Roee Kalinsky's RV-7A Project

2004.12.21: (2.0) Started making the stiffeners for the right and left elevators.  Much faster method than what I did on the rudder:  1. separate individual stiffeners using cutting disc in a die grinder, 2. rough cut (~1/16" from line) stiffeners on the band saw, 3. clean up the cuts on the bench grinder (scotchbrite wheel).

2004.12.22: (2.0) Finished grinding down the stiffeners to final shape.

2004.12.23: (3.0) Edge-finished the stiffeners.

2004.12.25: (1.5) Final-drilled the stiffeners to the right elevator skin.  Used a reamer instead of a regular jobber bit, which produced cleaner holes with less burr.  Deburred the holes.

2004.12.26: (2.5) Edge-finished the right elevator skin.  Dimpled the stiffener-to-skin rivet holes on the skin and the stiffeners.

2004.12.27: (1.5) Final-drilled the stiffeners and trim reinforcement plate to the left elevator skin.

2005.01.08: (1.0) Edge-finishing the left elevator skin...

2005.01.09: (1.0) Done edge-finishing the left elevator skin.

2005.01.10: (1.0) Dimpled the left elevator skin.

2005.01.16: (2.0) Fitted the parts associated with the trim servo installation.  The servo cover plate does not come with pre-punched holes for the servo support Z-brackets, so locating them is the first order of business.  The plans provide one dimension callout for the distance between the edge of the cover plate and the edge of one of the Z-brackets, and that's all.  Seems to me that referencing the installation to this dimension is not the best way to go about it, as it is only indirectly related to the truly critical dimensions and introduces several unnecessary sources of error.  It's critical that the servo be positioned such that the servo shaft (and jackscrew) be properly aligned with their respective exit cutouts in the elevator.  So I started by locating the servo shaft centerline on the elevator components to serve as the master reference.  Then located the servo housing centerline and the Z-bracket rivet lines based on the shaft centerline and dimensions of the servo and Z-brackets.  In the longitudinal axis I located the servo as far forward (toward the spar) as possible without modifying the Z-brackets, as limited by their contact with the trim reinforcement plate.  This dimension is not explicitly called out in the plans at all.  Locating as forward as possible minimizes its effect on elevator balance, and therefore the necessary counterbalance mass.  As noted in the plans, a small amount of trimming is necessary to the trim cover plate and reinforcement plate to prevent interference with the clevis pin when the servo shaft is in its extreme extended position.

2005.01.20: (1.0) Finished preparing (edge-finishing, c-sinking, dimpling) the parts associated with the trim servo installation.  Clearance is very tight between the servo and the aft rivet connecting each of Z-brackets to the trim plate, likely to interfere when dimpled for AN426AD3 rivets.  So I decided to substitute a NAS1097AD3 rivet for the AN426AD3 and machine countersink the hole instead of dimpling.  With no dimple, clearance should be ok.  The NAS1097 rivet has a smaller head and therefore will not leave a knife-edged hole after countersinking.  Although it has reduced tensile strength, I believe it is preferable in this location where it should experience primarily a shear load.  All other rivets are as called out on the plans.

2005.01.29: (1.0) Edge-finished the hinge reinforcement plates and one of the spars.  Then noticed that the outboard hinge reinforcement plates don't fit the spar.  Looks like Van's sent me the wrong part.  They look suspiciously like one of the hinge reinforcement plates on the rudder.

2005.01.30: (3.5) Applied corrosion protection to the right elevator stiffeners and left elevator trim reinforcement plate.

2005.01.31: (0.5) Installed nut plates to the trim reinforcement plate.

2005.02.01: (2.5) Applied corrosion protection to the right elevator skin.

2005.02.04: (1.0) Riveted the stiffeners to the right elevator skin.

2005.02.09: (3.5) Applied corrosion protection to the left elevator stiffeners and trim servo plate and brackets.

2005.02.10: (0.5) Riveted the trim servo assembly.  Even with the countersunk NAS1097 rivets in the aft position, clearance indeed turned out to be an issue (see 2005.01.20 entry).  I had to over-squeeze these rivets somewhat to fit the servo, and I may still decide to shim it up a little to prevent possible rubbing on vibration.

2005.02.12: (1.0) Edge-finished the correct hinge reinforcement plates just received from Van's.  Started edge finishing the ribs.

2005.02.13: (1.5) Edge-finishing the ribs...

2005.02.19: (1.0) Built a bending brake for the elevator trailing edges using some 1"x6" poplar and a piano hinge from Home Depot.

2005.02.20: (4.0) Bent the right elevator trailing edge.  Started drilling the right elevator counterbalance arm components.  Today I had help from my brother (and future homebuilder) Omri, and my sister (and future airsick passenger) Eynav.

2005.02.21: (1.0) Drilled the lead counterweight to the structure.  Drilling lead (Pb) can be a bit tricky as it has a strong tendency to bind.  I destroyed one drill bit discovering this tendency, but thankfully I managed to stop the drill press before it could toss the counterweight across the room.  After that I did ok, using WD-40 for lubrication/cooling and going in very small increments, backing out every few millimeters and clearing the lead out of the drill bit.  I also started with a #40 drill and incrementally enlarged the hole to #12 with about five drill sizes in-between.  A little time-consuming, but the end result was excellent.  Countersunk the weight, dimpled the counterbalance skin, did a fit check.

2005.02.24: (2.0) Drilled the right elevator skin to the understructure.  Disassembled and deburred the holes.

2005.02.25: (1.0) Dimpled the right elevator components.

2005.02.28: (1.0) Quickly reassembled the right elevator and match drilled the fiberglass tip (should have done this before, when drilling everything else).

Removed material from the lead counterweight as shown on the plans.  Rough-cut using the band saw, then filed down.

2005.03.01 (3.5) Applied corrosion protection to the remaining right elevator skeleton components.

2005.03.02: (1.0) Started riveting up the right elevator skeleton.  Found that a longeron yoke will be needed to rivet the counterbalance ribs to each other.

The control  horn weldments are 4130 chromoly steel and come powder coated, but the powder coat doesn't cover the inside of the torque tube, which is open on one side.  To help protect from corrosion I decided to coat the inside with Rustoleum primer and paint.  Did so by pouring it in, sloshing it around, then drain the excess and blow it out with compressed air. 

2005.03.03: (1.0) Ordered a longeron yoke from Cleaveland Tools ($135, ouch!!!), and for today I borrowed one from fellow builder Greg Larson.  Finished riveting the right elevator skeleton, except for the control horn, which is still drying.

The current design of the counterbalance arm has the lead mass mounted in such a way that it is not removable, and only minimally accessible for removing material via drilling.  The fiberglass fairing also gets epoxied to the lead weight, making it more or less a permanent installation.  Once in place, there is no practical way to add mass if it becomes necessary.  So I decided to install two 10-32 plate nuts on the counterbalance rib, where additional mass could be attached if necessary.

2005.03.04: (1.5) Riveted on the right elevator control horn and started riveting on the skin.

RTV folklore: there's a common practice of putting a glob of RTV silicone between each opposing pair of stiffeners near the trailing edge to "tie them together" thereby minimizing vibration and preventing cracks.  This measure struck me as dubious in its necessity and effectiveness, so I dug a little further into its origins.  I found that this dates back to a couple articles in the 12/89 and 12/91 issues of the RV-ator in response to some builders of early RV's experienced cracking in these areas.  Since that time however, the stiffeners have been redesigned to extend closer to the trailing edge, and the skins themselves have been thickened from 0.016" to 0.020", both of which should make the trailing edge much stiffer than on the early RV's.  I did not want to add any unnecessary weight that far aft, and especially at the trailing edge of the elevators (not just the weight of the RTV itself, but also of the added counterbalance weight), so I decided to consult Van's.  I spoke with Tom Greene, who concurred that the RTV is most likely unnecessary with the thicker skin, and told me that cracking was mainly a problem on early RV's with larger than recommended engines.  He also shared my doubts about the ability of RTV to permanently bond the stiffeners together.  So, I decided to omit the RTV from my elevators.  Will they crack?  Time will tell.

2005.03.05: (0.5) Finished closing the right elevator.

2005.03.06: (2.0) Applied corrosion protection to the left elevator skin.

2005.03.07: (1.0) Riveted the stiffeners to the left elevator skin.

2005.03.09: (1.0) Started bending the left elevator trailing edge with Vay's help.  I thought the left elevator would be easier than the right because it has less trailing edge (due to the trim tab cutout).  But in fact that just makes it more awkward and difficult to hold in position in the bending brake.  Still, with some strategy and a little yoga it's going ok.  Just a few more degrees to go.

2005.03.10: (0.5) Finished bending the left elevator trailing edge.

2005.03.12: (2.0) Preparing the left elevator skeletal pieces.

2005.03.13: (2.0) Drilling the left elevator skeleton.

2005.03.14: (2.0) Prepared the left elevator trim spar.  Beveled the counterbalance skin where the main skin transitions off.  Drilled the lead weight to the counterbalance arm components.

2005.03.15: (2.0) Today disaster struck...  I started to cleco up the left elevator for final drilling only to discover a serious problem.  The holes in the skins and the holes in the skeleton were just not lining up right, getting worse toward the tip.  Forcing the holes to line up would cause a substantial "hook" at the trailing edge.  After examining the geometry and taking a few quick measurements it became clear that the trailing edge bend in the skin was off its proper axis.  Worst at the tip end, the distance from the trailing edge to the spar was different on the top and bottom by about 1/16".  I'm not sure how this happened, whether it happened during my final bending or whether the initial bend was off out of the box.  But in any case, the skin will have to be replaced.  This sucks!

I spent the rest of the evening drilling out all hundred or so rivets attaching the stiffeners to the skin.  My one consolation is that this operation went well and the stiffeners will be usable with a new skin.

2005.03.16: (3.0) Ordered a new left elevator skin from Van's.  That's $60 and about 10 hours of work down the drain, but sometimes that's just how it goes.  Back to work.  Countersunk the lead weight.  Countersunk plate nut mounting holes in the counterbalance rib (my modification, same as right elevator).  Edge-finished the trim tab components and drilled the trim tab horn to the skin and spar.

2005.03.17: (3.0) Rolled the leading edge of the right elevator.  This actually seemed to go easier than on the rudder, despite (or maybe because) of the thicker elevator skin.  It took more force to roll a given amount, but seemed to have less spring back.

2005.03.18: (0.5) I decided to make a minor modification to the trim servo installation.  I didn't like the idea of routing the wiring through the same hole in the elevator spar that the jackscrew moves through (the wiring could flop around, catch, rub, etc.) as shown on the plans. So I drilled a separate 3/8" hole in the elevator spar just for the wiring. The location of this hole is closer inboard, right in the center of the lightening hole of the control horn weldment.  Although this is a very minor deviation from the plans, it is in a structurally critical area, so I cleared it with Van's for good measure.

2005.03.19: (4.0) Received my replacement left elevator skin from Van's.  I edge-finished it without use of the die grinder, as it was late at night, which took about twice as long.  Next time I'll wait until morning and make all the noise I want.

2005.03.20: (1.5) Did a quick fit check with the stiffeners and the new skin.  Then reamed, deburred, and dimpled the holes in the skin for attaching the stiffeners.

2005.03.21: (1.5) Alodined the new left elevator skin, spar doublers, and trim tab skin.

2005.03.22: (2.0) Shot AKZO on the new left elevator skin, spar doublers, counterweight, and trim tab skin.  Several hours later ... bent the trailing edge of the trim tab.

2005.03.23: (2.0) Bending the ends of the trim tab:  Made a bending block wedge (and its complement) from a piece of thick particle board left over from the material I used for the top of my workbench.  On the wedge piece, which actually functions as the bending block, I radiused the edges using just a file, sandpaper, and eyeball.  I made it just a simple wedge without the interlocking feature shown in Van's manual, since that design would only work for the trim tab and not the elevator.  I then made the first bend on the lower inboard end of the trim tab.  I used blue masking tape on the trim tab to both protect it from scratches and provide some friction to keep things from moving around.  With that and clamping the whole stack to the workbench, nothing was going anywhere.  First bend completed to about 90 degrees.  A tad more is needed due to the geometry of the trim tab, but I'll do that tomorrow.

Riveted the stiffeners to the new left elevator skin.  Later Vay came over and we bent the left elevator trailing edge, again.  Did a quick fit check with the tip rib, and this time the holes line up.  Whew!

2005.03.24: (6.0) Match-drilled, deburred, and dimpled the left elevator.

2005.03.25: (1.5) Finished bending the ends of the trim tab.  Match-drilled the trim tab skin to the spar, hinge, and control horn components.

2005.03.29: (0.5) Bent the left elevator tabs that close off the trim tab cutout.  Nothing to it.

2005.03.30: (1.5) Alodined the remaining left elevator and trim tab components.

2005.03.31: (3.0) Shot AKZO on the remaining left elevator and trim tab components.  Later in the day, riveted the bottom of the trim tab and riveted the left elevator skeleton.

2005.04.03: (2.5) Riveted the left elevator skin to the skeleton, except for the where the trim tab hinge attaches.

On the left elevator I decided to follow tradition and put a glob of tank sealant between each pair of opposing stiffeners near the trailing edge.  I stand by my reasons for not doing this on the right elevator (time will tell), but decided to do it on the left to alleviate my paranoia about using the stiffeners that had been drilled out from the original skin following the March 15 disaster.  Also, on the left elevator there are only four pairs of stiffeners that reach the trailing edge (because of the trim tab cutout), so the weight penalty is smaller.  Anyhow...  I chose to use tank sealant rather than RTV because 1. I believe it will form a stronger bond that will last longer, 2. I already had a tube of it laying around, and 3. I wanted to try it, having never used it before.  The stuff I used was FlameMaster ChemSeal 3204-B2 from Aircraft Spruce.  This conforms to MIL-S-8802F Type II (a.k.a. AMS-8802), and is equivalent to PPG ProSeal brand sold by Van's.  As everyone says, this stuff is very sticky and can get messy.  I did go through several sets of latex gloves and popsicle sticks, but it really wasn't bad at all.  When applying it I was careful to get it to the ends of the stiffeners but no further, so as to not obstruct the natural drainage channel at the trailing edge.  I also applied leftover tank sealant to a few test patches of different materials so I know how well it works for future reference.  It performed well with every surface I tried including clean but untreated alclad, AKZO epoxy primer (like the inside of my elevators), stainless steel, wood, PVC, and even delrin.  Good stuff!

2005.04.04: (1.0) Fitted and closed the trim tab.  The fit to the elevator was very good at the outboard gap and trailing edge, but the inboard edge of the trim tab protruded about 3/16" past the inboard edge of the elevator.  I called Van's to make sure this is not a problem.

2005.04.05: (0.5) Shot AKZO on the forward (elevator) half of the trim tab hinge.

2005.04.06: (1.0) Finished riveting the trim tab cutout area in the left elevator.

2005.04.07: (1.5) Rolled the leading edges of the left elevator.  Added a few extra rivets toward the outboard end to help with the spring back.  Primary construction of the elevators is complete.

2006.12.18: (0.0) See "Attaching the Empennage" for fitting elevators to the horizontal stabilizer.