<August 20, 2005>
Riveted Trim Parts & Elevator Stiffeners
Another decent day in the shop today. The elevator stiffeners and trim parts were dry after yesterday's priming session, so I go to work riveting them in place. Later in the afternoon my buddy Sean, a three time homebuilder [Sean's Awesome Pitts S-1-11B], brought his friend Steve over for a visit. Steve was visiting from the UK and is thinking about building an RV-7. I gave him a shop tour and he got to squeeze a few rivets (in scrap) while he was here. I think it was good for him, at least I hope it was, as he got to see first-hand the plans, parts, tools and a little bit of the process of construction.
As I mentioned the other day, I am going to use NAS1097 rivets to attach the nutplates to the trim reinforcing plate. While I don't know what their technical name is, NAS1097 are rivets with smaller factory heads, some of which are referred to as oops rivets. Why would I use these? It's pretty simple, the reduced head size of the rivet allows you to countersink thinner material than you normally would (in lieu of dimpling), therefore I don't have to dimple the nutplates that attach behind. You wouldn't do this for the skins or anything structural, at least I wouldn't, but for attaching nutplates it is fine as the rivets just hold the nutplate in place while the nutplate and screw provide the strength. Read on for more info...
The rivets standing up from left to right are an NAS1097AD3, AN426AD3, and a NAS1097AD4. Then on the right you see the difference in head size between the NAS1097AD3 and a common AN426AD3. I will be using the NAS1097AD3 rivets to attach the nutplates to the Trim Reinforcing Plate. The NAS1097AD4 rivets are commonly referred to as Oops rivets as the shank is the size of a 1/8" rivet, but the head is the approximate size of a 3/32" rivet. These are useful when you have to drill out a skin rivet and the hole gets enlarged. In that case you just drill out with a #30 and put in an Oops rivet (NA1097AD4) and nobody will ever know.
I laid out the parts just to see how it will all go together. Looks pretty cool!
I countersunk the holes for the NAS1097AD3 rivets by giving the hole a few turns with my Avery Deburring/Countersinking tool, testing for depth with a rivet as I went along. Normally you would dimple here as this material is too thin to countersink for a AN426AD3 rivet, but since the NAS1097 rivets have a reduced head, you only need a very small amount of countersinking to get the job done. Just be careful you don't go to far or you will end if with a sharp edge in the hole and you don't want that.
Here is what it looks like after the first rivets were squeezed. The picture makes it look like these rivets are sitting slightly proud, but they are not, they are perfectly flush with the skin.
It took about 30 minutes, but here is what I ended up with. All the rivets are perfectly flush, and I didn't have to dimple the rivet tabs on the nutplates
Test fit, everything checked out fine. I will mount the trim motor brackets to the cover later.
After dealing with the Trim Reinforcing Plate, I got down to back-riveting the stiffeners to the elevator skins. Here's a shot of the first one completed.
Next I moved onto the left elevator. Here you can see the reinforcing plate back riveted in place.
All done with the left elevator (stiffener riveting). Here you can see a good example of difference in rivet head size between the NAS1097AD3 rivets and the standard AN426AD3 rivets.