Repair done on Wednesday, May 19, 2010

Ron Duren to the rescue (Again). He graciously accepted my invitation to drive to my house to buck 4 rivets to finish the repair work that took me most of the week to complete. He handled the bucking bar (left hand), while I drove the rivet gun (right hand). Notice the cool EAA T shirt that defines a pilot, and, yes, the wing parts still in the crates in the back ground - still working on that project.

And the finished task - 4 nicely set rivets, 2 on each side of the repair flange. Although standard aluminum patch practices may call for at least one more rivet on the spar-side of the repair, I stuck with 2 rivets on each side. The reasoning is that the skin is providing support with all the rivets that are attaching it to the spar and to the rib, so I think that there is adequate support in this area. I used an offset dome headed cup set for the rivets that attach the new flange to the spar web, which is about 5 inches longer than the normal cup set I would use for AN470 structural dome headed rivets. This allowed sufficient clearance of the rivet gun from the skins so that they would not get all banged up during the riveting process. Note that the repair was placed on the forward side of the spar web, and not the back, although when I marked the holes for the location of the rivets, I had it placed on the aft side of the spar web. This was because this was the only side that I could fit a straight drill bit (used a 12 inch extended number 30 drill bit to drill the holes.) Yes, I could have used my angle drill attachment to drill the holes from the other side, but I find this tool to be very inaccurate in terms of being able to drill a nice, straight hole, unless you can slap it in a vise to keep it from moving. So I opted to drill from the back side using a longer drill bit, and it worked out pretty well that way.

And from the other side - 2 more nicely set rivets, all in the original holes of the new rib that arrived from Van's "just in time." For some reason we had a little difficulty with the holes in the repair piece lining up with the holes in the rib after the piece was riveted to the

spar. This was strange to me because everthing had clecoed together perfectly before we started riveting. If I had one thing to do differently about this repair (hopefully I will not have to do this again but...) I would not match drill the holes in the rib to the repair piece until AFTER I riveted the part to the spar web. What I did this time was match drilled the rib holes to the repair piece after clecoeing the piece to the spar, but BEFORE it was riveted to the spar. If I would have waited until after I riveted the piece to the spar flange to drill the holes for the rib attach points, they would have lined up perfectly, which caused the mis-alignment of the holes on the other side. I can only guess that the act of riving the rivets to attach it to the spar pulled everything up tightLesson learned, but hopefully will not need to be repeated! Whew, that was a lot of work! But at least its done, and so is the HS riveting, for the most part. More on the finishing touches later.... Thanks again Ron for all the help.

HS repair cont'd

Another blurry pic. Shows progress with th nibbler. The only draw back is that you cannot control the precision of each cut very well, so some are deeper than others. Here you can see some of the little pieces that have to be nibbled away - almost there...

For anyone with experience in such matters, no this is not mouse poop, even though it looks like it from a distance. Believe, me, unfortunately I know what mouse poop looks like! No sign of them in the last 8 months or so, so that's a good thing. These are the remnants of the metal removed from the flange by the nibbler.

The business end of the nibbler in its non-cuttting state

Now in the cutting position. It generally will remove about 1/8 inch of material by about 1/4 inch with each cut.

The end result after nibbling and grinding the edge to a smooth edge with no burs. You can also see the marks I have made on the spar flange when trial fitting the new flange in place. That was a lot of fun by the way, because I had to use 3 hands and some tape to hold everything into place. Then I had to fit my sharpee in there to draw some reference lines and mark the hole locations in the spar web. All the trial fitting had to be done with the end rib clecoed in place. Needless to say, since I was the only one present during this delicate balancing act, I have no pics of the part taped into place during this operation.

Another shot showing the degree to which the flange was trimmed. I only cut enough to remove the bend, leaving as much of the straight part of the spar web in tact. All of the metal dust and chips from drilling/nibbling were cleaned out of the areas as well. You don't want any of this material settling into the crack and crevaces where they can start to fatigue the metal between the spar and the skin over time. Everything was spic and span before closing it all up, hopefully for the last time.

Repair of HS Tip - Hobbs 140 hours

So the repair process began. All through last week, and ending with Ron coming over to help me buck the 4 critical structural rivets for the flange repair and the re-attachment of the end rib to the HS. A series of pics of the process follows:
A bit blurry - did I ever say how much I don't like digital cameras, except that you did get instant electronic pictures I guess. This shows the top hole that was also drilled through. This entire flange had to be cut and trimmed away, and a replacement flange fabricated and riveted in its place.

Just some of the many tools used to complete this repair, and a shot of the more or less finished part that I had to cut, bend, and drill. The wood form block is the same one from earlier posts where a 1/8 inch radius bend was required. The angle finder was used to verify that the bend was exactly 84 degrees to match the angle from the forward spar to the side of the end rib where everything attaches, resulting in a 6 degree angle, or the same angle that the roots of the spars and the support angle brackets were bent to long ago. The two holes have been measured and drilled to assure proper edge distance requirements are met. Other tools used were a nibbler, my dremel grinding wheels and articulating saw attachments, metal cutting saw blades, and more.....


Another bad pic - attempting to show the angle and how the part was positioned between the two blocks during the forming process










Fitting and sizing up the side that fits up against the inside of the rib. You can see the relationship of the rib holes to the flange. These are the two remaining holes that have to be drilled. The plan is to rivet the new flange to the spar first, then fit the new end rib into place, and use the existing holes in the rib as a guide to match drill the holes into the other side of the flange.



Shows the plastic hammer I used and the form blocks and the aluminum part in the vise and being formed. Just had to eyeball this a bit and make sure that I did not force the bend over the 84 degree mark. This is actually very easy to do, and my guess-timate was very close to where it needed to be - I was only about a half degree off. You just start tapping the hammer at the base of the bend and it starts to fold right over.

Shows the part up against the angle finder - 6 degrees - with a 1/8 inch radius - just as it should be.









Now for the other difficult part of the fix - how to trim off the damaged flange from the spar. Lots of measuring involved here - not to mention trying to decide what tool/method to use to remove the flange. The trick was to remove only enough material that would not compromise edge distance on the spar web, which meant only trimming off enough material right up to where the bend occurs, without removing any material running the length of spar web, if that makes sense. Then ensuring that it is straight and free from burs, all within the confines of a skin that is already riveted in place on the spar top and bottom. Dremel cutting wheel was out of the question - too much risk of skipping and cutting into the skin, causing even more problems. Hack saw was another possible solution - but it would have to be done by hand. In the end, as shown in the pic, I chose the nibbler (man I love this tool!) I could cut small chunks out at a time, with fairly precise control over the amount of material being removed. Yup, that's my fat hand in the foreground, next to the small opening at the end of the HS.

Good News/Bad News

So I was able to transport my almost-complete HS up to Erie Airport past Saturday, where one of the EAA chapters I belong to, Chapter 43, was having a hangar picnic. Lots of great food and great company. There were not one, but two completed RV 10s in the hangars, and so I spent a fair amount of time gawking at them, and drueling with envy at how big and roomy this home built airplane is. I met with a tech counselor, Bill Truax, who looked over the damage to my wing skin and basically told me that it could be filled, won't ever crack, and basically told me not to worry about it, and to KPR (keep pounding rivets). That was the good news.

Now for the bad news. Later that evening, after getting the HS back home, I should have simply started closing up the rear spar and the ends and called it good. Instead, there was one rivet that attaches the end rib on the right side that did not quite get set as well as I would have liked. So I thought that I would drill out this rivet and and replace it, and then finish everything up after that. the first removal went without incident, but the attempt to reset the rivet resulted in a very badly set rivet, so I made the decision to drill it out as well, and try again. As the following picture shows, my drill slipped and I ended up drilling a new hole right through the end rib and into the spar flange that it was attached to. I then had to get creative with a pair of needle nosed pliers in order to snip away at the remaining rivet head in order to get it loose enough to remove. It did not matter, though, since the damage was already done.

A phone call to Vans yesterday, followed by a comfirming phone call to EAA HQ tech counselors today, resulted in a recommendation to:

a. Completely cut away the portion of the forward spar flange that connects to the end rib (not shown in this pic but I will add other pics as I affect this repair.)

b. fabricate a new flange part for the end of the forward spar that will need to be riveted onto the end of the web of the forward spar

c. Order a new end rib (done today), locate and final drill all the holes, debur it, dimple the holes, flute the edges, and prime it. Then finally try to rivet it in place once again.

Obviously this will set me back a bit from finishing the HS, having learned yet another very important set of lessons in the process. I'm sure this will not be the last time I have to figure out how to affect a repair like this, but, needless to say, I am very disappointed in myself right now, and in hindsight I should have left well enough alone. That said, you just have to press on when things like this happen, and realize that problems like these can still be resolved, albeit with a bit of extra effort.

The fabrication will take me some time to complete, because there are some precise measurements that have to be made for the correct size of the repalcement piece, and an 84 degree bend that needs to be made to properly line of with the web of the end rib. Lots of cutting, clamping, and drilling to do. Looks like the dimensions needed to fabricate the part are to use .032 inch thick alclad aluminum, and both sides of the piece will need to be about 1.5 inches long x 1.5 inches wide. The real dimension turns out to be about 1.65 inches x 1.39 inches in order to achieve flanges that are 3/4 of an inch wide on both sides. Bending metal is yet another specialized skill that one has to become familiar with, and it involves quite a bit of math skills and knowledge of metal properties in order to get it right. I won't bother listing out all the detailed formulas involved in figuring out the correct dimensions, except to say that I have spent most of my evening reviewing and calculating all of this. I figure this will set me back at least a week on the HS. Wish me luck I guess.

The whole HS assembly - almost there......

What a nice pic of an almost finish airplane part! I can't finish riveting the skins until I have a tech counselor look at my damaged skin this weekend. Hopfully the verdict will be that I can proceed without replacing the skin, and then I can finish attaching the rear spar, shown here clecoed into position. The remaining rivets can be squeezed instead of bucked - a welcome relief from all the bad rivets I had to drill out and replace thus far.

Riveting is definitely a skill that has to be practiced. Unfortunately, I am finding out that not even the courses that you take from EAA, or the project kits that you can work on, provide the same challenges that you experience on the real airplane parts. You have to learn how to feel the bucking bar, how to hold just right in many different positions, and how to hold the rivet gun, how to contort your body and hands into just the right position, and so on. It will definitely be a challenge when trying to do this on my own, but the good news is that the wing and fuselage parts are somewhat bigger, making them at least a little easier to work with.

Left Side HS Skin almost complete

With Ron's help, this is the bottom side of the left half of the HS, almost completely riveted together. The only thing remaining is to attached the other half of the stabilizer and then finish riveting the ends and the rear spar. The whole assembly turns out to be about 8 feet 4 inches long.

Installing Pop Rivets for the first time

Perhaps I should add some pics of the tools and rivets to this post to provide a better understanding of what pop rivets are and how they are installed. This pic shows the finished result after the pop rivet has been installed to the center rib section of the HS. Pop rivets have a long stem that sticks out from the top of the rivet about an inch and half or so, which fits into a specially designed, manually squeezed rivet gun. The stem of the pop rivet slides into the end of the rivet gun, then you insert the rivet into the holes of the pieces you are joining together, and then you start squeezing the handles together until you hear a "pop." The reason you need to use these rivets instead of the other type of rivets is that certain areas become closed off and are no longer accessible on one side of the part, so you can't get a bucking bar on the other side to drive the rivet. Such is the case once you have riveted both sides of the skin to the nose rib, and the front spar has been installed.

This method provides a way to install a strong rivet without having access to the other side of the part. As you squeeze the handle of the gun, the shaft pulls on the rivet, effectively mashing it up against the blind side of the part, until the rivet is fully set. This is when the stem gives way and breaks or pops out of the hole in the center of the rivet head. It's a bit startling when it happens, and it only takes a couple of pulls of the rivet handle to make it happen.

The "pop" is the sound of the rivet stem separating from the actual rivet. There are three pop rivets that had to be installed to attach the center nose rib, forward spar, and the main rib together. the tricky part was that all this had to be done by sliding the rivet and rivet gun into the small opening in the back of the HS skin. As usual, it's all about fitting large things in very small openings, and trying not to damage anything in the process. If you look close you can see where the rivet gun contacted the web of the rib and scuffed it up a bit. This just proves that I need to take my pop rivet gun and grind down the shaft so that it will not interfere with the part that is being riveted. You have to make these kinds of modifications to your tools from time to time.

The installed pop rivets have a small hole in the middle where the stem was located. It's easier to show someone than to explain how this process works, so I'll take some pics of the rivets and the gun to help understand this process.

Another optical illusion

Another alclad mirror illusion. This is actually a pic looking inside the enclosed skin after riveting both sides of the center nose rib, which is the first thing that Vans instructs you to do. The actual rib is in the center of the photo, and the reflections from both sides of the skins are on either side of the nose rib.

A-riveting we will go...... A-riveting we will go....

So I asked Ron when he arrived last Saturday what he thought about the ding on the top side of the left HS skin, since he is also "knowledgable" about such things (he-he). His response was something like " well I tell you what, whatever we are going to do let's decide right now, before we start riveting!" meaning that before we pound hundreds of rivets into this skin I better make a decision. I decided that Van's had seen the photos and indicated that it looked like a fillable depression. and I guess I was also prepared to undo (drill out) any rivets should anyone else raise concerns. So I decided to KPR (Keep pounding rivets!) If nothing else, it would be excellent practice bucking and riveting with two people, which is something that you inevitably must do during certain phases of the construction of an RV aircraft. Here is Ron with the center nose rib riveted in place, and the left side skin clecoed to the rest of the frame on the bench.

Reflecting on the past few months - Hobbs Meter estimated at 110 hours. Priming for the First Time

I did some reviewing of my past posts and realized that it has been almost 5 months since I last updated the Hobbs meter on my progress. Sheeeesh, where does the time go? I remember January being unusually warm, and that was when I was busy dimpling and prepping/deburring the skins and other pieces. Then it got really cold and snowy through most of February, so not much was done during that month. Priming all the parts took a lot longer than I would have liked. A lot of that time was spent figuring out the process and preparation steps, and getting familiar with myspray gun settings, etc. So hopefully any future tasks for this will take much less time. I am estimating that my total time on the project is at least 110 hours now. I will start tracking this a bit closer from here on out.

Catching Up - Getting help with riveting

So you have seen my very ill-prepared attempt to start riveting my HS skins onto the frame. I have contacted several people from EAA HQ to local Tech Counselors to my friend Ron. This Saturday one of the local EAA chapters I belong to is having its annual picnic up at Erie Tri County Airport. One of the tech counselors suggested I bring it to the picnic where they can look at it in person. Sometimes pictures and describing things over the phone just don't quite cut it.

After I incurred the damage, I contacted Ron and asked him if he could come down and help me shoot all these rivets. Iwas no longer confident that doing this solo was something that I could do successfully. He gladly said that he could come down, so last Saturday we spent most of the afternoon riveting the skins to the HS frame. Lesson learned here - contact Ron or somebody to help BEFORE doing stupid things like attempting to rivet large pieces on a wobbly, uneven table at an improper height!

What a great afternoon that was. I learned a lot from Ron, and I can't even begin to tell anyone how valuable it was to have someone there with some experience to help you out. The following posts contain pics of all the activity over the past week. Thanks Ron for all your wisdom and help!