Month: August 2019

Tonight I set up and practiced with my pneumatic pop rivet gun. I cut and drilled some scrap aluminum and then set half a dozen pop rivets. The gun is so easy to use, I can’t believe I bothered with the hand riveter. Instead of two to three squeezes, a single trigger pull sets the rivet and pops out the stem. Within 5 minutes I set the remaining 8 pop rivets in the top of the rudder, all of them set perfectly. With that done, the next step is back riveting the trailing edge, then rolling the leading edge, and the rudder will be done.

Just a couple of hours in the garage today, but I managed to complete several more steps in the plans. First I riveted the skins and spar on both sides. This was fairly straightforward, with my 3-inch squeezer yoke reaching 90% of the rivets. I bucked several towards the bottom, and the top three, where access was a little more challenging.

Then I set the middle rivet in the forward skin overlap, and was disappointed to see the skin lifting a little. Looks like the break I put in the left skin was insufficient to pull the edge down completely flush. Here’s a picture of the overlap once I had all the rivets in place. There’s not much I can do about this now, without some major disassembly, or drill, increase the break, then pop rivet the end back together. I don’t think that would be worthwhile, and in any case, I’m going to leave it as-is for now.

I then riveted on the top rib, except for the pop rivets. I’m going to figure out my pop riveting issue before putting any more rivets in. There are pop rivets in the aft 3 holes on each side, and two more attaching the top rib to the spar.

Today I riveted in the rudder horn brace. I was able to squeeze all the rivets. I did run into one issue, when I inadvertently squeezed the wrong length rivet. Rather than a 3-4, I used a 3-3.5. The rivet had set nicely, but I decided to take it out and use the correct length instead. I was able to drill and pop the top off easily, but getting the shank out was a challenge. Mostly it was an access issue, as I had to reach in through a little access hole, and couldn’t get anything to really grip the rivet. Eventually, after a lot of uncomfortable pressure, I was able to pop it out. The hole and dimples remained intact, so I set the correct rivet and carried on. In hindsight, I should have checked the dimensions, and I may have just left the 3.5 in there.

I finished riveting along the bottom rib, and noticed how tight the tolerance is where the skin goes around the protruding rudder horn. The skin isn’t touching, but the slightest lifting of the skin, and it rubs against the horn. It’s perfectly symmetrical, with the same gap on both sides of the rudder.

Next I clecoed and riveted the counterweight rib.

Then it was time to fit the counterweight. With the rivets in position, I had to trim a little off the sides of the front section of the counterweight. After a few iterations it fit snugly in place.

Then I countersunk the attach plate, riveted on the nutplates, and screwed the AN509 bolts into place. Everything fit nicely, and I was pleased with the result.

It’s getting late, so I’m going to stop there for today. Tomorrow I hope to get the top rib done, and time permitting, make a start on the trailing edge.

I riveted the bottom rib together tonight. The rib is formed in two parts, one on each skin, and then riveted together. I started by riveting the aft-most 8 rivets on the right skin, For the aft-most two rivets, there is barely any clearance. Some builders use very thin bucking bars, but it’s easy to make a mess. Given my skill-level, I took the safe option and pop riveted the last two holes. These are counter-sunk pop rivets, and when the airplane gets painted, they will look just like the rest of the rivets.

Then I pop riveted the two parts of the rib together with 11 pop rivets:

These turned out to be a real pain, especially towards the aft end. I fabricated a “wedge tool” to act as a shim, allowing the rivet puller to angle away from the rivet, but still have the rivet head be flush with the surface. Several of the rivet shafts snapped off part way down the shaft, instead of flush with the rivet head. I trimmed them with side cutters, but it is frustrating to have it happen. I don’t know what I’m doing to cause the issue, I’ll have to do some research.

Then I clecoed the rudder horn brace, but didn’t have time to start riveting this tonight. It was a very tight squeeze, but I eventually coaxed it into position.

This afternoon I stopped by a fellow Chapter 338 member’s shop to check out his RV-9 build, and to borrow a 6 foot long bucking bar. It was a super helpful visit, and I picked up some good tips. The bucking bar is to back rivet the rudder trailing edge, once I finally get to that step, hopefully this weekend.

I switched to my other hand pop rivet gun, and it produced better results. I installed the spar and top and bottom ribs, pop riveting the spar to the shear clips. Everything went well, and the results look good.

The next step is to rivet the bottom rib to the right skin and attach strip. Looking at the last two holes, it will be very challenging to get rivets in there. I think I’ll follow the advise of some other builders (and Vans), and pop rivet the back two holes. Once the aircraft is eventually painted, it won’t be noticeable.

With some help from Jen and Joyce, I was able to rivet together the left and right rudder skins tonight. The stiffeners on each skin are tied together with a single pop rivet, and the forward ends are pop riveted to the shear clips. There isn’t a great deal of clearance, so an assistant is needed to hold the skins apart while setting the rivets, from bottom to top. I had an annoying issue with the pop rivet tool where the mandrel was breaking off half way instead of flush with the rivet head, after fully forming the rivet. I had to trim off the mandrel on about half the rivets, which was a real pain. With the lack of clearance, I couldn’t get very flush with the rivet head, but it’s good enough given this will be completely enclosed. I’m going to need to figure out the issue, but it worked ok for tonight.

For the trailing edge, I picked up a tip from my EAA chapter and bought a couple of shelving channels for $5 from Home Depot. They are straight, narrow, and have holes cut that are an almost perfect match for 3/32 clecoes.

I taped the trailing edge, and clecoed one channel to each side of the trailing edge, giving a perfectly straight edge while the glue sets. Hopefully this will help the edge to stay straight while riveting.

After a little practice on some scrap aluminum, I back riveted the stiffeners onto the right rudder skin tonight. It was getting late by the time I finished, so I didn’t try to tackle the left skin. Riveting at midnight isn’t ideal with young kids sleeping in the house. It was a little slow at first as I measured each rivet with digital calipers to calibrate my technique. In the end I was moving quickly and getting a consistent head on each rivet. A couple of rivets ended up driven slightly more than I was aiming for, but are still within tolerance.

This was my setup, with a practice piece on the back riveting plate.

I started with this stiffener, and was happy with the results. I later increased the PSI from 20 to around 22, and the difference was noticeable; fewer hits needed to form the shop head. I’m using a 3x gun, which has a lot of power.

Here are all the stiffeners fastened to the skin:

I realized yesterday that I don’t have a #40 countersink that will work on the trailing edge wedge. Because the countersink is flush with the side of the wedge, but the hole isn’t (it’s perpendicular to the chord of the wedge), I need a countersink with a short and/or tapered pilot. I could probably grind one down, but I only have one. So I went ahead and ordered the special part from Cleveland tools. $20, and will arrive on Monday. That means I can’t finish the rudder until next week, but what’s the rush? I can always start on the Horizontal Stabilizer.

I finished dimpling all of the rudder frame components tonight. It was a straightforward process, except for a couple of spots on the spar where the shop head interfered with the squeezer. If I had oriented the rivets so that the manufactured head was on the forward side, it wouldn’t have been an issue. At the time I set these rivets, I was thinking about putting the manufactured head on the side with the thickest material, but in hindsight I would have set these the other way around, since the shop head is a fraction of on inch too high to get the dimple dies to sit square to the hole. Not a big deal, I was able to use a hand tool to get a reasonable dimple on them.