[KatieB]

In the next couple of weeks (probably after Oshkosh, realistically) I hope to drill the rivet holes in the horizontal stabilizer skin of my -3. Van gave pretty detailed instructions on how to do this with the skin draped over the skeleton, which is mounted on the jig to keep it straight. Sounds pretty straight-forward.

However, my eyes cringe at the sight of uneven rivet lines, and I'm having doubts about whether Van's method will allow my lines to be as straight as I want them to be. Even if the rivet lines are drawn straight before I drill, I'm having trouble picturing accurate blind air-drilling in my head.

So, Old School kit builders out there--- Before the days of pre-punched skins, what methods did you use to make your rivet lines straight and accurate? Did anyone pre-drill the skins, then match-drill the skin to the ribs/spars? Or did most people do as Van suggested, with things turning out better than expected?

Thanks!

 

[apkp777]

One technique that I used "back in the day" was to use "Edge Margin" instead of "Edge Distance". What you do is using your scale measure back from the edge of the skin not for the center of the rivet hole but for the edge of the rivet hole. I found that it makes sighting the rivet line more accurate. A 12" scale also works better than a 6".

 

[Mike S]

Use a fan spacer.

 

[Ironflight]

Hi Katie,

If your concern is getting the holes drilled exactly where you drew them with your sharpie, an automatic center-punch is your friend. Just have something firm behind the sheet and give a light punch to give a little spot to give the drill bit a good centering start.

We have used a combination of pre-drilling skins and predrilling formers to do the -3. For the wing skins, with long straight lines of rivets, we found it easiest to predrill the skins, then draw a straight line on the rib flange, and sight through the holes to find the line on the rib to match-drill. This works well because the wing substructure is mostly straight lines and right angle corners. For the fuselage, with all it's curves and odd shapes, we found it easier to pre-drill the longerons, stringers, and bulkhead flanges, then strap the skin on with tie-down straps before drilling through from the inside to the outside. There is no one answer that works all the time.

(I also have a little set of magnets and a magnetic "viewer" that was sent to me by an old-time builder. You super glue the magnets on to the underside of the structure, put the skin on, then use the viewer to find the magnet and drill a hole through, popping the magnet off as you go. Useful in some odd places!)

Paul

 

[Rick6a]

......Before the days of pre-punched skins, what methods did you use to make your rivet lines straight and accurate?....

Back in the day, a builder had to use math to determine an X number of equally spaced holes in a given length. Even so, I discovered a better way to do that when I decided to build an airplane. At times while building my -6A, I actually clecoed 2 of the longer fan spacers together in order to quickly lay out some of the longer rivet runs. A fan spacer virtually guarantees a straight and equally spaced rivet line. The concept of actually laying out rivet patterns is completely lost to the current generation of quicky prepunched kit builders.

Note: You DO NOT drill through a fan spacer unless you want to trash it. You merely MARK the holes with a Sharpie and go from there.

 

[ChiefPilot]

Back in the day, a builder had to use math to determine an X number of equally spaced holes in a given length. Even so, I discovered a better way to do that when I decided to build an airplane. At times while building my -6A, I actually clecoed 2 of the longer fan spacers together in order to quickly lay out some of the longer rivet runs. A fan spacer virtually guarantees a straight and equally spaced rivet line. The concept of actually laying out rivet patterns is completely lost to the current generation of quicky prepunched kit builders.

Note: You DO NOT drill through a fan spacer unless you want to trash it. You merely MARK the holes with a Sharpie and go from there.

This is still one of my favorite tools, although I'm past the point of using it now on my -6A project. It's clever, simple, quick, and accurate.

 

[KatieB]

Hi Katie,

There is no one answer that works all the time.

Paul

I'm starting to think this is the standard answer for all RV-3 questions!!

Yes, drilling accuracy and getting rivets that look straight when you sight down the line is my main concern.

 

[JonJay]

Simple jig for end ribs

Your concerns are well founded. I have seen a lot of really poor rivet lines on the older kits. Some did it well, others not so much.

As noted, the distance from the web is consistent. The edge of the flange, especially on the early kits, is quite variable.

This is a simple jig you can make that makes quick work out of centering end rib holes. It only solves part of the problem. I used a combination of the other suggestions for internal ribs. You just have to work through it. In regard to the fan spacer, one of my favorite tools, don't forget about your flutes. You don't want a hole to fall on that area. You can use the fan space on the rib to insure your spacing is good and your holes fall in between, then carry that same spacing onto the skin.
http://www.vansairforce.com/community/showthread.php?t=39694&highlight=drill+jig
Some adjusting of spacing may be necessary. I found that slight adjusting of spacing row to row to be preferrable over making up on one or two rivets, but as long as you are consistant in your approach, it will look just fine. You will find that the spacing on the tips of the ribs need to be adjusted, but as long as you do all of the tips the same, it looks great.

I might be able to get you one of the magnetic viewer kits like I sent to Paul. As he puts it, they are helpful in some odd places. Not sure they worked out overall as the other strategies seem to be easier.

 

[KatieB]

Edge Margin

One technique that I used "back in the day" was to use "Edge Margin" instead of "Edge Distance". What you do is using your scale measure back from the edge of the skin not for the center of the rivet hole but for the edge of the rivet hole. I found that it makes sighting the rivet line more accurate. A 12" scale also works better than a 6".

I think this is a good idea-- I drew a pair of rivet hole edge lines on either side of the rivet centerline to help with accurate drilling of the rudder skin for my CX4 project. My build buddy/boyfriend thought that was overkill, but it helped me gauge the punch and drill position more accurately. I was happy with the results.

But that skin was drilled on the bench, not in mid-air over the skeleton...

 

[Louise Hose]

Love your blog!

Katie,
I loved visiting your blog. I don't know how people build AND maintain a blog, but it was great to see and visit. Enjoy the journey!

BTW, if you still need old wing plan pages, I may have a lead for you. PM or e-mail me.

 

[KatieB]

blogging! Sounds so nerdy, doesn't it?

Thank you Louise! It's been fun blogging this so far. I write for a few minutes each night after we come in from the garage. It doesn't take much time if it's fresh in my head, plus it's just vegetable time anyhow. Ben turns on the TV and I hit the couch and computer for some writing time and VAF surfing...

It's too bad you guys didn't build your tail, or I'd be hitting your photo album each night too! (Your album will have its own button on my toolbar when I get to the fuselage...)

 

[KatieB]

knowledge & tools

I might be able to get you one of the magnetic viewer kits like I sent to Paul. As he puts it, they are helpful in some odd places. Not sure they worked out overall as the other strategies seem to be easier.

Hi JonJay,

I love your little spacer tool idea. I'd also love to see one of your magnetic viewer kits. From what I've read, there are a lot of odd places on a 3...

I work with a local old-school RV-6 builder and asked him how he located the holes in his skins & skeletons. He said he did not blind-drill the tail or wings, but rather traced & measured the skeleton position on the back side of the skins with the skins clamped/strapped in place, then removed the skins and laid out & drilled his rivet holes into the skin on the bench. When he reinstalled the skins onto the skeleton, the rib/spar flange centerlines showed through the "pre-drilled" skin holes, making match drilling the skeleton pretty easy. I told him and a newer RV-6A builder about Van's blind-drilling instructions and they sort of went .

When I re-examined the horizontal tail structure, it will be insanely easy to do this method, especially if I make one of JonJay's little end-rib tools. (Now that I said "insanely easy," it will probably be a nightmare!!) This is also how I drilled the skins on my CX4 rudder last winter, but that was a flat, simple structure so I wasn't sure how it would work on the RV.

 

[JonJay]

Sounds like a decent plan

Hi JonJay,

I love your little spacer tool idea. I'd also love to see one of your magnetic viewer kits. From what I've read, there are a lot of odd places on a 3...

I work with a local old-school RV-6 builder and asked him how he located the holes in his skins & skeletons. He said he did not blind-drill the tail or wings, but rather traced & measured the skeleton position on the back side of the skins with the skins clamped/strapped in place, then removed the skins and laid out & drilled his rivet holes into the skin on the bench. When he reinstalled the skins onto the skeleton, the rib/spar flange centerlines showed through the "pre-drilled" skin holes, making match drilling the skeleton pretty easy. I told him and a newer RV-6A builder about Van's blind-drilling instructions and they sort of went .

When I re-examined the horizontal tail structure, it will be insanely easy to do this method, especially if I make one of JonJay's little end-rib tools. (Now that I said "insanely easy," it will probably be a nightmare!!) This is also how I drilled the skins on my CX4 rudder last winter, but that was a flat, simple structure so I wasn't sure how it would work on the RV.

Some of my 6 kit had predrilled holes and you drew center lines on the ribs and pushed them around to get them to line up, so that method your friend is describing works well. My 3 kit did not have any drilled holes in the skins. So, I used different methods. Just remember to mark your flute area so you don't drill through the flute seam. I used a fan spacer to approximate my hole locations on the ribs before I fluted them to lessen the chance of having them fall in the wrong place. If you have not fluted your ribs yet....
I pm'd you on the mag kit.

 

[az_gila]

Exactly...

I'm starting to think this is the standard answer for all RV-3 questions!!

Yes, drilling accuracy and getting rivets that look straight when you sight down the line is my main concern.

...which is why te straightness of the rivet line is more importnt than the actual spacing of the rivets along the line.

Mark a straight line on the skin and pre-drill #50 holes, making sure that the holes are exacttly on the line....

Then use the edge marking tool to mark the centerline of the rivets on the rib flanges. If necessary, temporarily stiffent the ribs to prevent them moving or curving. Make sure the fanges are correctly bent so the skin will lay flat. A yard stick is a good tool to check this...

 

[mcencula]

<snip>

Note: You DO NOT drill through a fan spacer unless you want to trash it. You merely MARK the holes with a Sharpie and go from there.

A possible idea to get the lines really straight without trashing your fan spacer: You could use a little piece of thinwall brass tubing (available from hobby stores) as a bushing to protect the fan spacer and drill 1/16 holes right through the fan. Kind of like this:

...although in this case I have three spacers nested together to allow me to correctly center a #40 drill (starter hole) where I already have a #12 hole for the mating part.

Of course, I'm building a -7A, so when it comes to rivet fans it's entirely possible I have no idea what I'm talking about.

Good luck.

 

[Bill Wightman]

A few techniques to help

Assuming you've got your rivet lines laid out with a Sharpie, you shouldn't worry too much about getting the drill to start on target.

First, do use a good sharp split point drill bit. Dull bits have a greater tendency to walk across the work surface before taking a bite. Place the drill point exactly where you want it to start; make sure you're holding the drill perpendicular to the surface. You want the drill to start in on target with no drift due to side loading.

Then, before you ease into the trigger, simply rotate the drill chuck by hand a turn or two and you should see and feel it begin to cut into the skin. This greatly helps to assure a clean start on target.

Finally, if you do miss just a little at first - or if the drill does drift initially - you can angle the drill back toward the target to guide it back to center. This should be done before getting too deep into the hole, then it gets harder to do.

 

[KatieB]

This is why...

This is why I posted the question. Figured I'd get lots of great tips like these. Thanks guys!

(More tips definitely welcome!!)

 

[danbenua]

More methods for drilling skins...

Just so you have more options, there are combinations
of some previously mentioned techniques that have
worked well for me on my RV-3B.

One way is to combine back-drilling through the skeleton
with pilot holes in the skin. First mark the rivet spacing
on the rib flange so that your flutes won't interfere with
any rivets. Then draw center lines on the flanges where
you want the rivets to go. With the skeleton assembled
and jigged, clamp the skin in place. Back-drill one hole at
each end of each rib out through the skin. Then remove
the skin and lay out straight lines between the holes at
the end of each rib. Use your rivet fan (or a marking template)
to lay out the intermediate holes and drill pilot holes in
skin on the bench. Now re-assemble the skin to the skeleton
and adjust the ribs to get the center lines on the rib flanges to
show through the pilot holes. This technique is slightly slower
because of the extra steps, but it guarantee's straight rivet lines
and no edge distance problems on your rib flanges.

I generally try to avoid blind drilling whenever possible.
With your HS and VS, you can drill the skins to the end ribs
and rear spar first, then unfasten and lift the opposite
skin to allow back drilling of the central spars and ribs.

It is likely that you will find some areas where blind drilling
is the only viable solution (small nose ribs for example).
Here the bold builder learns to measure 4 or 5 times
then drill gently so that the drill bit just penetrates the
skin. Then you peek through the tiny hole to see if
the flange center-line is visible. If the hidden rib needs
moving left or right, you can do it through the tiny
pilot hole with an awl. I know this sounds risky and
primitive, but this is how the hairy chested builders of
olden years did it .

At least half the fun of building an RV-3 is figuring out
how to solve all of these little "how do I do it" challenges.
Cheers,
- Dan Benua