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Match drilling for LP4-3 rivets on RV-12?

bsbarnes10

Active Member
Hi,
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!

Bruce
 
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.
 
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.

-Dave
 
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.
Have fun!
 
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.
 
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....
 
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 :D

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

On the whole - very good indeed.
 
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.
 
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.
 
Thanks to everyone for your ideas and responses. Unfortunately I'm worried all proposed mitigations (awl, rivet pusher, and reamer) have the same issue: burrs/cracks. Using the awl or rivet pusher are likely to create microtears and possible cracks in the future. I ended up ordering a reamer and I've found it does a much better job than a drill bit at NOT making burrs but there are still detectable ridges on some holes.

What I've decided to do is bite the bullet and final ream all the holes. This adds another step because I then have to disassemble and deburr. Not all holes can be deburred because of the order of construction but I'm more comfortable getting the holes I can access (which is most of them) versus reaming and then immediately installing the rivet with no deburring.

Am I being overly cautious? Probably. But I like the build process and although I do want to get a finished airplane, I also don't mind investing a little extra time now to avoid problems in the future. As always, YMMV.

Thanks again to everyone for the responses!
 
Bruce,

I’ve built 4 homebuilts, three kits and one plans built. My first project I obsessed over every detail. What I learned is to relax and use common sense. There is no one rivet that will cause me to fall out of the sky. Spar pins and control cables and their ilk require perfection. Other stuff is less important. I used the suggestions mentioned here and have over 1000 hours on my airframe with no issues.

My engineering career started in the nuclear Navy where everything was rigorously controlled. When I moved to the nuclear industry it was a bit of an adjustment to start using my brain to determine what things affected safety and what didn’t. There are only so many resources and they need to be focused on the important stuff.

Good luck with your build. It will be a great educational experience and give you a real feeling of achievement that first flight.

Rich
 
Final size Matched Hole Kits

Hope I don't get " flamed " for this, my first post...

I'm a potential builder of one of the " final size, matched hole " kits but am concerned the kits as advertised below aren't the real world experience ?

I would not be concerned with a bit of minor reaming as long as it doesn't require taking everything back apart to debur. Is that realistic ?

Thanks !

" Van’s Aircraft has initiated the process of phasing in the production of final-size, matched-hole RV-10 parts. Until now, all parts for the RV-10 have been produced with slightly undersized holes, which the builder must up-size with a drill and then debur prior to assembly. We will be transitioning the RV-10 kit to final-sized holes, much like the RV-14 and RV-12iS kits. There is no increase in kit prices associated with this planned change.

We are excited to remove a portion of the initial work that builders need to perform on certain parts of the RV-10 airframe assembly with this change. Aircraft parts with final-size holes may be dimpled and then assembled right out of the box, after deburring the edges of each part as needed. This removes the need to first cleco the parts together, drill them to size in assembly, then disassemble and debur."
 
working holes in aluminum

At the risk of being more detailed than anyone actually wants to hear, I spent 45 years as a structural design engineer in the aircraft world, 30 years of it teaching aircraft design in college. My experience was that aluminum is sufficiently ductile that it is quite forgiving of minor hole irregularities when rivets are being installed. This is because rivets swell to fill the hole as they are set. Bolt hole size is a much more critical issue because tension in the bolt as the nut is torqued actually makes the bolt diameter shrink a miniscule amount. Few textbook discussions point out this distinction.

When I was working in Air Force flight testing, one heavily stressed structural modification actually had a written requirement for interference fit fasteners. Rivets had to be tight enough in the holes that the rivets would not go into the hole without being pressed in. The concept was that slight cold-working of the hole actually made the hole/sheet stronger. I felt comfortable that my gentle twisting of the awl into my rivet holes was doing that.
 
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I would not be concerned with a bit of minor reaming as long as it doesn't require taking everything back apart to deburr. Is that realistic?
I hope so. I've used a reamer on many, many holes on my project, and usually only a few very small shavings were removed by the reamer. There were no obvious burrs after reaming, and rivets that wouldn't fit, even after trying to align the holes with an awl, easily slipped into place.
 
Final size Matched Hole Kits

Appreciate the replies.

Ironically I tripped across a " you tube video " last evening wherein this issue was covered in detail. Search for " Plane Lady " and you'll find it. I found it very informative.

These kits are obviously well thought out and crafted by the folks at Vans...the completion rate is simply amazing.... as were the flight qualities in the one I recently flew in... That was a mistake :D

Thanks !
 
A couple of comments regarding the fit of parts and a need to final drill when the expectation is that it shouldn't be required.

There are a bunch of factors that can have an influence on this. They have been mentioned before but they are worth repeating for those new to RV's.

- Hole size tolerance - Every part produced has to have a tolerance. In the context of holes, if they are punched at the small sized end of the tolerance, the rivet fit will be a bit tighter. This variation is usually influenced by the age and sharpness of the punch tool.

- Rivet diameter tolerance - there can be a tolerance induced variation in the rivet diameters from batch to another. Van's Aircraft has no control over this.

- Proper preparation of parts - Proper adjustment of flange angles and straightening via fluting is critical to having parts align properly. If fluting is done on parts to get them "pretty straight", they will go together, but not with the same level of ease as if it was done very accurately.

- Getting parts properly aligned - Even if the other 3 factors list above are not working against you, you can still get parts clecoed together that are just slightly mis-positioned enough to prevent clecos from being inserted. The difference between an easy slip fit of a rivet into a hole, vs wont go in at all is as little as 1 - 2 thousandths of an inch (.001 - .002) Clecos can't be relied on to assure that level of precision.

Tapered pins mad from dull #30 drill bits can be very helpful for this. Using them to help get proper alignment while clecoing can make the difference.
Just one single rivet, installed after reaming a hole because the rivet wouldn't go in, can be enough to lock in the slightly misaligned position and then require all holes in that are to be reamed. It is often helpful to get a bunch of rivets inserted in holes on an assembly, before setting any of them.

In the context of RV kits other than the RV-12, these factors are usually not relevant except for to a very limited degree because anywhere that flush rivets are installed, the dimpling process enlarges the holes a small amount making rivet fit much less critical.
 
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One additional note: For matched-hole, final-sized parts (on RV-14, -12 and -10 where applicable) our tool tolerances are also tighter. In other words, we monitor and manage our punch tooling for the production of those parts to help ensure the holes remain within the final-sized hole measurement standards/tolerances. When the punch tools reach the point where they are no longer within tolerance for final sized holes, they can sometimes be used for other punch jobs where the tolerances are not as critical.
 
To Ninerbikes comment: I fly both my 12 and my Cherokee 180 every week. I love the Cherokee (bought it in 1985), but honestly it’s like wrestling a Mac truck compared to the light controls of the 12. The heavy solid feel of the Cherokee is great for single pilot IFR when stability is a definite advantage, but landing the 12 is so much easier with the crisp responsiveness of the 12 in the flare.
 
I've clekoed all the top skin on the RV12 tailcone and after removing every other one to put in the Rivets majority would not fit. As you can see in the pic it looks like I should be able to push the Rivets in but I can't. What is the best method of installing the clekos? Start in the middle and place the Rivets as you cleko? (Which I redid that way and it's helped) What's the thoughts of just #30 reaming the holes so slightly? I was told by another builder drilling to a #29 is within tolerance so I would think a #30 would be just fine rather than forcing the Rivets in?
I'd appreciate your input.
 

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I've clekoed all the top skin on the RV12 tailcone and after removing every other one to put in the Rivets majority would not fit. As you can see in the pic it looks like I should be able to push the Rivets in but I can't. What is the best method of installing the clekos? Start in the middle and place the Rivets as you cleko? (Which I redid that way and it's helped) What's the thoughts of just #30 reaming the holes so slightly? I was told by another builder drilling to a #29 is within tolerance so I would think a #30 would be just fine rather than forcing the Rivets in?
I'd appreciate your input.

If it is alignment problem, try rotating the cleco next to the hole in a circular pattern while try to insert the rivet. If is a too small hole, a #30 bit should clean it up sufficiently.

A #29 is marginally too large.
 
Thanks for that tip. Would that be rotating it with or without the cleko pliers pulled?
If it is alignment problem, try rotating the cleco next to the hole in a circular pattern while try to insert the rivet. If is a too small hole, a #30 bit should clean it up sufficiently.

A #29 is marginally too large.
 
Clecos are not high precision devices when it comes to aligning holes.

One technique that can help is to use a #30 alignment tool inserted in a hole adjacent to where a cleco is being installed, to help get precise alignment before the skin is clamped by the cleco.

You can make a tool from a dull #30 drill bit.
Sharpen a point on the end that normally inserts into the drill chuck with a grinder and then press the drill bit into a dowel with a hole drilled in it to make a handle.

An additional factor in hole alignment at assembly is the level of precision when fluting flanges on bulkheads and ribs to straighten them. If not done thoroughly, you will always be fighting to get holes into alignment.

I would not recommend using a #29 drill to ream the holes.
 
Thanks Scott for the #30 alignment bit trick. I've been told to start in the middle when riveting. Is there any advantage using that technique when clekoing?


Clecos are not high precision devices when it comes to aligning holes.

One technique that can help is to use a #30 alignment tool inserted in a hole adjacent to where a cleco is being installed, to help get precise alignment before the skin is clamped by the cleco.

You can make a tool from a dull #30 drill bit.
Sharpen a point on the end that normally inserts into the drill chuck with a grinder and then press the drill bit into a dowel with a hole drilled in it to make a handle.

An additional factor in hole alignment at assembly is the level of precision when fluting flanges on bulkheads and ribs to straighten them. If not done thoroughly, you will always be fighting to get holes into alignment.

I would not recommend using a #29 drill to ream the holes.
 
Another way to describe what I think Mel is describing is wobble the top of the cleco in a circular motion after installing it.

Another method that is often helpful is to use rivets along with the pin tool I described, to help get everything lined up.

To do this you insert the pin tool and then wobble it slightly as you insert a rivet in a hole right beside it (this requires using less clecos than one every other hole). Do this for an entire skin before setting any rivets (once you start setting rivets it begins to lock the position of the skin and can influence the alignment of other holes elsewhere). Once you have all of the rivets inserted you can set them in whatever pattern is convenient.
 
"Pliers pulled" is a bit ambiguous to me. Does "pulled" mean the pliers are still squeezed, or does it mean you've released the pliers and pulled them away from the cleco?

I would phrase it as rotate the cleco into the desired orientation before releasing the pliers.

Edit: Now I've re-read the previous responses and see the recommendation is to rotate after releasing? Why not before?
 
"Pliers pulled" is a bit ambiguous to me. Does "pulled" mean the pliers are still squeezed, or does it mean you've released the pliers and pulled them away from the cleco?
I would phrase it as rotate the cleco into the desired orientation before releasing the pliers.
Edit: Now I've re-read the previous responses and see the recommendation is to rotate after releasing? Why not before?

If the pliers are held in the "release" position, the cleco isn't doing anything. If the cleco is in the position to hold the sheets together, rotating the top helps to align the 2 sheets. This is NOT that complicated!
 
If the pliers are held in the "release" position, the cleco isn't doing anything. If the cleco is in the position to hold the sheets together, rotating the top helps to align the 2 sheets. This is NOT that complicated!

Your use of "release" refers to releasing the cleco. I specifically said "release the pliers," as in stop squeezing the pliers, as in let go. Put the cleco in the hole, release the pliers, parts clamped. We all understand how they work. Phraseology is important.

As Scott implied in his response, simply twisting the body or plunger after the cleco has been installed will do nothing. Once it's clamped down you'd have to wobble the top off its axis in a circular motion while you watch the back side to see when it get's into the alignment you want. My question is why is it preferable to do that when you can just put the thing in the orientation you want before you let go of the pliers?
 
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Your use of "release" refers to releasing the cleco. I specifically said "release the pliers," as in stop squeezing the pliers, as in let go. Put the cleco in the hole, release the pliers, parts clamped. We all understand how they work. Phraseology is important.
As Scott implied in his response, simply twisting the body or plunger after the cleco has been installed will do nothing. Once it's clamped down you'd have to wobble the top off its axis in a circular motion while you watch the back side to see when it get's into the alignment you want. My question is why is it preferable to do that when you can just put the thing in the orientation you want before you let go of the pliers?

Never mind!
 
Never mind!

You can rotate the cleco to align the parts before you let go of the pliers!

When the plunger of the cleco is fully depressed there is sufficient friction force between the external body of the cleco and its internals such that you can use the pliers as a handle to rotate the oblong clampy bits to better align the parts.
 
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Using Scott's advice of making alignment tools out of old #30 bits did the trick. I used golf balls which works pretty good.
 

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I took a short piece of 1/2” aluminum tubing and partially crushed the end so the mandrel of a blind rivet slipped into it but the crushed edges rested on the rivet head. I found it useful for pushing stubborn blind rivets into the holes.
 
I've been hesitant to force a rivet in worried it could bugger up the hole or create some side loading on the rivet. Would it be better to just drill the hole in those circumstances?

I took a short piece of 1/2” aluminum tubing and partially crushed the end so the mandrel of a blind rivet slipped into it but the crushed edges rested on the rivet head. I found it useful for pushing stubborn blind rivets into the holes.
 
I've been hesitant to force a rivet in worried it could bugger up the hole or create some side loading on the rivet. Would it be better to just drill the hole in those circumstances?

Depends on the situation but yes.
I always caution builders about forcing rivets through a hole because of the light gauge material most of the parts are made from. It is very easy to push the flange or tab of the underlying part away from the skin and then end up riveting the skin to nothing at that hole location.

That is why I recommend using the alignment pins beside a rivet being inserted, and if a lot of them seem tight, to insert rivets in the holes of a large area before setting any of them.
 
My process was:

1. Try to insert by hand if no go
2. Push in a center punch and twirl it to ensure hole alignment if no go
3. Try another rivet (don’t know why it works, but sometimes it does) if no go
4. Try my rivet pusher gently if no go
5. Run a drill bit through the hole
 
One other thing that hasn't been mentioned specifically that seems to help is inserting some rivets before you put the clecos in - or if you have one cleco in, loosen it as you try and stick the rivet in. Having a few rivets in the holes prior to cleco-ing helps align the holes best possible before they get clamped in place by the imperfect clecos.

I've found that very helpful in getting pieces aligned to get the rivets in the easiest possible...although that golf ball tool looks cool. :)
 
One other thing that hasn't been mentioned specifically that seems to help is inserting some rivets before you put the clecos in - or if you have one cleco in, loosen it as you try and stick the rivet in. Having a few rivets in the holes prior to cleco-ing helps align the holes best possible before they get clamped in place by the imperfect clecos.

I've found that very helpful in getting pieces aligned to get the rivets in the easiest possible...although that golf ball tool looks cool. :)

I agree

From a previous post in this thread..........

Another method that is often helpful is to use rivets along with the pin tool I described, to help get everything lined up.

To do this you insert the pin tool and then wobble it slightly as you insert a rivet in a hole right beside it (this requires using less clecos than one every other hole). Do this for an entire skin before setting any rivets (once you start setting rivets it begins to lock the position of the skin and can influence the alignment of other holes elsewhere). Once you have all of the rivets inserted you can set them in whatever pattern is convenient.
 
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