Sat May 9 2009

Cracked rivets

First on the docket for today was to rivet nutplates on these two brackets which get riveted to the web of the forward half of the F-704 bulkhead. Those of you who are especially observant may have noticed that these nutplates are not K1000-8 nutplates. They're K1000-3 because when I match drilled these parts, I acidentally used a #12 drill instead of the #18.

I tried riveting these things on a couple times, but kept mucking up the rivets. So I drafted Kerin in to helping me buck them with me on the gun. The rivets in the center of the web went fine, but the ones near the ends just wouldn't get flush even though I countersunk the holes the perfect amount. I ended up with this dent in the web near on the lower left rivet. The problem here is that there's the huge spar carrythough bar right behind this spot, so when I was driving the rivet, the web would only flex on the side of the rivet set that was away from the bar. This created a slight gap between the rivet set and the web, so the rivet isn't quite flush. All 4 of the rivets adjacent to the bar are like this.

I'm thinking that tomorrow I may drill these out one more time and try to backrivet them with the large heavy duty back riveting bucking bar I purchased a while back.

After that, Kerin helped me drive these AN470AD4-5 rivets. They all came out perfectly.

After peeling all the blue tape off the F-770 side skins, I clecoed them to the longerons and decided to install the rivets through the F-704H doubler plates. The squeezer made quick work of these.

This rivet smooshed sideways a bit, so I needed to drill it out. However, when I was examining the shop head of this one, I noticed something odd...

Nearly all of the shop heads of these rivets were cracked. If you click on the full sized picture, you can clearly see one of the cracks. It's a 45 degree spiral running up the side of the shop head. Really weird. I drilled all these out and squeezed new rivets in their place except this time I used rivets from a different compartment in my storage container. They were all fine. No cracks at all. I'm not sure what was the problem with these rivets, but I threw out all the ones in the compartment that was problematic.

Come to think of it, this is the same compartment I used earlier in the day when Kerin and I riveted on the brackets to the F-704 bulkhead. I'll have to check those shop heads for cracks as well.

Last task for the day before going out for dinner and a movie was to cleco up the aft half of the F-704 bulkhead and the seat ribs. It's looking pretty good.

OK, so after getting back tonight, I did some more investigation. It seems that someone on VAF had exactly the same problem on exactly the same type and size of rivet just one day before I had the problem. That seems way too coincidental.

Here's an enlarged view of the rivet pictured above.

I also went down to the shop and took a couple photos through my loupe of the AN470AD4-5 rivets which Kerin and I had bucked earlier today. This one looks just like the ones I squeezed earlier today. Notice how the sides are very bumpy and there appear to be some voids in the end face of the rivet. Most of the rivets we drove to attach the brackets today look like this.

This one, however, was apparently from a different batch. Not only is the color on the outside darker indicating it came from a different batch, but the sides of the shop head are much smoother and there don't appear to be any voids in the end face of the rivet. It looks much better IMO.