Vertical Stabilizer - Machine Countersink - Re-order or build on?

I thought I was ready to prime the vertical stabilizer components and start riveting until I came across this. Is this a build-on moment or a re-order and try again moment.

Page 6-3 Step 8 - I machine countersunk the rear spar flange holes to accept the skin dimple. In order to get the dimple to fit nice and flat, I had to go pretty deep. When I went back to check prior to priming, I found that the rivet swims in the hole:



The rear spar cap sits behind the rear spar and accepts the rivet. Not sure if I’m OK to build on or if I should re-order the rear spar:



For clarity, here’s the rear spar machine countersink from the other side - Note that the skin dimple sits in this countersink. Rivet is shown for demonstration purposes:


Your thoughts would be appreciated!

Eric - check out this thread beginning around post 6:

http://www.vansairforce.com/community/showthread.php?t=110850

I think you're good with the hole size since the flange is sandwiched between the skin and the cap. The issue - although hard to tell exactly in the pic - is if the CS is too deep to set the rivet. Regardless, I would talk to Van's.

If I had a dollar for every discussion about CS too deeply for skin dimples... You will see a lot of threads about it - I think most new builders have a problem with this skill - especially for skin dimples. When you use your test piece to judge the depth of your CS, the dimple will not sit perfectly flush in the CS - too shallow and the skin will pucker around the holes when riveted. Eventually you will be able to gage what is deep enough - the riveting will then bring it flush.

I, in fact, replaced my VS rear spar for the same reason (even though Van's said build on). Guess what? The replacement turned out almost identical to the original - even with a few less clicks on the CS cage.

Eric,
Normally when you csink a hole to accept a dimpled surface you need to go around .005 deeper than a normal csink. Using the rivet inserted in the hole, measure the depth and see how deep you went. Here MIL-R-47196A(MI) is everything you wanted to know on hole diameter etc etc. It appears that it may be too deep and you may end up replacing the rear spar.

One other choice you have to use use and "oops" rivet. In this case, this would be a 3/32 rivet head with a 1/8" shank. As long as you have the proper edge distance you should be fine with this method. You can obtain the rivets from Vans or several other sources. the part number is NAS1097ADx-x.

Thank you! I'll call Vans tomorrow morning with my credit card prep'd and ready just in case.

Thanks for the references as well!

I would say to build on.

Bill.Peyton said:

One other choice you have to use use and "oops" rivet. In this case, this would be a 3/32 rivet head with a 1/8" shank. As long as you have the proper edge distance you should be fine with this method.

Click to expand...

Well, maybe. A couple of them where needed is OK. I asked Van's about using them in a location where I neglected to dimple the last 9 holes in a flange, and didn't realize it until too late. Since it was an area that would be under significant aerodynamic load, their advice was that if I did use NAS1097 rivets I'd need to double the number due to the reduced head strength. So... not always a safe 1-for-1 substitution if you're thinking about a bunch of them.

Eric,

What did you end up doing, reorder or build on? I ran into almost the exact same thing and after lots of research and thinking about how the spar cap will support the flange CS that seems too deep I decided to build on. I never talked to Van's though.

Sumit