I had the opportunity one day to follow a Gurmman Ag-Cat on his take off run. For those that don't know, an Ag-cat is a radial engined Bi-winged spray plane. This particular day there was very little wind and this cropduster was using the oil road north of my place as a runway. He was pulled off of the road and was being refilled with spray when I got there. After filling he pulled out onto the hiway so I pulled out behind him in my SUV. I left him about a hundred feet of space when he poured the coal to it. It was interesting to watch the rudder action as he gained speed and worked to stay on the narrow road that had ditches on either side.
Does anybody care to guess at what speed he lifted off the ground fully loaded[sm=confused.gif]

I'll be back with the answer.
Chris

P.S.
The climb rate was very low.