On February 28, 2004, at 1553 Pacific standard time, a Jerome Q-2 homebuilt aircraft, N143GJ, registered to and being flown by a private pilot sustained substantial damage during a hard landing at the Portland-Hillsboro airport, Hillsboro, Oregon. The pilot was uninjured. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was personal, was operated under 14CFR91 and originated at Hillsboro approximately 1530. The pilot reported that the Revmaster 2100DQ engine, a Volkswagen automobile engine modified for aircraft use, had just undergone maintenance work for a sticking valve and this was the first flight following that maintenance. He departed Hillsboro airport on runway 20 in light drizzle and flew a circuit in the pattern at the airport without problems. While climbing out on the second circuit, the pilot encountered "...heavy rain that obscured my vision...," and shortly thereafter the engine began running rough. The pilot, suspecting carburetor icing, applied carburetor heat. The reduced power condition continued and the pilot was cleared to land on runway 20 by the air traffic control tower. He reported that he executed a rapid descent and subsequently landed hard during which the left canard broke at the fuselage attach point and the aircraft came to rest near the midpoint of the 4,049 foot long asphalt runway (refer to attached NTSB Form 6120.1/2). The aviation surface weather observation for Hillsboro airport reported at 1553 the following meteorological conditions: Ceiling 2,700 foot broken, 3,100 foot overcast, 6 miles visibility in light rain and mist, temperature/dew point 8/6 degrees Celsius respectively and winds from 220 degrees magnetic at 10 knots (refer to Attachment WX-I). The temperature/dew point readings at the time of the accident were consistent with carburetor icing conditions (refer to Attachment CI-I).