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Old 10-09-2020, 05:00 PM
bsbarnes10 bsbarnes10 is offline
Join Date: Sep 2019
Location: Texas
Posts: 34
Default Match drilling for LP4-3 rivets on RV-12?

I tired searching but didn't find anything on this topic so hopefully someone can enlighten me. I just started an RV-12iS empennage kit and I'm having some issues with LP4-3 rivets (you know, the ones you 12,000 of). My understanding (please correct me if I'm wrong) is that one advantage of the RV-12 is that you don't need to match drill most places because of improved tooling/manufacturing techniques. However, I'm finding many cases where the instructions do not specifically call out to match drill but if I don't, an LP4-3 rivet won't fit through the hole.

Case in point:

I'm working on the Anti Servo Tabs and the instructions tell you to rivet the skins to the spar but do not instruct you to match drill first (they do call out other match drill locations in nearby steps). But if I don't match drill, you can't get the rivet into the hole any deeper than about 0.5 mm. Every hole is clecoed and they're lined up perfectly, i.e. there is no obvious misalignment. I checked with a #30 drill bit and it won't fit either so the holes are not physically large enough for the rivet. I had similar problems on the rudder and vertical stabilizer with 10-25% of the holes too small for a rivet, even when properly aligned.

Is it just unspoken that you have to check and match drill where necessary or and I doing something wrong / missing steps / etc???

Any input would be appreciated!

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Old 10-09-2020, 05:40 PM
greghughespdx's Avatar
greghughespdx greghughespdx is offline
Join Date: Nov 2011
Location: Aurora, OR
Posts: 970

Technically, what you're describing is the need to final-drill the already in-place matched holes. There are also a handful of places in the RV-12iS build where you need to match-drill (in that case you use a part with holes pre-punched in it as your drill guide to create brand-new holes in the material underneath).

There are situations when you may need to final-size holes in the build. Basically there are two common reasons why it might sometimes be required:
  1. LP rivets have a minimum and maximum diameter spec. In other words, they can be a little fat or a little skinny (relative to the nominal size) and still be within the spec. If they are on the higher end of the spec (slightly over-sized), they may be a tight fit and therefore require you to final-size-drill the matched-up holes.
  2. Sometimes when you cleco things together, unless the cleco clamps are aligned so that the "long" dimension of the clamp is in-line with the holes, it is possible for the holes to almost - but *not quite* - line up perfectly. Usually this doesn't tmatter much but in some places it can and will make a difference. Clocking each clamp to ensure the clamps' longer dimensions are in line with the holes is a good practice, especially if you happen to be obsessive-compulsive or like patterns a lot.
  3. Obviously, when the above two things happen in combination they can also have an additive effect.
I've done RV-12 building with batches of "fatter" rivets and had to touch the holes with a drill (a reamer generally works great for keeping the hole clean and free of burrs BTW), and have also built on -12's where it wasn't necessary. The holes are always pretty much the same size, it's the more so the rivets that can vary. When you run into this, you can also try to fit more than one LP rivet in a given hole (one at a time ) and see if none of your rivets fit, or just some of them.

Hope that helps.
Greg Hughes - Van's Aircraft - Director - Community, Media, Marketing, Support
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Building RV-8A since Sept 2014
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Old 10-09-2020, 05:51 PM
DaveLS DaveLS is offline
Join Date: Oct 2007
Location: Pensacola, FL & 2R4, Loveland, CO
Posts: 222

Wiggling an awl or ice pick in the hole after clecoing (that a word?) to align the parts helps a lot. Wiggle do not push.

As mention in the other post a reamer chucked in a drill is your friend.

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Old 10-09-2020, 06:06 PM
DaveWelch DaveWelch is offline
Join Date: Mar 2005
Location: Huntsville, AL
Posts: 451
Default Awl them holes!

If I may add to Gregs excellent advice...another technique I found useful was to use an Awl in holes that seemed "small". I'd insert the Awl thru the hole and firmly (but not too hard) rotate or "swirl" the handle in a circular motion. The effect was to "exercise" the two skins relative to each other. Usually I would hear one or more of the clecoes pop as they settled further into their holes. And often the rivet would fit through the hole(s) that they hadn't before. If that didn't work, then it's time for the 4-fluted Ream. Note: I also ended up with a can of "oversized" LP's that I gave up using.
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Old 10-09-2020, 07:27 PM
bobnoffs bobnoffs is offline
Join Date: Jul 2012
Location: n. wi
Posts: 831

when i built my 12 i used a #30 reamer in many hundreds of rivet holes. i don't care what has been written about this that it will fit. when the drill shank won't fit in either hole, one hole at a time it is not going to fit in 2 or more holes at once. many, many holes in my kit were too small to fit a#30 drill shank or a rivet into. a reamer in a small portable electric screwdriver does the nicest job compared to a drill bit.
Bob Noffs
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dakota hawk/jab 3300 built and flying. sold 6/18.getting serious about the 12. in the hangar now as of 10/15/19
RV-12 kit as of 9/13
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Old 10-10-2020, 06:54 AM
bsbarnes10 bsbarnes10 is offline
Join Date: Sep 2019
Location: Texas
Posts: 34

Thanks to everyone for the quick replies!

A couple thoughts:

1. Yes, I meant FINAL drilling, I'm still working on the aircraft building argot

2. I also discovered the variability of the rivets. As we were trying to figure out what the problem was I suspected it may be the rivets and ended up with a small handful of oversize (or at least at the large end of the allowable spec) ones.

This helps a lot! And the best part is that all your responses came in time for me to add a couple reamers to my Aircraft Spruce order this morning :-)

I'm also going to try the awl method and see what works best....
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Old 10-10-2020, 06:58 AM
mike newall's Avatar
mike newall mike newall is offline
Join Date: Jan 2005
Location: Yorkshire, England
Posts: 2,151

We built two 12's and I would say 10 - 15% of holes needed touching.

We just used a new #30 drill, you couldn't see anything coming off but just felt it.

We put it down to Friday afternoon punching and fat LP4's

Usually where skins are tight or on large expanses such as wing skins where cleco creep occurs.

On the whole - very good indeed.
"I add a little excitement, a little spice to your lives, and all you do is complain!" - Q

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Old 10-10-2020, 09:07 PM
RFSchaller RFSchaller is offline
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 3,072

I found it useful to crush the end of a 1/2 aluminum tube in a vise so that it fits over the rivet mandrel, but not over the head of the rivet and use it as a rivet pusher to insert the blind rivets.
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Old 11-06-2020, 07:12 PM
Charlie12 Charlie12 is offline
Join Date: Oct 2014
Location: Port Orange FL
Posts: 42
Default fat LP-4s?

I had similar challenges riveting my RV-12 a few years ago. Builder support suggested that the pre-punched holes sometimes are a little undersize when the machine punch gets worn, which makes sense to me. I had to adjust the size of most of my holes. Lucky me. Trying to understand the issue, I did measure a lot of LP-4s and some were a bit fat. Gently twisting a long-taper awl (Craftsman, I think) into the holes became my preferred adjustment. When my finger tips got sore from pushing rivets in, I made a rivet pusher tool by drilling an axial hole into one end of a 4-inch long piece of 1/2-inch diameter solid aluminum rod---just be sure to drill the hole deep enough to accept the whole exposed stem of the rivet so that you are pushing against the head of the rivet instead of shoving the stem out of the rivet.

I did #30 drill or ream some holes but felt like that might move the hole location slightly, partially defeating the concept of matched-hole tooling to locate the parts accurately.
RV-12 #120768, first flight Sept. 2016
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Old 11-09-2020, 05:55 PM
Jakmart Jakmart is offline
Join Date: Aug 2018
Location: Grayslake
Posts: 6

30-straight-flute-reamer Cleveland Tools is what i use.
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