Fabric On Left Hand Lower Wing

One advantage to working in the attic is I don't have to deal with the weather.  I can't do smelly work up there but sewing envelopes doesn't need smelly chemicals.

The lower wings have cutouts for the ailerons so I had to sew the long seam aft of the front spar first.  Once I got the wrapped piece properly positioned I marked a line for the forward of edge of the 36" lower panel.  To mark the line I measured from the aft edge of the wrapped panel.

The seam was pinned and the fabric rolled up for sewing.  The excess on the upper wrap was trimmed after the seam was sewn.

The seam was sewn as before.  The straight edge of the fabric makes a nice line to follow while sewing.  My 36" high work tables allowed me to sit with a tall stool while sewing, much easier than standing.

With the forward seam sewn the fabric was fit to the trailing edge and aileron cutout.  I didn't sew the short edge of the cutout.  I only want one layer of fabric in the aileron gap and that is easier done with glue.

After sewing, the envelope was put back on the wing and clamped in position at the root rib.

With the fabric in position the tip was pinned and sewn.

The envelope comes off very easily but it takes a little wiggling to get it back on.

The tip looks very loose but it shrinks very tight and smooth.

Once I cut the lower fabric to fit the root rib I ironed it smooth at 225 degrees to make gluing easier.  I then folded it under the fabric and Ironed a crease so it would fit snugly at the corner while gluing about 2" along the top of the rib.

The upper fabric was shrunk and stretched to fit the root rib and trimmed to overlap the lower fabric about 2".

I did glue in the attic by opening the door and keeping it aired out.  After the glue dried I closed the door and turned the heat back on.  There isn't much gluing with an envelope.  You can also baseball stitch these seams instead of gluing.

To prevent a build up of fabric in the aileron gap, the seam on the small end of the aileron cutout was made the same way we did it for that end of aileron.  The upper fabric was wrapped around and glued to the lower side of the cutout box structure.  The lower fabric was then glued to it and trimmed to the corner.

The long seam for the aileron cutout was placed in the center of the false spar.  I wanted it out of the way of the hinges but not near the lower corner.  Any build up of fabric along the lower corner limits the downward travel of the aileron.

A small cut was made to get the aileron push rod out of the wing  before gluing the root, etc.  You could install the rod after the fabric is finished, but it's hard to work through those inspection rings.

I did the first (250 degree) shrink of the outer rib bays before cutting the fabric to expose the pitot-static connections, then finished shrinking.  I wanted the fabric snug so it wasn't likely to move much after cutting the hole.

It's always surprising how tight the fabric gets when you shrink it.

We've got some wet weather coming so I'll get the fabric on the lower right wing and then start rib stitching the other upper panel.

The long seam came out very straight after all the shrinking.

Fabric on Left Hand Aileron

 Rowan and Duncan were only visiting for a couple days so we needed a simple project to apply fabric.  We chose the left hand aileron.  We used 2 scraps of Poly Fiber fabric from the wings.  They pinned and sewed them together to make a blanket big enough to wrap from trailing edge to trailing edge.  The seam runs down the middle of the spar.  Each got to do half of every operation.

They cut the piece to size.

 The fabric was glued, with Ploy-Tak, to the trailing edge and tip bow.  To avoid fabric Build up on the inboard end we wrapped the lower fabric around and glued it to the upper side of the 2" root box.  The upper fabric is glued over the lower and trimmed off at the corner.  This way there is only one layer of fabric on the root end.

Once the glue was dry, on the lower fabric, they glued the upper fabric to the top and bottom of the trailing edge, root box and tip bow.

 We let the glue dry overnight before they shrunk the fabric at 250 degrees and then 350 degrees.  They learned hot irons are not dangerous unless you touch the hot surfaces, which they didn't.

It came out real nice.  Now I'll need another warm day to get the Poly-Brush on, etc.

Thanks Guys!

Upper Right Wing Panel Rib Stiched

 The Poly Fiber instructions say that you treat the ribs withing the diameter of the propeller plus the next rib as being within the slipstream.  I laid out the hole pattern for the rib lacing on the first 3 ribs at 2 1/2" spacing and the outer 6 ribs at 3 1/2" spacing on the upper surface of the wing.  The lower surface is laid out using a rib pattern with the lower loops below the upper knots and perpendicular to the lower (flat) surface of the ribs.

 I found it easier to see where the reinforcing tapes should be placed by punching the holes first and then applying the tapes between the holes.

The ability to tip the stands to a comfortable angle makes it much easier applying the tapes.

 Needles were started at the leading edge of each rib.  Near the  forward and aft ends of the ribs you can reach around the wing to feed the needle through the holes.  As you stitch toward the center of the ribs you can't reach around far enough. It's easier if you position the wing vertical and work your way around the wing pushing needles through or tying knots at each rib as you go around the wing.  You need enough needles for every rib but it saves time if you don't have an assistant on the other side.  You need light on each side so you can see the holes on the other side looking through a hole on your side.

 The grand kids, Rowan and Duncan, visited for Thanksgiving so we spent the day working on the wings.  We started by watching the Poly Fiber rib lacing video.  The manual has a nice trick for tying the square knot for the first stitch.  After we tied the first hidden modified seine knot we watched the video again to make sure we were doing it correctly and then pressed on.  We found her Island and Palm Tree helpful as well as the  "X" on the needle.  We couldn't remember the rabbit story but had no problem with the needle motion and path.  That was much easier than the pictures in the manual.

 We started with about 12 ft. of flat lacing cord for each rib.  That got us about 1/2 way down the ribs.  Then we re-positioned the wing and started from the trailing edge.  The manual says you can work in either direction and you just have to lock your last stitch with a half hitch.  Because of the 42" wing chord we were able to reach easily to where we ended the lacing from the leading edge.

 It was a nice warm afternoon so we moved the wing back to the tent.  We located our inspection rings and cut all of our chord-wise finishing tapes.  We rolled and clipped the tapes to a length easy to apply to one side of the wing.

 The inspection rings were glued on with Poly-Tak.  While the glue dried the reinforcing tapes got a very wet coat of Ploy-Brush to fill and seal them.  While the first coat of Poly Brush dried we applied the doilies over the inspection rings.  A second wet coat of Poly-Brush finished the reinforcing tapes.

Even in an open tent the fumes can get a little much, a Carbon Respirator really helps.  We got a few chord-wise finishing tapes on before dinner.

Cessna 140 Wing Stands Modified to Fit Fly Baby Upper Wing Panels

When I recovered the Cessna 140 wings I made some wing stands which allowed me to rotate the wing, making the process a lot easier. On the Cessna wings the root rib is perpendicular to the leading edge and the spars extend past the root rib making it easy to attach to them. Because the spars extend past the root rib you can shrink the fabric and apply all the finishes with the stand attached.

At the tip I was able to use a wooden plug in the navigation light socket to attach the tip stand.  It wasn't so easy on the Fly Baby wings.

The geometry and construction of the stands are explained in the C-140 blog posting.

The root rib on the Fly Baby wing is 9 degrees out of square and on the upper wings the spars end flush with the root rib so there is nothing to attach to.  At the tip end the only way is to clamp onto the wing tip tube after the fabric is tight and has a coat of Poly-Brush.

At the root end I built some spar extenders to attach to my existing stand.

The wing fitting bolt holes at the root were opened with a soldering iron I modified for opening drain grommet holes.

The extenders bolt onto the root end of the spars so their pivot holes are aligned perpendicular to the wing.

I screwed a piece of 2x4 between them to make them into a rigid structure.  I didn't want to cause any strange loads on the spars.

To make it all work with the C-140 root fixture I added a piece of 3/4" schedule 40 PVC pipe to keep the wing from sliding forward.  On the C-140 the fixture is between the spars so the wing can't move fore or aft.  If I weren't lazy I could have made a fixture which fit the spar extenders.  The wing sets a little nose heavy but it works fine.

The plate with the circle of holes allows the wing to be locked at every 15 degrees when rotating it.

To allow the tip to pivot I used a piece of 1/2" schedule 40 PVC pipe with one end flattened.  The clamps are just some pieces of 3/4" plywood with sort-of round step cuts so it can clamp securely on the 3/4" tip bow tube.  Wing nuts tighten it on.  I've replace the long bolts you see with some 2 1/2" carriage bolts.  You just tighten it with the wing nuts.

A Tee is pushed on to the free end to hold it in the stand, simple but it works.

The stand will be perfect for Rib lacing and all of the tapes except at the root rib and tip bow.  I'll have to use the saw horses for those.  I'll also have some touch-up spraying on the finish coats. Still better than doing it all on the saw horses.