Pictured here is the rear spar (VS-803PP) and the rear spar doubler (VS-808PP).

All vertical stabilizer ribs and the front spar were dimpled in preparation for priming and assembly.

Van's has you countersink a number of holes at the bottom of the rear spar doubler and dimple the corresponding holes on the rear spar so that when riveted together the flush side of the rivet faces forward.

It took a number of tries to get the countersink depth correct so that the rear spar would lay flush against the doubler.  I started shallow and would cleco the two pieces together and re-countersink as necessary until I got the correct depth so that the rear spar and doubler would lay flat against each other.

Van's give you an option to cut out a series of lightening holes on the spar doubler.  I did not do this.  Main reason being that I did not have the cutting tool(s) to do this properly.  I checked the Yahoo RV-7/7A group and those builders who cut those out saved a little over 3 oz on the weight of the doubler.  In retrospect, I wish that I took the time to cut those out, however, it won't make any difference in the final product with the exception of the weight savings.

Pictured below is the dimpling of the vertical stabilizer skin.  I dimpled as much as possible with the pneumatic squeezer (SWEET!!! Love that Squeezer) and dimpled the remaining holes using the C-frame.  This was Tami and I's first attempt at using the C-frame.  I was pretty happy with the results.  Need a proper hammer to strike the C-Frame (A 16-oz claw hammer is not the right tool, I ended up purchasing a 12-oz soft face hammer- MUCH BETTER).  Also, if you drag the skin across the male dimple die (even very lightly), it will leave a scratch on the Al-Clad material.  A little time and attention on the 2nd side we dimpled resulted in fewer scratches around the hole.

The picture above is an example of two things.  One, I look for this "halo" mark around the dimple to ensure that I have a properly set dimple (if you see the "halo" and just inside the halo, the aluminum skin is a different shade, usually shinier when held up at various angles against the lighting, it means that you are hitting the skin to hard with the dimple die and are "crushing" the aluminum skin).  If I don't see the "halo" I re-dimple until I do.  It has been a pretty good GO-NO GO criteria.  The other example this picture shows is that if you are not really careful moving the skin around on the C-frame, you can expect to see surface scratches where the male dimple die runs across the skin.  This is not deep enough to cause concern, however, you want to be careful when moving the skins around.  If you have a 2nd set of hands, dimpling with the C-frame will go a lot faster and probably end up with fewer scratches.

The vertical stabilizer is ready for alumiprep and priming.