Ivan's RV-7

Riveting the stiffeners to the skinsTimer icon3h

June 20, 2022

Today I started riveting stiffeners to the skins.

The first thing I did was to dimple the trim access reinforcement plate and counter-sink the holes for the nut plates. Instead of dimpling the part and the nut plates, I went with the NAS1097 (also known as "oops" rivets). They have a smaller head than the "regular" AN426 rivets, which allows two uses.

The first case is to use them for damaged holes, so you need a larger shank. For example, a hole for the AN426AD3 could be upsized to -4 size. Then you can use a NAS1097AD4 rivet, which will have a factory head size similar to the AN426AD3 rivet.

The other use is to use them to attach nut plates. A smaller head size allows to counter-sink thinner materials (such as skins or various reinforcement plates) instead of dimpling them. This avoids the need to dimple the nut plate itself (which usually distorts it somewhat).

The trim access reinforcement plate dimpled and counter-sinked.

Then I riveted the nut plates using NA1097AD3-3.5 rivets.

Installed the nut plates.

Dimpled the skins.

The skins are dimpled.

And installed the plate and the stiffeners for one of the sides on both of the skins.

The reinforcement plate is riveted to the skin.

I did not buck the last rivet in the row (the aft one) as it would require bending the skin a lot, and if you don't do that, there is a risk that the stiffener will not sit tight against the skin (bending the skin pulls the skin from the stiffener).

I have already ordered a double offset back rivet set which should allow easier access to these rivets.

The aft rivets are waiting for the tool.