Traveling back in machine-shop time

The basics-of-machining class ended today, and I had a chance to do some work on a lathe. Renton Tech has a lot of equipment that dates back to its start as a training center for Boeing’s B-29 plant in Renton. The lathe I worked on was some of that gear.

American Pacemaker

I was learning how to handle a four-jaw chuck, which is kind of a pain. Nonetheless, I was able to get my work dialed in within a tolerance of a tenth, or .0001″. Not that I’m slick or anything, but that was 10 times more accurate than the work you would do with this lathe. It’s pretty amazing to see the degree of accuracy that is possible with tools from 80 years ago.

There’s been no new progress since completing the first take at a rudder and getting empennage parts delivered. Now that I’ve wrapped up machinist training it’s time to focus on nailing the checkride and making a few changes in the garage to make room for airplane stuff.

Playing with the look

I sometimes spend time I should be using to pull rivets thinking about the appearance of the final product. Here’s the latest concept, a military/not-military design of the Cascadian Air Service.

It’s not apparent from the illustration that design would use decals on polished aluminum. Stripes are 4 inches high, and the N numbers are 3 inches high. The Renton Technical College logo is 5 inches high. Squatch? 12 inches.

(Added: Discussion on the Facebook page)

It’s time to pull some rivets. And make a few mistakes.

The project as of 1 p.m. Thursday. It’s about half-way there.

I had a busy week on the rudder. The skeleton went together quickly last week, with all mating surfaces coated with an anti-corrosion film (Cortec) and the bits reassembled for riveting.

On Wednesday riveting began, with some missteps. I got carried away and put a half-dozen rivets in the skeleton where they won’t supposed to go yet, so got some experience in drilling out blind rivets without enlarging the hole. That turned out to be easier than I had expected. Everything aligned as expected, and in a couple hours every rivet was in its place on the skeleton and I was ready to put on the skin.

Thursday was a day of great progress. The skin went on with little difficulty — it’s a pleasure to work on an airplane kit where the vast majority of holes are drilled to size and ready for assembly. It didn’t take long to get the skin in place and cleco’d up.

One of the pleasures of this project is where I get to work on it. I’m taking classes in the aerospace program at Renton Technical College, this quarter learning precision machining and related skills like inspection. As part of that, I have access to an incredibly well-equipped aviation workshop, which I’ll detail a bit more in another post. I also have the benefit of working under the instruction of Vincent Phillips McLellan, who founded and runs the aerospace program. He’s given invaluable advice in how to attach the skin to keep it as flat and straight as possible, how to correctly use the tools, and many other skills. A lot of the reason I have confidence in what I’m doing (more on that later) is being able to draw on these resources.

On Friday came the fun part, pulling rivets on the skin. In short time I had the end cap assembled and cleco’d in, and the rudder horn in place. At Vince’s recommendation I’ve started at the trailing edge, in the middle of the rudder, and worked my way out and up. Shop lighting makes the skin exaggerates the waves between the ribs — outdoors and in regular lighting it’s straight. I’m about a third of the way through riveting, but will need to do a little remediation first.

Now, for some mistakes. Putting on the top cap assembly I inadvertently drilled a hole straight through both sides of the skin. After cursing, I followed the advice of the Zenith assembly manual — if you put a hole in the wrong place, just put in a rivet and don’t sweat it. In this case, the extra rivet is at the top a tall rudder, in a place where it will be inconspicuous. And lesson learned.

A bigger concern to me is getting the rivets in true. After wrapping up for the day I did a pretty thorough inspection of the rivets I’ve placed so far on the skin. There are a lot that aren’t sitting as flat as I’d like. The manual says it’s not seated correctly if you can put a fingernail under the rivet, and probably a quarter of what I’ve pulled so far fails the fingernail test.

I’ll be spending the weekend reviewing my Homebuilder Help videos and assembly manual to figure out what I’m doing wrong, and marking the rivets that need a do-over. On Monday I’ll get some help from Vince and starting drilling out some rivets.

Now I’m started to understand why Zenith includes the rudder in the tail kit, whether or not you’ve already built the rudder starter kit. Depending on how this piece turns out, it’s possible I’ll build a second rudder to get my work as high-quality as possible. Hey, it’s a learning process, right?

Let the drilling begin

Clecos on parade

I finally broke the seal today and started assembling the rudder from the pre-drilled kit.

It was a slow start, as I needed to get up to speed with the Renton Technical College instructor whose shop I have the pleasure of using as I toy with the idea of building a plane. As you’d expect from a shop that prepares Boeing assemblers, it has all of the tools I’ll need — pneumatic drills and rivet pullers; air chucks at every workstation; all of the right drill bits, tool chests full of files, fussy little clamps, deburring tools, machinist’s rules, well-organized clecos, cleco pliers, and everything else you might need to assemble an aluminum airplane. For a sloppy-workbench guy like me it’s a dream!

I’m starting with the skeleton of the rudder. In the course of an hour I got a groove on assembling the spar, first by cleaning off labels and markings off of the pieces, which all have been cut, bent and mostly drilled at the factory.

Cleaning with isopropyl alcohol

So far about two-thirds of the work is done to clean, deburr and drill the holes needed to attach the doublers to the spar. It’s super-easy because the spar already has the holes, it’s just a matter of putting in the doubler holes and enlarging holes in the assembled pieces to the final size. Honestly, as a kid I made more complicated plastic models.

Rounding sharp corners
Deburring and smoothing sharp edges

I won’t be back on the project until Wednesday. Next week’s goal is to see if I can complete initial assembly of the rudder skeleton in preparation for adding corrosion protection and starting to pull rivets. I’m guessing that dry-assembly work will take no more than several hours.

They’re more than just holes in metal

I present to you my initial work as a student of precision machining at Renton Technical College, in Renton, Wash. These are blocks of carbon steel and aluminum drilled to tolerances of no more than 30 thou. (That’s 0.030 inches.)

Eventually, this course leads to a program in Aerospace & Industrial Production Technologies — it’s a pipeline to Boeing, which of course builds 737s at a plant about two miles away from the college. It also gives me access to resources that will be useful as I build a Cruzer rudder and toy with the idea of building an airplane.