They’re in the insulation and roof coatings game, but Bob Gray and Steve Clingaman’s interests have lately been directed to something, shall we say, deadly—tornadoes.
No, they aren’t storm chasing. The two are busy constructing steel mesh, high-density foam and composite material-based storm shelters that can reportedly withstand an F-5 twister.
|The Tornado Cave, developed by a roof coatings and insulation company, is built to withstand an F-5 tornado.|
And after nearly three years in development, the “Tornado Cave” is slowly gaining a following.
Tornado Haven Composition
The igloo-shaped creation has a 6' x 6' footprint, Gray told Durability + Design News. The cave has a frame made of steel, a layer of steel mesh, and a layer of Kevlar encased in high-density polyurethane foam and bolted with expanding anchor bolts securely to a concrete slab. The inward opening door has locks, bracing, and louvered air vents.
The interior and exterior surfaces are sprayed with closed-cell polyurethane foam, which acts as a glue to hold everything in place and absorb energy, Gray said.
The cave can be installed on any concrete-reinforced slab that meets the team’s minimum weight requirements; a normal single-car garage’s four- inch-thick slab meets the minimum
The design and composite layers of the cave are protected by a provisional patent, Gray said.
By day, Gray and Clingaman are the general manager and sales and project manager, respectively, of Hoosier Square Inc., based in Frankfort, IN.
The company’s roof coating efforts focus on spraying two-component polyurethane foam on metal roofs of agricultural buildings, and topping it with an elastomeric acrylic coating to protect the foam from UV rays. The company also services residential, commercial, agricultural and industrial insulation needs for clients throughout Indiana, Gray said.
|The metal frame of the tornado cave.|
But, back to the cave. The idea for the side project was spurred by a study of area building permits.
“We saw an ongoing trend for new residential to be built on a slab,” said Gray. “[W]e were wondering where the residents in a 300-home subdivision which was 100% slab could go for shelter from a tornado.”
‘Then Came Joplin’
“At the time, we thought that basements provided a safe haven in a violent storm but have discovered that a basement only increases the survival chance but does not guarantee safety.
“Then came Joplin,” he said. On May 22, 2011, a catastrophic EF5 multiple-vortex tornado barreled through the Midwestern city. A third of the city was destroyed, and 161 people were killed.
Gray said, “We had suppliers in Joplin who gave us first-hand descriptions of families using closets or bathtubs for shelter and becoming victims as the winds tore children from the arms of parents or moved whole families into the flying debris and deposited the dead hundreds of feet beyond their home.”
The two even heard of survivors who had safely ridden out the storm in a freezer.
“We took that idea and put it on steroids,” Clingaman told a local news outlet.
So, 567 miles away, the two began designing their parabolic frame to resist debris falling from above, straight-line heavy winds, and those from a twisting tornado.
Tested by Cannon
“We built an air cannon to test the walls of the shelter,” Gray said. Specifically, they tested the sidewalls by firing a 15-pound, 13- to 16-foot-long 2 X 4 at 114 miles per hour at the structure.
What happened? The board bounced off with damage only to the surface of the foam exterior, Gray said.
|The surface of both the interior and exterior is sprayed with closed-cell foam, which acts as a glue to hold everything in place and absorb energy.|
In fact, the Tornado Cave design will “support over a ton of material on top with no deflection, has over 30,000 pounds resistance to lift, and resists shear from side impact up to 16,000 pounds,” Gray said.
The shelter “exceeds FEMA standards for tornado shelters and standards designed to keep occupants safe in an F-5 storm,” he said.
Currently, the team produces the cave “on order” and can usually meet an installment date of three weeks after the order, Gray added.
The pricetag for the cave runs around $6,500.
The company has the current templates and equipment to produce 10 of the shelters a week.