I completed one of these type of moves last weekend.
Check it out......
I think the crash happened due to the fin being too small for the board. I was using a 135L board, a 6.6m sail and quite a small weed fin. The setup felt unbalanced. I don't mind this fin but it does spin out a bit on one tack. Its a smaller weed fin. This time I think it lost grip and the windward rail caught and then I was pitched over the front.
As I went over the only thing going through my mind was whether the water was deep or shallow. Fortunately it was about next deep. The crash was pretty hard and I was sore for a few days afterwards with a bit of bruising. The crash also busted my GPS. I think the sudden impact, it was strapped to my right arm, knocked it out of action. After the crash and back on shore the GPS gave a strange message and then became unresponsive.
After this I swapped boards, using my 105L board with the same fin and sail. This felt much more balanced. I didn't have any problems with catapults or crashes. So for everyone sailing in shallower water, be careful.
