Coastal Motor Boat 4 Replica

The Coastal Motor Boat Replica is a fully operational reproduction of a 40ft Coastal Motor Boat (CMB). The boat was built by volunteers, guided by boatbuilding professionals. Although the build used modern glues, all the woodworking techniques are traditional ones that would have been deployed in 1916. The boatbuilders worked from reproductions of the original plans sourced from the National Maritime Museum.

The CMB is a single stepped hydroplane. If you look at the bottom of the boat, about halfway along there is a step in the hull. The purpose of this is to cause the boat to rise out of the water as the speed increases. At top speeds the boat rides on the edge of this step and the edge of a similar wedge at the stern which dramatically reduces the friction with the surface of the water. This means the boat can increase speed exponentially. When the original was built in 1916, this technology was highly experimental and cutting edge. The replica has been built to be able to experiment and fully appreciate the skill in the design. Further trials and experiments will reveal the true performance potential of this remarkable craft.

“Coastal Motor Boat” was originally a camouflage term for the vessel, to conceal its true purpose. In 1919, Naval crews – operating in the Baltic in secret – posed as yacht salesmen with the boats painted white to distract from their true purpose. This has been repeated in the replica.

The construction of the boat was a project funded by the Chancellor using LIBOR funds.