This has been a delightful part of building the RV-12. The builder gets to assemble a stall warning device for the airplane.
An aircraft stalls when the angle of the wings in relationship to the airflow increases beyond what is necessary for flight. In normal flying the angle of attack is a single digit number. The air meeting the bottom of the wing tends to lift the wing, and thus the aircraft, upward. The upper surface of the wing is usually cambered so that there is a smooth enlargement of the curve of the upper wing. The air going over the swelling of the upper wing has to move faster than the air below the wing. It therefore does not press down of the top of the wing as much as the air from the lower surface. This also causes a lifting of the wings.
When the angle of the wings increases into double digit numbers the lifting action becomes less effective because the smooth airflow over the top of the wing becomes turbulent. When this happens there is a settleing of the aircraft. and some air that would ordinariely pass below the wing now pushes upwards and over the wing.
Image 1 shows the Stall Warning device assembled. Looking at the metal piece projecting to between my thumb and first finger is a small, bent tab. The air pushing up from below over the front of the wing causes this piece of metal to rise. That trips a very small microswitch to prudece a small electrical sharge that is carried through an 18 guage wire to the fuselage where a warning is sounded. That alerts the pilot that a stall is eminant and requires lowering the angle of the wings (and usually applying engine power) to avoid sudden altitude loss.
To finish up here will require mounting this to a rib, attaching the appropriate wires, and attaching a terminal at the inward end of the wing. The terminal is shown in Image 2 surrounded by an aluminum attachment.
You have your Daughter -In-Law and Jamie to thank for Image 3.
