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First rivets/dimples are they ok?

BryanG

Member
Hello,

My father and I are getting ready to start an RV-10. These are some practice rivets. Wondering if anyone can see any issues or if they generally look good from the pictures. We have the gauge and everything checks out, specifically wondering if the dimples look ok.

Thanks,
Bryan
 

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You're getting there! If these are the veryfirstever, good on you.
Hard to be certain without side- angle view, but it looks like your dimples may be a little deeper than you want. The idea is the dimples are just deep enough that the manufactured head lies flush, not proud, or recessed. Deeper means the hole 'a 'defect' in the material] is not completely filled. Too deep also usually means the hole is enlarged. "Flush' means you might be a little proud [high] or a little recessed [low], but the target is 'fingernail' difference. I'm sure you're looking at the pics in AC43-13.
A tiny bit 'low' is easier to fill for a smooth finish, than proud...
I also see a couple of the shop heads showing slight 'slip', or angle. Not enough to cause re-do, but watch your work piece remains perpendicular to the dies.

If you were local, i'd show you the practice piece i keep to demonstrate every-bad-habit for flush riveting --- and i don't see them here.
 
dimples

Row 2 column 3 dimple looks good.

Rows 4-6 appear under-dimpled due to the gap around the edge of the rivet head.

There is little chance of over-dimpling with good dimple dies. The best dies were made by Avery and I believe that another supplier has taken over since Bob Avery retired.

It is difficult to comment on the shop heads as these need to be viewed from the side.
 
See pictures -- a proper dimple, regardless of the mechanism to impart (DRDT-2, Pneumatic Squeezer, Mainsqueeze, C-Frame, etc.) will:

1. Have a "witness" mark around the dimple; ~2D outside the hole
2. Not distort reflected light (pinched, watermelon) beyond the immediate edge of the dimple
3. Allow the rivet to sit slightly below the surrounding surface.
 

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You're getting there! If these are the veryfirstever, good on you.
Hard to be certain without side- angle view, but it looks like your dimples may be a little deeper than you want. The idea is the dimples are just deep enough that the manufactured head lies flush, not proud, or recessed. Deeper means the hole 'a 'defect' in the material] is not completely filled. Too deep also usually means the hole is enlarged. "Flush' means you might be a little proud [high] or a little recessed [low], but the target is 'fingernail' difference. I'm sure you're looking at the pics in AC43-13.
A tiny bit 'low' is easier to fill for a smooth finish, than proud...
I also see a couple of the shop heads showing slight 'slip', or angle. Not enough to cause re-do, but watch your work piece remains perpendicular to the dies.

If you were local, i'd show you the practice piece i keep to demonstrate every-bad-habit for flush riveting --- and i don't see them here.

I understand under dimpling I think. I was thinking some of them might be slightly too deep but I don’t know how this is possible. It seems the general consensus is you can’t over dimple very easily, so how do I make them less deep and at the same time not under dimple? Also which pics is 43-13, I can’t seem to find dimple pics.
 
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BryanG, will need a little more info on what tools/technique used to make dimples and rivets...it's not clear to me from your pictures.
 
I understand under dimpling I think. I was thinking some of them might be slightly too deep but I don’t know how this is possible. It seems the general consensus is you can’t over dimple very easily, so how do I make them less deep and at the same time not under dimple? Also which pics is 43-13, I can’t seem to find dimple pics.

The depth of the dimples is determined and limited by the dimple dies... it is just not possible to dimple any deeper than the depth of the female die! Another set of dies, from a different supplier, may give a different result.

Bryan, I believe that there are not any pics of dimples in AC43.13, at least not in my copy. So I am not sure what the other poster is referring to. :confused:

Can you perhaps find another RV builder or EAA chapter near to you? I think it would really help and be reassuring to look at dimples and riveting etc first hand. This aspect of building is actually quite easy (once you know how) and is not worth stressing about.
 
I understand under dimpling I think. I was thinking some of them might be slightly too deep but I don’t know how this is possible. .

It’s a bit tricky. If you under dimple the ‘dimple’ is a little short of filling the dimple or countersink in the other piece. But when the die pressure was released, the aluminum tends to ‘spring back’ a bit, and the aluminum around the dimple ends up slightly raised-a shoulder. So the rivet appears to be too deep. Not because the dimple is too deep, but because of the raised shoulder. Good dies are sometimes called spring-back dies, because they slightly over-dimple, and count on a slight spring back of the aluminum, to end up perfect!
I suggest more pressure on the dies. It’s pretty hard to over-do it. As others said, you should see a ‘witness ring’ around the hole.
As to the rivet, you can make or buy a gauge. The shop head should have a diameter of 1.5x the undriven rivet diameter, and a thickness of 0.5 the original diameter.
 
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Youtube

There is a Disney video of bucking rivets and countersink methods. Says it all as I see it. As you build you will improve ... its part of the journey
Billythekid
 
Single best video on the topic of dimples I've seen:

https://www.youtube.com/watch?v=Qo9QCMaNSoA

Part of the fun of participating in VAF is the lively and passionate discussion of topics like priming, dimples, tools, techniques, etc. And of course tapping the wealth of knowledge and experience here.

But the "downside" I've found is that - like politics and religion - there will always be "factions", dogma (that varies among "factions"), and to some extent "shaming" when something like a dimple, a rivet head, or other piece of work is shared here. What you will (hopefully) learn as you get into your build is what is "good enough" - for you - and more importantly safe and secure. Sometimes you just have to decide to live with a result that is less than perfect or ideal but is perfectly safe and functional.

One saying I heard early on in the process that stuck with me was "I want to build a go-plane, not a show-plane". Where you fall on the spectrum of acceptance of "good" versus (a debatable standard of..) "perfect" is a decision you'll have to make pretty much every time you go to the shop. Another favorite saying of mine: "perfect is the enemy of good".

I've tried to learn some practical lessons by listening to people like Vic Syracuse who see the results of workmanship over time and get a really good sense of what "matters" in building an airplane: what are the failure modes that result in unacceptable/dangerous outcomes? Should I care more about perfect rivets and dimples, or avoiding mistakes like loose/disorganized wiring, loose jam nuts, etc? (rhetoric admittedly as these are not mutually exclusive). This kind of expertise is practical in the sense that it will give you a much better perspective on where to focus your efforts.

Another good sanity check resource is to call or email the customer support team at Van's: it's very comforting to get a "build on" verdict when unsure about something. I've recently been in touch with them about a finding related to a service bulletin (fix it), a slight misalignment of elevator counterbalance horns ("build on"), and how to deal with a wire routing question. All by email, easy and helpful.

One thing is for sure: if you plan to build the perfect airplane, know that it will take a very very long time....
 
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