Note: This is slightly different from my usual tutorial because it was a collaborative project and we each wrote our own bit.
Time taken: 27 hours (mostly due to the complexity of the design – cutting and sewing the blanket took 18 hours alone)
Materials: 3 x 6m billboard tarp from Stash-It, 2.5m each of black and white fun fur 1.5m wide, thread, 4m unbleached calico, 9m black 5cm wide hook and loop tape, 2.5m white acetate lining fabric, 9m double-sided 1.5cm wide hook and loop tape, 3 standard sized foam yoga mats, 1L ADOS F2 contact glue, 500ml Bostik Ultragrip 777 PVC vinyl glue.* NB for details of the LED gubbins, see Jez’s bit.
Tools: Scissors, sewing machine, pens, graph paper, steel rule, spreaders for glue, clamps and clamping boards.
Techniques: Pattern making, sewing, gluing. Oh god the gluing.
Difficulty level: I’d say medium. Straightforward but the size of the work made it difficult to handle and involved a lot of very careful measuring – again because of the complexity of the design.
The idea was to create a textured, eye-catching picnic blanket that’s big enough for several people to sit or lie on, and is waterproof, warm, washable, and has mounts for programmable LED strips around the side. Easy, right? We opted to make a blanket that would attach to a waterproof base with velcro, so it could be removed for washing.
I would like to point out here that it wasn’t me that chose the design or the white fun fur. I’d strongly suggest anyone trying this at home uses a simpler design and a slightly more dirt-friendly colour. But you’ve got to admit it’s eyecatching.
Anyway, after drawing the design out on graph paper, the first step was to convert the measurements to achieve a 2m x 2m square when completed, then transfer the pattern for each strip to the back of the fun fur, leaving 1cm seam allowance each. This was easier on the white than on the black.
I couldn’t use a marker on the black so I used the edge of the corresponding white piece, laid as they would go together, and just cut it straight without marking. You can do this with fun fur because it sticks to itself (and your clothes, and the carpet) quite well. Traps for young players – you’re working on the reverse side so make sure you have the nap of the fabric running the right way before you cut!
Each black piece was then sewn to its corresponding white piece, then each couple to its neighbour, and so on.
Once the main sections of the design were together, each part was sewn in place to make up the square, the whole thing was hemmed and then the calico backing and the velcro (loop side so it doesn’t stick to everything it touches when washed) sewn on. Why velcro? So that the blanket could be removed from the base.
To make it wet-ground proof, the whole thing was to be mounted onto an old billboard tarp. One of the issues here was that if the base tarp were sewn at all, water would be able to seep up through the holes and make the blanket damp. We also wanted to have a fairly wide margin around the edge so that the electronics and fur would be well protected from long dewy grass. To do this I cut the tarp square at 2.5 x 2.5m, which would allow the edges to be folded over twice to make a good wide edge.
We needed a means of mounting the LED strips so that they could be removed for storage and transport. To do this we devised this mounting mechanism:
Yes the schematics I work off really are that crappy. So anyway, a strip of white acetate lining fabric 5cm wide was glued between the folds of the tarp edges, with 2cm exposed and some double sided velcro on the other edge. This would be sandwiched between the velcro edges of the blanket and the base, allowing for it to be lifted and the LEDs removed. Nifty!
We also wanted a bit of padding between the occupants and the ground, for comfort and some insulation. Here’s where the yoga mats come in – they were cut to size and glued onto the tarp underneath where the blanket would sit, and the hook side of the velcro tape glued onto the mats as mounts for the blanket. Once that was done, the Flying Carpet was ready for its LEDS.
Jez put together a couple of different designs. The first was a random heap of crap in a box; the second a custom PCB that was a little tidier. Three 18500 lithium cells provide the power, a Teensy microcontroller provides the control, and a little UBEC provides 5 Volts. All of this is in a metal case to protect the delicate electronics from the feet of munters.
The only remaining task was for Wendy to make the box to hold the electronic gubbins and provide a soft layer to stop the metal case from digging in to anyone sitting on it. The box is made from 2cm thick EVA foam with fun fur glued on using hot glue, and some googly eyes because googly eyes make everything better.
If we were to make a version 2, I would choose a simpler design and more hardwearing, stain resistant fabric for the blanket, and use plastic welding techniques rather than glue on the PVC where possible. Overall though, I’m very happy with the result – and very easy to find on dark nights in the outdoors!
* NB this type of glue is the only type that will stick PVC vinyl effectively, and it’s not available retail – I had to sweet-talk an upholsterer to sell me some. It’s horrible stuff to work with and in future I think I’ll look into plastic welding as a faster, easier and safer option.