Pirate ship!

When I was in the Sixth Form, we were sent to escort a group of new Year 7s on a trip to Alton Towers, which had far fewer ride sin the those days. I tried the Pirate Ship and hated it. The trouble was that I knew I had to outlast the Year 7s, so I had to stay on 10 consecutive times. What was the big problem? I don't think that the forces were large. I'm estimating the radius as about 12m. Using the rapid repeat photograph mode on the camera, I estimate that the ship moved 1.2m in 0.3 seconds through its equilibrium position. That gives a maximum speed of 4 metres per second. So the centripetal acceleration will be vsquared/r = 16/12 = 1.3 m/s/s. That's nowhere near g. But the problem came at the top. For a split second you and the ship stop. The you are in free-fall against the barrier which I found unnerving!