Forum Posts

m.whiting
Oct 24, 2020
In S-21 TECH QUESTIONS
When I assembled my elevator frame today, I found that with the horn in place between the two center ribs, the ribs are not even close to aligning with the spar and splice plate. Anyone else have this problem? I know I can bend the tabs on the ribs, but I don’t want to lengthen them too much and then cause the flanges not to align with the skins. I have checked and double checked and believe I have things assembled correctly.
What’s the best way to correct elevator horn ribs misalignment? content media
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m.whiting
Oct 20, 2020
In S-21 TECH QUESTIONS
The text manual says to drill the elevator trim tab servo mounting holes to #20 (0.161”), but the parts manual shows these being mounted with 8-32 screws which have a thread OD of 0.164” which is larger than a #20 hole. Is this a typo or am I missing something here?
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m.whiting
Sep 23, 2020
In S-21 TECH QUESTIONS
Anyone know why the HS spars are drilled smaller than the skins? By eye I would say the spars appear to be #40 rather than #30 as in the skins. Mine are a little out of alignment and I fear the spar hole will center the drill more so than the skin hole causing the skin to be drilled slightly oblong since the holes in skin and spar are not concentric. Anyone else have this “problem?” Or did the drill center in the skin enough to not allow the spar hole to move it off center? I am hesitant to try to move the skins enough to try to align the holes, if that is even possible. Or did you remove the rib clecoes, drill the spars and then adjust the ribs to match their skin holes?
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m.whiting
Sep 05, 2020
In S-21 TECH QUESTIONS
After pressing the bushings into the hinges, I decided it might be wise to place a bolt in them to hold them in precise alignment for riveting of the VS. I found the 3/16” bolts would not go through the bushings. I checked a bushing in the parts bag and the bolt slipped through that just fine. The manual does not mention a need to ream the bushings after they are pressed in, but it appears that is the case. I tried all four hinges and all were too tight for the AN3 bolt. I am assuming I need to order a #11 or #12 reamer.
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m.whiting
Aug 05, 2020
In GENERAL TOPICS
Any guidance on the size and shape tolerance of rivet holes? While drilling the last hole on the trailing edge of the top rudder rib, I let the bit go into the hole too far when it broke through and it hit the cleco on the opposite side. This tilted the bit and elongated the holes in the rib and skin, but mainly the skin as shown in the picture. This should be a low stress position at the end of the cantilever, so my inclination is to not worry about it and only replace with a larger rivet later if this one starts to “smoke.” However, if this requires replacing the skin and rudder ribs, now is the time to do it. Can someone offer guidance here? Replace skin and ribs? Rivet as is?
What is the ovality tolerance on pulled rivet holes? content media
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m.whiting
Aug 03, 2020
In S-21 TECH QUESTIONS
The text manual, rudder section, says “4. Bolt the rudder horn mount tube to the spar“. Since the holes in the spar are not sized for the bolts, it seems obvious they need to be drilled. However, there is a hold slightly higher up the spar and off-center that is the same size as the bolts, so I know the CNC machine can make a hole that size. Since the machine can make holes that size and did not do so for the rudder horn mount, and there is no mention of drilling these holes, I wanted to confirm that this is the process. I assume there are probably lots of places that need drilled to size where that isn’t called out, but since I have seen it called out in a number of other places, the fact that drilling was not called out in or prior to step 4, I decided I better check since I am just getting started and don’t want to screw up at the outset. 😁
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m.whiting

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