Sewing the Leading Edge [LE] together…
Sew down the seam line [1]. Then sew a second line 3 mm away from the first line [2]. Then fold over the seam and sew again, between the first two lines [3].
This reduces the overall seam size, and gives the thrid sew line 4 layers of cloth to pull against making it stronger. As the LE inflates, the left line takes the pressure, as that starts to stretch/fail, the middle line takes the pressure. Line two is very strong due to the four ply cloth and shouldn’t fail.
For the tarp sections I was afraid that the thread would cheese wire through the tarp, so I folded some ripstop and sandwiched it between the tarp [4]. This gives an eight layer ply of ripstop+tarp+tarp+ripstop+ripstop+tarp+tarp+ripstop for the third line of thread to pull against [5]. I also used this method in the tarp sections of the ribs.
The diagram doesn’t show the canopy, this is attached to the LE tube, but does not effect the sewing.
Here is a photo of the batwing semi inflated at my mums house. I wanted to check that the LE seams were correct before sewing lines 2 & 3 (see above), this test did not really inflate the LE correctly, I was afraid that pumping it up too hard would explode the ends of the bladder that were not in the tube.
I did notice that I had forgotten to sew one of the rib reinforcement’s to the LE, this was simple to fix with only one line of stitches to unpick.
I also tested the ribs with my old Wipika FreeAir 14.9 bladders. The bladders were too long by about 20cm, I folded the ends and pushed them down the sleeve. Inflated the rib looked ok, a little wonky, but not too bad.
Sewing the rocket struts to the LE was a nightmare. The seams are at different angles, so they don’t line up with each other. I ended up sewing these by hand. It was extremely frustrating.
The canopy, I sewed this together with a straight stitch (red dashed line, top pic) then with a zig-zag (green zig-zag, bottom pic) then finally a straight stich to tidy the seam (orange dashed line bottom pic). Make sure the seam is on the bottom of the canopy, and that folded flat if faces the tip of the kite.
Attaching the canopy to the leading edge.
1: shows the first sew line (blue), the canopy is attached facing the wrong way.
2: shows how the ribs are attached in relation to the first sew line of the canopy.
3: shows the second sew line ( can be zig-zag, tripple zig-zag or 2 lines of straight stitch)
4: shows the final cloth configuration, the LE seam hidden under the canopy.