Flaperon Hinge Brackets

On page 14-2, steps 3 & 4 we rivet doubler plates onto the inboard end of the stub spars.  Eight of the rivets are of the AN470 "mushroom" type and the three at the end are the tiny flush rivets.  Think of the ends as "Tab A" that slip into "Slot A" in the airplane fuselage near the wing's inboard leading edge.  To make the "Tab A" rivets flush on both sides, we countersink the three holes with the 100º countersink bit on both sides before squeezing the rivet.  The shop side of the rivet expands to fill the countersink.  The plans say to use the AN426AD3-3 rivets but I read in the builder blogs that those were a little short and that using the 3-3.5 rivets worked slightly better.  So I used those instead, but not before sanding a millimeter or so off the rivet length.  The main thing is that the "Tab A" rivets be flush on both sides and that's how they turned out.

In steps 5 & 6 we rivet together four hinge brackets for the flaperons (two per side) using the mushroom rivets.  Analogous to the stabilator (horizontal stabilizer & elevator), flaperons are a combination of wing flaps and ailerons.  Not sure who first thought up the idea, but it's quite clever.  Flaps help slow the plane down and ailerons are used to bank right or left.  Flaperons do both, and fewer moving parts means a faster build.  The Marine Corps' V-22 Osprey uses flaperons, but of course it transitions into helicopter mode to slow down and land.

The flaperon hinge brackets' holes are pre-drilled so all I have to do is deburr the holes and push a rivet through two halves of each bracket and squeeze it with a rivet squeezer.  There’s a possibility of warping the bracket during rivet squeezing so the plans say to install the rivets in a random pattern, whatever that means.  Although not very efficient, earlier I found a method that seems to work well in this situation:  Just give each rivet a half-squeeze –  enough to squish the rivet just a little, and then move onto the next.  Once all eight rivets are in, give ‘em a three-quarters squeeze, and then finish it off with a full final squeeze on each rivet.  That seems to result in good uniformity and kept the brackets nice and straight.  The technique seemed to work pretty well, which, as you know by now, meant that I was overdue for screwing something up.  One of the rivet holes was just a little too small, and instead of reaming it to the correct size, I tried to brute-force in a rivet and ended up with a deformed and stuck rivet that would neither go all the way in or come back out.  Then, in trying to get the rivet out using various techniques, I marred one of the two pieces that make up the bracket.  Just cosmetic of course, but the part will be visible on the finished wing and the scratches (plus a small dent - don't ask) would not be something that could be hidden under a coat of paint or smoothed out.  Besides, a replacement was only six bucks plus a couple bucks for shipping, so I went ahead and ordered it.  I knew that if I didn't I would cringe inside anytime someone inspected the flaperon hinges.

So with a replacement bracket half quickly mailed priority post from Oregon I braved the punishing heat of the garage for half an hour or so last night to finish the fourth and final flaperon hinge bracket thus completing Step 6.  Didn't take long but the heat and humidity was exhausting so I'm going to avoid doing that again.

With temperature forcasts in the 110-degree range this week (and the garage/airplane factory often several degrees above that) any further work in Section 14 is going to have to be moved indoors until, oh, September.  The CFO should like that.  She always appreciates it when airplane tools and parts are scattered all over her kitchen counter.