Back to the 3 "Ds" and Mounting the Wing Skins

You remember the 3 "Ds" of airplane building, don't you? Drilling, deburring, and dimpling. Today I finished deburring all of the holes in the wing walk doubler and inboard top wing skin that I match drilled yesterday. I also had to remember how to use the soldering gun to remove strips of the blue vinyl from the rivet hole lines while keeping the remainder of it on the rest of the skins as long as possible to prevent scratches.

With that all done, it was time to fit the top skins to the left wing. The inboard skin is a little tricky because you have to mount it over the top of the wing walk doubler. Actually this turned out to be fairly simple. I clecoed the top rivet holes to the main wing spar flange first, and then I slid the doubler underneath between the skin and the ribs. Everything lined up nicely and so it was easy to continue securing the sandwiched doubler to the wing frame. Vans says to cleco every fourth hole in the skin after that. Here is the inboard top skin W702 all clecoed in place with the doubler hidden underneath. The area on the right where the blue vinyl has been removed is the area where the doubler resides underneath the skin. One day I will be stepping on this area and then into the cockpit with the intent of taking my first flight.Yay! It is finally starting to look more like a wing.

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Next came the W703 outboard top skin. It covers the outer 2/3 of the wing and is so it is longer than the inboard skin. Now I have to rant again about Vans piss poor instructions. They mention installing the the W702 and W703 top skins,and then make no further mention about installing the bottom skins after that. You don't figure that out until you read down further where they talk about leaving the top skins clecoed while removing only the bottom skins in preparation for installing the leading edge. Anyway, here is outboard skin clecoed in place:

An interesting note that some may not be aware of  is that the direction that the writing appears on the wing skins is the same direction of the grain of the metal. Note how the grain runs differently from the inboard to the outboard. IN fact, you can't see it, but the wing walk doubler across the first four inboard ribs is also cross grain from the inboard wing skin. This adds strength to the overall wing and does have an affect on the way that the skin will bend and twist while in flight.

And now for the next problem.... I ran out of #40 clecoes.

Since I am building both wings at the same time, I need massive amounts of clecoes. Another lesson you learn is that the initial tool kit that you purchase will generally contain enough clecoes to complete the empennage, but you will need more for the wings and the fuselage. I will need to make some calls and send some emails tomorrow to see if I can borrow some more, but I figured I need at least 500 more clecoes, and probably even more than that. I have several builders in the area that I can ping, and then my entire EAA chapter membership, and then our Chapter Tool  Officer, so I should be able to scrounge enough without having to buy brand new ones.

Here is a view of the bottom of the wing with both top skins on:

Next is the W702 inboard top skin for the right wing on the bench with its wing walk doubler positioned underneath. Unfortunately, I need more clecoes before I can match drill these holes. I also made the mistake of keeping my bottom wing skins on my shelf, and now there is less room to maneuver with a ladder to get them down, but I will manage.

And then finally I just could not resist this. I have had my leading edge clecoed together in its jig for a very long time, Now that the wing assembly is in progress, I wanted to see what it looked like on the wing, so I temporarily mounted it on the spar just for kicks. Still alot of prep work to do before the LE goes on permanently, but hopefully this will be done in a few weeks. The "chunk" of the wing that is missing from this pic is the spot where the LE fuel tanks will go. They will hold 20 gallons of fuel per tank. Yup, looks like s great big Hershey bar, but it is a well proven and tested design that will suit my needs just fine.

Think Saturday Night Live starring Christopher Walken years ago when you read this next line:

"I gotta have more clecoes!"

Wing Frames are Ready for Skins (Finally)

After a solid week of airplane building I am happy to report that both the left and right wing frames are riveted and mounted on the stands. I started this morning by riveting the rear spar, and it was not long before I had my first fopah. I missed a rivet change at the center support bracket where the aileron pushrod exits the rear spar, so I had to drill out 2 rivets and replace them with the correct length. Once I got past that, I was faced with the dreaded flush rivets on the tip rib once again. The 3" C yoke I was using in my hand squeezer seemed to be binding up on things a bit, and I had noticed that the bottom of the yoke was still quite square because I had never ground it down to a more rounded shape. So I decided to grind it down a bit before I tried setting the flush rivets. I think it made a little difference as I was able to set these a whole lot easier than before. Here is the pic of what they look like after they have been set.

And here is the rear spar after the flap support and gap seal had been match drilled, and all the rivets had been set, with only the place-holder clecoes in place as reminders that no rivets are to be set in these holes until the gap seal and flap support are installed.

With the frames completed it was time to do some major shifting of parts to prepare for the next phase which is prepping and riveting the wing skins. My skins had been sitting between two layers of cardboard from the original packing crate for a very long time. They had been sitting on my shelf underneath the aileron and flap skins and the wing tips. So I had to remove all that stuff to get to the top skins for both wings, which are parts W702 (inboard top) and W703 (outboard top). I also needed to track down the aluminum sheet stock that is used to fabricate the wing walk doublers on the inboard side of each wing.



I managed to get all the skins down although I almost had a major catastrophe when I left one of the bottom skins hanging half way off the shelf when it decided to slide off on its own. I managed to save it before it became too badly damaged. That was a close one. Afterward I cleaned up the garage and shot this pic of both frames back in their respective stands:

It felt really nice to have a relatively clean workshop again and two frames waiting anxiously for skins. The first step for the skins is to take the inboard top wing skin and the sheet aluminum used to fabricate the wing walk doublers and match drill all the spar and rib rivet holes into the doubler by placing it underneath the W702 inboard skin. A note to other builders. The W702 and W703 top skins are NOT marked left and right from the factory. They are basically the same part with all the same holes, and you simply have to flip one set of them over and mark one set for the left wing and the other for the right. The bottom skins are marked for either side of the wing as their configurations are somewhat different for each wing.

Here is the stock that is used to fabricate the wing walk doubler:

It comes in a 48 inch long sheet that is not pre-drilled. It is also 10 inches wide. The plans call for the width to be 9 3/8 inches. I already checked this on VAF and confirmed that most everyone just leaves the width at 10 inches. It has to be cut down to 26 inches. Why did they give me two sheets at 48 inches long when they both have to be cut down to 26 inches? I have no idea. Yet another Vans mystery. ON the far left of the above pic are the two different shears that I used to cut the sheet down to size.

Once the sheet is trimmed,I had to clear away some serious space on my work bench to set the W702 skin down flat on my drill boards, and then I slid the doubler sheet under the skin per the instructions so that it sits back from the top edge about 9/16ths of an inch to clear the main spar flange. Then I aligned the inboard edges of the doubler with the skin, and clamped it in place. Then I used the prepunched holes in the skin to match drill the holes in the doubler. Here is the completed doubler:

I should also add that I drilled from the center and then outward for each row, and clecoed every other row directly to the drill board as I went, to ensure that the doubler would not change position on me while drilling all those holes. Then I drilled from the center downward until all the holes were drilled/clecoed, Worked like a charm. I must say that it felt weird doing this, since I had not drilled any new holes in anything for quite some time. It was good to know I had not forgotten how to do a simple layup on a blank sheet of aluminum.

I had enough energy left to cut the doubler for the right wing to size and decided to call it a day. After all the contorting and positioning it took to set all the rivets for the wing spars, my entire body is quite sore. Even so, it is quite satisfying to see the progress I have made this week, and even more satisfying to finally be back at work building my magic carpet ride!

Left Wing Frame Complete, RIght Wing Rear Spar Attach in Progress

Finished the left wing frame, at least as far as it can be finished at the moment, and mounted it up on the wing stand. I used one of two jacks that I purchased from home depot to "level" the center of the frame as per Vans instructions, which tell you to use some fishing line wrapped around the bottom-most spar flange #40 clecoes at both ends, and then use the jack to jack up the center of the frame until the rivet holes in the spar flange are aligned with the fish line. I was also pleased to see that as far as "level" is concerned, everything appears to be almost spot on. I may need to shim one side of the spar to get it  a bit more centered, but it is already very close. Why is this important? It has to do with the ease (or lack thereof) that the wing skins can be installed and aligned with each other. This is one time that you do not want gravity working against you.

After getting it on the stand and leveled, I tried to take the obligatory pic of the conduit holes all lined up with each other so you can see from one end to the other, which signifies that you drilled all your conduit holes in the right place, but the pic did not come out so good. Rest assured I could see all the way through every single rib and my conduit holes all appear to line up just fine. I settled for another pic that shows the first lightening holes all lined up which came out a bit better.

Here is frame on the stand with the jack in place to level the center by removing the sag that naturally occurs because of the weight of the entire assembly.

And a shot of the fish line across the rivet holes in the spar flange:

I used a small piece of 1x2 wood as a support under the jack stand .

Now on to the right wing frame. I mounted the rear spar and started clecoeing from the root to the tip just as I did for the left wing frame. Then I encountered a bit of a scare and a very embarassing moment. I got to the 13th rib, the one right next to the tip rib, and noticed something funny. the rear flange of the rib was not lining up with the rear spar correctly. Can you guess what I did? I was doing so well slamming the remaining rivets this morning that I lost concentration for a brief moment and managed to install rib #13 upside down. So off came the rear spar, and since I had already placed the left wing on the stand in front of the work bench, I could not easily move the right wing spar from the table to the work bench. Of course, I faced this problem AFTER I had to figure out how to drill out all five AN470 rivets from this rib with out damaging the rib or the spar.Not good odds for me either way.

My method was this:
Since I could not use my nifty AN470 rivet removal tool because it is too wide for the ribs and interferes with the rib web, I had to come up with a different solution. I decided I was once again going to drill the rivets out from the shop head side. I used a center punch to mark the center of the shop head as best I could. Then I took my #30 drill bit and manually ran the bit with my fingers until I knew I had a good hole started. Then and only then did I fire up the air drill and continue removing material from the shop head. I only drilled as deep as the shop head until it meets the spar web. Then I took my secret weapon, which is simply a small set of needle nose VISE Grips that I found at HD one day, and I set the jaws so they were as tightly closed as possible. Then I opened the jaws and clamped down the sides of the shop head and squeezed. Most of the shop heads disentegrated, exposing the actual rivet hole enough for me to run the drill the rest of the way and remove the rivets. I only enlarged one hole a little bit and figured this would be OK.


Then I had my son help me carefully move the spar and ribs back to the work bench, where I had to maneuver everything to reclamp the spar to the bench so I could re-rivet the rib back on, this time with the correct orientation. For some reason some of the rivets clenched a bit and I cannot understand why. I once again decided NOT to try to drill these out again for fear of doing more harm than good, and left everything as is. Then we moved the spar/ribs from the bench back to the table and I proceeded to re-attach the rear spar, the aileron gap seal, and flap support, and match drilled all the holes. Here are the shots of the right wing frame.

Tomorrow I need to debur all the holes and I hope to have the rear spar riveted on by the end of the day. Then I have to clear my work bench off so I can pull the wing skins down from the shelf where they have been gathering dust for way too long, and start prepping them. Still lots of work to do before I can claim the wing kit as complete, but this is significant progress nonetheless.

Lots of Progress at the Wing Factory Today

I spent about 6-7 hours in the factory today and made some good progress. I started by match drilling the holes for the aileron gap seal and the flap support. I had to leave 3 holes of the flap support because I need to trim excess material from the inboard edge which currently interferes with the spar doubler so it does not sit flush against the holes in that area. Once the holes were match drilled I removed the gap seal and the flap support. The trick here is that some of the holes are also rivet holes that attach the rear spar to the ribs. So you need to make sure that that you do something to remind yourself NOT to put any rivets in these holes because the gap seal and the flap support get riveted into place later on, but not right now.

I simply placed clecoes in the holes, but you can use tape or some other method that works for you. I started from the inboard section, which calls for AN470AD4-8 rivets to get through the two 1/8 inch thick spar doublers, the spar, and the rib. I was looking forward to using the pneumatic squeezer for this as a nice break from bucking rivets for all the ribs. I inserted the rivet into the first hole, and checked it with my gauge. I was disheartened when I saw that the rivet appeared to be too short for the material that it was sandwiching together. But, like an idiot that I sometimes am, I did not believe what I was seeing, and instead made the all too fatal mistake of believing that Vans had the correct rivet call out, so I decided to set the rivet with the squeezer. And of course that confirmed that it was too short. So almost immediately I had another repair to make to remove a rivet in a very hard place to do so. I decided to let it sit for a bit while I set the rest of rivets.

Here is a shot of the wing frame moved slightly back on the table to allow a small gap between the table and the rear spar so I could get my squeezer inside to set the bottom two rivets for each rib to the spar. This worked out quite well for me.

I had to put the squeezer underneath the spar to set the bottom two rivets, and on the top side of the spar to set the top two rivets. I used the flange yoke and the 1/8 inch  cup rivet set on the top of the yoke with a 1/2 inch x 1/8 inch thick flat set on the bottom. Per the plans I inserted the rivet so that the manufactured head was against the rib flange so I could pull the rivet head and the rib flange into the rear spar to keep them tightly held together  while riveting. This worked well, and it means that the shop heads are all on the rear spar as shown below. Note my place holder clecoes as a reminder not to put rivets in these holes just yet:

I continued this process until I got to the last rib on the tip. Here the rivets change to an AN426AD4-5, which is a flush rivet which the rear spar is already countersunk to accept. Basically what happens here is that the flush rivet needs to be used to retain a flat surface on this section of the rear spar because the outer aileron hinge bracket fits over this part of the rear spar and must be flush to the rear spar, which is why you cannot use round head rivets in this location. In short, this became almost as difficult as setting those pesky nut plates on the main spar. I could not use my pneumatic squeezer here because the flange of the rib is inward, not outward as it is at the root. The air squeezer is too bulky to set the flush rivets. SO I switched to my hand squeezer with the standard 3" yoke and two 1/2 inch x 1/8 inch thick flat rivet sets. Problem was that the hand squeezer did not provide much more clearance than the air squeezer did, and I was forced to try to set 1/8 inch rivets with it. This is not fun with a hand squeezer as it takes considerable force, but I managed to set them to my satisfaction.

This led to a problem with setting the rivets shown in the next pick. Because these rivets must be set with the manufactured head against the rear spar and shop heads formed on the inside against the rib flange (opposite of all the others), of course the rib flange separated from the rear spar web at the very top. I was really pissed about this, but decided I was going to leave it that way for two reasons:

1. Trying to drill out these rivets and reset them would most likely just cause more damage
2. That corner is further secured by the angle brackets of the beefy aileron hinge, which is riveted in place along the rib web and the rear spar,so I am not worried about any structural issues due to the separation of the rib flange in this area.

This is a risk I am willing to accept. Here is what the shop heads look like:

I failed to get a shot of the flush heads on the rear spar so I will post that tomorrow. But here is the aileron hinge bracket assembly which fits over the flush rivets similar to the way this was done to attach the elevator control horns to each elevator a long time ago.

After all that was completed I turned my attention to drilling out the first rivet I set at the root. I was able to successfully drill out the rivet from the shop head side (rear spar web) and was able to successfully knock out the rivet with a 1/8 inch punch without damaging the rib flange.I replaced it with an AN470AD4-9 rivet, which worked much better. Here is the shot after the holes for the first two ribs were set using these correctly sized rivets. Again note the clecoes as reminders NOT to set rivets in these holes until the flap support bracket is installed:

And as if that was not enough, after all these rivets were set for the left wing, I returned to the right wing spar on the work bench and managed to set rivets for over half the main ribs to the main spar. Tomorrow I will finish setting these ribs,then I will move the left wing frame onto the wing stand, and move the right wing spar/ribs onto the table for the same rear spar treatment. If this keeps up I may find myself neck deep in proseal and fuel tank assembly in the not-too-distant future.'Nuff for now....

And then there was the right wing........

All this recent work on the left wing spar was very rewarding for me. It proved that I could still rivet without destroying everything, and that my thought processes were still pretty much in tact as far as doing things in the correct order and using the correct method was concerned.

Then my attention turned back toward the right wing spar, and I realized that I had a lot of work cut out for me this morning.Basically, I needed to start with those three lousy inboard tank attach nut plates - you know - the same ones that I had to redo several times on the left wing spar, that resulted in several dings and multiple attempts to set the rivets. Needless to say I was not looking forward to this today at all.

Last night I managed to countersink the rivet holes for the nut plates, and I also remembered to use my gorilla tape to cover up the edges of the spar doubler to prevent the dings I experienced before. As you can see from this next photo, I was not taking any chances this time:

What happened next was just like the nightmare I experienced before. A slip of the bucking bar here, incorrect pressure on the flush head of the rivet gun there, and before you know it I had attempted to reset about 6 rivets, and destroyed two nut plates trying to drill them out. Oh, for the benefit of those builders that may read this to try to figure out how this is done, here are some details:

The nutplates to use for this are K1000-3, which are the nut plates used for ALL of the tank attach bolts. The rivets are AN426AD3-4, and for the large bolt hole you use a #13 drill bit followed by a #12 reamer. The rivet holes are enlarged using the #40 drill bit. The written plans do not tell you anything about these rivets, but trust me, you want to set these nut plates BEFORE you rivet the inboard ribs to the spar. It is difficult enough to set these rivets, let alone trying to do it if those ribs are in the way.

You find the details in the following plan diagram/sections:
DWG 16A (Which is the fuel tank diagram)
Section CC
Detail A

Detail A incorrectly labels the diagram as the main spar web, when in fact it is the bottom FLANGE of the main spar - not the web. Once you get the orientation of the diagram figured out it starts to make some sense.  

Anyway, after all that, and remembering to use the variable speed trigger on my rivet gun to SLOWLY slam these rivets down using the corner of my fat man bucking bar, I was able to set the rivets to all the nutplates. I swear that these have to be the worst things in the build that I have had to do thus far. I'm glad they are done, but I know there are other difficult areas of this project that will have to be overcome. One step at a time. here is the pic of the finished nut plates:

And then back to the left wing, I decided to cleco the aileron gap seal and the flap support bracket to the rear spar to see how they line up. There is  section on the inboard section of the flap support that needs to be trimmed away to account for the taper of the inboard spar doubler. This leaves a rivet hole in question because trimming the bracket in this area does not leave enough edge distance for the AN470 rivet that goes there. I may install it per the plans anyway unless my research finds that other builders who did this have experienced failure of the bracket around this rivet hole.

More left wing activity

It's amazing what you can do when you don't have to work all week and the weather is conducive to a lot of airplane building. I finished riveting the main ribs to the left wing spar. I had to flip the spar over and re-clamp it to finish the last rivet in each rib by putting it on the bottom as I described in my previous post. I have a few dings to dress out but nothing serious.

Once the ribs were riveted to the main spar, it was time to swap the left and right spars. I needed to put the left wing spar on my work table, and put the right wing spar on the work bench. To do this I had to place the left wing temporarily on the stand so I could remove the right wing spar from the work table and place it on the work bench. With the right wing off of the work table I could then remove the left wing from the stand and put it on the table. Thanks to my wife for helping me shuffle everything around.

The whole reason for putting the left wing assembly on the table was to prepare to mount the left rear spar  to complete the bottom half of the wing frame. I did not want to leave it on the edge of the workbench because I was afraid that the extra weight of the rear spar might cause the entire assembly to come loose from the clamps and end up crashing to the ground. The table is a much better solution because it allows me to clamp the main spar to one end of the table and have enough table left over on the opposite end to cleco the rear spar without fear of anything falling off. IOW the table is wide enough for the entire  assembly of the wing,as shown below:

I could not get the entire wing in a single pic from the rear so I took two separate shots of the right and left sides:

The rear spar is clecoed in place on each of the ribs. I also pre-assembled the the inboard aileron hinge just to get a feel for how it will be attached to the rear spar. I could not attach the outboard hinge because of the way it is assembled with several hidden  flush rivets that are covered up by the support angles of the outer aileron hinge assembly. Pics will show this more clearly later on.

I had not seen my rear spars for quite a while since they had been in storage on a shelf for a very long time. I had to blow off some residual roofing debris, but they were otherwise in fine shape. Since I was by myself, I had to figure out the best way to cleco the rear spar to the ribs. I decided to work my way from the root to the tip, clecoing one rib at a time. This proved to be a bit challenging, because as straight as I though the ribs were, all the torqueing that was needed to set the primary rivets to the main spar left some of them slightly out of perfect perpedicular alignment. So I had to nudge them into place as I clecoed them. Eventually I got them all to cooperate.

Here is a close up of the inboard aileron hinge assembly all clecoed together. You can see the exit hole for the pushrod that will actuate the aileron. There is also a small bearing sandwiched in between the two hinge halves that will be connected to a bearing when everything is completed.

Next are some shots of the inboard and front of the wing assembly that show the alignment of the 4 inboard wing ribs all squared up, and the tape mess still on the front of the main wing spar after the riveting exercise was done.

It sure was nice to see this coming together, but a review of all the next steps reminded me of just how much work remains before this will really start looking like a completed wing. The rear spar can be reached with the pneumatic squeezer and the flange yoke so at least you don't have to buck any of those rivets. The only problem is that there are two gap seals/supports that are also mounted to the rear spar, but the instructions say to wait to install these until AFTER the top skins are riveted on. I think I am going to at least match drill the holes for these, since many of the holes used to attach them are the same holes attaching the ribs to the rear spar. There are lots of "rivet in assembly with...." steps for attaching the rear spar, so you really have to pay attention to keep from accidentally riveting something together incorrectly.

I had to match drill the holes in the rear flanges of all the ribs anyway, because this was never done previously during the construction of the rear spar and its doublers. Three of the inboard ribs require new holes to be drilled in them by using the spar holes as a guide. I used a #30 drill bit where needed for new holes, and a #30 reamer to finish match drilling the existing holes. Then I deburred all the holes in the ribs and the rear spar and I am just about ready to rivet the rear spar to the ribs of the left wing. Hopefully I will finish that tomorrow in addition to getting most of the riveting done for the right wing ribs to the main spar of the right wing.

Finally riveting some wing ribs!

It has been over 3 months since my last post. During that time I have had to endure what I can only describe as the worst experience of my 20 year career as an IT professional. It was largely responsible for my inability to work on the plane, not to mention many other things. I'll just leave it at that. I made a promise to myself that that will NEVER happen again.

My left wing spar has been clamped to the edge of my work bench during all that time, just waiting for me to start riveting the ribs. I spent about an hour planning and rigging my clamping solution to keep the spar from vibrating or moving excessively. Many builders have problems with this because they do not secure the spar properly, and when they try to rivet the ribs the rivet gun jumps off the rivet head causing smileys and all sorts of other damage. I was aware of this so I wanted to ensure that the assembly was properly secured.

Step one was provide support at the inboard edge of the spar. I used 2 of my 4x4 padded blocks and one bar clamp to provide a kind of stop block that would prevent the spar from flexing backward. The blocks are laid flush with the workbench top on both sides of the spar and clamped together. I really wanted to clamp the blocks vertically onto the workbench but this proved difficult using my bar clamps since they did not have enough depth to reach the blocks on the back side of the spar. So I relied on this approach and the remaining bar clamps locking the bottom spar flange to the work bench to give me enough support of the spar to keep it from moving too much during the riveting.

My plan was to start on the inboard side since these are the most difficult ribs to rivet because they are so close together. These first 4 ribs are the support ribs for the area where the pilot and passenger will be entering and exiting the plane, so the extra strength provided by these closely set ribs is necessary to support the weight.

For the rivet gun I chose to use the double offset rivet set for the AN470AD4-7 rivets. I can't say enough about using masking tape on the rivet set to help prevent marring the surface. I think I also followed the advise from other fellow builders before me who suggested grinding down the rivet set head by about .001 or less to prevent smileys from occurring due to holding the rivet set slightly off-angle from the work surface during riveting.I have a very difficult time judging if a rivet set is truly 90 degrees to the work surface in all directions, and holding it there while you are pounding the rivet into place. Removing this small amount from the tip of the rivet set, and using the masking tape, seems to resolve that problem quite nicely.

Here is the clamping setup for the first inboard rib:

One of the frustrating things about this is that the primer on the ribs tends to close the diameter of the rivet hole just enough so that the rivets will not insert into the hole. The only way to solve this is to run a reamer into the holes to clear the excess primer.I had had to deal with problem repeatedly on other parts of the plane. It is problematic for me because I constantly have to switch out my air line between the rivet gun and the drill, and this takes extra time between rivets. Once the holes are cleared everything goes according to plan.

Here is the front side with all but the top-most rivet in place. I am proud to say that even though I had not riveted anything in a very long time, I managed to set the rivets of the first four of 28 wing ribs without any problems, dings, or smileys. It felt really good to get back to building the plane again. My clamping solution also worked very well. I kept solid pressure on the rivet with the rivet gun the entire time, and kept the bucking bar (I use the fat man bar for most all AN470 rivets) square to the rivet shank. I did have to adjust the air pressure on the gun several times by increasing it way more than I used to for the double offset rivet set. I think the reason was because in the past I had been setting AN470AD4-5 rivets, and these rivets are about 1/8 inch longer  (4-7). So it takes a bit more air pressure and energy to set these longer rivets.

I have never had much of a problem using the double offset rivet set, but others seem to have problems working with it. The reason it is ideal for this job is that it provides the clearance needed between the rivet gun and the rib web, AND it adds enough length to the entire assembly to allow the bulk of the body of the rivet gun to clear certain areas of the ribs, i.e. lightening holes,etc. that could potentially get in the way of things like the retaining spring, handle, etc. I found it to be the right tool for the job, as long as you remember to adjust the air pressure accordingly.

Here is the shop side of the rivets. Note the top most rivet is not set. I decided to wait until all the other ribs are set and then I will flip the spar over and set the last rivet. The reason - simple - I cannot easily see the top side rivet, and since that hole is so close to the edge of the large wing spar reinforcement bars, the bucking bar cannot be centered on the rivet shank and must use the bottom third of the bucking bar. Then, the bar must be held so that it will not mar the surface of the support bars. This, combined with the weight of the bucking bar, means that it is possible to screw this up in a heartbeat. So I am choosing to let gravity assist me by setting both of these outer-edge rivets while the hole is on the bottom so I can see what I am doing and allow gravity to help me position the bucking bar along the edge of the wing spar support bar. I also added some extra tape along the edge where the support bar meets the spar web of the wing spar to prevent damage from the bucking bar.

Here is how I began the riveting process for each rib. This pic shows the start of the third inboard rib. I clecoed each hole from the back side and then removed the center cleco and began riveting from there. I wanted to ensure that any slack in the rib flange would be removed, so I applied the same process that is used for riveting the skins to the frame by starting from the center and working outward. I set the center rivet and then set the two on the bottom, followed by the fourth rivet next to the top-most rivet, which I left alone for reasons as stated previously.

And finally then end of 3 hours of work: