For some reason the kids weren’t interested in using the very nice slide in the new playground at the church. Some top-notch detective work revealed that their main complaint was getting their gluteus maximi seared on the way down the slide by the stainless steel that had been baking in the sun all day.
The director, “Sally” (not her real name) asked me for advice on how to solve the problem. My suggestion that they wear thicker pants was not well received. Instead Sally wondered if I could install some sail shades over the playground equipment to ward off the blazing sun.
Sail shades come in a variety of sizes and two main shapes. The triangular ones look like actual sails from a sailboat. I chose the rectangular ones because they cover a lot more area for a given size. For example, a triangular sail shade 12′ on a side will shade only about half of the area that a rectangular sail shade 12′ on a side will cover. This playground required three 13′ x 20′ rectangular shades.
Each corner of the shade needs to be pulled at a 45 degree angle to keep it flat and tight. With three shades that is a total of 12 lines pulling in various directions and this quickly became a complex 3-D geometry problem. My initial thought was to use a program like SketchUp but in addition to the steep learning curve there is the issue of visualizing an intricate 3-D pattern of sails and rope on a 2-D screen and I just didn’t feel I was up to the task.
So I built a model.
I cut out “sails” from some heavy cloth and used string for the ropes. The model made it easy to try different sail orientations and attachment points.
The playground has a large building wall on one side that provides several places to attach some of the ropes. There is also a utility pole directly across from the building at the edge of the playground, which provides some more. But the model showed that these weren’t going to be enough to keep the sails flat and tight. So I added a new pole to the model in the form of a broom handle and adjusted its position until the sails attached to it had the right shape. (It turns out that adding the pole to the model is not enough. You have to actually install the new pole in the real world.)
The model made it easy to try different positions and heights until the playground was shaded and the lines were straight. Then I measured everything on the model and converted it to feet in the real world. A color-coded “map” of the sails and lines became the blueprint for the actual installation.
Since this is near the coast it is important to be able to easily get the sails down in the event of a hurricane and then to put them back up in the correct order and position. A set of colored zip ties makes it almost idiot-proof. At the end of every rope there is a zip tie that matches the zip tie on the wall or pole where it is attached. For example, one sail has a rope with a green zip tie on its metal ring that is attached to a hook in the building wall that also has a green zip tie.
The lines connect to the eye hooks on the utility poles with turnbuckles, which allow me to adjust the tension of the sails. I’ve found that the sails tend to stretch a little over time and it is necessary to retie some of the lines so they are a little shorter and then tighten them up with the turnbuckles.
Here is a video comparing the model to reality.
Sally was so pleased with the playground and the cool slide that she has gone into business. Sally sells sail shades by the seashore.
Parts (about $300 total):
Ollieroo Shade Sail UV Block Fabric Patio Outdoor Canopy Sun Shelter
5/16″ Double Braid Polyester Rope Blue/white (about 200′)
Yasorn M8 Open Cup Hook Screw Stainless Steel Expansion Heavy Duty Bolts (screws into building wall)
National Hardware N197-244 V2151 Lag Screw Eye in Stainless Steel (screws into utility pole)
Uxcell a16022600ux0043 M5 x 60mm 201 Stainless Steel Webbing Strapping Welded O Rings (connects rope to hook screw in building wall)