In my quest to fabricate the modification to leading edges, all my research into the method that I should use to safely complete the modification has led me down a path that will require me to be able to bend several pieces of .032inch thick alclad aluminum into a sort of combined leading edge and joint plate part. Since the part that I have to make must be slightly smaller than the shape of the leading edge skin, I don't think I can use a section of the already-formed leading edge skin.
Another reason I can't simply just cut out a section of of the existing leading edge skin is that the parts will not fit back together snugly due to the amount of material that is lost from the actual cut, plus any deburring and edge smoothing that may be needed. The only way to get a part that will fit correctly is to cut one to the exact size from a different piece of metal. Without going into more gory details that can't be clearly understood unless you "see" what I am talking about, I'll just finish this section by saying that there area number of different reasons why simply cutting a section out of an existing skin just won't work for what I am trying to do.
I have to create a sub-skin structure that will adequately support and provide sufficient attach points for the outer skin assemblies for an area in between two of the leading edge ribs that are about 9.5 inches apart. I guess the best way to think of it would be a greatly modified version of the original W-423 Joint Plate strip that is used to attach the outboard fuel tank skin to the inboard leading edge skin. The original part provided for the joint plate is just a strip of .032 alclad aluminum about 1.5 inches wide by 36 inches long. The part thatI will need to fabricate will be a large extension of that joint plate that will resemble a letter H that is curved around the 2 leading edge ribs. This will provide the mounting platform for the outer skin assembly.
The only challenge that I have is how to form the bend for the leading edge. I do not know the exact radius that Vans uses, nor the actual procedure that they use to form the leading edge skins. While doing some research I stumbled upon some information that came from builders of the Sonex kits. It turns out that they provide a scratch build kit from plans that requires the builder to fabricate just about everything from the spars to the ribs to the skins, etc. This includes the Leading edge skins for the Sonex wings.
Apparently someone came up with a rather ingenious way to vacuum form the leading edge for the entire wing by using some 4 mil standard landscape plastic, masking tape, an 8 foot long, 2 inch diameter black schedule 40 gas pipe, some car exhaust clamps, and a standard sized shop vac. Here is a link to one of many different you tube videos I found that shows the entire process. It works quite well.
Vacuum form leading edge skin
I plan on using a similar method to bend the parts that I will need. Luckily I only have to work with a 1 foot wide piece of metal so as soon as I figure out the right diameter pipe to use I will give this a try.
Thursday, January 23, 2014
Monday, January 20, 2014
Fixing my Nutplate Faux Pas
Well it took me a while but I finally got around to "fixing" my nut plate mess that I made per my previous post. My spar looks like crap with all the primer spots all over the place, but it is what it is.....
I drilled out two of the three nut plates and replaced them. Turns out I had to replace one of them twice because I still could not set the rivet properly. What a pain. The process was as follows:
I used the Gorilla tape to cover the vulnerable areas. I should have used it from the beginning,but oh well... I covers the areas with strips of tape, and then I also decided to switch bucking bars. I reasoned that the thin man bar has a longer moment when you use the end of that one as opposed to the fat man bar, which concentrates all of its weight closer to the surface being riveted. IOW it is easier to handle in tight spaces when using the small end of the bar compared to the smaller but longer thin man bar. I did not use it initially because I was afraid that the bar was too big for the area surrounding these nut plates. Turns out I could adequately get it into position for all but one of the rivets.
The other thing that I did differently was to be very sparing with the gun. NO quick squirts of the trigger this time. Instead I used very short taps to set the rivets in place, and then more short taps to slowly set the rivets the rest of the way. I also paid much closer attention to the placement and control of the bucking bar, being very careful not to let it slip or cant over to one side. I did have to use the corner of one of the bars for one of the rivets. I spent a long time working the positioning of the bar in my hand with my fingers in key positions to prevent the bar from sliding off and hitting the backer plate of the spar.
I set the rivets and new nut plates first, then I proceed to sand out the small gouges and scratches to the backer plate of the spar web, followed by some more 7220 primer applied with a Q tip. I am now satisfied with these three nut plates.
Here you can see the tape still in position with the new nut plates riveted on. I also wanted to share a little tip about close quarter clamping techniques. Note the empty cardboard tape roll that I slid down over the jack screw of the C clamp holding the wood block in position against the spar. I realized that this was just another accident waiting to happen. The threads from the clamp were so close to the spar web that I knew that the tapping from the rivet gun might cause more damage if I did not somehow find a way to protect the spar. So in a brief moment of creativity I came up with the idea to use the empty tape roll as a barrier between the clamp threads and the spar web. You just never know what you might end up using to build an airplane!
Next I start riveting ribs to the spar.
I drilled out two of the three nut plates and replaced them. Turns out I had to replace one of them twice because I still could not set the rivet properly. What a pain. The process was as follows:
I used the Gorilla tape to cover the vulnerable areas. I should have used it from the beginning,but oh well... I covers the areas with strips of tape, and then I also decided to switch bucking bars. I reasoned that the thin man bar has a longer moment when you use the end of that one as opposed to the fat man bar, which concentrates all of its weight closer to the surface being riveted. IOW it is easier to handle in tight spaces when using the small end of the bar compared to the smaller but longer thin man bar. I did not use it initially because I was afraid that the bar was too big for the area surrounding these nut plates. Turns out I could adequately get it into position for all but one of the rivets.
The other thing that I did differently was to be very sparing with the gun. NO quick squirts of the trigger this time. Instead I used very short taps to set the rivets in place, and then more short taps to slowly set the rivets the rest of the way. I also paid much closer attention to the placement and control of the bucking bar, being very careful not to let it slip or cant over to one side. I did have to use the corner of one of the bars for one of the rivets. I spent a long time working the positioning of the bar in my hand with my fingers in key positions to prevent the bar from sliding off and hitting the backer plate of the spar.
I set the rivets and new nut plates first, then I proceed to sand out the small gouges and scratches to the backer plate of the spar web, followed by some more 7220 primer applied with a Q tip. I am now satisfied with these three nut plates.
Here you can see the tape still in position with the new nut plates riveted on. I also wanted to share a little tip about close quarter clamping techniques. Note the empty cardboard tape roll that I slid down over the jack screw of the C clamp holding the wood block in position against the spar. I realized that this was just another accident waiting to happen. The threads from the clamp were so close to the spar web that I knew that the tapping from the rivet gun might cause more damage if I did not somehow find a way to protect the spar. So in a brief moment of creativity I came up with the idea to use the empty tape roll as a barrier between the clamp threads and the spar web. You just never know what you might end up using to build an airplane!
Next I start riveting ribs to the spar.
Friday, January 3, 2014
Obviously I Have Not Rivited Anything in a While
Today was rivet day for the three inboard tank attach nut plates before I start riveting the ribs in place on the main wing spar. I thought this would be a good way to practice setting some rivets after a long dry spell, and I was right - it was good "practice," but unfortunately the practice did not make "perfect."
It all started as usually does - with a lot of research and planning. I spent time reviewing Dan Checkoways info when he did both of his wings. I thought I had all the info I needed by reviewing his right wing posts, but I found additional very useful information in his left wing posts which came later.
The reason why it is good to go ahead and set the nut plates for this inbard tank bracket is that you can use them to secure the inboard Z bracket instead of a nut and bolt combination which he used to help properly position all of the Z brackets for the fuel tanks. I'll get more into all that in the months to come, but for now I will simply say that I will use Dan's method to properly position the Z brackets since Vans instructions for this definitely do suck.
The other reason you set these nut plates now is that it is easier to get to them without the ribs getting in the way. The holes for the nut plates are predrilled and just a bit undersized as usual. To drill them to the final size for the nut plate rivets as well as for the bolts, you use a #13 and #40 drill bit, and a #12 reamer. I ran the number 13 drill bit and the #12 reamer through the bolt holes, then I attached the nut plates with clecos drill those with the number 40 drill bit. I checked the fit for the bolts and they were spot on perfect.
Here are the first set of tools used. I have the drill bit and the reamer in two separate drills to make the process go a bit faster:
Next are the nutplates clecoed into position with one cleco. This is the way that they are positioned. Pay attention to the ones on the top and the bottom that are angled to account for the edges of the lightening hole cut out of the doubler plate of the wing spar. These presented several challenges.
I added another 2x4 piece of wood to the spar flange at the root and secured with a large C clamp to provide some additional resistance and rigidity to the wing spar which is critical during riveting. Before it is all said and done I will be using some beefy 4x4s and more clamps when I start riveting the ribs in place:
And here is shot of my work bench after leveling the front edge of both of them and placing two drill boards on top. I am finding that the bar clamps do tend to get in the way and if I am not careful I will snag one and maybe rip the hole spar onto the floor. C clamps and blocks of wood would probably work better for this, but I will stick with what I have for now:
A few more preparation items were to apply painters and masking tape to the spar bars and spar doubler areas. Turns out I probably should have used duct tape but I was afraid I might not be able to remove it very easily so I opted for something else. That may have been a mistake.
I also needed to run a test for my #40 countersink to make sure it is set to the correct depth. I already had the bit in one of countersinks but was not sure of the depth was correct. Turns out it was a good thing I ran some tests because for whatever the reason it was set way too deep. That could've potentially ruined the entire wing spar.
Here is the setup for the tests using my scrap 1/8 inch thick piece of aluminum from my empennage trim bundle:
And here are the three test holes. The one on the top was the original setting - note the rivet head sitting way to far down in the countersink. The other two were spot-on perfect:
Here are some of the tools for countersinking the rivet holes and the tape I used to protect various parts of the wing spar:
Now for the countersinking experience. As with most things about this build - some things are easy, and some things are less easy. I was able to use the Microstop countersink tool for all the rivet holes except for one - the one closest to the top side spar bar. the diameter of the cage was too big for the pilot to be able to fit inside the #40 drilled hole on the top side.I thought this was strange since I was able to use it on the bottom-most hole with no problem. So this meant that the rivet holes must be closer to the top spar bar than the bottom spar bar. Anyway,I had to figure out how to countersink that last rivet hole. I ended up doing it by hand using the debur bit and the countersink bit. I had to be careful to make the countersink as symetrical as possible, and it turned out pretty good.
After all the countersinks were done, I sprayed a cotton swap with 7220 primer and used that to prime all the bolt and rivet holes. When the primer was dry after a couple of minutes I taped up my flat rivet set that I have been using in the rivet gun, and used the thin man bucking bar to buck all the rivets for the nut plates. Here are the manufactured heads - some sitting slightly proud, but otherwise not too bad. There was no real issue with the flat set hitting up against the spar bars a little - the tape seems to have prevented any dings here:
And now for the problem side - the shop heads on the nut plates. It went something like this:
1.The first rivet was the top most rivet - I over drove it but otherwise it went well - or so I thought until I removed the tape to find a small ding in the double plate where my rectangular bucking bar contacted the edge of the doubler plate - dammit!
2. I did the same thing again on the lowest rivet - something about trying to fit a square peg into a round hole comes to mind. The problem is that you only have room to fit a small corner of the bucking bar onto the rivet shaft. Normally you try to center the mass of the bucking bar onto the rivet shaft so that it is balanced on both sides. This helps prevent slipping of the bar off the rivet shaft. If you move the bucking bar too far over to the side you run right smack into the spar doubler plate. Here is the pic:
With that pic you can see the nice ding on the lower left side of the doubler plate. I had tape on that similar to what you see on the top side, but it obviously did not do any good.
3. What is not visible in this pic is the condition around the bottom rivet of middle nut plate. You know, the easy one that I left for last after figuring AI would tackle the harder rivets first - easy access to the rivets with bucking bar, no interference with the spar doubler, etc. Well,on that rivet, the bucking bar slipped down and contacted the spar web - left a small scratch that I now have to dress out. The worst part is that it also chewed up the bottom of the nut plate flange so I have to replace this entire nut plate, and probably will have to replace the other two after I drill out other poorly set rivets on those. Six lousy rivets and I managed to make more work for myself. I can file out the dings in the doubler plate so I am not worried about that - but I really hate the thought of having to replace those nut plates again which means having to be careful with the bucking bar all over again.
Bottom line is that these nut plates really SUCK! I'll deal with all this tomorrow, but I had hoped to be moving on to riveting some ribs - guess that will just have to wait.
It all started as usually does - with a lot of research and planning. I spent time reviewing Dan Checkoways info when he did both of his wings. I thought I had all the info I needed by reviewing his right wing posts, but I found additional very useful information in his left wing posts which came later.
The reason why it is good to go ahead and set the nut plates for this inbard tank bracket is that you can use them to secure the inboard Z bracket instead of a nut and bolt combination which he used to help properly position all of the Z brackets for the fuel tanks. I'll get more into all that in the months to come, but for now I will simply say that I will use Dan's method to properly position the Z brackets since Vans instructions for this definitely do suck.
The other reason you set these nut plates now is that it is easier to get to them without the ribs getting in the way. The holes for the nut plates are predrilled and just a bit undersized as usual. To drill them to the final size for the nut plate rivets as well as for the bolts, you use a #13 and #40 drill bit, and a #12 reamer. I ran the number 13 drill bit and the #12 reamer through the bolt holes, then I attached the nut plates with clecos drill those with the number 40 drill bit. I checked the fit for the bolts and they were spot on perfect.
Here are the first set of tools used. I have the drill bit and the reamer in two separate drills to make the process go a bit faster:
Next are the nutplates clecoed into position with one cleco. This is the way that they are positioned. Pay attention to the ones on the top and the bottom that are angled to account for the edges of the lightening hole cut out of the doubler plate of the wing spar. These presented several challenges.
I added another 2x4 piece of wood to the spar flange at the root and secured with a large C clamp to provide some additional resistance and rigidity to the wing spar which is critical during riveting. Before it is all said and done I will be using some beefy 4x4s and more clamps when I start riveting the ribs in place:
I also needed to run a test for my #40 countersink to make sure it is set to the correct depth. I already had the bit in one of countersinks but was not sure of the depth was correct. Turns out it was a good thing I ran some tests because for whatever the reason it was set way too deep. That could've potentially ruined the entire wing spar.
Here is the setup for the tests using my scrap 1/8 inch thick piece of aluminum from my empennage trim bundle:
And here are the three test holes. The one on the top was the original setting - note the rivet head sitting way to far down in the countersink. The other two were spot-on perfect:
After all the countersinks were done, I sprayed a cotton swap with 7220 primer and used that to prime all the bolt and rivet holes. When the primer was dry after a couple of minutes I taped up my flat rivet set that I have been using in the rivet gun, and used the thin man bucking bar to buck all the rivets for the nut plates. Here are the manufactured heads - some sitting slightly proud, but otherwise not too bad. There was no real issue with the flat set hitting up against the spar bars a little - the tape seems to have prevented any dings here:
1.The first rivet was the top most rivet - I over drove it but otherwise it went well - or so I thought until I removed the tape to find a small ding in the double plate where my rectangular bucking bar contacted the edge of the doubler plate - dammit!
2. I did the same thing again on the lowest rivet - something about trying to fit a square peg into a round hole comes to mind. The problem is that you only have room to fit a small corner of the bucking bar onto the rivet shaft. Normally you try to center the mass of the bucking bar onto the rivet shaft so that it is balanced on both sides. This helps prevent slipping of the bar off the rivet shaft. If you move the bucking bar too far over to the side you run right smack into the spar doubler plate. Here is the pic:
3. What is not visible in this pic is the condition around the bottom rivet of middle nut plate. You know, the easy one that I left for last after figuring AI would tackle the harder rivets first - easy access to the rivets with bucking bar, no interference with the spar doubler, etc. Well,on that rivet, the bucking bar slipped down and contacted the spar web - left a small scratch that I now have to dress out. The worst part is that it also chewed up the bottom of the nut plate flange so I have to replace this entire nut plate, and probably will have to replace the other two after I drill out other poorly set rivets on those. Six lousy rivets and I managed to make more work for myself. I can file out the dings in the doubler plate so I am not worried about that - but I really hate the thought of having to replace those nut plates again which means having to be careful with the bucking bar all over again.
Bottom line is that these nut plates really SUCK! I'll deal with all this tomorrow, but I had hoped to be moving on to riveting some ribs - guess that will just have to wait.
Wednesday, January 1, 2014
Right Wing Main Ribs Primed and Sratches in Wing Spars Dressed and Primed
Got all the remaining main ribs for the right wing primed yesterday. I also had to address several areas on both of my wing spars that had some scratches that appeared to be deeper than surface level. These scratches have been bothering me ever since I received my wing kit. I basically had to use 220 grit aluminum oxide sand paper to remove the gold anodized coating, and then continued to sand until the scratch was removed. Here are some before and after pics, starting with the worst one on the web of the left wing main wing spar web:
After the scratch was removed, I primed the affected area:
And there was one more scratch on the opposite side, unfortunately in about the same general area toward the tip of the spar, but running in a different direction:
And then there were a couple of spots on the right wing spar that I also wanted to repair. I used a cotton swap to apply primer on these areas so they don't look as crisp and clean as the other ones, but it got the job done so I am satisfied:
Today was a bit chilly outside so I decided to quit for the day and enjoy the rest of the holiday watching football. Thank goodness 2014 is finally here! Next steps for me are to place the LE assembly and cradle on the work table and move the wing spars to the work benches. Time to start riveting some ribs together tomorrow. I also spent some time reviewing Dan C.'s method for drilling the fuel tank Z bars which attach the back of the fuel tank to the wing spar and ensures that there is little or no gap between the LE skins and the Fuel Tank skins. If I keep at it I figure I will be working on my fuel tanks in early spring.
dd
And then there were a couple of spots on the right wing spar that I also wanted to repair. I used a cotton swap to apply primer on these areas so they don't look as crisp and clean as the other ones, but it got the job done so I am satisfied:
Today was a bit chilly outside so I decided to quit for the day and enjoy the rest of the holiday watching football. Thank goodness 2014 is finally here! Next steps for me are to place the LE assembly and cradle on the work table and move the wing spars to the work benches. Time to start riveting some ribs together tomorrow. I also spent some time reviewing Dan C.'s method for drilling the fuel tank Z bars which attach the back of the fuel tank to the wing spar and ensures that there is little or no gap between the LE skins and the Fuel Tank skins. If I keep at it I figure I will be working on my fuel tanks in early spring.
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