2/27/2021 – 7.8 hours
2/28/2021 – 0.5 hours
This section marks the transition to the final assembly steps for the elevator, so it is time to prime the parts. My previous priming results have been OK, but not great; so I tweaked my process for this batch of parts to see if I can improve the results. Specifically, I hope to get the primer to adhere to the aluminum better. I switched from scrubbing the alclad coating with a grey scotch brite pad and Bon Ami followed by a water rinse and dry to scruffing (scruff ad scrub) with a maroon scotch brite pad and Dawn detergent followed by a water rinse and a wipedown with a degreaser. The change should give the metal more tooth for the primer to adhere to while removing more of the skin contaminants that a water rinse alone didn't clean. The process is also a little easier since I don't need to wear gloves until the final degreaser step.
[Maroon Scotch Brite Pad, Dawn Dish Detergent, Dupli-Color Degreaser, Dupli-Color Self-Etching Automotive Primer (Green – Rattle Can)]
2/28/2021
Today was a low point in the build. It started well with good initial results from my new priming process, but went downhill from there. The first assembly step for the trim tab was to rivet the trim tab spar and control horns to the bottom trim tab skin. The normal progression for riveting (from least risky to good luck with that!) is back riveting, squeezing, and bucking, This looked like a pretty standard back-riveting job. I set 20 rivets, and only 5 were acceptable. I found gaps between the skin and the spar, rivets that appeared to be very flat (i.e. mostly set beneath the dimple in the spar, and bent rivet heads (not sure how that's even possible with back riveting. After a brief pause, I decided to drill out the 14 bad rivets and try again. That also went badly because I didn't set the piece up to drill vertically, and I ended up with at least three holes that are beyond repair. I indulged in a brief moment of despair, and went inside to order a new bottom trim tab skin and rudder. I then decided to call it a day and approach the next task fresh. I need to do a post-mortem to see what went wrong with the riveting, so I don't have a repeat on other more expensive parts in the future.
[3x Rivet Gun, Back-Rivet Set, Back-Rivet Plate, Spring-loaded Punch Pin, #40 Drill, #43 Drill, Credit Card]
3/18/2021 – 3.2 hours
The new trim tab bottom skin and spar arrived about a week ago. Time now for the trim tab reset to begin! I went back to the beginning of the trim tab work (Page 09-03) to prep the bottom skin and spar. I started by trimming the pre-bent close out tabs on the bottom trim tab skin with the Dremel and metal cutting disk, completing the close out tabs with the flat file, and deburring the cut edge. I took this opportunity to debur all of the trim tab bottom skin and spar holes and edges.
The next trim tab preparation step was to dimple the holes in the close-out tabs for flush-set rivets. After dimpling the 3 holes in each close-out tab, I cleco'd the top and bottom skins and the spar together. I also taped foam ribs inside the assembly near the close out tabs to provide a little extra support and shape to final drill the close-out tab holes. After drilling the holes, I disassembled the trim tab and marked the locations of the trailing edge wedge and foam ribs. I finished this session by putting a slight break in the trailing edge of the bottom skin with the edge forming tool.
[Straight Edge, Fine-tip Sharpie, Dremel with 1 1/2" Metal Cutting Wheel, Deburring Tools, Maroon Scotch Brite Pad, C-Frame Dimpler, 3/32” Reduced Diameter Dimple Dies, #33 Drill]
3/19/2021 – 3.6 hours
Preparing the trim tab bottom skin and spar continued with countersinking the holes on the top flange of the spar. It was nice to have the top skin already dimpled and primed to test the countersink depth and ensure everything would fit tightly together. I transitioned to masking around the areas on the trim tab spar and bottom skin where the foam ribs and trailing edge wedge would end up. I scuffed the exposed areas with 150 grit Aluminum Oxide sandpaper, and cleaned the sanding residue with acetone. I then reversed the masking to prepare the parts for cleaning prior to priming. I ended this session by dimpling the spar and bottom skin. A quick test with the parts showed that the spar and skin should fit tightly together, so hopefully I can avoid the back-riveting issues I had the first time around. I also decided to save the dimpling until after I had cleaned up the parts for primer. The parts are much easier to scrub when the surface is smooth rather than dimpled. Everything looks great at this point and I don't expect any problems with priming or assembly!
[Microstop Countersink Cage, 3/32” Countersink Cutter, Masking Tape, 150 Grit Aluminum Oxide Sandpaper, Acetone, Maroon Scotch Brite Pad, Dawn Dish Detergent, 22” C-Frame, Reduced Diameter 3/32” Dimple Dies]
3/21/2021 – 3.2 hours
The trim tab is back to the same point as it was on Feb 28th when the back-riveting went terribly wrong. I corrected those mistakes, and back-riveting the spar to the lower skin went much better this time around. After attaching the spar and control horns to the trim tab lower skin, I dove into a new skill – applying tank sealant to glue the foam ribs into place. I read lots of builder logs that talked about how messy and smelly the tank sealant is to work with. It definitely isn't the best smelling stuff, but the smell dissipates quickly in a well-ventilated area. I also did my best to control the messiness by covering the work areas, setting up everything needed for the job before mixing the sealant, and using several pairs of nitrile gloves. The sealant itself isn't hard to work with. The cartridge I had fits into a standard caulking gun, and it spreads easily with a popsicle stick. The sealant is about the consistency of cake icing, so if you can spread peanut butter, you can spread sealant on a foam rib. Work with the sealant goes quickly since time is short before the sealant becomes unworkable. After setting the foam ribs in place, I taped the trailing edge wedge in place, dropped the upper skin in place, and cleco'd everything together. I used the pneumatic squeezer to attach the upper skin to the spar, and finished the work session by putting the trim tab on a flat surface with weighted boards on top to help the sealant attach and cure.
[3x Rivet Gun, Back-Rivet Set, Back-Rivet Plate, Flamemaster CS-3204 B-2 Sealant 3.5 oz Package, Popsicle Sticks, Disposable Nitrile Gloves, Caulk Gun, Pneumatic Squeezer, Small Diameter 1/4" and 1/8” Flat Sets]
3/26/2021 – 1.8 hours
The trim tab has taken a lot longer than expected due to some setbacks and curing time for the foam ribs and trailing edge wedge adhesive. This work session started by double-flush riveting the trailing edge. I used a straight board to clamp the trim tab to the bench with the trailing edge hanging over the edge for access to rivet. I also used cleco clamps on each side of the hole that I was riveting to help hold the skins tight to the wedge. I set the double flush rivets with the pneumatic squeezer and the special trailing edge squeezer sets for this wedge. I started in the middle of the trailing edge, and then worked left and right on every fifth hole and then splitting the difference from the center out until all the holes were riveted. The double flush rivets came out really nicely, and the trailing edge is very straight. Hopefully I can replicate those results on the rest of the elevator trailing edges! The finishing touch on the trim tab was three flush blind rivets in the close out tabs.
[Pneumatic Squeezer, “Safety Pin” Trailing Edge Double Flush Squeezer Dies, 1/2" Cleco Clamps, Blind (Pop) Rivet Puller, Bench Clamps]