Yeah, it's Ugly....But is it OK?

I have to admit that I just hate to drill out rivets. As a newbie who really likes using the pneumatic rivet squeezer, every once in a while I do need to pull out the gun and a bucking bar. No problem with flush rivets, but my universal rivet technique still leaves something to be desired.

Question for the forum: Should I drill these out and try again, or build on? Thanks for the straight advice.

During my pre-cover inspection I was written up for 2 rivets in the wing like the ones in your picture. I sent a picture of the rivets to Vans.

This was their response:

EXCERPT from Alcoa Aluminum Rivet Book, dated 1984.
?The standards to which driven rivets should conform are frequently uncertain. In addition to dimensions and perfection of shape,
inspection is concerned with whether the drive head is coaxial with the shank (not ?clinched?) and whether there is excessive
cracking of the heads. It has been determined that even badly cracked heads are satisfactory from the standpoint of static strength,
fatigue strength and resistance to corrosion. (Poorly set and cracked) rivet heads were tested in tension to determine how well
formed a head has to be in order to develop full strength. The tensile strengths of all the rivets were within five per cent of the
strongest. The test indicated that minor deviations from the theoretically desired shape of head are not cause for concern or
replacement. The second rivet that is driven in any one hole likely to be more defective than the first because the hole is enlarged
and rivet will be more likely to buckle and form an imperfect head.


I did not replace my two rivets - Feel free to make your own decision.

Paul

You mentioned you are new - If you do decide to drill out:

* Use an automatic punch in the hole on the head
* Use a #32 drill bit
* When you put your #30 punch in the hole, you can pop the shop head off easily

No expanded holes that way

Drilling out rivets

Well, I have to say, I've become a bit of a master at drilling out rivets. The technique I use is to get a good center (automatic punch or whatever, then drill straight through with a #40 or smaller drill. This seems to relieve the pressure on the sides of the rivet gripping the hole. Then I drill down with a #30 or slightly smaller just enough to enable me to pop the head off using a 1/8" punch. Then back the rivet up with a block of wood, socket, whatever (I prefer wood; less damage and marring to the structure) and punch it out using the 1/8" punch. I've found that although it takes longer to double-drill, it is easier to punch the rivet out and I rarely screw up the hole this way. Also, if the smaller 'thru'-hole is slightly off center you run less risk of ovalling the hole and causing a bigger problem. While this method serves *me* well; ymmv, use this method at your own risk.

See this thread with a similar question. I would think you do not need to drill it out unless you are confident you can do so without enlarging the hole.

If you are concerned about what other people who might see the rivet will think about your work more than the actual strength of the joint, then drill it out. I think a lot of people want their work to appear to be near perfect, so they will drill out a rivet that is structurally sound, failing to realize their their more-perfect looking replacement is actually weaker. Not that the replacement, prettier rivet, though weaker, will not still be strurturelly sound, too.

Try putting a piece of masking tape on the universal head before riveting.

mike647m said:

Try putting a piece of masking tape on the universal head before riveting.

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Yep Mike, that works for me. I saw it on the show "How its Made" when they were showing the building of an aircraft.

Another Question...

...to ask yourself....

Would you fly on a Boeing if it's rivets looked like that?

gil A

az_gila said:

...to ask yourself....

Would you fly on a Boeing if it's rivets looked like that?

gil A

Click to expand...

Well, I agree with Gill's comment. By the way, you WILL get very good at drilling out errant rivets. So take 3 minutes, get a fresh #30 drill bit, drill it out, punch it out and re-rivet. It really doesn't look that bad...but it could be better. You posted this for some constructive comments. Sounds like you weren't comfortable with this rivet. Well, is one rivet going to cause you to fall from the sky? No, no it won't. But I think it will give you piece of mind knowing that you did it right. We take on a lot when we commit to a project of this magnitude. It's one rivet then another then...the extra effort is worth it!

Why not squeeze?

I don't recall any rivets in that area that couldn't be squeezed. Maybe you need more squeezer yokes.

They look strong to me - assuming the shop head is well set and not cleated. It's possible to weaken the joint by drilling out and replacing if it doesn't go well. I'd only replace if you're worried about looks.

Jim Sharkey
RV6 - Wiring

BTW - Keep pressure on the rivet head until the gun has come to a complete stop. Smileys can be caused by the unexpected and random strike that the gun gives if you still have your finger on the trigger as you lift off the head.

Those smileys were created because the rivet set was not perpendicular to the rivet.

Personally, those rivets are "drillahs"! Take them out and redo.

It is WAAAAY easier to do it now than to do it later.

CJ

I wish I could tell you if those rivets are ok, I don't know. I don't know how strong the banged-up rivet is, and I don't know what the strength requirement for THAT particular rivet is. Vans may know, but I doubt any of us know. However, if I had to guess, I'd say no problem whatsoever, because if the design was so marginal that a few smiley rivets were a problem, then these RVs would be dropping like flies.

Nevertheless, I voted to replace it; the one in the close-up shot would bug me enough that I would either replace it, or if appropriate, drill a hole nearby and put in another one (need to carefully check drawings for potential interference before doing that).

The damage I see looks like what I get when I don't hold the gun firmly and straight against the rivet. It looks like the rivet set has bounced. Make sure you are holding the gun firmly in position until the noise stops completely, not just until you release the trigger.

John

Tom, I'm going to forgo advice on drilling out versus not drilling out as previous posters have covered pretty much all relevant issues. Hints on driving those AN4's. Of course keep your gun vertical and apply enough pressure to keep the gun from walking, experiment with air pressure, too little and you have to keep your gun hammering away thereby increasing your likelihood for walking, too much and it will want to bounce. Another point is experiment with bucking bar size, a little heavier one just might form that shop head a little quicker. Experiment, vertical gun, sweet spot air pressure and correct bucking bar weight will make bucking no different that that pneumatic squeezer.

With that said, when I was building (I like the right to that), you could had have my guns but you would have had to pull my pneumatic squeezer from my cold, head hands.

If you finish your RV it will ultimately represent a very substantial financial investment. Believe me, it will end up costing tons more money than you ever thought possible. And it will cost the same small fortune whether the plane is well constructed...or a pile of junk.

Buy a universal rivet removal tool from Avery and you can take those rivets out without fear of oversizing the holes. And you'll get a LOT more use out of the tool down the track.....an excellent investment.

No Offense....but

TomAniello said:

.... Should I drill these out and try again, or build on? Thanks for the straight advice.

Click to expand...

Originally Posted by az_gila......Would you fly on a Boeing if it's rivets looked like that?...gil A

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Tom,

You invited straight advice and at first I hesitated to do so but then my friend Gil stepped in and said it first. A bit of background. When I hired on at McDonnell Aircraft...long before it became Boeing and even before Douglas was added....new hires had to attend 12 weeks of sheet metal school at minimum wage before being turned loose on the production floor. It was astounding how many people did not make it through those 12 weeks of intensive sheet metal training. Some people simply cannot drill a straight hole. Those that remained were expected to produce perfect rivets 100% of the time. There is no way, I repeat, no way ANY quality control inspector on the payroll would ever sign off on at least four of the rivets in your bottom picture, much less the ever present Navy/Air Force liason office overseeing the company and its production practices. Without question, those defective rivets would be drilled out and replaced. On my RV's....I have on several occasions drilled out the same rivet hole over and over again until the rivet is finally made acceptable. So what if at times you have to bring the hole up a size.....or even two? You just do it. Those rivets shown in your photos are very easy to replace without damage...they are through a steel part. Drilling out and replacing rivets is an essential skill and I suggest you get really good at it.

Sometimes, I am troubled by the "Build On!" mentality that Van's seems to promote. The oft repeated mantra gives perfect license for some builders to settle for producing marginal work. The popular if somewhat misleading idea that you will cause more damage by removing defective rivets than replacing is rooted more as a pragmatic business decision by Van's in part to help move more kits out the door. Part of Van's genius is knowing that his designs must meet the lowest quality construction skill coupled with very basic tools possessed of the more challenged homebuilder. That is a very good thing for sure. Still, if I told any inspector I was going to leave such rivets in place....I can assure you one of two things was certain to follow. Either my immediate supervisor would have a "chat" with me prior to replacing the rivets or I would be escorted out the factory gate. Very high quality is rightly demanded by the customer and the taxpayer and is strictly enforced. Gil was correct....you will never see those rivets leave the factory on a Boeing produced aircraft. That is the way it is in the production world, but NOT the way it is in garage built experimental aviation. I have always said I would have far more confidence buying a random certificated spam can than buying a random experimental because at least with production aircraft, you know a minimum level of quality is guaranteed.....by the producing company and its FAA oversight. As a potential buyer of your aircraft.....if one saw those rivets such as they are...why would they not assume they could expect the same level of quality to be found elsewhere on your airplane? Your workmanship is on display here. You are free to build as you choose and only YOU can decide what is right for you.

In the end, it is not likely your airplane is going to fall from the sky because of those bad rivets, but their obvious presence does speak volumes about the overall quality you expect from yourself and what you are willing to settle for now and later in the construction process. I anticipate that some other builders will surely disagree with my OPINION and may well feel quite differently about this and other subjects. That's what a forum is all about. Straight talk....sometimes it ain't pretty.

Thank You

I really want to thank the VAF community for taking time away from your own projects to help me keep moving on mine. You all posted some excellent advice, and I greatly appreciate all of it.

I'm going to drill them out and try again. If I don't get comfortable drilling out rivets at some point, then I'm never going to get through the whole project.

And, I'm going to start paying more attention to my "gut instinct". If it doesn't look good to me, then it should be redone to the level which I am not only proud to show others, but feel safe strapping on and going flying.

Thanks, everyone!

Tom

Hello Tom,
You have to strike a balance between "build-on" and removing bad rivets. In some regards I agree with Rick. I have visited the Raytheon factory many many times. The tiniest flaws get rejected. In my opinion, if the rivets are easy to get to, replace them. If you're not confident in replacing rivets, get some scrap metal, rivet 20 or 30 "bad" rivets and drill every one of them out and install new rivets. Try some on slightly enlarged holes, grossly enlarged holes and oblong holes. You'll soon get a feel for what you can and can't do and when a larger rivet is required or when more damage than good will be done. There are some rivets that are so difficult to access, you'll be glad to get a rivet in the hole no matter how "ugly" it looks as long as it is structurally sound!

Tom, you have 4 out of 10 "ugly" rivets, which is a 60% batting average. The airplane will not fall out of the sky because of those rivets. But do practice drilling out rivets, get your confidence up, and replace those 4 rivets. You'll feel better about it anyway. three things may be causing you to produce rivets with smileys: 1) Not square on the rivet with the rivet gun or squeezer, 2) not holding enough forward pressure on the gun with your hand, or 3) to much air pressure on the gun causing the rivet set to bounce so much you can't overcome it with forward pressure on the gun with your hand.

I once had to drill out a bunch a rivets, maybe a hundred, maybe two hundred or so. When I was building my "canoe" while still in the jig, I had an air hose failure. The fitting came off the hose and almost took out my face. The impact of the hose on the forward side skin put a significant "outty" dent. I thought about pushing the dent back in and then filling but in my heart, I knew that wasn't acceptable. So I drilled out all those rivets and replaced the skin. Thank goodness for pre-punched skins! After all that drilling and riveting, there were only two that required a larger rivet. So my point is that sometime during the course of the project you will have to put your drilling skills to the test. Good luck and email or call if you have further questions.

Jerry
RV-8 N84JE
190 fun-filled hours, doing first condition inspection

Drilling out - How To

Tom... this might help in your drilling out of the rivets....

http://home.earthlink.net/~gilalex/Rivet/

As a previous poster mentioned, a back-up might be needed during the punching out operation...

gil A

How to hold the rivet gun

Tom,

The reason the rivet set bounced a bit on the head of your rivets could be because you're holding the rivet gun wrong. The following technique was shown to me by a couple aviation sheet metal guys each with 30+ years experience...

I'm holding my Chicago Pneumatic 4x Longstroke gun. Note the trigger is under my *middle* finger, not my index finger. This hand placement helps align the bucking action of the gun with the center of my hand and in line with my arm. This is important to get right, especially with a hard hitting 4x gun.

Triggering the gun (intuitively) with your index finger places the gun higher up in your hand and makes it harder to handle the bucking action of the gun. This, in turn, can allow the rivet set to bounce off the work.

One more thing to notice: I've got my ring finger under the trigger which helps to prevent over-throttling the gun and gives you a better touch on the trigger.

Try it - it'll take just a little time to get used to but you'll never again go back to holding the gun the old way (if you ever did). By the way, this is also a very good way to hold a drill.

How to hold a rivet gun


One last tip: I turn the pressure down to about 40psi for 3/32 rivets and up to about 60psi for 1/8 rivets with this gun. The 4x longstroke is a hard hitter, but it also cycles slower than a 3x and is heavier in your hand. I prefer it over the 3x guns for the control it gives, esp when throttled with less air pressure. Good luck!

Rick6a said:

Sometimes, I am troubled by the "Build On!" mentality that Van's seems to promote. The oft repeated mantra gives perfect license for some builders to settle for producing marginal work.

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Rick, your post was excellent. Good on you for promoting the merits of competent construction. It's a philosophy that embraces the welfare of the builder/flyer and of the Experimental category at large.

When I see rivets as in post #1 on this thread and some people say "build on and forget it" I just really wonder what sort of aircraft those individuals are throwing together. It's a bit frightening actually.

The fact that approximately one-third of respondents to the poll recommended leaving those disgraceful rivets probably is a good indication of the percentage of RVs being built that are not up to scratch.

Captain Avgas said:

When I see rivets as in post #1 on this thread and some people say "build on and forget it" I just really wonder what sort of aircraft those individuals are throwing together. It's a bit frightening actually.

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I think you miss the intent of our advice. No one is saying that making all or most of the rivets like that is acceptable. We only said that making a few like that would not present any structural issues that would make the plane unsafe or non airworthy. Even the people that recommend drilling them out admit the rivets are safe as they are. So, if a few ugly rivets are fine, why stress over it and imply that those of us who might happen to have a couple of dinged rivets are building unsafe airplanes?

I have been leery about posting on matters such as this, fearing that someone might think my plane will be unsafe if I admit that I have a couple of rivets with smilies. Well, I do have a few - not many, and some of the really bad ones I did drill out and replace - but those few that I do have are structurally sound and will not fail in flight. There is nothing frightening. I would actually be more frightened to fly in a plane where the builder had perfect looking rivets, but most of them he drilled out and replaced a time or two in order to get them perfect. Who know what unseen damage there is between the shop and factory head of those beautiful looking rivets?

Just use of some judgment based on solid engineering, and you will be fine.

Captain Avgas said:

When I see rivets as in post #1 on this thread and some people say "build on and forget it" I just really wonder what sort of aircraft those individuals are throwing together. It's a bit frightening actually.

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Not that I'm any riveting or building expert. But after 30 years of engineering I know something about perfectionism, and value engineering.

The experimental and practical evidence says rivets like those shown are not compromising the aircraft safety. That is the basis of my vote to move on, and I believe the basis of Vans and others. I've seen way too many engineering projects get derailed because of unwarranted perfectionism...while critical details or issues are glossed over. While the time for an airplane building project is somewhat elastic, in the end there's a limit to the time for any project. Where will you allocate finite resources? In doing perfect rivets? Maybe that time would be better spent in better flight testing, or transition training to RVs, or a more carefully installed fuel and wiring system....there's only so much time.

Few of us are going to devote 12 weeks to learn how to do perfect rivets. That perfectionism may have a place with blue-collar types in a production environment, but not for structural reasons, as has been well explained. It probably has a lot more to do with the potential sloppy work habits of the riveters if given any slack.

That doesn't mean I--or others--are throwing together aircraft "not up to scratch" and I resent the strong implication that because I voted to move on I'm therefore probably building a crappy airplane. It's fine if the OP does want to learn to properly drill out rivets and make better ones, but understand that it is not for structural reasons. Pride of craftsmanship is fine so long as we understand all the tradeoffs.

Engineering....

rfinch said:

Not that I'm any riveting or building expert. But after 30 years of engineering I know something about perfectionism, and value engineering.
.........
That doesn't mean I--or others--are throwing together aircraft "not up to scratch" and I resent the strong implication that because I voted to move on I'm therefore probably building a crappy airplane. It's fine if the OP does want to learn to properly drill out rivets and make better ones, but understand that it is not for structural reasons. Pride of craftsmanship is fine so long as we understand all the tradeoffs.

Click to expand...

There is an engineering view on this, and it is not perfectionism....

Designers use MIL-HDBK-5 (since re-numbered to MMPDS-01, but essentially the same data) called "METALLIC MATERIALS AND ELEMENTS FOR AEROSPACE VEHICLE STRUCTURES" as the only approved source of strength data for aluminum structures.

Check page 3 of this recent Battelle presentation....
http://projects.battelle.org/mmpds/Aeromat 2007_MMPDS_060407.pdf

This document gives the strength data for our aluminum material and riveted joints... but as with everything in engineering, there are tolerances. The document does not assume that all rivets are perfect, it assumes a strength tolerance with every rivet meeting a certain specification.

The long standing rivet specification is here on my web site (since copied by many, including Vans......) - other specifications exist, such as the Boeing one, but they are basically the same standard.

http://home.earthlink.net/~gilalex/rivet_spec/rivet_a.htm

Any other data (even the Alcoa stuff and certainly Bill Marvel's data) is speculative and not done under controlled conditions. Imagine a certified IA writing up a 337 on a factory plane and referring to that data... it just would not fly.... in more ways than one...

Engineering is full of tolerances and we should build within those tolerances... perfect 0.5/1.5D rivet heads are not needed, and the tolerance on them is given in the the specification above... there actually is a large range that makes a "good" rivet rather than a "perfect" rivet.

I believe we should strive for "good" on our rivets, and then we know we are not "eating into" any of the design strength that was calculated when Van designed our planes. He probably over-designed....... but do we know where, and the actual margins on every joint?

"Good" is not perfectionism.

However, you are the manufacturer, so it is your choice....

gil A - a 40 year engineer...

A sharpie is your friend

Tom,

During construction of our plane there was always a sharpie near by and the rivets that I didn't like were circled and the work continued. When enough of this built up I'd go thru and fix them all in one session. It seemed like stopping to fix one rivet often slowed me down where the other method didn't. Besides, often the rivets you are boogering up are in tricky spots and your skills might increase as you build on allowing these to be easy fixes later. It also served another function by default which was this. It seemed like neighbors or even relatives that found their way into the garage would look for an imperfection and run their index finger over it while talking about something unrelated. Everybody was an expert and a quality control inspector from the way I remember. This way you are already on the problem with your items already circled and ready for rework. I gives the looky loos something to focus on without running their nose picking finger all over your airplane and helps to keep them in check.

Interpretation can be an interesting thing. Two people can look at the very same object and see it in completely different ways. When I look at the rivet on the right....I certainly don't see your average cookie cutter "smiley" and I don't think Van's sees it that way either. Refer to page 5-23 in Van's own construction manual and as the illustrations in the construction manual show, the difference between a "smiley" which looks bad but is okay (I'd STILL replace it anyway) is not to be confused with a manufactured head that is obviously deformed and may well be cracked.....can YOU be sure that rivet head is not cracked? Of course, the builder is always free to interpret what his eyes sees any way he chooses to. Without question, there is not an airframe manufacturer in the world who would give that rivet a free pass, especially on the dubious premise that "you can cause more damage by replacing it."