Earlier we talked about the decision to specifically exclude use of a stern ramp in the specifications for the Offshore Patrol Cutter, “No Stern Ramp for Boats on the OPC-Mistake?”
I recently found a study that addressed this question. It’s conclusions seem particularly applicable to the Coast Guard:
The inclusion of a stern ramp has advantages in terms of deployment and recovery speeds, but ultimately a stern ramp lacks availability in the higher sea states in which a davit is still capable of operation. The stern ramp availability is driven by sill depth and pitch motions, whilst a davit needs to consider a range of constraints associated with the environment, including pendulum effects, hoisting speed and the safety of deck crew.
Hence, a vessel designed to operate in benign to moderate sea conditions and requiring rapid boat response times may be appropriate for a stern ramp, as illustrated by their use mainly in coast guard and smaller patrol vessels. A vessel operating in higher sea states such as offshore environments, including conducting MCM and environmental assessment may select davit arrangements, accepting the increase in handling procedures to gain a greater environmental envelope. A flexible, multi-role naval vessel is therefore likely to err towards the later, because of its greater flexibility and sea state envelope. A mixed solution may offer a compromise between these but suffers from the need to find space for both systems and requires training to cover several deployment methods, although the rapid response would be beneficial when operating in constabulary missions and may be an advantage to consider. In this case, the stern ramp is the secondary method of deployment and the mission space would be located midships with the davit system(s).
They also found that the relative success of stern ramps varied with the size of the “host” vessel, with it becoming more problematic as the size of the host vessel increased relative to the boat to be launched and recovered.
Late addition–Not sure why I did not link the original source when I posted, but here it is: Boat Launch and Recovery – BMT Group