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attackpilot

Active Member
I would like some advice on whether I should re-do these rivets on the forward spar of the HS on my RV-10 kit.

The ones I have concerns about are the top one and the third one down. I know the bottom one is chewed up. You can see how the edges of the head are smooshed (technical term) out. All of the shop heads are decent thanks to my wife.

It was difficult enough trying to get a offset rivet set into this area. These rivets attach the backside of the nose ribs to the forward spar through the spar doubler. I have scuffed the rivets with a scotch pad to remove the crud that forms from riveting for better viewing.

Ideally I would replace them, but I never have good luck drilling out rivets and I am scared that I will drill them out and make the same mistake again with a larger hole.

Thanks in advance.

Joe Hutchison

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I would drill out all three. If you are worried about making hole bigger use a #31 drill bit. It's a little smaller but you will find that the smashed heads drill out very quickly.
 
Joe-

I bet if you check with Van's they will say they're good enough, perhaps with the exception of the lowest one. Somewhere in RVator there was an article about how damaged factory heads had little impact on overall strength of the rivet. And, as you noted, drilling them out has problems of it's own, especially in this tight location. But, again, I'd check with Van's, at least so that you can sleep better.

One thing that will really help to keep the rivet set square on the head of the rivet (and avoid the "smilies") is to use the "SnapSocs" from Avery. They do a great job. They are a little pricey just for some pieces of plastic, but they sure do work well... better even, in my opinion, than using masking tape over the set, which also works better than nothing. I've never had a bad factory head with them.

Don't worry--you'll get better and better at riveting (and so will your wife!) as you go and those nose rib-spar-main rib rivets are really difficult ones. A lot of other builders in this forum have had trouble here as well. Van's should have you rivet those before putting the skeleton into the skin.

Good luck.
 
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You are not alone here

Hello,

This is one place on all the RV models that seem to give builders problems. I thought that I was a total idiot when I decided to put structural cherrymax rivets in this spot on my 7 emp. I tried to put the solid rivets in there at least 3 times before calling it quits and moving on.

Later I have seen pictures and a couple of other live examples of where the builders did exactly what I did, they gave up and put in the cherry's.

For some reason, that weird place, angle etc. is a real problem for those of us that are not experts with the gun.
 
Leave them alone and move on. They are fine. I tried fixing mine and made them worse. As mentioned before, this is an akward place to work in and difficult to drill them out without making the holes bigger. Its OK really...

-Jeff
 
Joe, I'd drill out the top one and definately the bottom one. As T and Steve said you'll get better. The smiles (and the really chewed up bottom one) are caused by the rivet set bouncing.... yes, you didn't keep pressure on it :D I know this :eek: As the other guys said use a #31 or #32 drill, go slowly just past the head then use a punch (butt of the drill bit) to break off the head. then drill through the rivet (not quite through), put a bucking bar next to the shop head and punch the rivet out. If the hole is to large put the next size rivet in. Keep on going...

Larry
 
I've found that the solution to driving those AN470AD4-x rivets is to use a piece of hockey shinpad tape over the manufactured head. It is clear, comes off easily after riveting, and prevents the rivet set from bouncing around and making those smiles.

http://www.canadiantire.ca/assortments/product_detail.jsp?FOLDER%3C%3Efolder_id=1408474396670129&ASSORTMENT%3C%3East_id=1408474396670271&bmUID=1156877007627&PRODUCT%3C%3Eprd_id=845524443269727&assortment=primary&fromSearch=true

How Canadian is that ? :D

Cheers
 
You're not alone

Don't feel bad, this is common.

Personally, I would drill out the top and bottom and replace them, but leave the others. If access is bad, I would opt for the Cherry to prevent making this problem worse. I did a similar thing on my empennage. I replaced the same rivet three times, making the same bad manufactured head every time, due to poor access. Finally, the hole was quite large and the metal was distorted. I had to put in a much larger Pop rivet. If I could go back in time, I would have drilled it once and used the Cherry.

In your emp, The other good rivets are holding quite a bit of structural integrity on their own. I doubt there would be a marked decrease in reliability from the Cherry's in those two holes.

To be sure though, call Van's.

Also when drilling out rivets, I find it VERY helpful to use a spring-loaded center-punch. Put it in the existing dimple on the manufactured head and punch a few times. This will really help keep that drill bit from wandering. I read that tip on a thead here somewhere quite a while ago.

Good luck!
 
A guideline

Some cutting or deformation of the manufactured head is completely acceptable.

You could use this paragraph as a guideline.

5.2.7.5 Marring of the manufactured head. A cut or ring
caused by the riveting equipment used shall be acceptable on non-
flush rivets providing the depth of the cut is not greater than
one-fourth of the head height. Cut or ringed flush rivets shall
not be acceptable.

Info came from this alternate MIL-Spec at a NASA site.

http://mmptdpublic.jsc.nasa.gov/prc/MIL-STD-403.doc

Looks to me that the lowest one should be replaced, and possibly the top one, just like the previous suggestion...

gil in Tucson
 
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Drill out and replace all three...Concentrate on securing your spar, etc. There are some great threads on this issue...(ie Dan C. just recently addressed this issue on riveting tips).
 
Ditto,

if it was me I would redo the top and bottom, taking care that you know how to remove the rivets the right way. If you do not know how to remove the rivets practise first. As said, start with a smaller drill and step up like techique advertised.

Regards
Rudi
 
Joe,

This is just my opinion but may I suggest the fact that you are asking the question suggests that your not happy with how the rivets were driven yourself. In my book this is a good enough reason to remove them.

No-one else will know they're there at the end of the day, but you will.

If it was my aircraft I would remove just to keep me happy. I can however be pedantic at times. In my book its not only whether its structurally sound but whether it looks good, even in the spots where no-one else gets to see.

As I said, just my opinion. Happy building.
 
Hello Joe,

I'm inclined to agree with Andrew on the subject of the rivets that you are not happy with; but may I suggest (at the risk of telling you how to suck eggs) that you sleep on it for a while before you take a drill to anything.

The fact that you have raised the question would seem to indicate that you are not happy with them now and will probably never be if you decide to leave them in place however the old saying of "act in haste; repent at leisure" has a fair bit of currency here and it would be a great shame to drill them out and wind up with a mess on your hands.

This of course is only my opinion; happy building,

Kind regards,
 
Joe, I might caution against drilling them out JUST BECAUSE they bother you. Just because they bother you does not make it a good reason to drill them out. Van's general recommendation seems to be leave them because people do tend to do more damage removing them, sometimes even when they know the right way to drill a rivet out (see Gil's description above). This might be especially true in your location where you are dealing with a tough angle and three or four thin layers.

Also, anytime you drill out a rivet you leave a larger hole, especially in the thinner material you're working with in this instance. Even if you get another rivet of the same size to set in there, realize that you must have a shop head that is wider and taller than the original hole. It must be 1.5x the diameter of the NEW (not the original) hole and .5x diameter of the NEW (not original) hole high. I bet 7/10 builders who replace rivets don't keep this in mind. Sometimes a rivet of the same size will accomodate this, sometimes it takes a longer rivet which introduces problems of its own.

In short, there are going to be a lot of rivets that are not "perfect" on your airplane by the time it is done. I'm not suggesting that you be sloppy. In fact, try as hard as you can to set every rivet perfectly but recognize that you will not be 100% successful at this. Occassionally they should be drilled out and maybe this is one of those times. At the same time, in many instances, they are sufficient as is, or at least better off left alone. (I too am guilty of violating that last premise in the attempt to make things "perfect"!)

One other thing to keep in mind... it is commonly understood that Van's has way more rivets in our planes than are needed structurally. (I've heard a couple different ratios given for this number). This is because it is acknowledged that we are going to have some "less than perfect" rivets. Once again, this is why I would check with Van's on this case.

Good luck, and remember that most rivets are far easier to set than those ones you are dealing with right now. I hope this helps. I remember very acutely worrying about these kinds of issues back when I was working on my HS.
 
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The hockey shin pad suggestion is a good one.
Additionally, I have found that it is much easier to set 1/8 rivets - especially those that are going through thick/solid material (for example, the forward tank attach brackets on a RV-6, or the difficult main spar to leading edge rib attach rivets) with a 3X rivet gun, as opposed to a 2X gun. The 3x hits harder, with less rapid beats. I find that the 2X gun on these 1/8 rivets is just not quite strong enough, even with the air pressure turned up, requiring many more hits on the manufactured head to properly set the rivet, risking dings and shop hardening.
So, I use a 2X for all the 3/16 rivets - less risk of damaging the skin than with a 3X, I think, and a 3X for the 1/8 rivets.
Bill Brooks
RV-6A
working on the fuselage (still)
 
replace them

when a rivet head is side loaded like that alot of times the rivet shank is in partial shear. replace them .
 
Leave them alone and move on. There aren't pretty but they are probably structurally ok. You will probably make the holes worse trying to take them out and then they won't be as strong.
 
This is why I sometimes wonder about experimental aircraft. THOSE RIVETS ARE NOT OK. Those that say they are not structural, and therefore strong enough may be right. However, when a person sees a AN470 rivet, they expect it to be a certain strength, and those certainly don't have that anymore. I highly recommend replacing the top, middle and bottom rivets with new. Skills must be honed, as what point do draw the line? If the specs call for an AN470, then it must be bucked in a way that retains the majority of it's strength. There are some mistakes in the plans as far as rivets call outs and stuff, but for the most part, I feel that the rivets must be put in I/A/W AC43.13 or else... how do we know the strengh of the overall airframe?
 
I will relplace the rivets but...

I appreciate all the responses to my question.

I knew that the rivets were not good, but I did not want to drill them out, just to mess them up again in a bigger whole. Besides, sometimes good enough is good enough. Believe me, I have flown in aircraft before that had structural issues way worse than those sloppy rivets to no ill effect (not recommended though).

My plan is to drill them out later before I attach the HS to the tailcone and replace them with some structural blind rivets as suggested by the technical counselors.

Joe Hutchison
RV-10 Tail Kit
QB Wing and Fuselage to be delivered Saturday Sept 16.
 
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Well, you certainly got a lot of opinions here as well as a little heat, so I'll throw in mine. I guarantee, my opinion is worth every cent you paid for!

First, I checked 43-13 and found no help. It shows rivet defects without addressing how bad they have to be to be unacceptable. You can find some guidance in the mil-spec, and it maybe should be considered the bible, since it is the standard the engineers follow when assessing strength.

Looking at the top rivets I wonder more about the top one than the bottom one. The head is very thin along one edge of the top one, providing virtually no strength along that side. The question, is how close to the hole does that ring get? How much meat extends & how far does it extend outside the hole?

The bottom one just looks ugly. From what I can see, the head thickness is probably still there and it probably still meets the diameter specs. I drilled out a similar one yesterday (mine was even uglier, kind of like a combination of your top & bottom rivets) and it was very difficlut holding the bit in place. It would catch an edge of the groove and spin off the rivet, even after centerpunching it. I used a die grinder to make a crater large enough so I could center punch it again and keep the bit in place. In addition, because of the distortion, I could not be sure of where the center of the rivet was. Thru dumb luck, I only enlarged the hole slightly, making it egg shaped just a little. I drilled all the way thru with a 3/32 bit and then I could see how far off center I was.

So, my 2 cents says check the specs first and you'll probably need to drill the top one but not the bottom.

One last note: As someone else suggested, a Van's an employee told me they had an engineer who did an analysis and concluded you could leave out every second rivet and it would still be safe. I suspect there are locations where this would not be true and since your questionable rivets are at the ends of a row, where there may be more stress than in the middle, they may be more important to have right. But remember, if you don't drill it out right, you could make things worse. So my rule of thumb is that a rivet has to be really bad before I will drill it. This rule came to me after drilling 3 or 4 rivets out of the same hole, enlarging the hole in the process & having to go with a #5 rivet. I would have been better off leaving the original slightly defective rivet.
 
Thanks

Thanks again everyone.

RScott, I appreciate your take on my dilema. Thanks for the encouragement.

I find it amusing that certain people who are building an amatuer built airplane question experimental aircraft in general. It must be wonderful to be such a self-assured youngster. I suppose I was that way once, then I grew up and realized that life is not perfect, and I am certainly not perfect.

It is a cliche, but airplane building is a journey, not just a destination.

Joe Hutchison
 
Joe,

I got a very interesting lesson in rivet relativism several years back at an airshow when I toured a CAF Heinkel 111. Inside the aircraft, fully 3/4 of the rivet shop heads were so bad that I would have drilled out every one of them, yet fifty years on they were still holding tight. As a result, I generally have to booger it up pretty good before I drill it out and redo it. On the other hand, if I were as good at riveting as I am drilling them out, I would never have gotten that good at drilling them out. :p Let's also remember that rivets are stressed in shear, not tension.
 
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