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Unpleasant Riveting Experience

Rick6a

Rick6a

Well Known Member
I've set thousands of blind rivets in my life, but this was a first.

One of the last tasks in the fuel tank assembly process is attaching the back baffle to the "Z" brackets using AD42-H blind rivets. To my chagrin, the stems were breaking off prematurely on approximately 33% of the fasteners installed. In an e-mail to Van's I noted using THREE different pullers to set the fasteners and the results were always the same. Once the stem breaks off short, there is no way the puller can grab it again. I also asked what I should do now. I included this photo:

fueltanks12625qr2.jpg


Van's response was that basically, they had no idea. I went out and brought a brand new blind rivet puller and (winced as I shaved the side off the nose to clear the side of the "Z" bracket) the results continued to be the same. After 2 rivets, I stopped.

I contacted Van's again and informed them that after using FOUR different rivet pullers, I have to strongly suspect that the fasteners are defective. It seems the stems on the AD42-H are too soft and tend to break off prematurely. I also informed them I installed the remaining "Z" brackets with Cherry rivets without further incident.

I have to ask if anyone else has experienced this phenomena and if so, please let them and us and the next builder know about it.
 
This won't help you but I quess you should sent those un-used rivets to the Van's which could ask from the manufacturer if they are defected. And I wouldn't use rest of those rivets but order (propably in your case "demand") new ones if you want to continue with blind rivets... Though case you got yourself into. :eek:
 
Before you send anything anywhere, take one of the supposedly defective rivets and pull it in some SCRAP material of the same thickness as the Z-bracket flange + baffle thickness + rib flange thickness.

Do this without the intrusion of the Z bracket web. Come at it straight-on with your rivet puller. See if you get the same results.

If you get the same results, ok then. But if not, then you know it has something to do with your technique and/or tool creating a stress riser or something of that nature on the stem.

I remember when I did these you were almost forced to come at it at a slight angle, bending the stem slightly. Not ideal.
 
I had the same issue with mine. I figured the rivet was probably pulled fully if the stem broke so I just cut the stems and moved on. A better quality puller would be better. Maybe. What brand were you using?
 
I had the exact same thing happen to mine. I think I had three or four of them do that. I cut the stem that was left, and didn't think about it again...
 
Like the others, I had it happen on a number of rivets. After a night of thinking about it I cut the stems and moved on.

--Ken
 
As mentioned in the original post, I shaved the nosepieces on three of the the pullers to insure perpindicularity with the heads of the fasteners. I do not believe either the quality of the pullers nor perpindicularity is the issue. The pricey puller on the right is designed to pull Cherry rivets and with plenty of clearance, the stems broke off prematurely in it too.
fueltanks12815tf4.jpg
 
Broken Stems

Gents,

I had a few stems broken when I was riveting the elevator if I recall. I switched to another hand pop riveter and I didn't have any problems. Switched back to the original pop riveter and started braking stems.

After closer examination I noticed that the stems that were broken off (the part that separated from the remaining stem) had sharp grip marks in them. When I compared these marks to the completed pulled stems I noticed there was a difference. The riveter used that broke the stems off prematurely left sharper (deeper) grip marks then the riveter that worked fine. The sharper grip marks created stress concentration areas in the stem which causes it to break prematurely (my opinion).

I retired the riveter that broke the stems off prematurely but I suspect that I could file/grind down the gripping surfaces so they don't dig in to the stems so sharply/deeply and that would have solve my problem. But haven't done that yet.

The riveter that failed me worked great when I used it to build my RV-4 many years ago.

Food for thought.
 
Depth

I think this is caused by excess material depth for the rivet grip length. Maybe a longer rivet is called for.
 
Rick6a said:
As mentioned in the original post, I shaved the nosepieces on three of the the pullers to insure perpindicularity with the heads of the fasteners. I do not believe either the quality of the pullers nor perpindicularity is the issue. The pricey puller on the right is designed to pull Cherry rivets and with plenty of clearance, the stems broke off prematurely in it too.
fueltanks12815tf4.jpg
Click to expand...

Rick, what a neat line up of pullers. Now we know where to go if one is needed locally. :)

Seriously, you must like pro seal. I ordered QB wings while building the fuselage mostly because I can't stand the stuff, it's so messy. I'd rather skin a racoon like when we were kids and hunted them for $1 per hide and donated the carcass to a local bar for a weekly free BBQ feed.

The rivet stems appear to not have the weak tension point where they transition to the ball that spreads the hollow shank. I've had a few break early on some little projects and wracked it up to "made in China". Perhaps in some cases, the puller is cutting too far into the stem and creating a weak point other than where is should be.
 
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TShort said:
You ate raccoon? :eek: BBQ, no less.
How did that taste?

T.
Click to expand...

Not bad.

In rural Minnesota we ate most anything (but not skunks), lots of squirrels, rabbits, and pheasant. Also kept tabs on the fish in the Little Cottonwood River.....back in the good ol' days....:)
But we did not have RV's flyin' around.....
 
Side load

I've noticed that when you are in a tight area the puller might have a side load from something (in this case the Z bracket), the stem will break before the rivet it 100% set.

Just grind more off. :)
 
My experience was a bit different; I built aux tanks into the leading edges of my -7 wings & needed extra rivets so I ordered from an on-line vendor. I got rivets that were definitely defective. The mandrel has a notch to weaken it that causes it to break flush with the head, if everything works correctly. The batch I got had the notch outside the head, *before* the rivet was pulled. Test pulls in scrap stock resulted in the same break point, about 1/4" above the head, every time. It appears that the factory used mandrels intended for rivets with about a 1/4" to 5/16" longer reach. The vendor replaced the rivets but acted as if they were using 'customer is always right' business philosophy, rather than interest in QC. They weren't even interested in me sending the bad rivets back.

Charlie
 
FrankK90989 said:
go to a pawn shop and try to find one of these oldtimers, they get in close.
img0606oa1.jpg
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Frank, Interesting that you bring up this particular puller. I recently had to find one of these for use on my bi-plane. I had to pull 32 stainless steel rivets down inside a 5/8" channel for the engine mount blocks. This is the ONLY puller that would do it.
 
I had the same problem, a second rivet puller did exactly the same. I unscrewed the nose of the puller allowing the jaws to grip lower down the stem and it worked.

Paul
 
There seems to be own puller for Cherry rivets. Does "standard" rivet puller work with Cherrys at all?
 
I did my tank baffle just a few hours ago and two of the AD41-H pop rivets (Baffle to Rib only) broke off prematurely. All of the AD42-H's for the Z-brackets were fine. One thing that I did note was the two that broke off too soon didn't seem to take less pressure when they popped, compared to the ones that set correctly.

I chopped mine down with some snips and will ground the stems down more once the proseal sets. I don't feel like picking a million metal specs out of wet proseal.
 
Stems Breaking

I would think that one would use the same rivets with the steel stem, not the aluminum stem.

Marson does make them. I don't know the details of exactly what Vans is starting out with, because I am building a 6, and they use a similar looking rivet to hold the tank ribs to the back baffle.

Mine were button head, closed end, Aluminum body and had a phosphate coated steel stem. They worked fine. I also had no side clearance issue with the gun though. I do think that the aluminum stem is just not adequate to for the best blind head.

If someone lets me know how much aluminum these are going through I will figure out what the Marson part number for the steel stemmed rivets actually is.

If they want to try some, I can get rivets from Marson directly, as a matter of fact I have to order some other Marson product for my Dad's Skyote project tommorow, so let me know.

I will also post back once I get more info.

[email protected]
 
I had the same thing happen on my first tank so I cut them off. I suspected the rivets Vans supplied might be at fault so I bought 50 rivets from a supplier here in the UK to play with on some scrap. The new rivets were no different, the stems would snap just as easily unless they were pulled dead square and very smoothly. On the second tank I clecoed all the brackets in place first and riveted from a direction that allowed me to rest the lower handle of the riveter on the next bracket along. I tried not to put any weight on the bracket but use it just to steady the rivet puller and provide a reference for squareness. It seemed to work ok as all the stems pulled out as they should do.
Andy Smth, RV7, Doing the wings.
 
I am pretty close to doing this little task and I simply wonder about the structural integrity of having some blind rivets not pulled completely. It would seem to me that this is a very critical area of attachment to the rest of the wing. I know the flush screws also add some integrity with their attachments to the wing spar, but only minorly so. It seems that these Z brackets are pretty dog-gone important.

Has this always been a problem on Vans airplanes, and does anybody know what they have to say about this?
 
jdmunzell said:
...I simply wonder about the structural integrity of having some blind rivets not pulled completely.
Click to expand...

Jeff,

When I pulled my two that broke prematurely last night, I didn't notice any less pulling strength compared to the ones that broke on time. Today I collected all of the stems and compared the ones that broke correctly with the two that didn't. Both breaks occured at the bottom grip mark on the stem that the puller created.

Personally, I am not worrying about my two that broke because none of them were connected to the z-brackets. To truly know how weak these rivets are, a pull test would need to be done.
 
jdmunzell said:
I am pretty close to doing this little task and I simply wonder about the structural integrity of having some blind rivets not pulled completely......It seems that these Z brackets are pretty dog-gone important.

Has this always been a problem on Vans airplanes, and does anybody know what they have to say about this?
Click to expand...
To me, the saving grace of the "Z" bracket arrangement is that the inboard and outboard brackets are attached to the fuel tanks with AD4 rivets. Those two brackets alone and with all the 8-32 screws attached around the tank perimeter should hold the tank in place. Still, I sure didn't like having so many stems break off prematurely. And it galled me to have to drill them out into fairly soft proseal. I only drilled them out on one bracket where 3 of the 5 AD42-H rivets were defective. You'd be surprised at how easy they are to drill and punch through. I think a much stouter rivet is called for in this area so I replaced those rivets with 1/8" Cherrys. On the other tank, I used Cherrys exclusively. Heaven help the lad who ever has to try to drill them out though!

As I mentioned before, when I contacted Van, their position was they had no idea why it was happening to me. Maybe I am the only one who has bothered to report the condition to them. The fact that so many people are reporting the same thing on this thread alone suggests to me that far more people are experiencing this than anyone expected.

I do know from past experience that quality control measures are in place for good reason. It is not at all unusual for bad fasteners to make their way through the food chain. Now I really don't expect Van to fund a QC department to test every piece of hardware that goes through their doors. If they did, we'd all be paying far more for our kits and we'd be better of going certified! :eek:

In this case however, I truly believe the AD42-H rivet is a marginal weak sister choice for this particular application and it wouldn't hurt to replace it with a more reliable fastener.

But hey...what do I know?
 
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Maybe it's overkill because I'm not an engineer or even a rocket scientist, but installing Cherrys here seems prudent.

I can't believe Vans doesn't know what to make of it, especially seeing as how so many other folks on this post are reporting similar issues.

Any A/Ps or I/As want to render an opinion?
 
Cherrymax CR3213 rivets

I used CR3213 Cherrymax for riveting the wing leading edge ribs to the main spar in order to eliminate the problem of driving rivets in tight quarters and bucking them in the blind.

For pulling the rivets, I bought the cheapest no-name rivet puller that True-Value Hardware sold, and ground the nose down to give access to the rivet stems up against the main ribs. The process went flawlessly with the cheap tool. From my experience, it is not necessary to purchase the high-dollar Cherrymax puller to pull a few -4 rivets.

I then used the same ground-down rivet puller to pull the AD-42H rivets on the Z-brackets. This process went flawlessly as well.

While I don't share the experience of broken rivet stems that several of you have had, I think that Cherrymax rivets would be a good choice for the fuel tank Z-brackets as well. And I wholeheartedly recommend Cherrymax rivets for the wing leading edge ribs.

If you decide to use Cherrymax rivets, be sure to get the proper grip length for each application. For example, on the leading edge ribs I had to use CR3213-4-4 where the rivets went through both the spar doubler plate and the spar web, and CR3213-4-2 where they went only through the spar web.
 
One thing still bothers me here.

AD42-Hs has closed shop head side while Cherry Maxs are more like normal pop-rivets. Do you seal manufactured head side of the Cherrys as you do for the shop heads for normal rivets in tank? Or how do you ensure that fuel doesn't leak through the rivet? Would it be possible to put so much sealer to the rib that actually the rivets never come out to the tank...

Does pop-rivet heads have own naming? Manufactured and shop head doesn't sound good but I quess you understand what I mean.
 
Pop Riveting close to structure

The pictures of shavaing off the nose of the rivet puller is a good idea. The EAA video site of Helpful Hints has another idea that I used to place the F-7129 ELT Strobe bracket.
Take 1/4 inch diam Aluminum rod and cut off 3/8 inch of this so as to create a wedge of aluminum cylinder. Then drill a hole through the center (or off center if preferred for fit) and use as such:
In a locatition where the aluminum stringer is preventing placment of a pop rivet puller, place the rivet in the hole (e.g. LP4-3) then place the Aluminum cylinder spacer you made with the stem of the pop rivet inserted in the drilled hole. Then pull with the pop riveter (manual or pneumatic). The wedge will allow for more room for the large nose of the rivet puller and yet allow for the rivet head to lay flat in the hole. This also allows the nsoe of the rivet gun to clear the stringer.
 
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