Smooth the airflow to reduce drag. When you performed the drag analysis of a Kitfox/Avid, were there fundamental design features which caused the drag (which could not be fixed), or was it just due to unstreamlined struts, gaps above horizontal stabilizers, no wheel pants, no fairings over intersections such as strut/wing, strut/fuselage, landing gear/fuselage, etc? Jonathon Brent These were the estimates based on a typical Avid Speedwing (24' span): The more noticeable result was a 4mph increase in cruise speed for the same power level. Least that's my excuse for rarely washing it. Graham Laucht