Australian Surf Boats Recover from a Dive
Australian surf boats are designed to recover out of a dive. The boats successfully resurface most of the time. Bow shape and quick weight shift are factors to success.
Surfboards do not recover out of dives. The videos below may explain why.
Flat bottom boats work well in flat smooth conditions. The same may apply to surfboards. Smooth clean conditions are preferred to flat bottoms.
The next video demonstrates how the bow pushes water aside as the boat follows in its wake. Two wakes are created, a bow wave and a trailing wake. When producing two wakes, the vessels speed is restricted. Some vessels always generate two wakes, and cannot over take its forward wake. Speed boats rise and plane on the aft its aft section, eliminating a bow wave.
When a boat porpoises it is dipping in a trough between swells or hitting waves and chop. It is pushing water aside with its bow. A flat bow does not push water aside efficiently.
All vessels must displace water to move. A speeding flat surfboard cannot move water out its path fast enough. When a surfboard cannot move water out of its path, the board stops and catapults its rider.
A surfboard does not have to dive under the surface to stop. The underside rocker bend is speeding and pushing against water. Speeding objects cannot move water. Instead it generates hydrodynamic force and blocks the board. The flat bow surface produces lift as it is designed to do. Due to the rocker bend it thrusts the board backwards. A few examples are seen in the following video.
A round or Vee Bow can recover from a shallow dive or poke. A video from the past demonstrates recovery on a round bow.
There is a future for alternate bow shapes.