RedactedNarrative: Operator of vessel 1 was proceeding Northbound in the Milton Harbor channel, after calling the American Yacht Club dock house on VHF 71 to report he was coming to the dock if there was free space. Operator and his single crew member had difficulty dousing and securing the mainsail approx. half-way down the channel due to strong and shifting winds. Operator proceeded down the channel while crewmember prepared docking lines and the operator prepared the stern line while turning sharply to starboard through the mooring field in a clockwise direction around the port side of vessel 2 which was swinging on her mooring. Both crew member and operator of V1 were looking down at the spring line amidships of her mooring. After impact the two vessels moved approx. 20 feet and V2 remained secured to its mooring.