Poor Anton Flettner must be doing pirouettes in his coffin over my ham-handed building of his eponymous anti-servo tabs. Last night, after buttoning them up for the final riveting scheduled for tonight, I was perusing a builder's log on the web and found that the guy had run into a problem when trying to install the tabs onto the stabilator. The problem was that the fit where they meet is very tight and he had gotten a gap between the control horn and the rib when he riveted them together. I thought that it might be a good idea to head back down to the shop and inspect mine.
What I found was that the right side was tight and flush with the edge of the skin, but the left side had enough of a gap that it was slightly outside of the edge of the skin. Rather than wait to find out whether it was going to cause a problem later after everything was all riveted shut, I decided to drill out the five rivets and re-do it while it was still easily accessible. Drilling the rivets out was easy-peasy, now that I've had a bit of practice at it, but when I clecoed the control horn back into place I saw that there were a couple of problems. One was the issue that caused the gap to form in the first place, while the second was caused due to the riveting problem.
The first was that the edge of the skin was not quite flush with the outside of the rib. This caused the control horn to not sit flat against the side of the rib. When I squeezed the rivet, this gap allowed the rivet to fatten up just a little bit between the two surfaces. That fat part of rivet in the gap caused the second problem: the hole in the rib got a reverse dimple in it. In other words, it was now an outie, not an inney. That prevented the horn from sitting flush against the rib and virtually guaranteed that I'd get the same result if I just tried to rivet the part back in place without some form of corrective action.
The first thing to do was to file down the skin to that it was flush with the rib. That didn't take much filing at all - it was a very small overhang, but just enough to cause the potential fitting problem. The second was to fix the outie. I did that by putting a very slight dimple in it with the dimple/die set that I used to dimple the holes in the vertical stab front fairing.
The control horn is now clecoed back into place and sitting tight against the rib - no more gap. I'll rivet it tonight just before going to the hangar for the final skin riveting.
Showing posts with label Page 08-03. Show all posts
Showing posts with label Page 08-03. Show all posts
Friday, November 6, 2009
Thursday, November 5, 2009
Almost done with the Flettners
I had a long-ish day at work today and by the time I fought my way across town through rush hour traffic, relaxed for a half hour while the Co-owner prepared dinner, and wolfed down my share (and a little more) of same, there wasn't much time or energy left for a long session on the Schmetterling production floor.
Perhaps my mental fatigue had carried over from work. How bad was it at work? Well, I commented a piece of programming code thusly:
// I'd be disappointed and more than a little perplexed if this ever happened
Someday my replacement will look at that with the same level of confusion and WhatDaHellism that I looked at this tonight:
Follow me as I try to do the math:
"Remove the hinge pin from one AN257-P3X6'"
Ok, after having done so I have two pieces of AN257-P3X6', right?
Then there's some blah blah blah, followed by an all-caps (that must means it's important!) "MAKE FOUR HINGE HALVES"
Huh? Out of what, exactly? The two pieces I have now?? Am I supposed to cut them each in half? Well, no. I'm supposed to trim them to 32 1/2 inches. I gave up and figured I'd worry about the other two hinge halves later. I won't need them until section 11. In the meantime, the tin snips cut the two halves off at the 32 1/2 inch mark quite easily:
The second half of the page provided detailed instructions and drawings regarding the use of the HS-1223 drill guide. What it didn't provide was any hint at all regrading where to find the HS-1223 drill guide. After a prolonged search, I found it in one of the little bags. That was after finally resorting to pulling out the inventory sheets and looking at them a half dozen times before finding the location of the HS-1223 drill guide at the very bottom of the last page.
The HS-1223 drill guide is supposed to fit between the hoops of the hinge and get clamped into place. Unfortunately, it's a very tight fit. So tight, in fact, that trying to push it into place bent of the hoops on the hinge, a sin that I will pay dearly for in section 11. I finally threw caution to the wind and filed off a nanometer of one of the edges of the HS-1223 drill guide. Things went swimmingly after that:
The HS-1223 dill guide had to be unclamped and moved to the next area of the tab for drilling. It took awhile. The second tab went much faster and easier, primarily because I knew exactly where the HS-1223 drill guide was.
Both parts are clecoed up and ready for transport up to the hangar for riveting, a job that I have (wisely, in my opinion) decided to defer until tomorrow night.
Perhaps my mental fatigue had carried over from work. How bad was it at work? Well, I commented a piece of programming code thusly:
// I'd be disappointed and more than a little perplexed if this ever happened
Someday my replacement will look at that with the same level of confusion and WhatDaHellism that I looked at this tonight:
Follow me as I try to do the math:
"Remove the hinge pin from one AN257-P3X6'"
Ok, after having done so I have two pieces of AN257-P3X6', right?
Then there's some blah blah blah, followed by an all-caps (that must means it's important!) "MAKE FOUR HINGE HALVES"
Huh? Out of what, exactly? The two pieces I have now?? Am I supposed to cut them each in half? Well, no. I'm supposed to trim them to 32 1/2 inches. I gave up and figured I'd worry about the other two hinge halves later. I won't need them until section 11. In the meantime, the tin snips cut the two halves off at the 32 1/2 inch mark quite easily:
The second half of the page provided detailed instructions and drawings regarding the use of the HS-1223 drill guide. What it didn't provide was any hint at all regrading where to find the HS-1223 drill guide. After a prolonged search, I found it in one of the little bags. That was after finally resorting to pulling out the inventory sheets and looking at them a half dozen times before finding the location of the HS-1223 drill guide at the very bottom of the last page.
The HS-1223 drill guide is supposed to fit between the hoops of the hinge and get clamped into place. Unfortunately, it's a very tight fit. So tight, in fact, that trying to push it into place bent of the hoops on the hinge, a sin that I will pay dearly for in section 11. I finally threw caution to the wind and filed off a nanometer of one of the edges of the HS-1223 drill guide. Things went swimmingly after that:
The HS-1223 dill guide had to be unclamped and moved to the next area of the tab for drilling. It took awhile. The second tab went much faster and easier, primarily because I knew exactly where the HS-1223 drill guide was.
Both parts are clecoed up and ready for transport up to the hangar for riveting, a job that I have (wisely, in my opinion) decided to defer until tomorrow night.
Wednesday, November 4, 2009
More Flettner work: yet one more job saved or created
After gracing my family with my cheerful, gregarious presence for the last one and a half evenings, it was back to work on the Flettner tab tonight. Having resolved the mystery of the too-small holes in the rib flanges to my satisfaction, I went ahead and drilled them out with the #30 to make them big enough to take a blind rivet. Having done that, they all had to be removed for deburring.
Deburring the inside of the tiny little rib flanges can't be done with the normal power-driven deburr bit. Rather, I have to use this tool:
I don't like the looks of it. It looks too much like a dental tool or an instrument of torture. Granted, the distinction between the two is almost vanishingly subtle. With this tool, though, I can reach through the top of the hole and deburr the other side.
At this point, Van's says to rivet the top of the skin to the top of the ribs. If you read ahead, the step after that has you riveting in the control horn. Some folks on the Vans Air Force site said that it might be easier to rivet the control horn in place and then rivet down the top skin. I clecoed everything together and practiced both methods and found that the Van's method worked best for me. Differences of technique such as this with different builders more often than not come down to slight differences in the tools being used. With the rivet squeezer and rivet pullers that I have, the Van's method provided easier access, although I did end up bending one of the rib flanges. That was easy to bend back into shape, though. I went ahead and riveted the top skin to the ribs:
Here's the "raw" control horn:
It gets riveted in with solid flush rivets, so it needs to be countersunk:
There's nothing prettier than a countersunk hole, in my opinion. The machined look of it just makes it look more sophisticated somehow.
Here it is clecoed into place:
And here I am reaching back inside there to squeeze the rivets:
All done:
Your eyes didn't deceive you in the pictures if you noticed that one of the pictures shows a control horn labeled 'L' and one laebled 'R': there are two tabs, actually, a left and a right.
Here they are in their relative positions as they will be installed on the airplane:
Tomorrow night I will fabricate and rivet on the hinge strip that will attach the Flettner tabs to the horizontal stabilator. After that it's a simple matter of riveting the bottom skin to the ribs.
Deburring the inside of the tiny little rib flanges can't be done with the normal power-driven deburr bit. Rather, I have to use this tool:
I don't like the looks of it. It looks too much like a dental tool or an instrument of torture. Granted, the distinction between the two is almost vanishingly subtle. With this tool, though, I can reach through the top of the hole and deburr the other side.
At this point, Van's says to rivet the top of the skin to the top of the ribs. If you read ahead, the step after that has you riveting in the control horn. Some folks on the Vans Air Force site said that it might be easier to rivet the control horn in place and then rivet down the top skin. I clecoed everything together and practiced both methods and found that the Van's method worked best for me. Differences of technique such as this with different builders more often than not come down to slight differences in the tools being used. With the rivet squeezer and rivet pullers that I have, the Van's method provided easier access, although I did end up bending one of the rib flanges. That was easy to bend back into shape, though. I went ahead and riveted the top skin to the ribs:
Here's the "raw" control horn:
It gets riveted in with solid flush rivets, so it needs to be countersunk:
There's nothing prettier than a countersunk hole, in my opinion. The machined look of it just makes it look more sophisticated somehow.
Here it is clecoed into place:
And here I am reaching back inside there to squeeze the rivets:
All done:
Your eyes didn't deceive you in the pictures if you noticed that one of the pictures shows a control horn labeled 'L' and one laebled 'R': there are two tabs, actually, a left and a right.
Here they are in their relative positions as they will be installed on the airplane:
Tomorrow night I will fabricate and rivet on the hinge strip that will attach the Flettner tabs to the horizontal stabilator. After that it's a simple matter of riveting the bottom skin to the ribs.
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