Stabilator Hinge Brackets

Page 9-7  has us bolting in the stabilator hinge brackets and hinge stops (that's what the 21/32" pieces of alumninum tube were for).  The page has a nice figure that explains everything.  What it does not have, however, is anything reminding you to use a torque wrench.  Apparently you're just supposed to know that you need it.  Indeed, way back on page 5-10 (which also covers topics like canopy protection and scratch removal) it does say to use a torque-wrench on all the bolts.  I suppose I must have read it back in June sometime, but somehow didn't stick in the right brain cell.  At any rate, I've accidently sheared off my share of bolts (including one for the water pump on my truck that bolts into the engine block) so not wanting to break anything or strip any threads I bolted in the brackets and hinge stops to what I felt was a safe place somewhere between "snug" and "tight".  Then, as I cleaned up to go inside and enjoy a nice cold beverage, I remembered reading something about using a torque wrench on these bolts.  Sure enough a quick check of DaveG's 11/24/09 Schmetterling Aviation blog entry showed that a torque wrench was needed at this point, and that the specified torque is 20-25 inch-lbs.

Since page 9-7 of the manual said nothing about using a torque wrench, the revelation caught me by surprise, but okay, no problem.  The guy at work who loaned me the precision calipers, drill press, band saw and all the other airplane building tools I've been using also loaned me his torque wrench.  First thing I wanted to do is to measure how tightly I had torqued the bolts with a regular socket wrench.  Next thing was to re-torque them to spec.  Turns out I had wayyy over-torqued the bolts - about 45 in-lbs or so.  So I backed 'em off to 15 or so and then re-torqued to about 25 as required for AN3 nuts and bolts.  25 inch-lbs is just five pounds of pressure on the end of a five-inch wrench, and really is not very tight at all.

Page 5-10 also says to torque the nut, not the bolt, whenever possible.  If the figure on page 9-7 had the bolts for the hinge stops pointed inward, instead of outward, it would be possible to get a torque wrench on the nut to tighten it.  As it is you have to torque-wrench the bolt head and not the nut because the inboard ribs are in the way.  I just have to trust that Van's has a good reason (yet to be revealed) for pointing the hinge stop bolts in the outboard, rather than inboard, direction.