Wing Spar Rivet Question

I purchased a set of mostly completed wings about a month ago and upon inspection I'm noticing some what I consider poor riveting where the forward skins attach. I want some second and third opinions from those that know. It appears that someone set the original rivets at an angle. Half of the rivets have subsequently been drilled out. This caused an indentation on the spar where the original rivets were set. My question: is this OK? Can I just set rivets on top of this. Do I need to resize the holes and use larger rivets? Fire away. I'll be checking with Vans tomorrow as well.

Somewhat hard to tell from you pics, but it appears that some of the rivets are cleated and they do not even fill the hole? Pretty sure those will have to be replaced. If the hole is oversized from drilling out bad rivets, you'll need to drill out to the next size, but contact Van's. I had a one like that and they told me to upsize it, which worked just fine. Bottom line, check with Van's.

What to do

This is what I would do. Reshape the dimples using a 401 rivet set/bar combination that will hold the die, and a hammer. Do not use a rivet gun, things happen to fast and you risk marking the skin if you are not square and breaking the die. Or, cut a countersink into a bucking bar and reform it using a rivet as the die. Go one half size longer or use the first oversize (1/32" NAS1241AD3- http://www.gen-aircraft-hardware.com/images/pdf/solid_rivets_Oversize.pdf). It is likely that this NAS rivit will go in without reaming the hole larger. When you drive a slightly long rivet, the power needs to be set on the low side because the first few "contacts" with the bar need to be a very light touch so it will go down square. Excess power risks deforming skin. This bucking method really works. Try it out on some scrap. I have re-skinned the upper flap well skins on a DC-6 where all the rivets are dimpled. What happens is the rivet swells the hole because its dimpled. So all the material should be there, it just needs to be reformed. Next oversize would be a NAS1097AD4- rivet, And I would use those sparingly Find out from Vans how many of what type fastener in a row you can go before going to the next actual size larger (MS20426AD4-)

Drilling out 3/32 rivets often damages the underlying structure, unless you're good. Although the rivets in the photos are not perfect, you may cause yourself more problems by drilling out than you solve. I would leave them as is - only you and the original builder will know once it is finished.

It is entirely normal to have a slight indentation after drilling out. If the indent is deep you could buff out using something like a 1" scotchbrite wheel, but take out the minimum possible material and re-protect afterwards.

I would try to avoid using larger rivets, if possible, as you will have to enlarge the dimple unless 'cheater rivets' are used. If the hole is very out of round it could be drilled out slightly (say #39 or 38) to recover the hole. Slightly squeeze a longer rivet to make it fatter so that it fits in the hole - using regular rivets will make them liable to fall over. Setting these rivets with a hand squeezer held exactly square will likely provide the best results.

Pete

Checking my riveting knowledge

I didn't get a chance to call Vans today due to work. If it was just a few rivets, I might let it go. It's actually about 80% of the rivets (on the top side) that fasten the outward forward wing skin to the spar. It looks like the previous builder tried to rivet with the wire conduit in place, and therefore bucked each rivet on one side at an angle. Roughly 80% of the rivets on that side were set at an angle (approximately 40 rivets). You can easily see the rivets that look smashed down and to the left in the second picture. It appears the previous builder drilled out approximately 20 of the 40 bad rivets. Subsequently there is an indentation down and to the left on every drilled-out rivet hole. The opposite row has nice round well-driven rivets.

I drilled out a few bad rivets when working on my empennage. None left an indentation like that at an angle. To be clear, the holes are round. There's just an indentation where the rivet was squeezed down and to the left.

Looking for inputs. Here's what I think my options are before talking to Vans, in no particular order:

1) Replace all the rivers with larger diameter rivets. Why the recommendation to not drill the hole larger and go to an AD4 rivet? In order to do this, I think I would have to enlarge the bad holes, pull off the skin (this means drilling out about 100 rivets), countersink and dimple again for the AD4 rivet. Anything I'm missing with this process?

2) Use OOPS rivets. My understanding is these are larger diameter with smaller head. I think I also read that due to the smaller head, these are not as strong and to use sparingly. Is this is viable for 40 of about 55 rivets on that row?

3) Use a slightly longer rivet and squeeze it a bit to make the diameter slightly larger before I set it in a larger hole. This seems like a frugal man's version of an oops rivet. Will this work?

4) Use some type of doubler plate inside the spar. This would mean skin on spar on another piece of aluminum. Is this feasible?

Thanks in advance for any advice I get.

Drill them

If the holes are still round I would drill them out and set some new AD3 rivets. If a few holes are enlarged a little, pre-squeeze a new rivet and set normally. I don't think the deformation on one side of the hole will hurt anything but it is hard to tell from the pictures. It probably wouldn't hurt anything to leave them as is, but I wouldn't.

DaAV8R said:

If the holes are still round I would drill them out and set some new AD3 rivets. If a few holes are enlarged a little, pre-squeeze a new rivet and set normally. I don't think the deformation on one side of the hole will hurt anything but it is hard to tell from the pictures. It probably wouldn't hurt anything to leave them as is, but I wouldn't.

Click to expand...

I agree. Why not try drilling one or two out to see exactly how the holes are? It looks like the shop head of the rivets got toe nailed (bucked at an angle). If the holes are round press forward and replace them with the same rivets. Just be extra careful when drilling them out and you should be fine. I have replaced lots of rivets in airplanes that were bucked incorrectly without any problem. It is when you get to "D" and "E" rivets that they actually enlarge the hole when you buck them due to the hardness of the rivet. But we don't use those on our RV's.