Tanya Brown, research engineer at the Insurance Institute for Business & Home Safety, helped create the first-ever full-scale indoor hailstorm earlier this year, firing 9,000 handmade hail stones at a test house inside the IBHS research center in South Carolina to test roofing and other building materials.
Tell us about the experiment:
We took the basic concept of propelling one ice stone at a time and expanded it so we could propel thousands of ice stones in a short time period. We really wanted to cover the entire footprint of our test building with hailstones. All of the hailstones were delivered at the correct terminal velocity according to the size of the stones, and we had a distribution of sizes to mimic Mother Nature. The largest hailstones were two inches in diameter, and their speed was about 76 miles per hour.
How did you propel the hailstones?
We use an air cannon system. There are 12 stations, each with six barrels, so 72 individual barrels that are computer controlled to fire. It was about four minutes to do the whole 9,000 hailstones. We were really excited to see that we were able to produce a very realistic looking storm. We had a good random distribution of hailstones, and the damage that we simulated was realistic.
How do you make hailstones?
We fill molds with liquid and freeze them overnight. We use a ratio of 20% tap water and 80% seltzer to try to trap some of the bubbles in the ice. One of the things we’re doing this year is looking at ways to automate that process.
Was it fun?
Yes, but it’s so fast and there’s so much activity going on that it passes by in a blur. Watching the video later was even better than watching it live, being able to pick out individual impacts and individual dents—that was really interesting.