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Building a 7A v. 12

LettersFromFlyoverCountry

Well Known Member
People had opined that they wanted to hear my opinions (whaaat?) once I started the RV-12 and how it compares to the RV-7 project. I suspect very much my initial thoughts would mirror those of RV-6 owners v the 7 and 9 "crowd" when the prepunched kits came out.

Anyway, a few main thoughts.

1. I'm not building (at least not yet), I'm assembling. Because I'm building as an E-LSA, I have to do things exactly the way I'm told. These kits are incredible. There's (at least so far) nothing much to do but take the piece and match the piece to another piece that has been finely punched and pre-punched and pre-formed. The extent of "getting your hands dirty" is snipping off a part, kind of like when you had those plastic models and had to snip them off from all the other parts. Fortunately, no airplane glue needed.

2. I miss the ISO drawings.
The step-by-step instructions are completely dummy proof although once you build via the old method, it's REALLY hard to get used to the RV-12 instructions. It's like assembling something you just picked up from Ikea. I find myself longing to see how every part relates to every other part in the big scheme of things. But with the 12 plans, you just have to trust that eventually everything will fit together, so just shut up and do what the step tells you to do.

3. It's really nice not "tooling up." You have to really guard against cockiness on a second build. My goal with the RV-12 is not to order any replacement parts. Not one. When I built the 7A, I actually built two airplanes -- one flew. The other is still in the box marked "scrap."

But it's really great having (most of) the tools needed to build -- excuse me: ASSEMBLE -- the 12 and having the knowledge of what needs to be done (the instructions on the 12 won't tell you to pre-drill (mostly) and deburr, or prime or any of that stuff (that's contained in the pre-build chapters of the instructions.

4. Things go together FAST. I think it took me 4 or 5 months to build the VS on the 7A. That was back when you had to use the jig to do things, and also when I was too stupid to know what I was doing. I build the VS in just a few hours. Working on the rudder now. It took even less time.

5. Van's is really good at this stuff. But I already knew that.
 
Nice Post Bob!

This is probably the way plans-only builders felt when they built their first pre-punched airplanes. Eventually, I fear, the right of passage for our community might only be governed by one's bank balance.
 
Out of curiosity, for those building an RV-10, is it like this also?

On the RV-12, I heard you don't need to final-match-drill the skins like you do on the 7/8/9, is this true? What about deburring?
 
Not quite

I built my RV-10 empennage, tail cone and fuselage at Synergy in Oregon. Per the plans, the skins need to be match drilled, then deburred and dimpled.

In most cases, we went right to dimpling and skipped the match drilling and deburring steps. Synergy has approval from Van's to do this. We had zero issues with anything lining up. We also back riveted as much as we could of the skins and they turned out beautifully.

They build RV-12's there (Synergy is the "factory" for the S-LSA models) and there were also several RV-14's under construction while I was there. The RV-14 goes together much quicker than the 10, as much of the match drilling seems to be eliminated.
 
To echo what Bob said the biggest challenge for an "experienced traditional RV builder" is to follow the RV-12 instructions exactly. I slowly build my 9A and with that experience did not spend much time with the plans on 7 construction since construction is nearly identical. That did not work for the 12. Every time I jumped the gun and did economy moves like riveting in all the nut plates at once, I had to redo because something unexpected went in place and you did not have clearance. The fuselage main section is very different than the other RVs. You would have caught it with the traditional RV full size plans since they show everything but you don't as easily get the full picture with just the illustrated instructions. Not bad, probably better for the first time builders, just different.

To put everything in perspective, it took me 7 years to build a painted flying RV-9A but only 15 months for the 12 even with building lapses.
 
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In most cases, we went right to dimpling and skipped the match drilling and deburring steps. Synergy has approval from Van's to do this.

This is totally false

On kits that have the holes punched slightly undersized (RV-10 is one of them), the holes are expected to be final drilled.

Wally has been promoting this for quite a while but it is not with Van's approval.
 
This is totally false

On kits that have the holes punched slightly undersized (RV-10 is one of them), the holes are expected to be final drilled.

Wally has been promoting this for quite a while but it is not with Van's approval.

I can't imagine even being able to dimple without drilling. Of the thousands of holes that I drilled, deburred, and dimpled, I always knew when I missed one, because my male dimple die would not go in the hole without a considerable (uncomfortable) amount of force. Would imagine that force/stretch isn't doing much good for the hole...
 
All you have to do is look at a dimpled hole that you didn't predrill through a jewelers loupe and you'll understand why drilling is essential.
 
In most cases, we went right to dimpling and skipped the match drilling and deburring steps. Synergy has approval from Van's to do this.

Wally was talking about this at OSH last year and I asked him about it during audience questions and he insisted Vans told him it was approved. I walked down to the Vans tent after and was told it is NOT approved and NOT to do it unless I planned to inspect every single dimple for cracks with a loupe.

The problem is not the holes lining up, it is cracks getting created in each dimple from the stress. I was under the impression that this was no longer an issue with the RV12/14 but it sounds like it's still not true?
 
I can't imagine even being able to dimple without drilling. Of the thousands of holes that I drilled, deburred, and dimpled, I always knew when I missed one, because my male dimple die would not go in the hole without a considerable (uncomfortable) amount of force. Would imagine that force/stretch isn't doing much good for the hole...

Wally was talking about this at OSH last year and I asked him about it during audience questions and he insisted Vans told him it was approved. I walked down to the Vans tent after and was told it is NOT approved and NOT to do it unless I planned to inspect every single dimple for cracks with a loupe.

The problem is not the holes lining up, it is cracks getting created in each dimple from the stress. I was under the impression that this was no longer an issue with the RV12/14 but it sounds like it's still not true?

The issue of driving a dimple die pilot through the under sized hole is the concern.

Fatigue tests have been done to confirm that the surface finish on the interior edge of the holes is not a concern (that is why dimple countersinking without final drilling is approved on the RV-12 and 14... their holes are punched to a larger size).
Stretching an un-final drilled hole with a dimple die pilot is a concern and not recommended or endorsed by Van's


Apologizes for the extreme thread drift Bob......
 
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Well, now you've got me wondering too because the RV-12 instructions only sporadically mention match drilling. But I match drill everything anyway, and then deburr everything whether it mentions it or not.

The hardest thing for me to get over is the riveting of skins when I pull a pop rivet and then have this "OH, NO! I forgot to dimple" moment. That happens a lot.
 
Well, now you've got me wondering too because the RV-12 instructions only sporadically mention match drilling. But I match drill everything anyway, and then deburr everything whether it mentions it or not.

The hardest thing for me to get over is the riveting of skins when I pull a pop rivet and then have this "OH, NO! I forgot to dimple" moment. That happens a lot.

Match drilling on the RV-12 is only required in a few limited circumstances.
The same with final drilling, and that is primarily only on larger diameter screw holes that get large dimples formed in them.

BTW.... per the details in Section 5 of the manual, Match Drilling is when you are using the hole in one part as a pilot/locator hole to drill a hole in another part that does not yet exist.
Final Drilling is enlarging an already existing hole (as in pre-punched holes) to a desired final size.
 
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Match drilling on the RV-12 is only required in a few limited circumstances.
The same with final drilling, and that is primarily only on larger diameter screw holes that get large dimples formed in them.

BTW.... per the details in Section 5 of the manual, Match Drilling is when you are using the hole in one part as a pilot/locator hole to drill a hole in another part that does not yet exist.
Final Drilling is enlarging an already existing hole (as in pre-punched holes) to a desired final size.

I misused the term. I meant "final drilling", not "match drilling."
 
The same with final drilling, and that is primarily only on larger diameter screw holes that get large dimples formed in them.

Just working on the rudder skin last night, there's no way I'd rivet the skin without final drilling the holes. I don't recall seeing a note to final drill the holes but maybe it was there.

Anyway, I'm choosing to final drill and deburr everything and every hole.

You can't take the 7A out of the boy.
 
Just working on the rudder skin last night, there's no way I'd rivet the skin without final drilling the holes. I don't recall seeing a note to final drill the holes but maybe it was there.

Anyway, I'm choosing to final drill and deburr everything and every hole.

You can't take the 7A out of the boy.

Totally up to you but it is not required on the RV-12 (though some times it is necessary).

Keep in mind that if you automatically final drill all holes, you may actually be enlarging some holes that are already might be final size.

Say you haven't flutted a rib as well as it could have been which is causing some holes to be mis-aligned..... and you instead final drill to "improve" hole alignment. The holes may have been already final size but they are now slightly oval.
 
Reaming holes

Rather than drilling the under sized holes I would ream them then cleco then ream the next ones. Only needed to ream about 5% of the total holes
 
Rather than drilling the under sized holes I would ream them then cleco then ream the next ones. Only needed to ream about 5% of the total holes

I actually built a 12 and am thinking about building a 7 next, so just the opposite way of what has started this thread.
The way for me to put the skins on and other larger structures was to first deburr the side where the punch excited as the holes had sharp edges there. Then cleco the part on and if he pop rivet would go into the hole by hand, fine. If not, I ran a #30 drill bit through the hole manually turning the chuck of the drill to just ream it to size. Insert rivet, pull, done.
Most rivets went in without any further treatment. After 3 years of flying, no cracks and nothing has fallen off yet.
 
It turns out I may have jumped the gun in my earlier post regarding the dimpling topic? my apologies.

Yesterday it came to my attention that in 2009, Van?s Engineering staff released a specific approval (*with qualifications) to Synergy Air regarding dimpling without final drilling.

*Note that the approval calls for use of special dimple dies with pilots that slip fit into the smaller prepunched holes to avoid unnecessarily stretching the hole while dimpling. (Van?s does not have information on a specific source for these dies.)

With permission from Van?s, I?ve provided a link to the approval below:

Link to Dimple.pdf

Van?s covers the topic of dimpling in Section 5 of the builders manuals and recommends that builders read and follow the recommendations there.

Link to Section 5
 
Thanks for following up!

It turns out I may have jumped the gun in my earlier post regarding the dimpling topic? my apologies.

Yesterday it came to my attention that in 2009, Van?s Engineering staff released a specific approval (*with qualifications) to Synergy Air regarding dimpling without final drilling.

*Note that the approval calls for use of special dimple dies with pilots that slip fit into the smaller prepunched holes to avoid unnecessarily stretching the hole while dimpling. (Van?s does not have information on a specific source for these dies.)

With permission from Van?s, I?ve provided a link to the approval below:

Link to Dimple.pdf

Van?s covers the topic of dimpling in Section 5 of the builders manuals and recommends that builders read and follow the recommendations there.

Link to Section 5

It's certainly comforting to know that the method I was taught at Synergy was indeed approved and acceptable. It was difficult to believe that they were doing something unapproved, as they are (in my opinion) the best Builder Assist shop out there for RV's.

Kudos to you Scott, for taking the time to dig a little deeper and research this with Van's. A huge thank you for letting all of us know that the direct to dimple die method had been tested by Van's and was approved under controlled conditions!
 
Mfg process

I've often wondered that if you are able to pre-punch the hole with a hole die with a level of precision, then would it be plausible to pre-punch with a dimpling hole die? Two birds with one stone so to speak.

I'm sure if given the option, some would prefer to dimple their own holes. Dimpling was one of those repetitious steps I did not enjoy. Given that many Kit mfg are moving towards making assembly "more" error proof, then this may be a profitable option for Vans. Predimpled skins would require more handling precautions, but hey, that's what money is for.
 
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Getting back to RV-12 vs. RV-7/9, I have only built one RV-9A, but am now working on the fourth RV-12. Each of these has been supervising kids that knew nothing of aircraft construction when they started, just like me when I started the 9.

I have seen all skill levels, and builder attitudes. It is always good to see a builder who realizes he/she doesn't know what they can get by with, and strives for perfection. But even that builder brings on their own set of problems! No, you don't have to drill out that nutplate rivet, it is perfectly fine for holding a nutplate, and you run the risk of damaging the part if you drill it out.

To me, it boils down to changes vs. improvements. I try not to do changes, but always want to improve. I think Van's procedures would be hard to improve and don't need to be changed. If they say dimple without drilling, that is what I would recommend. There are areas where we can improve, but they are very limited. Over thinking, over preparing, and adding extra work adds little value, slows the process, and can even reduce quality and structure. Spend extra time on things that matter. Always remember what the FARs say; we are building for our education and entertainment. Keep it fun!

Bob
 
Building different RV types

If you builders are looking for a challenge build a 3B


Bob Grigsby
Flying J3C-65. Pure flying experience
3-B. close
 
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