The motor minesweeper was a design by Richards Ironworks ( actually an experienced wooden shipbuilder ) for the clearing of rivers and estuaries of acoustic and magnetic mines.
The piece of equipment which dictated the vessel's dimensions was the 'Twin Longitudnal' ( LL ) wire sweep for dealing with magnetic mines. It comprised of two bouyant copper cables 750 feet long unreeled from a large drum on the aft deck. A battery bank ( charged by a 50kW generator ) pulsed a set current pattern down these wires, creating a large magnetic field and thus detonating magnetic mines. The vessel was obviously built of wood to reduce magnetic signature, and the machinery was de-gaussed to reduce the signature even further.
The other equipment carried was an acoustic 'hammer' on a large A-frame fixed to the bows forward.
Post war, the MMS fleets were transferred to other navies to allow them to sweep wartime mines from their own waters, and because of their merchant lines and origins, it was the preffered vessel to replenish the depleted fishing fleets ( more so than the more military BYMS. )