How To: Make Hinge Pockets

AN EASY TECHNIQUE FOR NO-BIND, REMOVABLE CONTROL SURFACES

An easy technique for no-bind, removable control surfaces

All flight-control surfaces need a hinge to make them operate correctly. There are a variety of hinges on the market for our use, the most common of which is the CA hinge. Most of the ARFs we assemble have this type of hinge, with pockets ready for assembly, making it easy for us to install. I have seen a few with pin hinges but never any with flat hinges. Some modelers don’t care for CA hinges and want to install their own. Recently, while putting together a Dynaflite Super Decathlon, I decided to use a large Du-Bro flat hinge with a removable pin so that I could remove the control surface if I had to. This allowed me to install, pin, and glue in the hinge before covering. All this sounded great—until it came time to put in the hinge pocket, because the supplied wood was extremely hard. Having been a builder for many years, I pulled out my Great Planes Slot Machine. The blade went in about 1/4 inch and would go no farther because of the hard wood. You had to hold the machine square in a gauge to center the slot and make sure it went in straight. Too much fussing. It was then that I began to think of a better way to do this task: Why not build the pocket in the wood?

HERE’S HOW

This method will require extra wood but will be much easier than digging away at a bunch of slots. When doing the fin and rudder, I had to replace the wood supplied for the leading and trailing edge. In my case, the wood thickness was 3/8 inch. I cut four strips of 3/16-inch wood to length; two pieces stacked were 3/8 inch thick. On one piece of wood, I positioned the centerline of the hinges. I laid a hinge on the centerline and added 3/32 inch on each side to allow for any misalignment. Using 1/32-inch sheet balsa, I cut pieces to fit between the hinge marks and glued them in. I then transferred the dimensions of slots and 1/32-inch pieces of balsa to another 3/16-inch strip so that I had mating pieces for fin and rudder. When laminating the top piece, the total thickness was 3/8 inch plus 1/32 inch; this can be taken care of by block sanding the finished part. Before laminating the top piece, make yourself a sanding tool. I took a block of wood the width of the hinge pocket and glued some 100-grit sandpaper to it. The hinge is 0.045 inch thick and the shim is 0.032 inch thick, so each pocket required a little sanding for a good fit. Check the fit by laying on the top piece and installing the hinge in the slot. The hinge should slide in with little drag. If it doesn’t fit, sand some more (it won’t take much). Now laminate the top piece. I used white glue and applied weights. You now have your own custom hinge pockets. I wanted to make my control surfaces removable, so instead of using the pins supplied with the hinges, I used a 0.040-inchdiameter music wire to go through all three hinges. This makes it much easier to remove the control surface, and the wire helps close the gap on the hinge line. I glued in my hinges before covering. I then pinned each with a round toothpick, applied thin CA, and cut and sanded them flush.

Building in the hinge pockets ensures accuracy in hinge alignment along the hinge line, providing free movement of the control surface with no binding.

FINAL THOUGHTS

Building in the hinge pockets takes away the frustration of dealing with digging those slots and provides a good clean procedure for the process. It also ensures accuracy in hinge alignment along the hinge line, providing free movement of the control surface with no binding. You may never have to remove a control surface, but if you need to, you can. I was so pleased with the way this turned out that I just had to pass it on to you. Good luck with yours.

2 Using 1/32-inch sheet balsa, I cut pieces to fit between the hinge marks and glued them in. I then transferred the dimensions of slots and 1/32-inch pieces of balsa to another 3/16-inch strip so that I had mating pieces for fin and rudder.

1 When you install the fin and rudder, you’ll need to replace the wood supplied for the leading and trailing edge, which, in my case, was 3/8 inch thick. I cut four strips of 3/16-inch wood the length required to replace them. Two pieces stacked gave...

4 Check the fit by laying on the top piece and installing the hinge in the slot. The hinge should slide in with little drag. If it doesn’t fit, sand some more. Now laminate the top piece. I used white glue and applied weights. You now have your own...

3 Before laminating on the top piece, make yourself a sanding tool. I took a block of wood the width of the hinge pocket and glued some 100-grit sandpaper on it. The thickness of the hinge is 0.045 inch and the shim is 0.032 inch, so each pocket...

CA hinges are popular, but if you are building a giant-scale airplane, I recommend a more robust hinge. When building my giant-scale Decathlon, I chose Du-Bro heavy-duty hinges, which are dependable and flat, work freely, and are easy to disassemble.

6 I wanted to make my control surfaces removable, so I didn’t use the pins supplied with the hinges. I used instead a 0.040-inchdiameter music wire to go through all three hinges. The benefits are that the control surface is easier to remove and the...

I glued in my hinges with epoxy before covering. I then pinned each with a round toothpick, applied thin CA, cut them, and sanded them flush. 7

8 The completed fin and rudder. You will note that the rudder moves freely with no binding.

5 When gluing in the hinges, apply petroleum jelly to the hinge joint to keep them from sticking. I used epoxy to install them.