By Chris Batcheller
Why fiberglass landing gear? They’re tough, easy to make and won’t permanently deform as a result of a hard landing. The same technique can also be used to make high-tech, carbon-fiber landing gear, but you will have to experiment with the number of plys (layers of cloth) to use. The fiberglass gear described works great on profile, trainer and other RC aircraft. You can easily make these in an afternoon or a lazy weekend. All of the needed materials can be found at your local hobby shop and hardware store.
Tools and supplies needed (from left to right):
-Tin snips for cutting aluminum bar
-Vice grips or vice for forming aluminum bar
-Clamps for securing form
-Mold-release wax (paste car wax works too)
-Fiberglass (four pieces at 45 degrees, six pieces at 0 degrees)
-Sharp, but not expensive scissors
-Polyester fiberglass resin
-Disposable bristle brush and mixing container
-Latex (or similar) gloves
-1/16×1 1/4 inch-wide flat aluminum bar stock
-Dremel tool with cutoff wheel
-Drill and drill bits
-Paper towels or rags for cleanup
First, draw a pattern for your gear. You will use this as a template to form the bar stock. Form the bottom so that you have some “ears” to clamp to the table.
Tip: If you want your landing gear to have any special angles (like toe-in), now is the time to put them in.
Tip: A good design practice is to make the width of your gear (viewed from the front of the airplane) a minimum of 25% of the wingspan. For trainers I would use 30%. A 60-inch model would have gear that is 18 inches wide, if it were 30% of its span (60 x 0.30 = 18).
Next, form a second piece to fit on top of the first. Lay the fiberglass up on the piece that has the “ears” and then clamp the top piece on so that both sides of your finished part are smooth.
All your fiberglass strips should be 1 inch minimum longer than the gear. They should be wider than your finished gear by at least 1 inch. This will make placement a lot less critical. When the resin has cured, you will cut the excess away.
Cut your fiberglass so you have six pieces with the fibers running parallel to the long edge of your gear. This will give the gear strength in bending under hard landings. The more plys you add here, the “stiffer” the gear will be. You can add more if you model is heavier, or less if it’s lighter. With six plys in this direction, this gear will easily support a 5-pound model. These pieces will end up in the middle of our layup. Next, cut four pieces so that the fibers are running 45 degrees to the long edge of the gear. This will give the gear strength in “twisting.” These layers will form the outside of our layup with two pieces going on first, and two pieces going on last.
Next, put a piece of waxed paper down and clamp the form to your work surface. Wax both the upper and lower forms, and don’t forget the edges. The wax will keep the fiberglass from getting stuck to the form. You should apply at least three coats of wax. Let each coat dry before applying the next.
Next, prepare your work area. Once you mix up the fiberglass resin, you will have only 15-20 minutes of working time. Make sure your fiberglass is laid out and you have extra gloves available.
Mix up your fiberglass resin thoroughly according to the directions on the package. For this small layup, I used 5 oz. of resin.
Tip: When applying resin, don’t use brush strokes. This will distort the fiberglass and make it hard to do a good layup. Instead, dab the brush with short, quick motions.
Dab the resin onto the form and put your first 45-degree layer down. Dab resin until it’s nearly saturated. If you see air bubbles, use your brush to dab them away. Then put the next 45 degree layer down and saturate it with resin.
Now lay your “0” degree layers down. Repeat until all 6 “0” degree layers are on.
Finish the fiberglass layup with the two remaining 45 degree layers.
Make sure that all the layers are on the form and there are no air bubbles.
Put the top form on the layup and very lightly clamp it to the bottom form. Stop clamping when you squeeze just a little resin out. Make sure that all the clamps have about the same pressure and that the top and bottom forms align. You don’t want to squeeze all the resin out!
Caution: When using power tools, always use safety goggles and other protective equipment!
When the layup cures (6-12 hours), use a cut-off wheel to remove the excess fiberglass on either side. A sanding bar is helpful to get all the edges even.
Next, drill holes for the axles. You can use bolts from the hardware store or the hobby-shop variety. Be sure to use a lock washer or lock nut for the fist nut if you are not using hobby shop axles.
Last, drill the holes to attach the gear to the airplane. I have used 1/4-20 nylon bolts for this task. The nylon bolts shear in a crash, but hold up well in hard landings.