If you let the video clip "Ferry From Hell" run until the clock reads 30 seconds, then let the clip continue to run the bow is high at 30 seconds and is all the way down at 33. On closer examination the ship looks like it might be 600 feet long, not 400, which puts the middle at 300 and of course when centered, the bow is pivoting around a point 300 feet away. I would estimate that the bow travels 100 feet in 3 seconds. Keeping in mind that the travel is not straight up and down, but approximating a sine wave. The real acceleration forces could be calculated pretty accurately since the time and approx. shape can be determined pretty well. If the actual distance is 100 feet, whereas it most likely even further due to forward motion, and the time is about 3 seconds. Then G force averages on the order of 2 G. Some parts of the travel would be less and some of it might be quite a bit higher. Something else to consider. If all this were scaled down to a boat of say 100 feet and waves to suit, and the up to down were 3 seconds, the distance traveled would be much less. The G forces generated would be much smaller. As a practical matter if the waves were the same height for both vessels, the smaller boat would just ride up and down without the bow coming clear of the water. Which is to say that sometimes bigger is not better. Here is the URL again. http://www.youtube.com/watch?v=j7KBgptJZho Mike _____________________________________ Capt. Mike Maurice Beaverton Oregon(Near Portland)