VS-808 Countersink (Vertical stabilizer doubler)

[Lou]

Have not had any countersink questions until now. I've read the other threads and I'm still not sure the spar channel and doubler are mating correctly.

I followed the suggestion of countersinking the doubler until a test rivet shows just a small ring of aluminum around the rivet head. When test fitting the parts, I can still see the spar channel sitting just a bit proud. The parts are not flat.

I don't want to countersink too deep. Should I just keep notching the countersink down a few steps at a time until they are fairly flat together.

The test rivet seems to be sitting the recommended .005 or more below flush. I'm way beyond Vans suggestion of just a few clicks deeper than flush.

 

[Lou]

Hi there Lou,

Bottom line, you will not get the pieces to lay perfectly flat since the countersink hole and dimple will be slightly different. As suggested in another thread, sometimes a crisper dimple can be made with a good whack on a C-Frame and good set of dimple dies which may help the fit vice using a squeezer.

It is normal to have a very small amount of space between the pieces, if you have countersunk to the recommended depth (.005) or just to the point where the rivet sits just a little below flush in the countersunk hole.

Keep everything tight when riveting, the thinner material VS-803 should pull tight into the VS-808 when riveted together.

If you achieve a flat fit by over countersinking, you will not achieve a proper fit between the pieces when riveting. The only other concern is over countersinking and enlarging the hole. This could be a problem on a thinner piece but probably won't happen on the VS-808 due to it's thickness (unless grossly over countersunk).

-Build on

 

[flion]

Dimples have a radius around the edge; countersinks do not. As mentioned, if you countersink until it fits flat, there will be a gap under the body of the dimple. If you don't countersink enough, rivets won't pull the pieces together. You can test your countersinking on scrap. There have been some attempts to give a guideline in 'clicks' or thousandths but experience has shown me that the thickness of the dimpled material affects how much you should countersink and you quickly get a feel for it with some sample pieces.