Joshua's RV-9A Project

Snuck out to the shop for a bit tonight and drilled the ribs to the spars, then the bottom skins to the ribs.  Clecoed on the top skins and hung the nose skins from the bottom of the spar.  Need to weight these guys down before clecoing the nose skins in place…must…stay…flat…

After lunch, work begins on the flaps.  Pulled lots of blue plastic, then assembled and drilled all the nose rib/hinge assemblies.  Them drilled those assemblies to the spars.  Fabricated (hacksaw–oh joy!)  the heavy inboard reinforcing angles and the spacer plates that go behind them–all turned out well, so they were clamped and drilled in place.

Next, the bottom skins were set up on the table and the spar assemblies attached, then the skins drilled to the table.  A woodworking project ensued–drilling 54 5/8″ holes in the flat table…followed by a thorough shop-vac session.  Finally, the main ribs were clecoed to the spars, ready for match-drilling in the next work session.

Finished up the ailerons by drilling the brackets to the spars, then bolting them in place.  Those bolts/nuts are hard to get at with even a small open-end wrench, so I once again had to estimate the torque by “feeling” the torque wrench and trying to apply the same force to the bolt.  Spot-primed where the tigthening process had scuffed some primer off, and added torque-seal to all the bolts.  Messed around attaching them to the wing, and left them attached for storage; not all the attach hardware is in place, and none is tight, as the book seems to indicate that they’ll come off again in the process of fitting the bellcrank & pushrods.

The up travel on the aileron is limited by contact in the hinge brackets (later by the physical stop, once installed); down travel seems to be limited by the nose of the aileron contacting the bottom of the top wing skin/gap fairing.  This is the same on both sides and appears to be normal, but I don’t have a tool handy right now to measure the up/down travel to verify things are to spec.

Ailerons are done!

A good long day (and a beautiful weather day, at that) with ailerons.  Started off by finished up the deburring, drilling, dimpling, countersinking, and the like remaining from yesterday’s session.   Followed that up with an etch-and-prime lunch, wherein I managed to tear a hole in my rubber etching glove with enthusiastic scotchbriting (luckily, on the final piece).  The full sun really makes the priming go much faster, as the light coats dry quickly.  Leaving them in the sun after they’ve dried to the touch also seems to provide a harder finish faster, allowing progress to move forward.

Let the assembly begin!  I riveted the reinforcements plates to the spars, then added the counterbalance assembly, main ribs, then skins, following the recipe.  Riveting of the skin-to-spar lines was easy enough with the ailerons clamped upright; standing on a short stepstool gave the right height, and the tungsten bar slips inside easily.  Left first, then right.

Clamped and weighted everything down to the flat table for riveting the skins to the ribs, then riveting the trailing edge closed.  I used the same process I used for the empennage surfaces, where the TE rivets are squeezed entirely, not back-riveted like the manual shows.  No Proseal, either.  Just dropped clecoes in every hole, using a random pattern to insert them, then removed them randomly, one at a time, and squeezed a rivet in its place.

Both TE’s are straight, and the left aileron is straight, with no measurable twist.  The right one might have 1/32″ or so of twist evenly across it’s length.  My guess is that something got out of whack during the initial riveting process (counterbalance, perhaps?) and all the clamping & weighting couldn’t hold it true enough for the rib & TE riveting to take it out.  I don’t know how big of a factor that may be, so I’ll do some reading and see if others have made notes.  The manual doesn’t have a clear “x amount of twist is acceptable” like it did for the wings, but it seems like this is a small amount.  It wouldn’t be difficult to build a replacement aileron at a later date, should it prove to have undesirable flying characteristics.

No work today, so I was able to get in a long afternoon/evening session.  It’s supposed to be a beautiful weekend after the last few days of clouds…thoughts of flying in the clear fall-like weather are a good motivation. Allison has been after me to schedule a flight review (my flight review currency expires at the end of August), but I haven’t yet.  It’s been over a year since my last flight (7/4/08).

Bought a couple bags of pea gravel from the hardware store for weight; discovered that lead shot is expensive!  The gravel was a couple bucks a bag; not as easy to handle, but cheap and gets the job done.

Finished off the drilling of the left aileron components and the trailing edge, then took it apart for deburring, and countersunk the various parts.  Drilling the stainless tube went alright…used Boelube and cranked the air pressure down to 20psi on the drill for a slower speed.  Didn’t even use up one bit (I had extras on hand, as I’d read reports of others going through several).

After the left one was set aside (ready for skin dimpling and priming), I brought the right aileron through all the steps the left one has seen in the past week.  It’s now disassembled, awaiting deburring ans countersinking.  With luck, tomorrow I should be able to get everything finished, primed and ready for assembly.

Built the flat table for aileron & flap assembly tonight…that sucker must weigh upwards of 100 pounds.  The top and bottom are half-sheets of 3/4″ MDF, and the structure is most of four 2×4′s, put together with plenty of screws.  It checks out flat with a 4′ straightedge, so I imagine it will serve the purpose.  Also reading up on the trials and tribulations of building the control surfaces on others’ build logs.

Back-riveted the stiffeners to the aileron skins, then proceeded with the assembly of the left aileron.  Clecoed the bottom skin in place, drilled the ribs, deburred and dimpled.  Then installed the bottom skin with the two “keeper rivets”, and clecoed the top & nose skins in place as described.  The nose skin puts a great deal of force on the aileron, and the trailing edge goes really wavy, but I’ve read this is normal.  Tomorrow’s task will be building the flat table for the driling & riveting of these guys, and I need to get some weights of some sort–sandbags or lead shot, I’m thinking–to hold the aileron flat to the table.

Allison helped out tonight, dimpling the aileron skins & stiffeners while I etched for primer.  After everything was dry, I went ahead and shot the primer–in a race with the setting sun–so the stiffeners are ready to back-rivet to the skins.

Back home after two-and-a-half weeks away on “vacation.”  Almost three weeks since I did any work on the plane, but I’m ready to dive into the ailerons.  To that end, I started out with the tedious work — cutting, shaping, and deburring the 28 aileron stiffeners using snips, disc sander, and scotchbrite wheels.

Next, clecoed the aileron spars together with the nose ribs, then marked and drilled the counterbalance pipes (after deburring the ends to remove the very sharp stainless steel burrs).  I cut a V into a scrap of 2×4 to make a holding fixture for drilling the pipe — slowest speed on the drill press, light pressure, and Boelube made easy work of the holes.

Put in the temporary rivets to attach the counterbalance to the nose ribs, and clecoed the ribs back onto the spar, then clecoed the end ribs in place.  I goofed when I was match-drilling the reinforcement plates, and drilled out a couple wrong holes, which were the two holes intended for -3 rivets on the left outboard rib.  I can’t see any reason why simply upgrading to -4 rivets won’t work there, or even oops rivets.  Luckily, I caught myself before I had drilled all four sets…just one set is big.

Identified the various top & bottom skins and marked the for left/right, top/bottom, inside/outside, then drilled the stiffeners to all four skins.  Finally, more tedious work — deburring the holes in all four skins and 28 stiffeners.  Finished up by edge-finishing the four skins, and scuffing the lines where dimples are to go.  The stiffeners & skins are ready for dimpling, prep, and priming.

Hit the ground running today and riveted on the flap brackets and associated angles.  Nothing major different than the left wing process; the only “problem” rivets are those three spar-angle rivets nearest to the top skin, but with added experience from yesterday, then came out passably.  One ugly “smiley” in that awful root-end rivet, but after yesterday’s lesson, I decided to leave it as-is.  After the brackets were in place, I riveted on the gap fairings, and the right wing is done.

Wrapping up, I vacuumed the aluminum shavings out of both wings, then went through them and spot-primed the scrapes and scuffs from the riveting process.  Torque-sealed the fuel tank bolts on the right wing (I had anready done the left wing while it was in the jig).  Bolted the bellcrank brackets in place on the right wing (the bottom bracket replaced by the Trutrak servo mounting bracket; I have left the top servo support bracket out for now, because with no servo, one end is loose in the air, and would be free to vibrate.)  Torqued and sealed the bellcrank bolts.

Spent some time at the end putting tools away, sweeping the shop, and re-organizing to fit two vehicles into the garage bays.