CONNECTING AIRFRAME PARTS TOGETHER

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

As previously discussed, the bulk of the metal work is in the empennage section when you order the quickbuild fuselage and wings.  With the quickbuild options, the fuselage and wings are built for you by Vans Aircraft.  So, with the empennage section complete and the quickbuild wings and fuselage, there is no significant metal work remaining.  I say no significant metal work, but there is some.  Each of the airframe kits are different, but with the larger more complicated RV-10 there is a bottom panel of the wings left off so you can run wiring and hook up the push/pull assemblies.  The fuselage of the RV-10 comes pretty close to complete, but there are some interior panels that are left off so that you can run wires there as well.  Also, the fuselage must be riveted to the tailcone, which involves some additional metal work.

That being said, the next major push with the project is to connect up all of the individual parts and bring the overall aircraft structure to form.  This may seem to be a daunting task, but it is actually quite easy work and the instructions walk you through each step very clearly.  You will need some space and this is the point where you'll want to consider moving the project to a hangar.  Once the airframe is put together, you won't want to take it apart to take it to the airport on the roads. 

The parts are connect using aircraft bolts and nuts or nutplates.  The nutplates are permanent nuts that are riveted to the parts when they are assembled, typically used where it would be difficult to reach a nut.  For parts that move, rod bearings and bolts are used to enable the hinge action.  This is pretty much the same for all of the parts - either bolts or bolts and rod bearings are used to connect virtually everything together.   The nuts are tightened using a torque wrench and the appropriate setting the bolt size, which is given in the instructions.  

Some of the parts need to be connected to the control stick and to the rudder pedals in order to enable movement of those parts from the cockpit by the pilot.  These include the ailerons on the wingtips to enable banking of the aircraft, the elevator on the tail to enable pitch changes of the aircraft, and the rudder on the tail to enable yaw movement of the aircraft (e.g. left and right pointing of the nose).  Again, this would seem to be a difficult task, but it is really quite simple.  For the elevator and the ailerons, there are long rods that travel the length of the tail or the wing and connect up to the control stick.  Movement of the control stick moves these rods which in turn moves the respective elevator or aileron parts.  These rods are visible in the pictures below.  The rudder is even more simple.  It has two cables that travel the length of the fuselage and connect up directly to the pedals.  Movement of the pedals pulls on the cables which moves the rudder.  Deceptively simple.    

Once the parts are connected with the specified bolts and/or rod bearings and the push pull rods are installed, the airframe is essentially complete save for the finishing kit parts and some fiberglass work.

The instructions will help you get the airframe assembled and they are very clear about the steps need to do this.  However, they are lacking when it comes to certain add-on components like wiring, autopilot motors, antennas, and pitot/static port tubing.  I bring these up here because these add-on components are easier to install when the airframe is partially disassembled; yet, the instructions won't give you much help on how to do it.  By the time you figure out what is needed, it is too late and the airframe is already put together.  

The wiring is simple, lay a few guide wires in the wings, below the rear seats to the tail, and to the aft most part of the tail.  This way, you can easily drag any electric or antenna wires you end up needing through the wings and the fuselage without much trouble.  

If you are going to install the Ray Allen trim motors or Dynon autopilot motors, you should mount those before you close up the airframe.  The trim motors are mounted in the wings and in the tailcone.  These motors are covered in the Vans installation manual.  The autopilot motors are mounted in the wings and in the tailcone at different points from the trim motors.  These motors are not covered in the Vans installation guide, but rather are covered in the Dynon intallation instructions.  Getting these motors installed before you close up the aircraft will save you trouble later.

The pitot/static port tubing is also something that should be installed before closing up the aircraft.  Most new builders and even most experienced pilots have no idea what these tubes actually look like or how they are connected.  This was true for me, so I avoided it until the end - big mistake.  Let's be clear, these are just 1/4 inch tubes and there is one for the static port on the side of the aircraft and two for the angle of attack and the airspeed both going to the pitot tube.  All you have to do at this point is lay two 1/4 inch tubes in the wing with the pitot tube.  You can connect them up later, but having them in the wing will save you trouble.  The 1/4 tube for the static port can be left out because it isn't so difficult to reach.  I recommend the SafeAir kit available from Aircraft Spruce.  This kit includes all the plumbing, fittings, and instructions for connecting up these tubes to the respective parts.

After the metal work and the connection of the parts, the airframe really takes shape.  We will next discuss the finishing kit.

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.