Pinning Hinges

from the Miramar Radio Control Flyers, San Diego CA

 Pinning Hinges for Increased Security When Flying

     If you’ve ever had a control surface come loose in flight and lost an aircraft as a result, you’ve probably given serious consideration to pinning hinges for added security. Sometimes you get away with a detached control surface, but when you have no elevator, or an aileron is partially pulled out at an angle, you can lose an aircraft quickly. The most common hinge types used today are the nylon hinge and the flexible CA hinge that Sig markets as the "Easy Hinge." You’ll also find metal hinges used in some of the Almost-Ready-to-Fly (ARF) airplanes. Nylon and metal hinges are normally glued into position using epoxy glue. To avoid epoxy from getting on the hinge joint, modelers sometimes coat it with Vaseline or oil.

     The installation of nylon or metal hinges is a more time-consuming and tedious process than the installation of the Easy Hinge. The Easy Hinge is slipped into slots in the control surface and in the wing or tail structure after which CA is dripped on to the exposed portion of the hinge and wicked into both ends of the hinge by capillary action. In order to provide assurance that control surfaces won’t detach in flight, many modelers pin their hinges.

There are two basic methods:

     The first is the use of the classic, round toothpick. Using a ³/₃₂ size drill, drill through the hinge on both the control surface side and wing or tail structure side. Install the toothpicks using epoxy or white (aliphatic) glue. When the glue sets, clip the toothpicks as close to the surface as possible and then sand the ends flush. Because sanding is impractical when covering is already on the aircraft, you can carefully grind the toothpick ends flush using a Dremel tool. Cover or paint as appropriate. Note: Some articles recommend the use of CA glue. I don’t because CA can set so quickly the toothpick may not be properly installed.

     Another method for pinning hinges involves using two types of steel pins in combination. This method won’t work well with metal hinges because of the difficulty of drilling through the metal with the larger pin used as a drill bit, but I have used it with nylon hinges and it is especially suited for the Easy Hinge. I’ve found using the steel pin method with Easy Hinges is the quickest and most secure method. Here’s how the steel pin method works. First, you need two types of pins—a box of "Tailor" pins and some modeler’s T-Pins. You can get the Tailor pins from any store that carries sewing items. Modeler T-Pins can be found at your local hobby shop. You may encounter some difficulty drilling through nylon hinges. Conversely, your T-Pin drill bit will go through the Easy Hinges like butter. Note: You might use a ¹/₁₆-inch drill bit versus the T-Pin bit. The diameter is slightly bigger than the T-Pin shaft but it should work and may make the job easier when dealing with a regular nylon hinge, and especially a metal hinge.

     Now that you’ve drilled your pin holes, it’s time to install the Tailor pins. Since the shaft of a Tailor pin is thinner than the T-Pin, the Tailor pins fit easily into the drilled holes. Install them in the holes from the top down so the pin top will appear on the upper wing, tail, and control surface.

Leave roughly ³/₈-inch of the pins exposed. Mix up a batch of 30-minute epoxy. Dab some epoxy on the exposed portion of each pin and slide all the pin tops flush. Let the epoxy set. Then, clip off protruding pins on the underside of the wing, tail structure, and control surfaces (or one side of the vertical stabilizer). This method is fast! When you get done, the tops of the Tailor pins will show but they are quite small and far neater in appearance than the toothpick method, particularly when used to pin the hinges of an ARF.