.

Root rib support structure. Simply made from two 8' lengths of 1-1/2" x 1/4" stain-grade pine furring laminated together with Tightbond II wood glue (Lowes doesn't have 1/2" thick stock). These were measured and cut as shown, glued to the inside of the root rib, and drilled for regular ol' 1-1/8" U-bolts. These vertical "ribs" will prevent the polyester fabric from warping and breaking the rib when it is heat shrunk. UPDATE:  I was seriously wrong about the root ribs not warping. They did... badly! So, add cap strips. The warpage has become so bad that, after a year's time, the TE section has broken away from the rest of the rib at the TE spar. Luckily, the loose fabric doesn't impact flight performance to any serious degree. I intended to fix the root ribs over the winter, but wasn't able to get around to it this year (2017). Winter 2018 for sure. Nope. How about 2019? Nope again. Root rib installed using the first inboard compression strut as the main support member for the rib.

April 29, 2015: Applying 3M 5200FC (fast cure) or Attwood 7200 polyurethane adhesive to the ribs on the abraded 1-1/2" OD trailing edge tube AFTER the abraded areas of the tube were thorough cleaned using copious amounts of acetone and a clean shop rag/cloth. 5200/7200 cures to a Shore A hardness of 68, or almost as hard as automotive tires, and has a elongation/stretch factor of 700%, The procedure goes like this: With a Sharpie pen, mark the location of each rib on the TE (in this case every 12-3/4"). Slide the end of the rib over 1 inch and "scrub" 5200 into the abrasions in the TE spar, forming a 1/4" wide flat bead around the circumference. Slide rib back into place and shimmy it back and forth to wet the inside surface of the rib's cutout hole. Apply a bead of 5200 around and on either side of the rib to create a "weld," using the applicator tip to work the adhesive down into the junction, filling any gaps between rib and tube.

Place a carpenters square on the inside edge of the TE and the corner against the rib and move the rib's LE until the rib is square to the TEspar. Mark the LE location... and apply 5200 in the same way as the TE. Each wing will need one 10 ounce tube of adhesive.

3M 5200FC (or Attwood 7200) cures in three days at 70 deg F and 50% humidity. However, 24 hrs later, the adhesive had hardened quite well to about 1/4" deep, despite mid-60's for daytime highs and mid-40's overnight.

---

May 1, 2015: With all the ribs firmly glued in place, I'm now able to cut, trim, and glue the remaining foam D-cells into the empty bays." Dry fitting the aluminum trailing edge "V's."

May 3, 2015 Here's the finished D-cell foam leading edge, all sanded smooth and flat after hot wire cutting the odd numbered bays. Here's the underside detail of the LE, along with a shiny, new, longer, two-bolt, stainless steel wing strut attachment tang.

Laying out, measuring, and marking the cut line for vinyl roof flashing that will provide a smooth bearing surface for the ceconite fabric covering. After cutting and trimming. The flashing will be glued to the LE and foam with 3M 30NF water-based contact cement.

Inter-rib X-brace lacing. Close up of inter-rib lacing. Two wraps around each rib still allows the rib to move side-to-side, but adding a final third wrap locks it all up. The lacing is a single length, starting on the root compression strut, secured to it with two square knots, Xing back and forth to the tip rib, then looping back around and ending where it started.

---

May 12, 2015: This is aluminum trailing edge from Aircraft Spruce. I marked and snipped the folded edges at each rib tip to allow the ribs to enter the V. Then I filed all the sharp edges and corners. The edges came bent at about a 45 degree angle, which wasn't sufficient enough to keep them from buckling, so I used a rubber mallet and hammer to bend them further until both sides were roughly parallel (flat) to each other, eliminating the need to epoxy in span-wise reinforcement tubes. Flattening the edges will make the TE bow slightly, so carefully unbow them by very slightly bending them in the opposite direct a foot or so at a time until the TE V is straight again. Do Not push/pull too hard or else the TE will suddenly bend and kink the wrong way.

Abrade the inside surfaces of each rib bay in order to remove the factory finish and coatings. A Dremel with a very small abrasive cone bit works well. When done, use cotton swabs dipped in acetone and vigorously scrub the abrasions clean - one tip per side, or else adhesives will not adhere. Ask me how I know. Butter each rib bay of the TE and splice joints with 3M 5200FC or Atwood 7200 adhesive and work it into the abrasions using a cotton swap minus the cotton.

Butter each rib TE tip with a generous helping of adhesive. The TE was ordered cut to 5' lengths so that they could be shipped UPS. I could've spliced them one of two ways... cut them so the joints lined up on the center line of a rib, or leave them 5' long and glue in a wood wedge at the floating joints. I opted for the latter, because it was much less wasteful and just as strong.

Bungee cords pull the TE firmly against the tips of the ribs, while spring clamps on each rib ensures the metal makes firm contact with the top and bottom of the rib cap strips. Overall, the TE is rather straight, not absolutely perfect, but darn good enough. This is also a good view of how I hammered flat the trailing tip of the wing tip spar.

And here she is... FINISHED and ready for fabric covering! However, I'll wait until the other half is built to do that. And the answer you all have been waiting for... How heavy are the wings? In this bare-frame state, 38 pounds per wing! This includes all the bungees and clamps along the TE that I left on to simulate the weight of fabric and paint. When fully finished, they could be 40 pounds, so 80 pounds total.** Compare this to my OEM wing (sail, 10 rib battens, and tubular frame with reinforcement sleeves) that weighed 65 pounds. 15 pounds more for a wing of this structure isn't bad at all. **See Wing Rebuild under the New Articles menu for new weight.

---

May 15, 2015: It's on to building the other half of the wing. This is the aftermath of cutting out all the web triangles and ribs from the 4x8 sheet of 1/4" underlayment plywood, fresh from the CNC router. Next up is repeating steps 10 through 31 in the Wing Page... which is just a joking guess as to the number of steps there really is. During this time (I estimate a month or so), I won't be updating this blog (since I've taken all the photos already).  However, I'll return with the next big step in assembly... covering with ceconite fabric using my "DIY Stewart Systems™ Method."

---

June 28, 2015

Five weeks later and the port (left) wing is finished!

Here are the two, together at last... ready for fabric covering.

The plan is to take the tail feather frames off the fuselage and cover them first, then do the wings. Learn on the small ones, so no mistakes on the big ones.

---

September 13 through 27, 2015:

Herein are the details for covering the wing, starting with the process of extending the 70-inch wide ceconite fabric to 80 inches via a simple overlap seam (the wing is 72" at the root, plus add 4" for margins and 4" for rib curvature).

Note: The 3M 30 NF contact cement is very pale in these photos, because I used up my first quart and unknowingly ordered the neutral (cream colored) version of the cement, not the green version. I tried "fixing" it by adding 20 drops of green and 10 drops of blue food coloring to the bottle. Sadly, being that they're dyes rather than pigments, the color fades completely back to neutral on exposure to heat and air, but at least it helps during application.

Start by cutting backing strips of news- or craft-paper 2 1/4" wide to prevent gluing the fabric to your work table. Draw a pencil line 2" away from the edge of your fabric that you've cut to size.	Place a strip of paper under the fabric and begin generously applying glue to the top of the fabric with a 1" foam brush, pushing and working the glue down into the weave.
Continue adding strips of paper, butting them up against each other (do no overlap) and gluing the fabric, using the 2" pencil line as your guide for both positioning the paper under the fabric and applying contact cement.	Allow the cement to dry for an hour or so, then place the fabric extension on top and overlap 2". With a sealing iron set to 250 degrees, use the tip of the iron to tack only the very edge of the extension to the glue along the 2" pencil line.
Then go back over the seam with the full plate of the iron, pressing down hard (use a piece of wood to press down on the nose of the iron as well) slowing advancing at around 1 inch/second. At this temperature, the fabric is only partially shrunk as it is set into the glue, allowing the seam to be shrunk and flattened later on at 275 F.	Finish the seam by painting cement back over the fabric, working it down into the weave. Allow to dry for an hour before proceeding to glue the fabric to the wing spars.
To make handling the wing easy (like the "big boys") I used two shop light tripod stands and replaced the lights with this little pivot gadget; a scrap of U-channel and an AN-4 bolt. This is the wing tip end where a 1/4" hole was drilled mid-way between LE and TE in the 5/8" OD tip spar. A similar hole was drilled in the solid cap rib at the root end. Getting the balance point took 4 holes to find, but being drilled in wood, they can be easily patched.	With the wing balanced on the tripod stands, contact cement was applied to the wing frame just the same as was done for the tail feathers. Here you can clearly see the overlap extension seam for the bottom surface fabric.
Unshrunk bottom fabric fully glued to the wing frame.	Unshrunk bottom from the opposite side.
After shrinking at 275 degrees. Due to the flimsy nature of the 1/4" thick plywood root cap rib, even though reinforced with a compression strut and wood sub-ribs, shrinking at 300 or higher would result in even greater warping of the rib (see the eighth photo below).	Holes for the wing strut attachment tangs were not made prior to shrinking the fabric. This allows for precise location of the hole after shrinking, because shrinking will cause an existing hole to "drift" and enlarge unpredictably.
Cut a slot for the tangs into the shrunk fabric by melting with a pencil soldering iron, then reinforce with a pre-shrunk patch.	Inside view showing glue penetration.
Don't forget to run any wires or other accessory items before gluing the top side fabric in place! Though I don't have any now, I will eventually install LED wing tip nav lights/strobes.	TIP: Do Not wrap the wires around any of the ribs or secure with square knots, as shown here. You will regret it, because you'll learn, too late, that you won't be able to replace or add to the wires without cutting the wing fabric open to UNDO the knot.
The top wing fabric attached to and hanging off the bottom side of the TE.	Wing rotated over for gluing the top surface fabric to the LE, tip spar, and root rib.
Top surface shrunk. If you use vinyl roof flashing, like I did, on the LE "D-Cell," don't be alarmed when it puckers badly as you heat shrink the fabric. Just continue to evenly and thoroughly heat the vinyl, firmly pressing it against the foam blocks underneath. It will soften and "reflow," smoothing right out, as long as your underlying foam blocks have been sanded flat and smooth.	Guess I should have used a 1" board for the root cap rib instead of 1/4" plywood, but I didn't want to add that much weight to the plane and believe this amount of warpage, although a bit more than expected, will not be structurally critical or impair performance. The cap ribs were already slightly "wavy" due to moisture absorption before applying and shrinking the fabric.
Applying 1/2" reinforcing tape to prevent lacing stitches from cutting through the fabric.	Tapes applied to both surfaces.
Chalk snap lines for rib stitch spacing applied every 4". I'm waiting on the arrival of 500 feet of flat waxed rib lacing cord. I already bought what was called rib lacing cord from Aircraft Spruce, but it was not waxed, way too thin, and totally unacceptable for rib stitching. I didn't notice this months before, because I didn't look at the package label when it arrived, which said "Ceconite Hand Sewing Thread." AC Spruce gotz it wrong, boys and girls! The flat stuff made by SuperFlight is what you want or identical material used for marine sailmaking (and 4 times less expensive, because it's not FAA certified).	Close up. Rinse and Repeat all of the above for the other wing waiting in the background (as of this writing the bottom fabric has been applied and ready for shrinking).

---

October 1 through 11, 2015:

Here's a few extra details not shown in the last blog entry.

To minimize scalloping between ribs when shrinking dacron, start by shrinking at 250 F over each rib, first. Start with the middle rib, alternating left and right every other rib. Then return to the middle and shrink the fabric over the skipped ribs, again, alternating left, then right.	Continue shrinking between the ribs, alternating from the middle outward, left, then right. Repeat the whole process again at 275 or 300 F.
After marking rib stitch locations with a chalk snap line, use a pencil soldering iron, with a tip filed to a sharp point, and melt small holes less than 1/8" in diameter.	Melted holes make it much faster to locate the needle on the bottom by touch and a much cleaner hole than those made by needle or pencil pokes.
Ribs laced using the SuperFlite knot (see video below).	Measuring 2" wide pinked-edge finishing tapes.
Gluing the finishing tapes down by applying a generous amount of contact cement, 12" at a time, with a 1" foam brush...	... then laying the tape over the wet glue and painting more cement on the tape, aggressively working it completely and thoroughly into the tape. Brush back and forth several times to evenly spread and sop up the excess, until the tape is basically "dry" and free of brush marks and glue ridges.
Two down, 11 to go...	It took about 4 hours to glue all 13 rib finish tapes down on just one side of the wing. This was done on a warm, dry day, so by the time the last rib was done, the first tape was dry and ready to have its pinked edges heat "sealed" using the sealing iron set to 300 F, followed by the others on down the line.

This video demonstrates how I stitched the wing fabric to the ribs using the super-easy-to-use "Superflite™" knot.

(there is no sound on this video)

January 28, 2016

Four World War I British-style roundels were painted on the wing tips (top and bottom times two wings). Each one took 3 - 5 days to create. This video shows you how to paint them.



The process shown here is:

1. Make a series of string compasses (measured lengths of thread, a push pin, and an ink pen) to draw out the various sizes of circles of the roundel.
2. Spool out several feet of 1.5" wide Frog Tape brand painter's masking tape and cut a 1/4" wide strip the full length.
3. Mask the outer-most circle with this thin "pin stripe" tape.
4. Tear 3"- 4" lengths of the remaining tape and place them around the outside circumference of the pin stripe mask.
5. Brush on a thin line of paint around the inside edge of the pin stripe mask using the same color as the base. This activates the tape's sealing "gel" in its adhesive, preventing the desired ring color from bleeding under when this thin band of sealing paint dries.
6. Paint the ring the desired color using a cabinet-grade fine foam roller. Repeat one or two coats more when each is dry.
7. Remove the masking tape.
8. Redraw the next inside ring that's been painted over and repeat steps 2 - 7.

---

May 19, 2020:

I decided to conduct an experiment to see if I can reduce RFI from my LED strobes. This required gaining access to the unshielded power wires inside my wings, in order to replace them with two-conductor, shielded cables (100% foil wrap with drain wire). This entailed the addition of an inspection hole in the underside wing tip, so that I could untie the individual power wires from the wingtip rib and more easily wire up the wing tip nav strobes (including the addition of two ferrite chokes as close as possible to the lamps). For the tail strobe, I replaced it's 4-conductor, shielded cable (which I did not ground, for some unknown reason) with a 2-conductor and grounded the shield, connected to the negative side of the terminal strip inside the instrument panel. Standard 4-3/4" diameter inspection hole rings and recessed covers from Aircraft Spruce. I glued the rings to the painted fabric with 3M 30NF contact cement (same stuff the Stewart System uses), then overlaid it with a circular "patch" of dacron/ceconite. I used the tip of my aircraft iron to "activate" and bond the fabric along the inner and outer circumferences of the ring, then covered the patch with glue, wiping off the excess, standard Stewart System style.

It took five thin coats of exterior semi-gloss latex paint to cover the glued patch. When dry, I cut out the hole with a razor knife. Precision not required. Strobe power wire replacement complete. On go the painted covers.

May 22, 2020:

The experiment didn't work. RFI noise is exactly the same as before (squelch breaking level 7 in certain areas of the sky where terrestrial RF transmitters are present). This must mean RFI is being radiated directly from the LED strobes themselves and not from or through the +V power lines. The only way to verify that theory is to power the strobes from an external DC power source, in order to 100% isolate them from the instrument panel and radio.

May 23, 2020:

I did some more investigation today by using the radio, handheld with its rubber ducky antenna, to sniff around the trailered plane. I powered the instrument panel with a 14 volt DC power supply. Turns out that the wing tip LED strobes are not emitting RFI from the new shielded power cables and only very weakly from the lamps themselves. However, the tail strobes very much do, despite the presence of THREE ferrite chokes and a 0.1 uF capacitor installed on the leads coming out of the lamps. Then I discovered that the new fuel level sender was putting out a constant whine, so I added two clam shell chokes on the leads coming out of the sender, along with a 0.02uF cap across +V and gnd. This cleaned up that noise nicely, though it wasn't very strong to begin with. This left the puzzling reason of why the pulsing tail strobe RFI was coming down its shielded power cable that runs the length of the boom. I found a strong node of radiation coming from it right above my head,  so I put two clam shell chokes on the cable at that location. This significantly reduced the noise. Now to test it all again with the engine powering everything, which adds around 2 squelch "units" of its own hashy noise to the mix. June 7, 2020: I was able to get back in the air this morning. I'm happy to report that the "RAP (RFI Abatement Procedures) above were a SUCCESS! Squelch level is now down to 4, which is its normal value (out of 9) for the noise floor with the engine running. No more whine, hash, and strobe chaa-chaa-chaa.