The stall-warning tab, which protrudes from the leading edge of the left wing (second pic), is to be adjusted such that the normally open switch which is actuated by the tab closes with minimum upward travel of the tab a few knots prior to stall, thereby actuating the stall horn. This adjustment is accomplished by trial-and-error, using the continuity function of a volt meter. The problem is that the wing skin panel with with the slot for the tab has to be temporarily installed for the adjustment to be
made, since the tab rests on the lower edge of the slot when the airplane is not at the critical angle of attack. At this point, the tab is supposed to be perpendicular to a tangent to the leading-edge curvature. If this condition doesn't exist, it is allowable to bend the tab (which I didn't do). I found it difficult to judge this. I ended up holding a straight edge at what appeared to my eye to be tangent, then eyeballing the perpendicular. The leading-edge curvature is not a circular arc, which would be much easier to judge, but appears to have a constantly changing radius of curvature. Compounding the problem is that the slot cut into the leading edge is much bigger that it needs to be if the builder does as instructed and minimizes movement of the tab.
I ended up doing three trial installations of the skin to get what seemed to be the correct angular
position of the switch (correct meaning the tab was perpendicular to the tangent). I started with the screw in the center of the housing slot, and that was surprisingly close to what I ended with. I suppose the adjustments could be made through the access hole (shown in the first pic) thereby avoiding all but one trial fit, but I found this difficult.
With the Skyview providing angle-of-attack information with programmable stall warning (and a female voice saying "angle, angle, push" just prior to stall -- I can't wait to hear this!), some builders are electing to not use the tab stall warning system at all. I plan to use it.
Kerosene heater is back
Yesterday was the first day of the year that I had to fire up a kerosene heater. During the coldest nights of the year I use as many as three at once in my uninsulated garage, the fumes from which usually give me a headache. I did buy a carbon monoxide detector last winter, and according to it, the CO levels are OK. It can't be good for me, however. I'm probably being saved by all the air leaks.
