May 6, 2010
… driving fast on small country roads.
The testing this weekend went pretty well! As always though, there were some obstacles along the way.
The testing was done on Visingsö, where my family has a country house. There are many straight and open roads there, with little traffic, so testing like this could be done safely.
It was very windy on Saturday, with gusts of wind in excess of 5 m/s, the tip of the waves breaking on the lake Vättern. As I didn’t have a wind speed meter (d’oh!), I had no idea of the exact wind speed. Since I didn’t know yet whether I would have time for more tests, I decided to have a go anyway. I had a number of streamers, and we decided to drive both with and against the wind with some of them. I had streamers 4, 6, and 10 inches in width, 8, 10, 12.5, 15, and 20 times as long, and in a number of different materials from airbag cloth to nylon and even super light mylar plastic film.
The test were carried out by attaching the streamers directly to a dynamometer (which measures force in Newtons) stuck to the end of a pole, then sticking it out of the window of a car. Our little high-def camera was mounted on the pole to film the readout and streamer. I was lucky enough to have access to a convertible (a Saab 900 Aero nonetheless! What else to do aerospace research in?), which I thought would make measuring easier, but it was way too windy to work with the roof down so it didn’t matter in the end.
I ran though the tests on Saturday with all the streamers, but I wasn’t very happy with the windy conditions. Luckily, Sunday was nearly completely calm so we ran some tests at different speeds that day too.
I’m really happy that I got all that data out of the testing, but I haven’t had time to draw any hard conclusions yet. However, the weight of the material makes a huge difference. A heavy streamer provides a LOT more drag than a light one! I’m sure we can now make one that can help deploy our parachute just right