Vertical Stabilizer Countersinking

Hey Guys,

Please, could you tell me if the countersinking is too deep on part VS-808PP ? the vertical stabilizer beam? Please, see attached picture?
I thought it should be deeper because of the dimpled spar which is riveted on top of the VS-808PP.

Many thanks for your help!

Best regards,
Anna

Yes, too deep, you will not be able to set those rivets.

Hi Anna
On page 5-4 of your builders manual Vans mentions being able to countersink up to .005" deeper when nested with a dimpled skin."Just a few clicks more than flush" Throw some calipers on it and measure the depth and you'll be able to make your own determination.
If you are just a little deeper than that contact Vans on Monday. But from your picture I do agree with Bret that they do look too deep. I use scrap aluminum angle in my shop and dial in my countersink until I get it just perfect. I like to see just a slight halo around the rivet head on my countersink if I have a dimpled skin nesting in it.
Have fun with your build.

checking countersink

Make some samples tabs with various thickness aluminum sheet. Put a hole in each #30 and #40 on opposite ends so you can use them to check countersinks. Dimple the holes. Use the test piece to check the countersink. The sample should sit flush with the surface. If it bottoms and leaves a gap, the countersink is not deep enough. Creep up slowly on the right setting using scrap. As others mentioned, it's not much from perfect to too deep.

I have made this mistake, what will happen when you go to squeeze the rivet, the manufactured head will rise out of the CS to meet the set that is flush with the surface of the material you are riveting, leaving a gap on the underside of the rivet and the CS. It will be loose.

As others have said, if it is going to receive the rivet directly, then it is too deep. If a dimpled piece goes over it, it may be Ok depending on how snugly the dimpled part fits; try it with a piece of scrap dimpled but if the scrap wiggles around then it is probably too deep.

However, in that case, you can use some structural epoxy (Hysol, liquid aluminum, etc.) to fill the countersinks, re-drill and countersink again, and it will be Ok. You just want support under the dimpled part and a thin layer of epoxy will provide enough. The parts themselves have not lost significant strength. You can also use this trick on single countersunk holes where the rivet head goes directly in the countersink, but I would replace a series of holes like that, or if the countersinks were in thinner material (chance of opening up the rear face by countersinking too deep). Even then, if it's just one hole, you can make a tab to go behind the enlarged hole, fill and re-drill as before, and use a slightly longer rivet and still maintain structural integrity.

All that said, you will almost certainly feel best if you replace a part where you have made an error in several places.

I don't know if I should have, but I did. I had a similar dimple situation. I cut a piece of 0.021 (I think this measurement is correct) aluminum into a tiny circle, placed it over the machine head, they compressed the rivet. The machine head did not rise and the shop head looks good. The machine head looks great, just is setting lower than I intended. It occurred on a nutplate installation for I believe the battery holder.

Vans recommended ordering a new spar doubler. And I countersunk this one just such deep that the rivet head is flush.

Thank you all for your answers and your support!

Good Progress!

That looks much better! Now you can sleep peacefully.

Also, do not dispose of the first piece. Mark it as "SCRAP" and keep it in a bin or under a table. In the future you will probably need a piece of scrap aluminum for practice before you do a step for "real."

You are learning and soon will be an expert!

Anna said:

Vans recommended ordering a new spar doubler. And I countersunk this one just such deep that the rivet head is flush.

Thank you all for your answers and your support!

Click to expand...

Anna,

Be careful when using the coutersink that the bit doesn't warble (i.e. move around), enlarging the hole. Your countersink depth may be correct, but enlarging the hole is also bad news when it comes time to set the rivet. That said, there are "oops rivets" you can buy which could be used in such a case (the rivet diameter is slightly larger with the same sized head). Keep building, and don't get discouraged.