On August 13, 1998, about 1700 Alaska daylight time, a float equipped Cessna 170B airplane, N8181A, sustained substantial damage during takeoff from a remote lake located about 85 miles northeast of Arctic Village, Alaska. The airplane was being operated as a visual flight rules (VFR) personal flight under Title 14, CFR Part 91, when the accident occurred. The certificated commercial pilot, and the one passenger aboard received minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated at the accident lake, about 1655. In his written statement to the National Transportation Safety Board (NTSB), the pilot stated that he was attempting a southwesterly departure from a 2,000 feet long lake. He reported that about midway in the takeoff run, he reduced the flap setting from 20 to 10 degrees. He said that as the airplane became airborne and passed over the departure end of the lake, a sudden wind shift caused the airplane to lose altitude. He said that as the airplane continued to lose altitude, the right wing and right float collided with brush covered tundra, and sustained substantial damage. The pilot noted that there were no preaccident mechanical anomalies with the airplane. The pilot reported that wind conditions at the time of the accident were about 240 degrees at 15 knots with peak gusts to 20 knots.