Week 4: Empennage

Day One: Frozen Fingers and Counterweight Prep

Holy CaMoly... IT IS COLD! Despite our heating setup doing its best, it felt like winter had parked itself inside the hangar. We soldiered on, bundled up but determined.

We went into the hangar thinking we would start riveting today. However, we first needed to finish the machine countersinking we didn’t get to last week. Just as we thought we were ready to start riveting, we realized there was another step: preparing the counterweight to be mounted on the rudder.

The rudder is the first part of the empennage we’ve built to use a counterweight. Why is this counterweight important? It balances aerodynamic forces acting on the rudder, helps stabilize it, and prevents potentially dangerous vibrations at high speeds.

We noticed that our current pneumatic squeezer setup doesn’t allow enough versatility to complete most rivets. Sam plans to research alternatives. Otherwise, we’ll use the rivet gun. We’ve become a good team with riveting, so this will save us money and keep us moving forward but still worth looking into other options.

Day Two: The Waiting Game: Tools, Mail, and Mystery Solving

We were expecting our nose ribs to finally arrive today! With the frigid weather, we decided to stay home and wait for the mail so we could bring the ribs with us to the hangar. While waiting, I tackled chores around the house, and Sam dove into research mode.

Sam discovered a tool manufacturer, Clemson Aeronautics, whose yokes have a thicker and therefore sturdier design to prevent flexing under squeeze pressure. After a great conversation with the owner of the company, we ordered two new yokes: a longeron yoke and a 4-inch no-hole yoke. The longeron yoke is designed for reaching over angles, hinges, and obstructions. The no-hole yoke, with its tapered nose, allows access to tight spaces and lets us set rivets right against the yoke’s edge.

Additionally, during his research, Sam found reports from other builders about issues with the rib brace (R-710). Some builders discovered that when they match-drilled the part with the skin, the drilled holes didn’t meet the required edge distance. Curious, we decided to check if we had the same problem.

We drove to the hanger to pick up the rib brace in order to check the edge distance measurements at home. When we got back home, our package with the missing ribs had arrived!

So.....

Good News

We finally received the missing nose ribs for the horizontal stabilizer.

Bad News

Our rib brace had the same edge distance issue other builders reported. Although Van’s Aircraft indicated that this particular edge distance wasn’t critical due to low pressure on the part, we decided to reorder it for peace of mind. Sam plans on trimming it carefully until it just fits to ensure there is plenty of material for the edge distance requirement.

Day Three: Rudder Woes and Horizontal Stabilizer Wins

With yesterday’s discoveries, we couldn’t make much progress on the rudder, which was disappointing. However, we riveted the top two reinforcement plates and nut plates to the rudder spar. Managing the rivets around the spar lip with our standard 3-inch squeezer yoke was a challenge. Sam kept mentioning how much easier this would be with our new yokes from Clemson Aeronautics. We’re eagerly awaiting their arrival!

Luckily, we had the nose ribs for the horizontal stabilizer to work on. We pulled out the partially finished horizontal stabilizer frame that had been sitting in a corner of the hanger waiting on the nose ribs. We drilled the brackets Sam had fabricated last week, and primed them. Then we bent the nose ribs to the correct angles and fluted them to ensure the proper shape. After clecoing them into place, we match-drilled them to the front spar of the horizontal stabilizer. The skeleton of the horizontal stabilizer is now complete.

Day Four: Deburring Marathon and Cradle Triumphs

Today was our long shop day, and we aimed to make significant progress on the horizontal stabilizer. We started by taking everything apart to deburr the parts we’d match-drilled so far. Why is deburring so important? Burrs at the edges of drilled holes can keep metal sheets apart, loosen rivets over time, and even cause stress cracks. While this process can feel repetitive, it’s a crucial step to ensure a strong and safe build.

While I taped and prepped the cradle jig for the horizontal stabilizer, Sam smoothed the edges and lightening holes in the spars. Then we reassembled everything to match-drill the skin to the skeleton, one half at a time. Seeing the assembly in the cradle was exciting. The cradle is an invaluable tool, holding the skin securely and making the process much easier. We ended the day pleased with our progress, ready for another round of deburring tomorrow.

Day Five: New Tools, New Ideas, and Late-Night Progress

Today was supposed to be a short day. Sam had an eye-doctor appointment, and I caught up with a friend. By lunchtime, we were back home, anxiously awaiting the mail. Our new yokes from Clemson Aeronautics arrived quickly—only three days! We felt like kids on Christmas morning unboxing them.

The new yokes exceeded our expectations! They’re sturdier and higher quality than our current setup. We immediately switched out the pneumatic squeezer to the Clemson longeron yoke. Sam had me test it, and it was clear how much easier it will make working around spar lips. Unfortunately, we couldn’t use it today, but it’ll be put to good use next week!

We spent the rest of the day dismantling the horizontal stabilizer halves to deburr the skins and ribs we final drilled yesterday. We also dimpled the ribs using the pneumatic squeezer. Sam had to hold it sturdy on the workbench while I went hole-by-hole. We also countersunk the spar, and prepared for riveting. Though we worked late, we’re eager to start riveting early next week.

At dinner, Sam brainstormed ways to hold the pneumatic squeezer upright on the workbench for easier dimpling. He messaged Mr. Hassan, the owner at Clemson Aeronautics, explaining his idea. Although Clemson doesn’t have exactly what we envisioned, Mr. Hassan offered to send us a workbench-mounted yoke made specifically for what we are doing. We’re excited to try it out when it arrives next week! It should prove very helpful in many of the dimpling and riveting operations.

This week taught us the importance of perseverance, preparation, and collaboration. We can’t wait to tackle next week’s challenges with our new tools in hand!

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