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

[Bill Wightman]

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!

[Captain Avgas]

Originally Posted by Rick6a

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.

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.

[Jeff R]

Originally Posted by Captain Avgas

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.

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.

[rfinch]

Originally Posted by Captain Avgas

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.

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.

[az_gila]

Originally Posted by rfinch

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.

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/A...PDS_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/r...ec/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...

[Bryan Wood]

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.

[Rick6a]

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."