A few weeks ago I discovered very small cracks in the skin of the LH elevator around 4 of the rivet heads. I noticed that the skin panel in the area would oil can and pop in and out. Originally thought it was just cracks in the paint as we had sprayed the rivet lines on the airplane pretty heavily to get good coverage 9 years ago during construction. The airplane has been flying for 8 years and has 620 hours with no aerobatics. I built the plane from a quickbuild kit (therefore I did not build the elevators) and it has the 0.016 skins on the tail surfaces.
I removed the paint, which was pretty slow, as I only wanted to use chemicals to not possibly add scratches with sandpaper that may obscure any small cracks. The paint is PPG Concept acrylic urethane so used a MEK soaked q-tip covered with aluminum tape to fumigate and soften the paint. What I saw was very faint cracks around the front side of four of the rivets.
Next issue was how to stop drill the cracks that were so close to the rivet heads and also not go through the E-606 spar and trim tab hinge. I removed the rivets, used dye penetrant (MagnaFlux brand) around the areas and marked the ends of the cracks. I used a #50 drill bit to stop drill with a 0.063 piece of AL between the skin and spar to make sure I did not drill into the spar.
I made a doubler plate from 0.025 AL and drilled #30 holes for cherry max pulled rivets at AC-43 recommended spacing and patterns.
Wet installed the doubler with very thin coat of proseal. Checked elevator balance to make sure it was still properly balanced. Also noted that there is no longer any oil canning in any of the skin panels as before. It?s ugly but should be plenty robust.
Trading emails with Ken at Vans, he indicated this fix (actually a simpler version that did not extend outbd of the trim tab) looked acceptable and agreed that the cracking could be due to the skin fatiguing from it oil canning locally.
I removed the paint, which was pretty slow, as I only wanted to use chemicals to not possibly add scratches with sandpaper that may obscure any small cracks. The paint is PPG Concept acrylic urethane so used a MEK soaked q-tip covered with aluminum tape to fumigate and soften the paint. What I saw was very faint cracks around the front side of four of the rivets.
Next issue was how to stop drill the cracks that were so close to the rivet heads and also not go through the E-606 spar and trim tab hinge. I removed the rivets, used dye penetrant (MagnaFlux brand) around the areas and marked the ends of the cracks. I used a #50 drill bit to stop drill with a 0.063 piece of AL between the skin and spar to make sure I did not drill into the spar.
I made a doubler plate from 0.025 AL and drilled #30 holes for cherry max pulled rivets at AC-43 recommended spacing and patterns.
Wet installed the doubler with very thin coat of proseal. Checked elevator balance to make sure it was still properly balanced. Also noted that there is no longer any oil canning in any of the skin panels as before. It?s ugly but should be plenty robust.
Trading emails with Ken at Vans, he indicated this fix (actually a simpler version that did not extend outbd of the trim tab) looked acceptable and agreed that the cracking could be due to the skin fatiguing from it oil canning locally.
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