Sunday, September 7, 2014

Tools and Jargon

To help understand the various steps involved in the build, I thought it would be helpful to spend some time discussing the activities and the tools we use to perform them. I'll add to this list as the build progresses and new techniques are learned and applied.

Firstly - let's introduce the general airplane construction since that defines the techniques and tools that will be used.  The majority of the skeleton and surfaces on the Sling 4 will be aluminum; a few fiberglass pieces complete the picture.

The primary method of joining aluminum pieces together is riveting. In the Sling 4, the majority (and perhaps all) of the rivets are called pull rivets (also called blind or pop rivets).  You have probably seen this style of rivet on many items around your house, and the ones I'll be using are similar in function, but of a higher quality and strength. Installation of a pull rivet starts by placing the rivet tail into a hole that is common to the pieces of aluminum you want to join. Using a pneumatic or hand riveter, the mandrel is pulled back, which compresses the tail and locks the pieces of aluminum together between the head and tail of the rivet. The mandrel snaps off on its own,leaving behind the final rivet holding the work together.  There will be thousands and thousands of the rivets in the Sling 4.

Examples of various sizes of pull rivets to be used in the Sling 4 empennage

Here are a couple of the tools I'll be using to set the rivets
Hand (left) and pneumatic (right) riveters

However, there are several steps than one needs to complete prior to riveting to prepare the pieces to be joined and to ensure longevity of the components.  The majority of parts in the Sling 4 kit are pre-shaped and pre-drilled so that little modification is required to enable the pieces to fit together properly.  However, there will be a few pieces that need to be drilled in spot to ensure an accurate fit, and every piece needs to be deburred and prepped.  Deburring is the process of removing any burs or sharp edges to reduce the potential for metal fatigue and cracking. Every piece in the kit needs to be inspected and deburred to at least some degree.  In addition, there are sharp edges and corners on every piece that need to be rounded.  There are a wide range of tools used for deburring - some are hand tools:

Hand deburring tools

.....and some are electric:
Scotch-Brite Deburring Wheels (these are not stone grinding wheels)

Finally, many individuals choose to prime the pieces to reduce the long-term potential for corrosion.  There are many different primers and ways to apply them, but I have chosen to work with an epoxy primer that is sprayed on.  To prepare for priming, the aluminum be cleaned, degreased, and abraded to provide an optimal surface for the primer to adhere to - a lengthy process but it will be much more durable.

Here is an example of a primed piece of aluminum (bottom).
That green color will be a tell-tale sign of what I have and haven't primed

Here is an example of a couple pieces of aluminum being riveted together.  First step is to cleco the pieces together to hold them in the final desired position.  A rivet is then inserted into one of the match-drilled holes. A riveter is used to pull the mandrel of the rivet, which compresses the tail and sets the rivet.  As the riveter continues to pull the rivet, the mandrel snaps off and the rivet is complete.

Rivet ready for setting
Rivet head set

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