Joshua's RV-9A Project

A quick stop in the shop before heading off to work this morning finished up the remaining rivets on the right flap trailing edge.  A check for straightness & twist (all looks good), and the flap is attached to the wing — because it’s a good place to store it out of the way, and because moving parts are exciting!

Almost finished the right flap — just a portion of the trailing edge rivets remain.  First, the top skin is riveted to the spar & ribs in a manner similar to the ailerons.  The tungsten bar is great for this–it’s small enough to nest into the spar channel and tuck into the ribs.

After riveting the top skin on, the flap is flipped topside-down on the table and weighted in place, then the bottom skin riveted to the spar & nose skin.  This is a tight operation, squeezing inside the flap with the weights/clamps/boards in the way.  Finished it up without a problem though, then the whole thing is weighted flat to the table, and the bottom skin-rib rivets inserted.  These are blind rivets everywhere but the outboard end rib, which can be squeezed.  I also used blind rivets at the most aft location in the top skins, same as on the elevators & rudder…those ribs are so narrow at the aft end that it’s nearly impossible to buck anything in there, and certainly not with any of the bars I have.

Once the skins are in place, the weights are put back in place for the trailing edge riveting, which I’m doing using the same squeezing process I’ve used on all the other control surfaces.  I had to leave for work before finishing up this flap, but it’s nearly done.

Started out with a few hours spent priming all the flap & pitot mount components.  Had some trouble with that, but nothing major…the tip of the gun continually clogged up with a “skin” of primer, a result of (I believe) the warm temps, direct sunlight warming the primer in the gun hopper, and the fact that I was using the last slug out of a quart of primer.  When I opened a new jar, I realized that the old stuff was noticeably thicker–because the solids settle to the bottom, and even though I stir thoroughly, my stir skill must not be up to par.  Some of the solvent portion of the mixture probably flashed off over time too, since this can has been used for spot-priming, as well as several gun sessions.  Oh well, everything that needed primer got coated.

The first task is assembling the flap brackets/nose rib assemblies.  I clecoed the brackets and spacer blocks together for each bracket, then ran a Q-tip dipped in primer around the inside of the lightening holes to coat them better, as that spot is difficult to get good coverage on by shooting, at least to a painting amateur like myself.  Then added the nose ribs, which form the outside of the assemblies, and riveted them together.

Clecoed and riveted the bracket assemblies to the spars.  The first one took some head-scratching to figure out the best way to get at all the different rivets.  Combination of the longeron yoke and standard yoke, with various set configurations, got most of the rivets; the only ones needing to be shot were the three in the “elbow” of the heavy angle on the inboard end of each flap.  The second spar went much faster, since the figuring was already figured.  After the brackets were in place, the main ribs were added to the spars, and those rivets are easy to get at with the longeron yoke.

Continuing on with the right flap, I clecoed on the top skin, followed by the nose skins.  Weighted to the table, I drilled the nose rib holes to 7/64″ for the blind rivets, then installed all the skin-nose rib rivets.  The right flap is ready for top skin riveting.

Took advantage of a day off work–probably the last for awhile with the semester starting next week.  Hopefully progress won’t come to as dreadful of a stop as it did last school year, but I lose at least two nights a week, often more, from here to the end of May ’10.

Countersunk the spars and TE wedges, then dimpled all the skins & ribs, followed by several hours swimming in etch.  These flaps have a great lot of parts.  Ready for priming, but not enough time before sunset to get it done, and past experience priming in the dark wasn’t a pleasant experience.

More flap deburring tonight…wrapped it up with the flap skins.  Countersinking & dimpling remain.

Deburred the nose skins, main ribs, and hinge bracket pieces for both flaps, as well as edge-finished the spars and skins.  Remaining work before primer is deburr all skins, and countersink the TE wedge and spars.

Taking a break from deburring flap parts, I decided to knock out one small task remaining on the wings — install of the pitot tube mount.  I’m not sure yet whether or not I’ll be initially installing a heated pitot (primarily to save the extra cost of the heated tube, though provisions would be made to add it later as part of an IFR upgrade), but I came across a Gretz pitot mount for sale via RivetBangers, and bought it.  This unit has a mounting bracket that installs permanently to the wing, but the mast itself is held in place via four #8 screws, so is removable for service, or simply to keep from banging shins against it.  The install is really pretty easy, once you determine where it’s going to be mounted.  There’s plenty of discussion on that in the forum archives–accuracy generally isn’t affected as long as the pitot is not in the propwash, so the choices come down to things like how close is it to the tie-down rings, tube routing in the wing, etc.  I chose to go with a common location, and the once described in the plans — mounting to the outboard side of the rib just outboard of the aileron bellcrank access plate, on the left wing.

The bracket comes pre-cut, and pre-bent with a joggle to clear the main spar flange.  I fabricated the reinforcement angle that runs fore-aft along the rib out of a trimmed-off piece of stiffener from some control surface or another (I keep a pile of trimmings, anything large enough to reasonably have a chance of use elsewhere for a bracket or whatever).  Cleco clamps hold everything in place and square for drilling, then I drilled the bracket to the spar.  Adjusted the plate to sit even with the rib by using a piece of aluminum sheet to align them, then clamped that in place and drilled the angle to the rib.  On the bench, I marked and drilled the skin-to-bracket hole pattern, and drilled the angle to the bracket.

Clecoed the drilled bracket to the backside of the wing skin using the main spar rivet holes, and back-drilled the holes in the skin, then cut and filed the center mast hole to size, using the mast itself to test fit.  Disassemble and deburr everything, then dimple the holes as appropriate.  I’ll prime these parts along with the flaps, then rivet the bracketry to the rib; the rest will get riveted along with the bottom skin.

Attached the left flap nose skins, drilled the skins, and inserted/drilled the trailing edge.  Then disassembled the left flap, and got to work deburring flap parts…much like the wing nose ribs, the ribs for the flaps have numerous little tabs on them, and the main ribs taper into a very tight gap at the aft end, making the process more of a pain than usual (sometimes quite literally, as the attempt to slide a finger into that narrow aft end can remove skin).  I got through all of the hole deburring on the hinge assemblies, ribs, and inboard end pieces before going slightly nuts and needing a deburring breather.

Still hoping to wrap the wings (with the exception of bottom skins and tips) before school starts in earnest after Labor Day…which may or may not actually be possible.

Drilled the right flap: nose skins, top skin, and spar.  Also attached and drilled the inboard reinforcement plate, and the nutplate which attaches the actuator arm.  Disassembled the flap in preparation for deburring.

Weighted down and clamped the right flap flat with a pair of 2×4′s, several buckets of clecos, and a bag of pea gravel, then proceeded to attach the nose skins.  Double-checked flatness, inserted the trailing edge wedge, and drilled the TE to the table.  I’ll need to finish this flap to the point of disassembly before continuing with the left flap, since the opposite flap’s TE wedge is used to locate the wedge for drilling, and the right wedge is now securely clecoed in place.

Also looked through the book, and, failing to find a specific notation to install the bushings into the flap brackets, decided they must have been part of the “assemble bracket per drawing” instruction.  So, I pressed them into place using a C-clamp and block of wood.