On April 27, 2000, at 1250 hours Pacific daylight time, a Piper J3C-65, N146TM, collided with terrain on the takeoff initial climb from runway 31 at the Healdsburg Muni Airport, Healdsburg, California. The airplane, operated by the owner under the provisions of 14 CFR Part 91, sustained substantial damage. The certified flight instructor (CFI) and the private pilot/owner were not injured. Visual meteorological conditions existed for the flight review (FR), and no flight plan was filed. The flight was scheduled to terminate at the accident airport. The CFI stated that the airport is situated on a plateau surrounded by vineyards. At the departure end of the runway is a windsock that is attached to a 30-foot steel pole. The pilot stated that a 6-knot, 90-degree crosswind prevailed during takeoff. After takeoff, at an altitude of 25-30 feet, the airplane was pushed by a gust of wind from the left. He noted that the airplane was operating at full power, but did not respond to control inputs to return back to runway alignment, or to climb. At that point the CFI took control of the airplane; however, the airplane continued to sink. The pilot indicated that a windsock mounted on a steel pole approximately 30 feet high was in their flight path. The CFI raised the nose of the airplane to avoid a collision with the windsock and the airplane impacted terrain to the right side of the runway. The pilot noted no discrepancies with the airplane or engine. The CFI reported that the surface conditions did not appear to be gusty but the winds were at 6 knots, and oriented about 80 degrees from the active runway. There were no anomalies experienced on the takeoff roll. On the initial climb out the airplane encountered turbulence about 30 feet above the runway, and did not gain altitude. The CFI took control of the airplane from the pilot as it started to drift towards the right of the runway. He noted that the airplane was descending, and the airspeed was low. To prevent a stall he elected to keep the throttle in the open position and maintain a nose low attitude, while keeping the descent rate at a minimum. He noted that the windsock was in their flight path and they were still not able to climb. In order to avoid the windsock he raised the nose of the airplane and impacted a grassy area approximately 100 feet from the runway edge and 20 feet below the airport environment.