The science behind Schlitterbahn’s Verrückt
Physics and engineering experts on Tuesday questioned the wisdom of loading lighter passengers toward the front of the raft that slides down the Verrückt water slide while placing heavier riders toward the back.
Kansas City, Kan., police confirmed that the three people riding the raft involved in the death of a 10-year-old Olathe boy on Aug. 7 at the Schlitterbahn Kansas City water park weighed a combined 545 pounds.
Police said 73-pound Caleb Schwab sat in the front seat of the raft, while a woman weighing 197 pounds and another woman weighing 275 pounds occupied the next two seats, respectively.
Officials are continuing to investigate the death of Caleb as he rode the Verrückt, the world’s tallest water slide located at the park in Kansas City, Kan.
Mariusz Ziejewski, a professor in the department of engineering and director of the Impact Biomechanics Laboratory at North Dakota State University, said a balanced weight distribution should be a priority for a ride like Verrückt. Too much weight positioned toward the back of the raft, he said, could push the front of the boat upward.
“You kind of have this catapult upwards,” Ziejewski said. “Maybe this was a contributing factor. That’s not good.”
If the raft goes airborne, passengers run the risk of hitting the netting and metal supports that cover the slide. Police have said Caleb was decapitated on the ride. Investigators on the day of the death removed a section of netting on the ride’s second slope.
The laws of physics dictate that the greater the weight of the raft, the greater momentum it would have as it reached the bottom of the first 168-foot drop and began its 50-foot ascent up the ride’s subsequent rise.
The only slowing forces on a raft at that point would be gravity and friction from the water.
“If gravity is not enough to slow it down, and friction is not enough to slow it down, it (the raft) could go airborne. That’s a possibility,” said Paul Rulis, an assistant professor of physics at the University of Missouri-Kansas City.
Other riders have told The Star about difficulties while on the world’s tallest slide. Several have experienced their harnesses coming off and in two instances since mid-July, people have said their raft went airborne.
One was reported about three weeks before Caleb’s death and the other on July 28.
Dawn Gentry of Wichita was on Verrückt on July 28 with her daughter when their raft left the slide as it crested the hill to the second drop.
“It launched us up, and then we came down, boom,” Gentry told The Star.
Her boat — with a man she didn’t know in the back and her daughter in the front — weighed the maximum 550 pounds. The one Caleb and the two women were in weighed 545 pounds.
The weight was more evenly distributed in Gentry’s boat than in Caleb’s. She said her daughter weighs nearly twice as much as Caleb weighed.
Weight distribution in the raft could also, possibly, make a difference, Rulis said. If the weight in the boat is evenly distributed, the boat’s center of mass moves close to the center of the raft, which would also become its pivot point.
But if the raft is loaded significantly heavier toward the back and lighter toward the front, Rulis explained, that would shift the center of mass and the raft’s pivot point toward the rear. Should a raft go airborne, it’s possible the boat would essentially pop a wheelie — the back of the raft would stay low while air resistance pushes the nose upward.
“There’s no question that having a light person in front made it worse,” said Charles Horton, an aerospace systems engineer from Charlotte, N.C.
It’s not yet known how the ride was tested for weight distribution.
“The question really is whoever was designing and verifying the rides, in what kind of extreme conditions did they test it?” Ziejewski said. “We are worrying about what could go wrong. What are the extreme conditions that are still allowable?”
Carl Finocchiaro, an engineer who works for Spectrum Forensics in Denver, said testing of slides typically checks for extreme scenarios. For the Verrückt, that would include not only running tests at both the 400- and 550-pound limits, but with extreme distribution of weight.
“You would attempt to have every condition of loading,” he said. “You’d want to test some combination of weights to arrive at 400-550 range. Loading in the boat is a completely different variable, and the hydrodynamic behavior it shows. ... I would expect testing to have addressed that. Put the heavier in the front and light in the back, you reverse it just to see what it does. ... I don’t know if they’ve ever tested for an individual that light in the front and two relatively heavy riders in the back.”
Ziejewski also questioned the use of hook and loop restraints for passengers on the Verrückt, suggesting instead a buckle system like those found in automobiles.
“There is a technology that assures that the (automobile seat) belt is properly functioning or properly engaged with the body,” Ziejewski said. “One of the limitations with Velcro is how it positions, where it is, how well it restrains the person.”
The two women who were on the slide with Caleb are sisters and live in a small community near the Kansas-Nebraska state line.
The sisters reportedly suffered facial injuries and did not return phone calls from The Star. A story in the Hays Daily News last week quoted a husband of one of the sisters. He said his wife received eight stitches in her chin and a broken jaw. His sister-in-law reportedly received five stitches above her left eye and bruising on her eyeball. She also had a fracture under her eye.
A family member of the two women told The Star on Tuesday that they could not comment at this time about the incident. The women have told their story to their attorney.
The Kansas City law firm of Shamberg, Johnson and Bergman is representing the two women.
“We’re hopeful that answers will come out in the investigation,” said the family member, who didn’t want to be identified . “And then information will be shared.”
The Star’s Tony Rizzo, Scott Canon and Eric Adler contributed to this report.