This page will be dedicated to mistakes I make throughout the build (hopefully a short page:). This will act as a reminder to me, and others who are building, to; follow directions, take your time, quit when you get tired/frustrated, need the right tool for the right job, etc.etc!
October 2015
My first mistake of the build where I actually had to order replacement parts from Van's occurred while working on the stiffeners for the rudder. As seen in the picture below, I felt that I trimmed he stiffener tip just a little too much.
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| I cut the tip of the stiffener a little too much off the tip with the band saw. Probably would have been ok, but just didn't like it. Replacement part ordered and turned out much better. |
November 2015
This mistake occurred while I was countersinking "the middle 9 holes" of the forward spar of the horizontal stab. These are #40 holes are machine countersunk for #3 flush head rivets. I used the countersink cage and bit to accomplish this. Unfortunately, I didn't have any similar spare material to "practice" and get the depth consistent before using on the stab. I was very careful with the first few and checked them carefully after each one. Unfortunately, I continued to countersink the remaining holes without carefully checking each one. After I had finished, I found about 5 holes that I felt were countersunk just a little too much. Additionally, because I mistakenly had in my head that these holes would have skins over them ( which allows a little deeper countersink) , all holes were slightly deep to begin with. My solution was to drill these 9 holes out with a #30 bit and countersink for a #4 rivet. This was an "ok" plan except that I was now a little shy of the required edge distance from the center of the rivet to the edge of the spar. I wasn't happy and ordered a new spar. The replacement cost for a part like this isn't that bad.. it's the shipping cost! Lesson learned.
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| This is the lower flange of the forward spar on the horizontal stab. These center 9 holes are properly countersunk for #3 flush head rivets. |
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| This is the upper flange of the forward spar on the horizontal stab. These center 9 holes were the ones I felt were countersunk too deep so I re-drilled with a #30 bit and countersunk for #4 rivets. Unfortunately, with this fix I was a little shy of recommended edge distance requirements from center of rivet to edge of material. |
December 2015
This mistake (not really a mistake. I just did't like how some parts fit together after riveting), occurred after I used a rivet gun and bucking bar to rivet the horizontal stabilizer ribs to the forward HS spar. After the rib was attached, I noticed there was a small gap (approx. .004) between the rib flange and the front spar. I think this would have been acceptable, but I wanted to try for a tighter fit. I initially had the rivets shop head on the rib flange because I didn't believe I could get a pneumatic squeezer in position to set the rivets. So, I put the rivets manufactured head on the outer part of the spar because it would be easier to access with the rivet gun. Even though I had the parts clecoed together and even clamped, I still end up with the gap. Typically, when able, the manufactured head of the rivet should be on the thiner material ( in this case the rib flange).
So, I went to plan B. I looked thru my friend Mark's selection of yokes for the pneumatic squeezer and found a combination that would work. I was even able to reverse the orientation of the rivets and put the manufactured head on the rib flange. After successfully drilling out the rivets, I replaced and they turned out great. No gap at all. Below I will show the process beginning with rivet removal.
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| Here's the gap between the rib flange and the front spar of the horizontal stab. |
The rear spar for the elevator has several holes that needed machine countersunk to accommodate the trim tab. The plans say to machine countersink these holes for the elevator skins. Typically, when there are skins over countersunk holes, the countersunk holes can just a bit deeper to ensure a nice fit for the dimpled skin. However, there are minimum recommended thickness requirements when machine countersinking. The thickness for the elevator trailing edge spar is right at this minimum thickness. Unfortunately, after countersinking these holes, I felt I may have countersunk these holes just a little too much. I ended up with more of a "knife edge" in the spar flange than I liked. Long story short..I ordered a new rear elevator spar.
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| The spar in the lower part of the picture is the one I felt the holes were over countersunk, so I replaced it. The replacement spar can be seen clecoed in position in the picture, but not yet countersunk. I'm learning the hard way to be more careful with machine countersinking. |
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| Here's the thickness of that rear spar. Section 5 of the plans can be seen underneath the spar. The paragraph to the upper left explains the thickness requirement when machine countersinking. This spar is right at the minimum. |
March 2016
Right elevator re-build.
I was in the final steps of finishing up the right elevator when I did something I wasn't completely satisfied with. It occurred after I installed the six foam ribs in the aft portion of the trailing edge of the elevator. These foam ribs are cut to shape using a template supplied in the plans. The ribs are then installed between the top and bottom skins using proseal. The plans say don't exceed 1/32" inch of proseal when installing the ribs.
Long story short, after I installed the ribs using the proseal, I added weights to the skins per the plans to ensure good contact while the proseal cured. When I removed the weights, I noticed "ridges" in the skins where the ribs were located. These "ridges" also formed "valleys" between the ribs. These "ridges" and "valleys" were very slight and probably not an issue in any way but I just didn't like it.
The cause of this issue was probably a combination of trimming the foam blocks slightly larger than the template and using more than the recommended 1/32" of proseal.
Again, I don't think this issue would have caused any structural or controllability problems later on, but I just didn't like it. I had been very pleased with the quality of workmanship on the elevator up to this point and hated to go out on a bad note.
It was a tough decision, but I decided to order new parts and build another right elevator.
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| This straight edge shows "ridges" and "valleys" created by the oversized foam ribs and probable over use of proseal. |
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| Close up view of one of the "valleys" in the aft portion of the right elevator. There were six of these created by the "builder induced" oversized foam ribs. |
December 2016
Rudder Re-Build.
I ordered the parts for the rudder rebuild just after I finished the first one. There were a few things I wasn't happy with. Looking back, I should have thought about it for a few days before ordering the new parts. Now as a more "experienced" builder I would probably just build on. However, since I had the parts I went ahead with the new one. I think the main reason I wanted to redo was because of a twist in the rudder. When placed on a flat surface, once side of the rudder was completely flat and the other was raised about .5" and would "rock" back and forth. The twist could have been due to several reasons, but I believe it was caused when I incorrectly (prematurely) pulled the final side the adhesive tape off and the the trailing edge stuck together in the incorrect position (one hole off on the trailing edge). I pulled back loose and re-stuck, but think I may have pulled a twist in the process. For the second rudder, I followed the plans exactly regarding using the tape (section 5), and did not pull the final backing from the tape until all other riveting was complete. I think for the first one, I was concerned that if I waited until all other riveting was complete I would not be able to the get to the tape and peel it back. It turned to to be a non issue on the second one and the tape worked perfectly. I had every hole in the trailing edge clecoed and bonded with the tape on only one side. I then started slowly removing the protective backing from the final side slowly and removing/replacing clecos as I went. Worked great and the "new rudder" has only a very slight twist and overall build quality is much better (as it should be with a few more rivets under my belt). I did have a slight setback during the new rudder though. I had just finished priming all the parts and had them inside the shop drying. I had the skins propped up against my work tables. I was cleaning up at the end of the day and happy that things were going pretty smoothly. However, I have a retractable electrical cord hanging from the ceiling and as I went to retract it, the plug end slipped out of my hand as it was retracting and the plug end of the cord slammed into the right side skin and put a solid golf ball size ding right in the middle of the skin. Had to reorder a new skin. Lesson learned..you can never let your guard down with most parts of this project or it WILL bite you.
Additionally, another thing that I did different on the second rudder was to not rivet the lower rib together (using the 11 blind rivets) until I had those aft 9 (not 8 as stated in the plans) rivets set. This way, I was able to lift the skins easily and squeeze those rivets. The first rudder, as seen on my blog, I actually used solid rivets on that lower rib and was not able to "separate" the ribs to get to those aft rivets. Think I set with a very thin piece of metal. I followed plans on the second rudder and it worked out much better.
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