I Really Like Clecos

Man, I really like Clecos.

A few years ago,when a group of us on staff built a Zenith CH 750, I must have installed and removed hundreds of them, and yet I’ve never ceased to be amazed at their ridiculously clever utility. When building an airplane out of sheet metal, you spend a lot of time assembling two or more pieces, drilling holes that are matched just perfectly, and then disassembling those pieces to smooth out — deburr— the sharp edges caused by drilling, trimming, etc. When you’re assembling these pieces, you need some way to temporarily hold them together: enter the humble Cleco. If you don’t know, Clecos are a family of fasteners originally produced by the Cleveland Pneumatic Tool Company, hence the name. (If I’d invented them, I would have called them Cleptcos, so be grateful that I didn’t.)

EAA Zenith Staff Build Group Photo

Clecos are extremely simple to use, but maddeningly complicated to describe. They’re generally cylindrical, with a set of what I used to call “contracting prong things,”until I learned that they were called step-cut locks, sticking out of one end. Operating a Cleco consists of applying some form of pressure to the other end, in some cases by turning a wing nut but most of the time by using a specialized set of pliers to depress a plunger. As that force is applied, the contracting prong things are pushed out of the body of the Cleco and simultaneously away from a set of spreader bars which causes them to contract so that they can fit through holes in a couple of pieces of metal.

Once the Cleco is in place, the plunger is released, the step-cut locks expand and withdraw into the body, pulling and securing the two metal parts together. This not only joins the pieces temporarily, but keeps the holes lined up perfectly which is crucial when it comes to drilling additional holes, attaching other parts, etc. While they hold very securely, removing them is, if anything, even simpler than installing them, involving just another squeeze with the purpose-built Cleco pliers. Because Clecos are, thankfully, reusable, there’s no way of knowing how many times one is installed and then removed on a given project, but the number must be well into the thousands.

These little things are ingeniously clever in their design and utterly indispensable on a build like ours, but they’re so ubiquitous that we absolutely take them for granted. I know I did, that is, until a friend of mine off-handedly asked “what they did use when they built airplanes before Clecos?” and I realized I didn’t know. I didn’t even know within a decade when they were invented, which meant I had no idea if people were even building sheet metal airplanes before they could use Clecos to make it easier.

Because I A) hate unanswered questions and B) had too much time on my hands, I searched and found United States Patent No. 2,136,875, which I believe to be the first U.S. patent issued for what we now know as a Cleco. The patent was originally filed on March 16, 1936, by a Frenchman named Jean J. Blanc, who had filed the same patent in France in May of 1935. (I also found a British patent for a somewhat similar device from 1934, but my emphasis there is on the “somewhat.”) With this, the patent had answered one of my questions; with the following introductory text, it answered another:

Heretofore, it has been found in practice that before plates or the like could be riveted together, it was necessary for the workman to first secure the plates together by screws or bolts, which were inserted in the holes provided to receive the rivets. This long and expensive operation was necessary not only to secure the plates together but also to assure a perfect coaxial alignment of the rivet holes. In a great number of cases, this operation necessitated two workmen, one on one side of the work for inserting and holding the bolt in place, and the other on the other side of the work for screwing and tightening the nut on the bolt. It is therefore an object of this invention to produce a plate securing and locating device which is applied to or removed from the work from only one side thereof, thus eliminating the assistance of another workman from the opposite side of the work.

So, before Clecos, people used nuts and bolts, which, in retrospect, seems stupefyingly obvious.What wasn’t as obvious, however, was the fact that this process frequently required two people which differs profoundly from the way we do it now.

The other important bit is that using Clecos only requires access to one side of the work.Looking back on our CH 750 project, or any sheet metal build for that matter, the idea of forcing a second person in behind every part to tighten a nut would have been, in most cases, preposterous and impossible, and in some cases, a felony. So here’s to Monsieur Blanc; My simple research has told me next to nothing about him, except for the fact that he made building metal airplanes(and whatever else you might build, but we all know that airplanes are the most important) one heck of a lot easier. I started this by saying how much I like Clecos, but it’s more that I just really, really appreciate having the right tool for the job. Just about everything that most of us do in aviation finds us standing on the shoulders of giants, but I don’t think most of us grasp just how many.

Post Comments