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Trailing Edge riveting

mulde35d

Well Known Member
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I know I have seen a lot of threads on riveting the trailing edge and thought I would share how I decided to rivet the rudder trailing edge which turned out with zero twist (as far as I can measure with a digital level) and very little pillowing.

1. Before rudder assembly attach a 90 degree piece of aluminum angle to the side of a workbench (long enough to fit the entire trailing edge and use shims with a digital level to ensure it remains straight across the bench.

2. Match drill holes from one of the skins into the aluminum angle that you just installed in step 1

3. Complete all other steps up to the double sided tape on the trailing edge.

4. Tape the trailing edge together per the instructions and cleco the taped edge to the aluminum angle. Allow it to sit overnight.

5. Remove the cleco's and replace the aluminum angle with steel angle of appropriate thickness for back riveting. (shim the steel just like the aluminum to get a flat surface).

6. Use rubber clamps to secure the end of the trailing edge to the steel angle and back rivet the trailing edge IAW the instructions provided by Van's.

Their were a lot of steps such as priming, riveting the skeleton and so on that I left out as I solely focused on the trailing edge here, but this worked out really well as you can see in the photo. The rudder trim tab that I fabricated got in the way of viewing the entire edge, but it has zero twist all the way to the end as far as I can see and measure.

Hope this helps someone who may be approaching this step.

7_12_5.jpg
 
Perfect timing as I'm working on the rudder as well. I like the idea of using a steel angle to back rivet, but how did the rivets come out?

Some advocate alternating the shop heads as it makes for a symmetrical trailing edge. I came across one who suggested a flat set with a 8 deg angle to better form the shop head into the dimple (minimize the acorn look).

My plan is to use the aluminum angle (match drilled to TE) to cleco the wedge and skins together while the adhesive (3M 5200) cures. Then back rivet on a steel angle.
 
Rivets

I ended up riveting all of them on the same side (no alternating) primarily due to the piano hinge I added on the trailing edge for electric yaw trim. It would have made it impossible to keep the entire edge clamped flat to the table during riveting with the hinge installed. I also determined that if you use the vans suggested method of only partially setting all the rivets first then it would be impossible to alternate sides and maintain a flat surface. The shop heads came out nice and flush with no smileys in the metal. I used the standard 1? flush set in the rivet gun with pressure turned down to about 80 psi. Simply followed as much of Vans suggestions as possible.
 
Careful with the match drilling!

I got the opportunity to build a second rudder when I did the match drilling as described above. Read the details here and go to the 21 April 2018 post.

Don't do what I did and screw up each and every hole on the trailing edge causing me to scrap the rudder. I'm on the elevator now and as soon as that's completed I'll tackle the new rudder.

Good judgment comes from experience. Experience comes from bad judgment.
 
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I know I have seen a lot of threads on riveting the trailing edge and thought I would share how I decided to rivet the rudder trailing edge which turned out with zero twist (as far as I can measure with a digital level) and very little pillowing.

1. Before rudder assembly attach a 90 degree piece of aluminum angle to the side of a workbench (long enough to fit the entire trailing edge and use shims with a digital level to ensure it remains straight across the bench.

2. Match drill holes from one of the skins into the aluminum angle that you just installed in step 1

3. Complete all other steps up to the double sided tape on the trailing edge.

4. Tape the trailing edge together per the instructions and cleco the taped edge to the aluminum angle. Allow it to sit overnight.

5. Remove the cleco's and replace the aluminum angle with steel angle of appropriate thickness for back riveting. (shim the steel just like the aluminum to get a flat surface).

6. Use rubber clamps to secure the end of the trailing edge to the steel angle and back rivet the trailing edge IAW the instructions provided by Van's.

Their were a lot of steps such as priming, riveting the skeleton and so on that I left out as I solely focused on the trailing edge here, but this worked out really well as you can see in the photo. The rudder trim tab that I fabricated got in the way of viewing the entire edge, but it has zero twist all the way to the end as far as I can see and measure.

Hope this helps someone who may be approaching this step.

7_12_5.jpg

Nicely done! Very similar to the method I used with very similar results...
 
I got the opportunity to build a second rudder when I did the match drilling as described above. Read the details here and go to the 21 April 2018 post.

Don't do what I did and screw up each and every hole on the trailing edge causing me to scrap the rudder. I'm on the elevator now and as soon as that's completed I'll tackle the new rudder.

Good judgment comes from experience. Experience comes from bad judgment.
I read your blog on the double holes in the trailing edge. I think the main reason is that you match drilled through aluminum into steel which likely took quite a while with the drill bit and caused it to wander slightly resulting in the elongated holes.
Since I instead match drilled into aluminum (like we all do constantly on this aircraft), their was no elongation of the holes. Looks like your methodology was sound, just unfortunately bad results due to the material type.
 
I read your blog on the double holes in the trailing edge. I think the main reason is that you match drilled through aluminum into steel which likely took quite a while with the drill bit and caused it to wander slightly resulting in the elongated holes.
Since I instead match drilled into aluminum (like we all do constantly on this aircraft), their was no elongation of the holes. Looks like your methodology was sound, just unfortunately bad results due to the material type.

The one good thing is I have a rectangular steel tube pre-drilled with the correct spacing for the rudder TE. I expect the next rudder build will take about 10 hours less (50 instead of 60).
 
Please take this advice as a suggestion rather then criticism. Yes your trailing edge is straight, not perfect but acceptable. Where I would make a change is that there are noticeable gaps between the skins, and the triangular metal wedge. Ideally the three parts, two skins and the wedge, should be firmly together at the trailing edge.
Go to your local EAA chapter and find out if there are any Oskhosh winners in your area. Those are airplanes and builders to emulate.
Keep up the good work, clearly you are motivated to have a nice airplane.
 
TE Gap

I do appreciate the sharp eye. I double checked the entire edge and found the very last half inch of the rudder TE (closest to the camera) had a small gap of about 0.020". I put a clamp on it for about an hour and it appears to be holding closed now. Thanks
 
Please take this advice as a suggestion rather then criticism. Yes your trailing edge is straight, not perfect but acceptable. Where I would make a change is that there are noticeable gaps between the skins, and the triangular metal wedge. Ideally the three parts, two skins and the wedge, should be firmly together at the trailing edge.
Go to your local EAA chapter and find out if there are any Oskhosh winners in your area. Those are airplanes and builders to emulate.
Keep up the good work, clearly you are motivated to have a nice airplane.

For future TEs on the flaps, ailerons and elevators, perhaps this is something a light edge break can address. E.g., this is called out on Step 5 of page 22-07 for the ailerons.

Also, in the spirit of learning like Tom offers, it appears that the skin on the top follows the trajectory of the wedge, then bends inwards towards the centerline. That can happen if the rivet set overlaps that edge at a shallow angle. I experienced this issue on my first rudder but with the benefit of 2,200 hours of experience, my second rudder came out much better.
 
If you have a table saw, almost required to make jigs and what not, it can act as a perfect back plate.
I used my table saw for big pieces to rivet, including the tail cone bottom skin. It worked so nicely and was easy. Did not require any shimming or support since it is a good size table saw.
 
great timing! Just getting to this step and I?ve been going back and forth between using pro-seal or the double sided tape called out in section 5. Only problem I see with pro-seal is on page 7-10step 2.... it states that the trailing edge will have to be pulled apart ?slightly? to access the aft two rivets. Any recommendations?
 
No reason whatsoever not to use double-sided tape. While I preferred the bent trailing edges from my old -8 (quick & easy to do and never gave any trouble in service), the riveted edges on my new -14A project, while requiring a bit more time, are also easily done.

This is the tape you want: double-sided tape
 
No reason whatsoever not to use double-sided tape.

I pondered the pros and cons of proseal vs. double-sided tape on my trailing edges and ended up going with proseal. My reason is that the tape doesn't form a perfect bond between the skins and the TE wedge, and (from looking at a number of completed RVs with riveted TEs) there are typically some gaps that open up between the wedge and skin. Any time you have a narrow gap between two unprimed surfaces, it's a perfect place for corrosion to start. Just large enough for moisture to get in, but not large enough for it to easily dry out. I've seen this occur on parts stored with the plastic still on in a humid environment...moisture gets in between the aluminum and plastic near the edges and you can see corrosion after a few years that is worse than what you find on the unprimed exposed surfaces of 70 year old spam cans.

Proseal doesn't prevent some gaps from forming when you rivet, but at least both the wedge and skin surfaces have a coat of proseal over them which will inhibit corrosion better than unprimed bare aluminum.

I don't expect anyone will be falling out of the sky due to corrosion on TE surfaces, and most builders won't own the airplane long enough for it to become their problem, but as a matter of principle I felt the proseal method offered the best long-term protection of the airframe.

FWIW...
 
I pondered the pros and cons of proseal vs. double-sided tape on my trailing edges and ended up going with proseal. My reason is that the tape doesn't form a perfect bond between the skins and the TE wedge, and (from looking at a number of completed RVs with riveted TEs) there are typically some gaps that open up between the wedge and skin. Any time you have a narrow gap between two unprimed surfaces, it's a perfect place for corrosion to start. Just large enough for moisture to get in, but not large enough for it to easily dry out. I've seen this occur on parts stored with the plastic still on in a humid environment...moisture gets in between the aluminum and plastic near the edges and you can see corrosion after a few years that is worse than what you find on the unprimed exposed surfaces of 70 year old spam cans.

Proseal doesn't prevent some gaps from forming when you rivet, but at least both the wedge and skin surfaces have a coat of proseal over them which will inhibit corrosion better than unprimed bare aluminum.

I don't expect anyone will be falling out of the sky due to corrosion on TE surfaces, and most builders won't own the airplane long enough for it to become their problem, but as a matter of principle I felt the proseal method offered the best long-term protection of the airframe.

FWIW...

Only problem with proseal is how do you access the aft two rivets on page 7-10 step 2. I guess you just wait until the end to use the proseal....
 
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