Sunday, September 21, 2014

First Month Complete!

The first month of building has come to a close, and after spending the first few weeks of doing preparatory work, I have finally started to set some rivets.

I started construction with the horizontal stabilizer (HS).  It was very straight-forward to put together and no issues came up as it was riveted.  I have only riveted one side of the skins because I have a tech counselor who will be visiting in the next week to review my work to date - after his inspection I'll close out the other side of the skins.

After completing one side of the HS, I moved on to the rudder.  Similarly, no particular issues arose building the rudder skeleton and riveting one side of the skins. As with the HS, I've leave the other side of the skins non-riveted until the tech counselor drops by.

Next on the list will be the vertical stabilizer (VS)  - stay tuned for an update on that, including mounting a VOR antenna.

See below for some photos of progress over the last couple weeks.

Horizontal stabilizer clecoed and
rivets positioned, ready to be set

The very first rivet set!
Horizontal stabilizer skeleton complete
One side of horizontal stabilizer skin riveted
Rudder skeleton riveted - note the counterweight
One side of rudder skin riveted

Sunday, September 7, 2014

First Couple Weeks

It has now been a couple weeks since I received the empennage (tail) kit.  I have managed to find some time to work almost every day  - sometimes it is only half-an-hour, but the plan is to work on it every day to some extent to keep the progress going.

I've had to split time between working on the build and finalizing the layout of my workspace. I still have a few things to set up in the garage, but going forward the majority of time will be spent on the build instead of the shop.

To help familiarize myself with the empennage construction, I test fit all the individual pieces (elevator, vertical stabilizer, horizontal stabilizer, and rudder), using clecos instead of rivets to hold everything together.  Going through the test fitting helped me sort through how the pieces will eventually all fit together, and will help me plan the sequence of riveting when that is started.  All the components fit together very well, which is a great start.  There are also a couple pieces that need to be match-drilled to ensure a proper final fit, so I also took care of that during the test fit.

After the test fit, I broke down all the components and started the process of deburring and cleaning all the structural components and the skins.  As of today, all the empennage pieces are deburred and cleaned, and the framework for the rudder, horizontal stabilizer, and the horizontal stabilizer has been primed and is ready for riveting.  I did have a minor set-back when I ruined a couple pieces as I was shifting things around in the garage - fortunately it was before I had done much work on them so I won't lose any time, but it will take a while for the replacement parts to make their way to me.  Also had one piece that had a crack in it that the factory will be replacing for me.

So, all-in-all,  it was a productive first couple weeks and I am thoroughly enjoying the process!

Here are a couple of photos from the last couple weeks:

Doing inventory - these are all rudder components
Test fitting the elevator trim tab
Test fit of elevator  with skins
Test fitting the horizontal stabilizer
Match-drilling the horizontal stabilizer
Test-fitting the vertical stabilizer
Horizontal stabilizer cleaned,tagged and ready for degreasing
Horizontal stabilizer degreased and ready for priming
Horizontal stabilizer primed and ready for riveting
Rudder (left) and vertical stabilizer (right) components
primed and ready for riveting

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