On our first attempt, we trimmed the horn brace on the inside of the guide hole which is pre-punched in the center of the part. As you can see in the photo below, Dad has drawn the new cut line well to the outside of the guide hole this time. Any shorter than this, and you’ll have the same rivet edge-distance problems we did with our first R-710.

When the old and the new part are placed side by side, you can clearly see how much we over-trimmed the first horn brace.

After the cut, Dad fit the horn brace into the rudder understructure assembly, to verify that the rivets would have adequate edge distance.

Here’s a side view of the two parts — the new R-710 is on the right, after drilling, and you can see the difference the correct trimming method makes. The “notch” in the center of the edge is from filing out the guide hole, which should be left in your part if you’ve trimmed correctly.

Finally, here is the new, finished R-710, primed and ready for installation.

More photos of the rudder construction are available in the Gallery.

So, we picked up a 4″ no-hole yoke from Avery Tools, and with this we were able to squeeze those tight-quarters rivet placements. And if the photo below were at all legible, and/or there wasn’t a bookshelf in the way, you’d see that, yes, we do in fact have a set of completed tail feathers.

We then jumped right into riveting the stiffeners to the rudder skin, since Dad had spent the last several weeks doing the trimming, drilling, dimpling, deburring of the rudder components. We used the C-frame backriveting technique for most of this job, but found that is was not quite as foolproof as we would have liked — we still ended up with some clubbed rivets.

We’ve since decided that the thin skins of the moveable surfaces, coupled with #40 holes and dimples, cause the rivets to move around a little too much in their holes, resulting in some of them bending over while driving. We might try a slightly smaller drill bit (#41?) next time.

We then moved on to bending the rudder trailing edge with the great 2×8 press brake that Dad fabricated (I’ll get some pictures of that process when we do the elevators), and we were pleasantly surprised with the results. Following the advice of several other builders, we taped a wooden dowel to the inside of the trailing edge to ensure that we got the proper bend radius.

Finally, we assembled and drilled the rudder understructure, and prepped the parts for priming.

Of course, no airplane work session can be without its pitfalls and heartbreak, and this one was no different. While match drilling the rudder understructure, we noticed that we’d over-trimmed the R-710 rudder horn brace, pictured above. This caused our drilled holes to be too close to the top edge (the bottom edge in the picture) to meet minimum edge distance requirements for a 3/32 rivet.

After much debate and hand-wringing, we decided to order a replacement part, and we moved on to priming and riveting what we could of the rudder skeleton.

Oh yeah, and last but not least, here’s a picture of me, doing … something.

For some reason, while using the Cleaveland squeezer, we ended up with some “clubbed” shop heads, illustrated below from MIL-R-47196A, the military specifications for driven rivets.

Although we carefully aligned the flush sets of the squeezer, and watched the shop heads as they formed, the fact that these rivets had “dumped over” escaped our attention until we took a closer look. Some example photographs are included below.

With the tiny AN426AD3-3.5 rivets, it’s difficult to get a properly-sized shop head that adequately covers all of the drilled hole beneath it. If we moved the set or bucking bar just a little off center, we got results like these. We found we had a much easier time forming acceptable shop heads with the bucking bar rather than with the hand squeezer.

At this point, we’re still not comfortable using the squeezer without it being solidly mounted to the workbench.

We called our Tech Counselor, Tom, and he graciously agreed to return just a few days after his first visit, to confirm our suspicions that these rivets needed to be replaced. Before his arrival, I carefully inspected each accessible shop head with a flashlight, then marked any suspect rivet with a permanent marker.

Tom agreed that some of the clubbed rivets would need to be replaced, but also added that the odd rivet here or there with an imperfect shop head might be considered acceptable, while several bad ones in a row should be drilled. We’re still developing our own sense of quality workmanship, so Tom’s advice was again invaluable. Thanks again, Tom!

So, after completing the vertical stab, we went back to the HS, and spent a couple of hours drilling out and replacing rivets. We got fairly adept at the process, and won’t have any reservations about replacing bad rivets in the future.

The good news, however, is that the horizontal stab is now done! Both the HS and the VS are now in temporary storage, as we move on to the empennage control surfaces.

We’d had great luck with the bench-mounted squeezer while riveting the HS rear spar, and this time was no different. Everything turned out great, including the countersunk AN426′s near the base of the spar. Having the unwieldy squeezer affixed firmly to the bench makes a big difference in the finished product.

We’ve also gotten fairly adept at riveting with the Sioux 3X gun and tungsten bucking bar, although we seem to have type-cast ourselves a bit. Dad’s been doing all the shooting and I’ve been doing the bucking. We’ll have to learn to switch up sometime soon, but we’ve really got a good rhythm down so far.

Ah, “The Robot” — a Christmas gift from my sister to Dad — has made all of our riveting success possible. This little oddball from Mars has illuminated the inky depths of our shop head ignorance with its eerie blue LED light since the very beginning. It has become virtually indispensable. I highly recommend picking one up next time you’re in that neck of the solar system.

We’ve had a bit of bad luck when using the Cleaveland squeezer free-hand (more on that later), so we used the rivet gun and bucking bar for the remainder of the riveting. You’ll notice the duct tape on the bucking bar — it helps to pad the sharp corners and keep them from scratching the primer while the bar is “bucking” on the shop head of the rivet.

After getting the forward spar and ribs together, we clecoed on the skin and started tacking it down from the center outwards. Once again, “The Robot” came in handy for inspecting the shop heads deep inside the assembly.

Once we were done reaching inside the stab to buck, we clecoed on the rear spar assembly and began riveting around the edge of the skin. Although we could have reached most of these with the squeezer, we kept up the gun and bucking show, with good results.

There were a couple of rivet placements — the leading edge of the stab and near the big rudder hinge bracket — that we couldn’t reach with squeezers or the bucking bar, so I went ahead and ordered a 4-inch “no-hole” yoke from Avery. Hopefully that will aid in accessing those tight spots.

Other than that, however, the vertical stab is done. Bwahhaaa! On the the rudder!

Today we began work on the vertical stabilizer, which — being very similar to the horizontal stab — went much more quickly than we’d anticipated.

Dad had already done most of the prep work on the VS parts, including edge deburring the ribs and finishing the rear spar doubler on the Scotch-brite wheels. Dad reported that the 1″ diameter 3M Cut & Polish Wheel from Cleaveland Tool (mounted in the Dremel) made deburring the big lightening holes a breeze.

So, we blasted right into match-drilling the understructure and the skin, including the rudder attach brackets on the back of the spar. The VS skin is much easier to get on and off the ribs for some reason, maybe due to the fact that there’s no center nose rib.

After drilling, we flowed right into deburring and dimpling, and — even though we planned ahead of time not to dimple the fairing attach holes on the lower edge of the stab — we got a little ahead of ourselves and dimpled a few holes that didn’t need it.

We also dimpled and countersunk the holes at the bottom of the rear spar — the ones that butt up against the fuselage attach point and thus must be flush riveted. Once again, the microstop countersink mounted in the drill press made short work of this task.

Next, we moved right into the surface prep and priming process, exactly as we did on the horizontal stab. This time however, we had the benefit of good weather and temps in the upper 60s. We decided to stop with only two coats of the SEM primer this time; it saves weight and primer, and leaves just about the same finish as the three coats we did the first time.

So in a single day’s work (thanks to the great preparation by Dad) we managed to knock out a sizeable chunk of the vertical stab. We should be able to finish up the riveting in just a few more hours.

The first order of business was to have our progress and skills reviewed by an EAA Technical Counselor. A tech counselor is an experienced builder or mechanic who volunteers his time to help newbies such as ourselves with the inevitable problems and questions that crop up during the build. So last night Dad and I hosted Tom Olson of EAA Chapter 33, and he gave our work a thorough inspection.

Happily, Tom seemed pleased with the quality of our work, and we spent a couple of hours chatting about tools, techniques, components, and those amazing flying machines called RVs. Tom’s endorsement really boosted our confidence, and we hope to see him at regular intervals as the project continues. Thanks, Tom!

This morning we set up the shop to continue where we’d left off, which was on the left half of the stab, with only the HS-707 nose rib riveted in place. We began by riveting the forward spar assembly to the HS-706 and HS-708 ribs, and then we got busy putting the skin on.

As many others have mentioned before, a tungsten bucking bar is worth its weight in gold, and after today, I’d have to agree. This little baby fits into all kinds of hard-to-reach corners, and it’s so dense that you really only need to have a couple of fingers holding it to get a good shop head on the rivet. I’ll stand by what I’ve said many times in the past: Good tools make all the difference.

Dad and I worked all morning, and developed a good rhythm between shooter and bucker. Good communication and a steady rhythm seem to be the key to setting perfect rivets. We set 200 rivets today and didn’t drill out a single one. Good stuff.

In just a few hours, we managed to finish all of the bucked rivets on the interior of the stab, so all that’s left for tomorrow will be squeezing the edge rivets with the hand squeezer. Almost there!

Riveting began by wrestling the HS-707 nose rib into place on the left skin. This baby does not want to squeeze its way forward very easily, and takes some muscle to get the skin into position over the holes. Then, once it’s finally in place, the forward nose of the rib doesn’t like to “sit down” on the skin. We had put a flew clecoes in the bottom side of the rib as well, just to hold things together while riveting the top side.

This was our first real test of riveting skin to ribs since completing the Van’s airfoil practice kit. We set the air compressor output to roughly 38 psi, and adjusted slightly down from there with the Brown Tool swivel regulator on the gun. We also followed the advice of several builders on the VAF Forums, and covered the factory head and surrounding skin with a couple short strips of masking tape to help eliminate slippage and scratching from the flush rivet set.

Everything worked beautifully. I think we may have drilled out one rivet with a malformed shop head due to lifting the bucking bar off the rivet too early, but other than that I think our confidence and skill are definitely improving. Oh, and we’re also getting pretty good at drilling out rivets.

Then, while moving things around in preparation for the next few steps, we dropped the rear spar assembly, causing one of the HS-603s to bend about 20° toward the flanges, just outboard of the ends of the riveted HS-609s.

Using the hand seamer, we were able to mostly straighten it back out, but there are still some damaged areas visible from the bend line. I was concerned that we may have caused unseen structural damage, so I decided to email some photos to Van’s.

Several hours later, Van’s Aircraft builder support rep Ken Scott returned my email, with this reassuring statement:

Probably not any disaster. Certainly the fix is straight enough to use. There’s no way of knowing what the future holds, but it seems unlikely that there will be problems. If that’s not enough reassurance, simply taking the spar apart and installing a couple of new HS-603s will eliminate all uncertainty. It might add a day’s work to your airplane project …

So we decided to at least cleco the spar to the ribs and skin, to see if we could salvage the part.

We got everything to align fairly well, and the damage seems minor, so at this point I think we’ve decided to “build on” after a brief hiatus. The right side of the rear spar on the stab will just have to be a place we keep our eye on down the road for any abnormalities.

I’m sure this little catastrophe is only the first of many to come.

The squeezer yoke bench mount and Cleaveland Main Squeeze made setting the -4 rivets a breeze — or, at least, as breezy as manual squeezing can get.

Van’s rivet callouts for this section are just a hair too short, but the instructions are adamant that you stick with what’s called for, so we ended up with shop heads that were just a bit too small, but adequate.

We had trouble getting the squeezer yoke over the HS-814 angle, so we ended up breaking out the gun and bucking bar. Yep, we had to drill out a couple of rivets as a result.

Things look pretty scratched up, but close enough for government work. (I hope.)

SEM 39683 Self-Etching Primer (Gray)

Well, today was the big day — priming day. I’ve been thinking about how I’d do this properly for nearly a year, so it was great to finally get started. I had read just about everything I could find on priming and corrosion control, and while I had initially considered going all out with alodine and a two-part epoxy primer, in the end I followed the logic of builders like Randy Lervold, who determined that a good self-etching primer was the best compromise between corrosion protection and ease of use.

So I ordered two rattle cans of gray SEM Self-Etching Primer from Amazon, and decided to see how it worked out. Our prep and painting process is detailed below.

Surface Preparation

(1) Dry abrasion with maroon Scotch-Brite pad to remove the Alclad coating, smooth surface anomalies, and give the part some “tooth” for the primer. The part should have a dull, matte gray finish.

(2) Abrasive wash and rinse using maroon Scotch-Brite pad, hot water, and Dawn dish liquid to remove surface contamination and aluminum particles left from step one. The hot water rinse should “sheet” off the surface, rather than beading up, indicating that it has been properly cleaned.

(3) After drying, a final wipedown with a wet cloth soaked in naphtha, followed immediately by a wipedown with a clean, dry cloth, to remove any residual oils and contaminates left from the previous step. Impermeable gloves must be worn from this point on, to keep skin oils away from the parts.

Primer Application

It’s a good idea to read the MSDS before using any product like SEM self-etching primer. We picked up a pair of 3M 6000 Series respirators with 6001 organic vapor cartridges for lung protection and all-around Darth Vaderness. Eye and skin protection are recommended as well.

Temperature, moisture and dust control are important for any painting process. As you can see, we had none of the above. The SEM has such a strong odor that we couldn’t bear to set up any kind of paint booth indoors, but temperatures outside today were in the single digits. Our solution was to spray each part individually outdoors — a process taking roughly 90 seconds per coat — then rush it back inside for drying before the primer started to freeze. Ideal? Hardly. But the SEM dries so uniformly that it seemed to work okay.

The SEM dries well enough for recoating in five to ten minutes, and we put on three coats per part. We also prepped and primed the rivet lines on the inside of the skins, since we’d scratched up the Alclad so badly during layout and drilling. All in all, we used almost all of two 15.5 oz. rattle cans for the horizontal stab.

I’m very happy with the end result, although we got a run or two and a few spots that could have used a bit more coverage. As you can see, even with the poor conditions, the SEM is very forgiving of amateur painting techniques. Next up, riveting!

The Avery and Brown swivel deburring tools worked great for everything, skins included, and the extensions enabled us to access the inside flange of all the ribs and spars.

The real heroes of the day, however, were the Brown Tool C-Rex squeezer yoke and bench mounting bracket, which we used with the fabulous Cleaveland Main Squeeze hand squeezer.

Having the squeezer mounted solidly to the bench made short work of the dimpling process, and with one person handling the part and one person operating the squeezer, I doubt a pneumatic unit could have done the job faster. Good stuff.

Tomorrow, final edge finishing and Scotch-Brite surface prep, then — gulp — priming!!