only by measuring with instruments (no matter how crude) will you ever uncover what the forces actually are.
On Hiram Maxim's propeller and wing dynamic measuring rig.
"Maxim knows we'll have to separate the wing from the propeller. So he's built a central tower with a 32-foot rotating arm to measure the effectiveness of propellers and wing surfaces. A steam engine drives the arm. At the end of the arm is a propeller with a streamlined engine pod and a short section of a wing. That test configuration circles the tower at speeds up to sixty miles per hour, while an electric motor inside the pod drives the propeller. The apparatus offers means for measuring power input to both the propeller and the rotating arm.
Maxim's instruments let him separate out lift, thrust, and drag. He finds that, at sixty miles per hour, the propeller might use sixteen horsepower to lift the wing and another 35 horsepower to overcome drag and its own inefficiency. With such detailed preliminary work on flight, Maxim had done superb work on the power inventory of flight"
Ref:
The Pioneers : An Anthology : Sir Hiram Maxim (1840 - 1916)
This was about a decade before the Wrights' small wind tunnel.