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20yo RV-6 belly skin extensive rivet repairs

BruceMe

BruceMe

Well Known Member
I purchased a damaged RV-6 project, the previous owner was getting on and losing his health to the point he was no longer able to safely pilot. He had likely repeatedly hard landed this aircraft and unfortunately the last landing was a flip-over.

Needless to say, there's a long list of repairs and I've been working on it for 6mo now. One thing I noticed early on in the pre-buy was that all the belly skin rivets where smoking. This isn't an accident issue, but a long-term ongoing maintenance and safety concern.

20160703_175804.jpg


This is a link to my blog post on my thorough repair, it was extensive. If any of you are flying with belly sheet with even a few smoking or pulled-through rivets like this... please fix it. It's not oil and it's not "ok".

Before / after belly skin repair

-Bruce
 
Make sure the supports where put in that tie the spar to the angles on the floor. Easy to add if they where not there before. This is the exact symptom of what will happen if the floor angles are not tied into the spar.
 
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JonJay said:
Make sure the supports where put in that tie the spar to the angles on the floor. Easy to add if they where not there before. This is the exact symptom of what will happen if the floor angles are not tied into the spar.
Click to expand...

SB or picture?
 
There is an angle behind the spar that connects the spar to the fore/aft belly sheets at the seem... sound right? I'll take a picture asap and post it.
 
What JonJay is referring to is that there are angle brackets on the forward side of the spar connecting it to the longitudinal floor angles. These must be in place.

Also, smoking rivets are fairly common on the early sixes that have floor mounted rudder pedals. If you have floor mounted pedals, have someone sit in the plane and push on the brakes while you watch the floor. It will get your attention.
 
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Missing brackets

So I poured over the old plans :confused: and I don't see any connecting brackets between the spar and the floor stringers. And I'm pretty sure they aren't there.

14cz8r9.jpg


Here's the modified plans... is this what you had in mind?
idrupv.jpg
 
There are details on another plans page (I don't remember what number) that contains some misc. drawings showing the attachment of the aft end of the floor angles.

Also, the middle two floor angles are supposed to be bolted to the two uprights that the fuel valve is mounted on.

Smoking rivets was common on the early 6's at the bottom center section flange regardless of whether the angle brackets were installed. A revision was issued at some point to change the rivet call out to AN426AD4's
 
rvbuilder2002 said:
There are details on another plans page (I don't remember what number) that contains some misc. drawings showing the attachment of the aft end of the floor angles.

...
Click to expand...

It got snuck away on the top left of Page 46.

However no bolt call out is give for the two bolts that attach the bracket to the floor stiffeners. I used #8 bolts.
 
You only need to support the angle on one side. I see all kinds of strategies to accomplish this but the most common is a simple "L" bracket out of .063.
The idea is to add support here so the hammering and vibration of the floor during flight does not work those rivets. The plans where very weak in this area, as well as for the fuel line routing. I was not aware they changed the rivet call out for that seam. You may be fighting two things - no brackets and the wrong, or discovered to be inadequate, rivet size.

My floor brackets serve dual duty, similar to the newer 7 and 9. I riveted an .063 angle on top so I could install an Adel clamp to support the fuel line. This also gives a more finished look to the part.
34eqjxt.jpg
 
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JonJay said:
My floor brackets serve dual duty, similar to the newer 7 and 9. I riveted an .063 angle on top so I could install an Adel clamp to support the fuel line. This also gives a more finished look to the part.
34eqjxt.jpg
Click to expand...

Good idea.
It could just be a flange bent on the part when it is made.
 
SIX PACK?

...We had a guy stop by at our airport facility, asking if we could fix his "Six-Pack" issue with his belly? We thought he was jut pulling our leg until we saw the bottom of his airplane (RV-6). It was wrinkled from end to end, from what must have been the most ridiculous landing ever! Even the gear legs were toast. After we told him that he pretty much was in need of a new fuselage, he got mad, jumped in and took off for parts unknown.:eek::eek:
Thanks, Allan
 
BruceMe said:
This is a link to my blog post on my thorough repair, it was extensive. If any of you are flying with belly sheet with even a few smoking or pulled-through rivets like this... please fix it. It's not oil and it's not "ok".
-Bruce
Click to expand...

Smoking rives? Some of mine look like that. I assumed that it was oil from the engine. Are you saying they are lose and friction is causing the black marks?
 
Reboot said:
Smoking rives? Some of mine look like that. I assumed that it was oil from the engine. Are you saying they are lose and friction is causing the black marks?
Click to expand...

Yeah, that's bad. It happens, you can tighten them and it will probably stop. If it's just a poorly driven rivet, replace as-is, if you need to go larger, do that.
 
Me Too

My -6 was an early 90's kit, and has the same smoking rivets. It was obvious that they need to be replaced, but now I know about the reinforcing brackets that need to be fabricated.
Thanks, guys!
 
jetjok said:
My -6 was an early 90's kit, and has the same smoking rivets. It was obvious that they need to be replaced, but now I know about the reinforcing brackets that need to be fabricated.
Thanks, guys!
Click to expand...

Super easy to miss this on the plans. It was a topic of much discussion when I built mine or I might have missed it too!
 
JonJay said:
Super easy to miss this on the plans. It was a topic of much discussion when I built mine or I might have missed it too!
Click to expand...

YES!!! Page 46 Upper left corner it is not even in context. I would have totally missed that too. I have access to a great bending-break, so I will put a 1/4" curl in the longer "adjacent" (remember trig) curl to make that second edge you depicted instead of using another angle as I don't have any handy.
 
Why isn't this an SB?!

Normally "missed steps" in building shouldn't be an SB. But this is almost a flaw in the building process and you'd think they'd issue an SB to ensure these brackets are actually there.

Maybe we should lobby? I'm guess I have fears of some poor Young Eagle is paying the price for an all-to-easy overlooked facet that so directly affects safety.
 
rvbuilder2002 said:
There are details on another plans page (I don't remember what number) that contains some misc. drawings showing the attachment of the aft end of the floor angles.

Also, the middle two floor angles are supposed to be bolted to the two uprights that the fuel valve is mounted on.

Smoking rivets was common on the early 6's at the bottom center section flange regardless of whether the angle brackets were installed. A revision was issued at some point to change the rivet call out to AN426AD4's
Click to expand...

Scott,

My 6A has no attach brackets and I will definitely add them now; Thanks for posting this issue Bruce. at 150 hours, I found a couple of smoking rivets on the long support angles. My rivets are -3's, not -4's (apparently the factory doing the QB's didn't get the memo). If I add the attach brackets, should I take on the task of replacing the -3 rivets with -4's or just replace as they fail? Also, can I use an oops rivets to get the larger shank without dealing with re-dimpling?

EDIT: after re-reading your post, I think you may have meant that -4 rivets were called out only at the double row of rivets under the spar. I may have -4's there and will have to check. I have no smoking rivets there yet.

Larry
 
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lr172 said:
.....

EDIT: after re-reading your post, I think you may have meant that -4 rivets were called out only at the double row of rivets under the spar. I may have -4's there and will have to check. I have no smoking rivets there yet.

Larry
Click to expand...

Only the forward row of the double rivet row. The rivets that go through both skin layers and the F-604 flange.
 
az_gila said:
Only the forward row of the double rivet row. The rivets that go through both skin layers and the F-604 flange.
Click to expand...

Thanks for the clarification Gil. My QB was built in '99, so I am guessing it probably has the bigger rivets there. I vaguely recall them being -4's and expected it based on the spar being there. I will check on my next trip to the airport.

Larry
 
lr172 said:
Scott,

My 6A has no attach brackets and I will definitely add them now; Thanks for posting this issue Bruce. at 150 hours, I found a couple of smoking rivets on the long support angles. My rivets are -3's, not -4's (apparently the factory doing the QB's didn't get the memo). If I add the attach brackets, should I take on the task of replacing the -3 rivets with -4's or just replace as they fail? Also, can I use an oops rivets to get the larger shank without dealing with re-dimpling?

EDIT: after re-reading your post, I think you may have meant that -4 rivets were called out only at the double row of rivets under the spar. I may have -4's there and will have to check. I have no smoking rivets there yet.

Larry
Click to expand...
The brackets aren't part of the qb, they're in the finish stage after you have the wings on. That's why it's so easy to overlook.
 
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