Hilst, 14, said the three decided to test various combinations of plywood, chicken wire, spray-on rubber truck-bed liner and polystyrene foam, most of which are shock-absorbing materials.

“The sheet rock is already pre-existing in the house, so the whole idea of this is to layer these on. The plywood was something everything could be masted on and added a layer of rigidness, as well,” Mackey said.

The girls tested their mock-ups using baseball pitching machines and radar guns and by dropping 20- and 30-pound weights from a crane 50 feet in the air.

The fifth test was deemed successful with the ability to withstand flying debris in an EF2 tornado. The distinction between that mock-up and the others was the rubber bed liner spray, they said.

This isn’t the first time the teammates won regionals and went to nationals. They won regionals in sixth grade. But this year, Kaul said, they hope to not only win nationals in their grade level, but to earn a $5,000 grant to extend their project a year with the goal of finding the combination of materials that could withstand an EF3 tornado. That testing would require the use of air cannons.