Destroyed house

Hurricane Michael destroyed the neighbor’s home next to this Monolithic Dome. (Margaret Clayton)


Hurricane Michael smashes power transformer into Monolithic Dome home

Hurricane Michael smashed a power transformer into Margaret Clayton’s caterpillar shaped Monolithic Dome home. The home is a few miles southeast of Mexico Beach in Port Saint Joe, Florida. Clayton stayed in her home during the hurricane. Everything was going well — until her neighbor’s house exploded.

“I watched their house explode,” said Clayton. “The transformer on the other side of that house came flying into my dome wall. Then from attached wires, swung back, then returned, smashing the side garage door. It was quite the show!”

The transformer swung like a medieval flail weapon into the window augment. It did cause a small hole in the dome wall — at the inverse curve — where it is arguably weaker than the standard dome wall.

Clayton calls her home, Golden Eye. It’s situated on a narrow lot — hence the caterpillar design — about 12-feet above sea level. With storm surge maxing out at 9-feet, Clayton felt she didn’t need to evacuate.

“I stayed during the hurricane,” said Clayton. “If the transformer had not hit me and the neighbor’s house hadn’t exploded, I would have been fine.”

Clayton covered the hole with some plastic sheeting. It will get repaired. Even with the damage, the home is safe. She was protected during the shockingly powerful storm.

How much momentum?

It is almost unheard of for a dome wall to be penetrated. An early Monolithic Dome home had a dump truck roll backward down a hill and strike the dome with the corner of the truck bed. A typical house would’ve been flattened and Marjorie South — mother of David, Barry, and Randy South — may not have survived. As it was, the truck left only a small hole which was quickly repaired.

In this case, the transformer became an airborne “missile.” Even without the attached wires, whipping the transformer, the moment it carried had to be huge.

In Safe Rooms for Tornadoes and Hurricanes, FEMA specifies testing for P-361 tornado shelters to use 15-pound wood 2×4s at 100 miles per hour. The resulting impact momentum is about 69 pound-seconds.

A typical residential transformer weighs hundreds of pounds — the smallest transformers are 200 pounds to the largest at nearly a ton. If we use 500 pounds as the transformer weight and halve the velocity to only 50 mph, the calculated impact momentum is 1,146 pound-seconds. That’s 16 TIMES the impact momentum of a 2×4 piece of wood.

Of course, this is an estimate based on Clayton’s observations. We will never know how much force the dome withstood. It was still an extraordinary impact on a dome not designed to FEMA P-361 standards.

Augment damaged by flying transformer

A power transformer — still connected to the power cables — whipped around and smashed into the Monolithic Dome augment. The augment is the inverse curve of the dome and took an unbelievable hit. The impact did penetrate the dome — creating a small hole — and split the exterior coating and foam. (Margaret Clayton)

Transformer and damaged garage door

The transformer whipped around, again, and struck the garage door. It clearly did not have the same force of the first hit. (Margaret Clayton)

Hurricane Michael debris

Debris from the neighboring houses are everywhere. (Margaret Clayton)

Plastic covered door

The garage door and augment are covered with plastic until they can be repaired. The dome is structurally sound. (Margaret Clayton)