METAL WORK

By Jim Ruttler, Instrumented Rated Pilot, RV-10 Builder, Patent Attorney
www.ruttlermills.com
jim@ruttlermills.com

The metal section of the plane that you will build yourself are the empennage.  We've discussed in previous posts that the wings and fuselage are completed for you via the quickbuild kits.  The finishing kit is not metal work, but rather hooking things up, installing wheels and brakes, etc.  The avionics section and the engine sections don't involve metal work.  So, the bulk of the metal work occurs in the empennage kit.

If you've never worked with metal before, you aren't alone.  I hadn't either.  Don't worry though because there isn't much skill required, it is repetitive, and you'll pick it up very quickly.  Remember that the parts come pre-cut, bent, and punched, so the metal work that you'll be doing while time consuming isn't very complicated.

So what exactly is involved in experimental aircraft metal work?  The empennage contains the horizontal stabilizer, the vertical stabilizer, the rudder, the elevators, the trim tabs, and the tail-cone.  The empennage kit includes everything you need to make these components and they show up in one big box as you can see with this picture of me.  Hard to believe that everything needed for the empennage of an aircraft fits in this box, but it really does.  

Upon opening the box, you will first organize all the parts according to the specific section they are used in.  For instance, you'll find all the parts labeled vertical stabilizer and put them together.  Some small parts and the hardware are best stored together and organized with bins or shelves. 

You will then begin with the first section, which is the vertical stabilizer.  The instructions are very detailed and are written with the assumption that the builder has very limited knowledge of how to construct an experimental aircraft.  The first step is to sand the edges of each of the parts.  As you can see here in this image, the parts are already cut, bent, and the holes punched.  The reason you sand the edges of the parts is because the tool used by the kit manufacturer to cut the metal leaves little barbs on the edges of the metal.  I found that a belt sander accomplishes this task very well in combination with a Dremmel tool for the tighter spots.  

Once the edges of the metal are sanded, you'll then connect all the parts together using the Clecos in your toolkit.  The Clecos will hold all the metal together as can be seen in these images.  This assembly goes very quickly and within a couple of hours, your entire stabilizer will be temporarily assembled. 

Once assembled, you'll drill through all the pre-punched holes.  I know - if all the holes are pre-punched, why are you drilling through them?  I asked this very same question.  The official answer is that you want to make sure that the holes are exactly lined up before you slightly enlarge them.  This might be true, but another reason I think has to do with getting the builder to the 50% level of contribution.  So, you drill through all the holes to slightly enlarge them.  There are essentially two different sized bits that you use for this process: #30 (inside holes) and #40 (outside holes) - these bits come with your toolkit and are called out when needed by the instructions.

Upon completion of the drilling, you disassemble the parts and deburr all the holes.  The deburring is to clean out any debris or loose metal from the holes and ensure a tight fit between overlapping metal parts.  The toolkit comes with a deburr drill bit and you can use a small battery powered hand-drill to quickly move between the holes.  

After deburring, you'll then dimple the holes that you drilled so that the rivets sit flush on the surface of the metal.  The inside holes that are not visible when the part is complete are not dimpled - only the outside holes.  A flush rivet reduces drag because the surface is smooth instead of bumpy.  The dimpling can be accomplished with the rivet squeezer or the C-frame dimpler (both included in your toolkit). 

Once the dimpling is complete, you final assemble the parts by riveting them back together.  The riveting is what most people are afraid of, but it is actually the easiest and most fun activity.  The deburring and dimpling is actually the most time consuming and tedious work.  So, once you get past the deburring and dimpling, the parts come together very quickly.  

The riveting can be accomplished with the rivet squeezer for the holes that are near the edge.  For the other holes, you'll need to use the rivet gun (both tools are included in your toolkit).  The riveting consists of holding the gun against the flat side of the rivet and holding the bucking bar against the other side of the rivet and then pulling the trigger for around 2-4 seconds.  The rivet is set properly when the rivet has been smashed to the correct diameter, which is 1.5 times the original diameter. 

The completed part can then be placed aside and work can begin on the next part, which involves the same steps.  Here is a completed stabilizer and rudder that were both completed using this same methodology.

So the process is not difficult and is easy to master.  You just drill, deburr, dimple, and rivet until each of the stabilizers, elevators, rudder, and tailcone are complete.  

However, if you aren't convinced that you can quickly master the process, or want to learn on something that is inexpensive and unimportant, I suggest the practice toolbox offered by Vans.  This toolbox actually involves constructing the toolbox using the same parts and rivets that you'll use on the airframe parts.  The nice thing about it is that after you are complete, you'll have a place to keep some of your tools. 

In the next post, I'll discuss the process of connecting the completed empennage parts with the completed quickbuild parts.