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Riveting trailing edge

AndyWAUS

Member
Hi builders. I'm looking for a picture example of a good looking shop heads of the riveted trailing edge.

I started very carefully squeezing the elevator trailing edge with an angled rivet set. The rudder I did with the back riveting technique from section 5, and it looks terrible. Now with the squeezer I expected the result to be nice and clean like any other squeezed rivet, but it's still not. If I squeeze too much, the two skins joining at the trailing edge separate and create an ugly deformed gap. If I squeeze too little though, the shop head isn't nearly flush with the skin, with the forward side protruding more than the aft side. In any case, the shop head doesn't swell to the required diameter of a typical 3/32 rivet - I guess this is because it is pushing against the dimple on the shop side as opposed to a flat piece. I'm thinking about finishing with the back rivet technique, but still afraid of the skins separating and making this gap. So I would appreciate if you could show me the underside of your elevators.

Thanks!
Andy
 
I used a hybrid technique on my rudder TE. First, I set all the rivets about 30% using a squeezer. I started at one end, and did every 6th rivet. Then, repeated doing every third. Then I finally did the remaining rivets in as even distribution as I could. Once all the rivets were 30% set, I repeated going to about 60% set with the squeezer again. Then, I came back and did the same thing with the backrivet set to get the last 30%. On the RV-7 with the angles TE, The trick with the backrivet set was to start square to the rivet shank, then angle the gun down so the set was then parallel to the skin face. Nerve wracking for rookie builder but the results far exceeded my expectation. Virtually no bow and the TE is pulled tight.

Note: No one has told me these shop heads look good but I think they meet the standard.
 

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I just finished a flap for an RV-14A. I hand squeezed all the rivets using a Main Squeeze and the Cleveland tools beveled rivet set. The trailing edge wedge was countersunk .007 beyond flush, used the 3m adhesive tape. With the elevator laying top down on a flat table with training edge hanging off about an inch. I would insert the rivets with the manufactured heads on the top side of the skin which would be upside down. The rivets would stick in the hole due to the adhesive left by the tape. I started in the middle and then did every tenth rivet then came back center and did every 5th rivet and keep the sequence up. The problem you have is getting the manufactured head to seat nice and flush in the dimple. My solution is to first squeeze the rivet about 1/3 and then take a #10 washer and place over the tail of the rivet and lightly squeeze the rivet which will seat the manufactured head firmly in the dimple. Then remove the washer and finish squeezing the rivet. My rivets came out perfect and the trailing edge is nice and straight.
 

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Looks great, thank you. I love the trick with a washer!

I think I now understand my mistake. I was trying to set the rivets fully in one go using only the squeezer. I was over squeezing and not getting a good shop head. On the second elevator I squeezed just about 30% on the first pass, then 60% on the second pass, then finished with a flat set and a back rivet plate. The result is much better.
 
What I did:
- Once the parts are prepped, I applied a thin coat of proseal on the mating surfaces.
- I used two lengths of 2”x2” 1/4” thick steel angle to sandwich the trailing edge. The bottom angle over the edge of the work bench, the surface covered with clear packing tape. Shims are placed under the control surface so it was flush across the angle. A cleko in each hole, the trailing edge hanging over the edge of the bottom angle just enough so the cleko ends clear.
- The second angle is placed on top of the control surface, the trailing edge against the clekos.
- 3-4 C clamps applied between the table edge and the top angle, LIGHTLY tighten. Four or so Ziplock bags wiht some lead shoot placed on top of the control surface. The objective is to not squeeze but to make sure there is no twist.
- Let the proseal mostly set up (not quite to the point that you cannot clean up any excess).
- Remove the clekos, insert rivets held in with rivet tape. Light use of a deburring bit in the holes with excess proseal comes in handy. Invert the control surface.
- Back rivet the rivets using the bottom angle as the back rivet plate. Drive enough so the rivet is set, but not yet fully flush.
- Shift to a flush set and finish setting the rivet shop heads (go easy so you don’t mess up the skins). For this you will need to have the trailing edge of the control surface flush with the edge of the bottom angle so the flush overhangs the trailing edge (because of the angle).

Carl
 
I'm impressed with the amount of effort, and sharing, of a technique managing opposing physical properties and effects.

I'm being truthful and sharing, not critical, as I'm speaking from the teaching perspective of a guy who had FAA authorization to give IAs and A&Ps Continuing Ed in sheet metal.

The trailing edge "warps" because of localized stretching of the skin around a rivet, installed via a technique that increases those stretching forces.

A "new assembly", skins and rivets, has the best potential for being installed with lowest stretching forces. You can't escape these stretching forces because they are built into the "system," but you can limit them and the stretching and warping that follows.

Partial or "Step forming" the rivet increases the hardness of the rivet shank with each hit and, at the same time, it increases the stretching forces the, now-harder, rivet imposes on the surrounding skin.

I suggest, along with this diligent procedural process, that the set up directions include getting everything ready but the riveting step, pausing work until you get the softest rivets possible.

A "soft" rivet, in my experience can be driven at 40 psi, with 4 "plops" of a good rivet gun with its trigger tickled to deliver one hit at a time.

No sheet distortion shows.

A focus on soft rivets should greatly reduce the anxiety that attends this step in building a "Quality" RV.
 
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What I did:
For this you will need to have the trailing edge of the control surface flush with the edge of the bottom angle so the flush overhangs the trailing edge (because of the angle).Carl

Carl, could you clarify this for me? ...so the flush overhangs the trailing edge...
 
Carl, could you clarify this for me? ...so the flush overhangs the trailing edge...

You add a spacer the same thickness as the bottom angle on the workbench so that there is a flush surface across the bottom angle that is overlapping the edge of the workbench. In other words the entire bottom of the control surface is on a flat plane.

Carl
 
You can also attach an angle to your bench so it’s flush. I just install this for trailing edges and remove it when I’m done. It makes a great backriveting plate. In fact I use the Cleaveland angled squeezer set and squeeze the rivets between the top half of the set and the angle, so it’s kind of a hybrid between squeezing and backriveting. Arrow straight.
 

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