3/30/2021 – 0.9 hours
3/31/2021 – 2.1 hours
Each elevator tip rib gets 2 lead counterweights (4 total) to help balance the control surfaces. The counterweights are attached with bolts through the tip ribs, and the holes in the counterweights need to be final drilled for the bolts. The instructions for drilling the counterweights were a little confusing, so I skipped this step to review the plans more before drilling.
I moved on to shaping the counterweights to allow them to fit inside the rib flanges correctly. The plans describe the material that should be removed from the top and bottom of all the counterweights as well as material on the inside of the inboard counterweights, and I transferred the measurements from the plans to each of the counterweights. Very little material is removed from the tops of the counterweights, so I used my flat file to remove that material. The file did a nice job of quickly and accurately shaping the top of the counterweights. I don't have a band saw, but a hacksaw and some elbow grease did a good job of cutting off the excess lead from the bottom of the counterweight. The inboard counterweight has an additional section to remove from the inside face. A bandsaw would be the best option, but the flat file also got the job done with admittedly more time and effort.
[Ruler, Fine-Tip Sharpie, Flat File, Hacksaw]
4/2/2021 – 3.4 hours
I finished trimming the counterweights for the right elevator. I tried to use the Dremel and metal cutting wheel to speed things up, but it wasn't very effective and I got better results with the hacksaw and file. Eventually I got the counterweights trimmed to fit inside the elevator tip ribs.
As I trimmed the first counterweight, I noticed that the drawings in the plans very clearly indicate that the inside surfaces of all the counterweights are supposed to be the faces with the ridge down the middle. The ridge is filed off of the inboard counterweight, but left intact on the outboard counterweight. It eventually occurred to me that to make that setup work, the cuts on the outboard counterweight have to be opposite (mirror image) of the inboard counterweight. If you don't do that, one of the counterweights will be backwards and will not fit in the rib. As an alternative, the hole locations of the counterweights are symmetrical after they are trimmed (the holes are closer to the top before trimming), so you could also cut all of the counterweights the same way as shown in the plans and then flip one of each pair upside down. The end result should be the same.
The final step was to bolt the counterweights into the ribs. I'm still getting used to my inch-pound torque wrench, so it took me some time to figure out what the drag on the bolts was to calculate the final torque. The final torque for each AN3-13A bolt and MS21042-3 Self Locking Nut is 28 in-lbs plus the drag on the bolt. I ended up adding 9 to 15 in-lbs to the final torque since the drag on each bolt was a little different.
[Torque Wrench (In-Lb), Torque Paint, Flat File, Hacksaw, Sharpie]