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Wing spar countersinks

StressedOut

Well Known Member
Just got started on my wing kit. I've been reading Section 13 thoroughly before I do anything irreversible and cause a $2400 + shipping bill. There is a note on page 13-03 just above Step 3 that says:

NOTE: Machine countersink in all rib locations

This is a confusing note. I looked ahead in Sections 14 (Wing Ribs) and found that the ribs are all attached to the spar with AN470 rivets so a countersink is not warranted.

Countersinks are needed on the flanges for the screw holes and nutplate attach holes. On the spar web there are four nutplates on the outboard end fastened with AN426AD3-3.5 rivets (page 13-02, Step 2 and Figure 2). There are also three nutplates requiring countersinks on the inboard end (page 13-05, Step 3 and Figure 1). However, I do not see anywhere in the instructions that you countersink the rib locations.

What am I missing here?
 
All the little holes along the flange that are two in a column eventually get countersunk to rivet the ribs and the skins. The end of the rib is the big rivet you’re seeing but the top corners of the ribs are the smaller countersunk rivets that go from the skin to the spar to the rib.


Edit: just realized this was the rv-14. But I can’t image it’s that different.


 
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I too was confused by this note. The ribs attach to the spar web with AN470AD4s, no countersink as you mentioned.

I believe this note refers to just the #40 holes in the flanges. The countersinking in Steps 3 and 7 on that page include the #40 ribs attach holes, so why is this note needed? I contend it's not.
 
All the little holes along the flange that are two in a column eventually get countersunk to rivet the ribs and the skins. The end of the rib is the big rivet you’re seeing but the top corners of the ribs are the smaller countersunk rivets that go from the skin to the spar to the rib.


Edit: just realized this was the rv-14. But I can’t image it’s that different.



Actually, it is different on the RV-14A. The aft holes in the spar flanges are not countersunk. The top and bottom wing skins that are riveted there have a machine countersink in them so no countersink is in the flange itself for those holes.

Edit: Looks like all of the holes in the flange are countersunk. I was under the mistaken impression that the wing skins were countersunk and not dimpled.
 
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I too was confused by this note. The ribs attach to the spar web with AN470AD4s, no countersink as you mentioned.

I believe this note refers to just the #40 holes in the flanges. The countersinking in Steps 3 and 7 on that page include the #40 ribs attach holes, so why is this note needed? I contend it's not.

I agree. Maybe this is something that Van's can review and revise if they deem it necessary.
 
When Van's makes a note, it refers to the step following the note.

The step is before step 3 - and step 3 says:
Step 3: Machine countersink the #40 holes indicated in Figure 2.

If you look a figure 2, it is referring to countersinking all the holes which correspond to where the little tabs on the wing ribs are located. You are countersinking to take the head of a rivet only (the fuel tank skin goes over the top of these rivets) [edited for correctness]

The rest of the holes in the spar flanges are countersunk in other steps.
 

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Well I finally got my confusion on this issue cleared up. I called Vans and in general every single hole on the upper and lower spar flanges will have a countersink.

The only difference is that some will be flush and some will be 0.007 in. deeper than flush. For locations with screws, the C/S is set by diameter instead of flushness.

I still think the note above Step 3 confuses more than clarifies.
 
When Van's makes a note, it refers to the step following the note.

The step is before step 3 - and step 3 says:
Step 3: Machine countersink the #40 holes indicated in Figure 2.

If you look a figure 2, it is referring to countersinking all the holes which correspond to where the little tabs on the wing ribs are located. You are countersinking to take the dimple in the skin in these locations.

The rest of the holes in the spar flanges are countersunk in other steps.

Trent is correct.
This note (and related step) is trying to indicate holes in the fwd. row of the holes in the flanges that get machine countersunk for a flush rivet at locations that they are only attaching the rib to the spar (no skin) because it is in the zone where the fuel tank attaches.
 
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