10 below again this morning. Worked in shop off and on during day.
Finished prep work on HS spar parts. Decided to prime all these parts because of doing so much fabricating work on them that disturbed the protective coating, and because of the structural importance of this assembly. Assembled and riveted spar assembly. Discovered two problems:
1. On page 09-04 I missed Step 8 where the counterbalance brackets get riveted into the forward and aft spars. Dumb mistake. Now the spar box is all closed up and I will either have to drill out a bunch of rivets and take it apart again, or get permission from Van's to use blind (pulled) rivets in place of the solid AN470AD4-5 rivets called for.
2. Back on Page 09-02 Figure1 calls for countersinking several holes for CS4-4 rivets. The instructions did not say anything about using the 120 degree countersink tool rather than the normal 100 degree tool. Being a first-time builder I did not realize that the CS4's have the 120 degree head, so I did not change the tool. Then on Page 09-03 you are told to rivet the parts together. After riveting I noticed the supposedly flush CS4's are not really flush. This may be due to the wrong countersink angle, or maybe I just didn't get the holes deep enough. I am afraid those slightly raised heads will cause a bump in the skins when they are attached. I think those rivets need to be drilled out and the holes countersunk a bit more with the corrrect 120 degree tool. Unfortunately I don't have enough CS4-4's left so I will have to get more.
After all this I went ahead and started deburring HS ribs to get a head start on the next steps.
To add insult to injury today, my "el cheapo" brand bench grinder went to the great tool crib in the sky with a loud "ZAP" and a big cloud of smoke!