To paint or not to paint

Science will help me know how I should prevent rust on steel bits inside the plane that no one will see? Here’s my experiment.

Here’s one issue that I hadn’t considered until it came up on a Zenith discussion group: Do I need to paint steel parts that no one will see, like push-pull tubes for flight controls? Surely bare steel will rust, but do I need to go to town on paint or powder coat, or will a simpler solution work?

Three pieces of steel, hanging from a wooden fence.
Painted, left; WD-40, center; control, right.

I’m kind of science-y, so set up an experiment today. I cleaned up three pieces of hot-rolled welder’s stock, painted one with Rust-Oleum enamel, coated one with WD-40 Specialist Corrosion Inhibitor, and left the control piece untreated. They’re hanging on the fence, and we’ll to see over time how the different treatments hold up.

My money’s on WD-40. But no wagering, please.

Building an airplane workshop: How at long last I got organized

I’m pretty notorious for being sloppy with my workshop. Notorious, at best. I guess I’m my father’s son. Dad is a metalworking artisan, and even though tools were apparently randomly arranged on his workbench, he never had trouble finding what he needed when he needed it. On the other hand, I would spend more time looking for tools than using them.

That’s no longer possible facing the intensive-building phase of the Cascadia Cruzer project. It would add many hours to the build if it’s necessary to dig around for the right drill. It’s all behind me now.

In large part I’ve been influenced by the fantastic aerospace lab at Renton Technical College, where I’m learning about machining and building aluminum airplanes. It’s amazing how much faster and enjoyable it is to work in a well-organized and well-equipped shop. Amazing for the old me, at least.

Here’s how the tool chests are organized at Tech.

So, in the break after my most recent post, I’ve been acquiring a few specialized tools and upgrading some general-purpose tools, like power tools. (Also, I’ve been knocking off a bunch of small projects around the house on the backlog, which will help me focus on the airplane.) And I’ve overhauled the workshop to accomodate what’s coming. All redundant tools are now stored away, and only “live” ones are in the toolbox. The airplane tools — pneumatic cleco pliers, hand drill-powered rivet puller, deburring tools and the like — are in their own drawer. Other drawers are for socket sets, SAE wrenches, metric wrenches, drivers, bits. On the pegboard are shears, hand cleco pliers, hand rivet puller.

About half of the clecos required are in stock — I got a great deal on used pieces from a fellow EAA’er who built a Sonex. They were a little dirty, with light surface corrosion, and an overnight soak in mineral spirits made them as shiny as new. The rest of clecos are coming in a week or so from an eBay seller. Rivets are laid out in a plastic container, labeled and structured. I also made a handy little tool from a dowel that will make it easier to grab and place thousands of rivets I’ll be playing with over the next year.

This need for this kind of organization is pretty obvious, but it’s never been much of a priority for me. Until now.

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)

Zip ties, duct tape and wire hangers

There’s a brief but useful piece in this month’s Sport Aviation (p. 102) with tips on securing engine compartment wiring with zip ties. I had never heard of GripLockTies, designed specifically for use with electrical wiring. Noted for future reference.

Screengrab excerpt from June 2021 Sport Aviation

(Added: Discussion on Facebook)

Speaking of which, the four methods of countersinking

I wonder how any homebuilder ever had the time to countersink their rivets.

I’m driving only blind rivets, which means they’re inserted into a hole, then pulled into shape using a tool on one side of the rivets — commonly called “pop” rivets. On the way to looking up something else, this excellent old-school instructional showed up on how to drive countersunk rivets, that is, rivets that are flush with the skin of the airplane, eliminating a source of drag at high speed. Watching it, I wonder how any homebuilder ever had the time to countersink their rivets.

Rudder is riveted. Mostly.

I recover from some earlier missteps and BUY MORE TOOLS.

Work progressed so quickly this week that I barely had time to take photos.

All of the pieces are now firmly attached, and all but a half-dozen or so holes are still waiting for rivets. I spent a fair amount of time drilling out rivets in a few spots where I prematurely went to town along the rivet line for the piano hinge, which I’m attaching in the photo.

The gap between the end of the top cap and the back of the trailing edge seems weird. Here’s what that looks like:

I messed around trying to close that gap as much as possible without distorting the bend. The top cap is about 5 mm forward of the position specified in the plans, but there’s no way to move it back farther without trimming off material and/or bending the curve. Based on a review of a lot of photos online of Cruzer rudders, it looks it is what it is. Hopefully there will be some insights in builders’ forum, but I believe I’ve done this correctly. It seems weird to leave an gap like that, even on the trailing edge, so a little bit of silicone might close it up in the final product.

I’ll still be drilling out some rivets that didn’t get seated properly, as noted earlier. I’ve actually run out so have ordered more via Aircraft Spruce. The concave rivet gun nose I was using may be close-but-no-cigar, and that’s what caused circles around many of the rivets and not-fully-seated rivets. With the Official Zenith riveter and noses in hand there was no problem at all getting the rivets in cleanly. Lesson learned.

Speaking of rivet guns, I picked up a very useful tool that you see in the first photo. It lets you use a drill to smoothly pull blind rivets. This works great, and avoid the “bounce” from pulling out a mandrel with a hand or pneumatic riveter. I love the air tools that I get to use at Tech, but there are some advantages to the smooth action of the drill attachment over the fancier tools. A hundred bucks well-spent.

After a little rivet revision next week I’m planning to move on to the polishing stage with some Nuvite purchased this week and a cheap random-orbit polisher on order. The goal is to see how closely it’s possible to get to a mirror finish.

Considering all of the lessons learned building this piece, including some minor scratches and bangs from driving the part back-and-forth from Tech, I went ahead and included the rudder parts in my order this week for the rest of the empennage. The rudder kit has been a great tool for learning, and the skills and tricks I’ve been learning will be very useful for making airplane parts as accurately as reasonably possible.

What is a Zenith 750 Cruzer?

It’s an all-metal, two-seat aircraft that meets the requirements of the sport pilot license. The Cruzer is the cross-country member of the CH 750 family, which includes a STOL “off-airport” plane and a stretch “super duty” version.

Stock photo of Zenith 750 Cruzer
Cruise102 knots
Stall Speed34 knots
Never Exceed Speed 126 knots
Rate of Climb1200 fpm
Range450 nautical miles
Endurance4.5 hours
Empty Weight780 lbs
Gross Weight (LSA)1320 lbs
Useful Load (LSA)540 lbs
Design Gross Weight1440 lbs
Design Useful Load660 lbs
Load Factor +6/-3 g
Take-off Roll350 ft
Landing Roll350 ft

Here are all the details at Zenith’s site.