Written by Walt Wilson Create exactly what you want, for the fun of it How To Do It As seen in the April issue of Model Aviation.
Scratch-Building EssentialsTo build from scratch, or even from a kit, you need several basic tools. A hobby knife set is necessary for any building project—even assembling ARFs. Inexpensive sets are available almost anywhere hardware and crafts are sold. If you want better quality, purchase an X-Acto set from your local hobby shop. You can use others, but a #11 blade will be the most used; stock up with lots of extra blades. They’re available in packs of for a good price, and you’ll use them if you build much. In addition, they dull quickly when cutting MonoKote and similar covering materials. Every household, even if it has no model builders in it, should have an electric drill. Cordless drills are convenient and versatile, but the good ones can be expensive. And if you don’t charge them after use or keep them on a trickle charger, the batteries tend to run down when you need them most. Many cordless drills can be used as forceful screwdrivers too. Although it is a bit more trouble, you can also use a drill with a cord. It is generally less expensive and always ready when you need it. Obtain a drill press if you can afford it. Many are inexpensive and have amazing capabilities besides making accurate-size holes that are perpendicular to surfaces. A drill press can be adapted to use as a milling machine, sander, lathe, and probably some other things. A set of hole saws will prove to be valuable. Those are available at most stores that sell woodworking tools. A Dremel, or equivalent, power tool has all kinds of uses and is an important part of any shop. Cutoff wheels and sanding drums are indispensible. Most plywood and thicker balsa parts can be cut with a basic coping saw, but it’s much easier to use a band saw or a jigsaw. The latter will do most small jobs, but I much prefer a band saw with a metal-cutting blade. The metal-cutting blade allows you to cut aluminum for landing gear, gear covers, and other applications, as well as all types of wood. Other helpful tools are bench-type belt/disc sanders and, if you plan to carve much balsa, Great Planes Power Planers. There are many good-quality brands of power tools. The Sears Craftsman line is competitively priced. Since you’ll probably find uses for these tools far beyond modeling, get the biggest (within reason) and best you can afford. It’s unnecessary to have all of the equipment I’ve mentioned just for building models, but it does make it easier. Hand tools can be used for most applications. Okay, let’s cut some wood!
Scratch-BuildingIf you've accomplished building model aircraft from kits and want to go a step further, try building from scratch. There’s a lot of satisfaction to be gained from constructing an airplane from a pile of balsa and plywood. The major reason for scratch-building is to have something unique. Don’t worry if you’re not an aerodynamic wizard; borrow from an established design. Producing a model from plans and converting a glow-powered design to electric can be a good start. “Quarter Midgets,” or size sport aircraft that were popular in the s, can be great designs to convert to electric power. Plans for many of them are still available from magazine plans services.
The scratch-build method in this case was to reduce and paste up plans of a favorite kit of a larger model. Not all kit plans are complete, so prepare to exercise your imagination.
Reducing a large favorite aircraft and converting it to electric power or a different size glow engine can also be a good first project. And it isn’t as difficult as it might sound. If a complete kit or set of plans from an old kit is unavailable, check with fellow club members who build their own aircraft or purchase plans from your favorite aeromodeling magazine or plans seller. Plans for some kits that became popular were first published in modeling publications. Decide what size you want the airplane to be and what power system you’ll use. A to inch wingspan is nice for electric or glow power. That size of model is big enough to fly well, and the components can usually be fitted with little difficulty. Aircraft in that size range are easy to transport too, if you don’t have a van, SUV, or other large vehicle. And in most cases, the cost of electric power components won’t break the bank. Use a copy machine at the local office supply store to modify the plans to the size you want. Use 11 x inch paper. You can also resize plans with a scanner attached to your home computer, but scaling could be more difficult and the printing size is usually limited to 81/2 x inch paper, requiring many more copies. The reduced plans set will be in pieces, so line up and overlap the segments, and be sure that all major parts are shown. Then trim and tape the pieces together with outlines and centerlines aligned, and mount them on a piece of white cardboard, or poster board. You can get it from most dollar stores or art-supply shops. Now you need a piece of vellum, or similar translucent paper, that is large enough for the project. This kind of paper is available at artsupply stores. Tape the vellum over the plans. If you want to modify anything, such as the shape of the fuselage, wingtips, or tail surfaces, now is the time to draw the changes. If you want a more aerobatic model, such as for 3-D flying, examine the relative sizes of control surfaces on aircraft that are capable of the maneuvers you want to do; increase or adjust your design’s surface sizes appropriately. Trace the significant parts, and sketch any details you might want to change.
The author admired the Sig Four-Star design so much that he wanted a version that would be suitable for small-field flying.
Begin construction with the fuselage. Determine the thicknesses of balsa, plywood, or other materials to be used. If the model will have electric power, most parts can, and for weight savings should, be somewhat lighter than those used for glow power. The firewall, or engine-mounting structure, should be plywood, but it can be thinner than is normally used for a glow engine. You can typically replace non-load-bearing plywood bulkheads with balsa. Measure your components, such as motor, battery, ESC, servos, and receiver, and figure out where they will be located. If necessary, add, remove, or change the locations of formers to accommodate the components. Formers can ordinarily go where the original design has them. The motor will usually be in the front (some models are pushers), so measure the distance from the propeller drive surface to the back of the mounting plate for your motor, and add roughly 1/16 inch. That’s how far the firewall must be from the front of the fuselage. Formers are normally required at the front and back edges of the wing. They have to bear loads, so they should be plywood. Landing gear mounting blocks and related bulkheads should also be plywood. Most motors are fairly lightweight, so the battery must be placed as far forward as possible in the fuselage for balancing. Is the forward fuselage large enough to accommodate the required battery? If not, modify the height or width so it will be. If possible, provide space to move the battery fore and aft a bit to aid in balancing. Provide for passage of cooling air for the motor, ESC, and battery while developing your design. Most plans sets show the formers and wing ribs, so tracing the outlines is easy enough. If formers are not shown or must be moved fore or aft, measure the height and width of the fuselage in each location and then adjust dimensions as necessary. Consider what size holes must be cut in the formers to accommodate components, pushrods, etc. The formers can be figured out fairly easily, based on making everything fit. If you want rounded corners on the fuselage, add pieces of triangular stock to the appropriate areas. Trim the corners of the formers to accommodate the triangular stock. The wing saddles usually need additional thickness or reinforcement, so add thin plywood or an extra, thicker layer of balsa in those locations. The firewall and landing gear mounting can normally use reinforcement too. On the Sig Manufacturing Four-Star replica shown, the 1/16 plywood reinforcements run from the former at the TE of the wing to the back of the firewall; they are used for supporting the landing gear mount. The firewall is 3/16 plywood, and the other formers are 1/16 plywood. The fuselage sides and miscellaneous parts are 3/32 balsa. Once you’ve adapted and redesigned to your satisfaction, it’s time to cut wood. Trace the parts onto the appropriate material and cut out all required parts, to make a “kit” before assembly. I’ll address building in the traditional manner, with balsa, spruce, plywood, etc.
Scratch builders make a kit before starting assembly. Dry-fitting the parts can help detect design flaws before glue makes the errors permanent.
Cut out most of the parts needed before starting construction. Trace or lay out the fuselage sides on a piece of balsa in the desired thickness. Some models, such as those in the Four-Star series, have formers keyed to the sides of the fuselage. It helps to install the formers straight if this feature is used when building a spin-off. Tape another piece of balsa to the fuselage side marked for cutting, and cut both sides at the same time. This assures that they are the same. Use a band saw to cut the slots for former tabs. If you want lightening holes in the fuselage sides, hole saws can be used to cut the ends and an X-Acto knife to cut between the holes. Trace or otherwise lay out the formers on the appropriate thickness of plywood or balsa. Most formers will require holes for the battery, ESC, wires, pushrods, etc. If the wing LE will be held in place with a dowel, or center rib extension, now is the time to cut or drill that hole. Cut out the landing gear mounting block if it will be installed in the fuselage.
A frame with flat sides is an excellent choice for a first-time scratch-build project. Because this model borrows its de sign from a kit, the assembly instructions can be helpful.
It’s usually safest to drill or cut all required holes before cutting the former outline, because larger pieces of wood are easier to hold and less likely to break. If the hole is to be essentially square, drill small holes at the corners and use a Dremel cutoff tool or coping saw to cut between the holes. If holes are to be round, use the nearest-size hole saw. Remember that this is your design, so you can take liberties where necessary. Clean up any rough edges or adjust hole sizes with a sanding drum in a Dremel tool. Locate the centerlines (vertical and horizontal) for the motor on the firewall, and lay out the pattern for motor mounting holes. If there will be offsets, plan for them now by offsetting the centerlines so that the propeller drive hub will be centered when the engine is installed. Drill the holes and install blind nuts before installing the firewall in the fuselage. Allow for passage of any wires through the firewall to the ESC. If you’re building an electric model, provide for intake and egress of cooling air for the ESC and battery. If you’re using a glow engine, locate and drill holes for the throttle pushrod and fuel lines, or tank plug, now. It’s easier to do all this before installing the firewall.
Scratch-building requires provisional thought. In this case, air passes through the corners of the square fuselage to cool the motor and electronic components.
The type of airplane you have chosen will dictate building procedures. With the 60% Four-Star replica, when laying out the formers for the fuselage, I was sure to mark top-to-bottom centerlines on all of them. If you plan to round the nose or other areas, install triangular stock at the top and bottom of the sides. Start assembly by gluing doublers, wing saddles, triangular stock, etc. to the fuselage sides. Be sure to make a left and a right side. Install the formers at the front and rear of the wing. The fuselage sides are usually parallel in this area, so mounting the formers perpendicular to the sides is easy enough. Lay one side flat on the building board and glue the formers 90° from the side. When dry, cured, or whatever, depending on adhesive type (I recommend one that dries slowly for this operation), adhere the other fuselage side in place on the other side of the formers. Carefully maintain the 90° angles, ensuring that the sides are parallel to each other and the ends are aligned. If your model has slots and tabs, as the Four-Star series does, alignment is easier, but check it again before it dries to be sure. When the center formers are secure, lay out a centerline on your building board. Position all aft formers while pulling the tail end together. Line up all centerlines on the formers with the centerline on the building board. It helps to put heavy weights on each side of the previously assembled center part of the fuselage, to hold it in place. Make sure that the fuselage sides are aligned, vertically and horizontally, at the aft end. When satisfied that all parts are centered, use CA or your preferred glue to install them. Repeat the procedure with all forward formers except the nose ring (if you have one), being careful to align the centerlines.
Fuselage designs with flat sides make it easy to bui ld a square structure. All formers are perpendicular to the long fuselage side.
If engine offset is planned, make sure that you install the firewall at the necessary angle to provide it. I prefer using epoxy for installing firewalls. When the glue is dry, cut out and add the servo trays, battery tray, landing gear block, cockpit floor, and any other internal structure. These parts might be provided in a kit but not detailed on the plans. They can be cut to fit in most cases, preventing bad fits caused by tolerance buildup, etc. For easy access I installed the rudder and elevator servos and pushrod tubes before sheeting the bottom of the aft fuselage. In the 60% electric-powered Four-Star, the Hitec HS servos are mounted in the same general location as those in the larger Four-Star 40s. Determine where slots or holes for rudder and elevator pushrods should be, allowing for the lengths and locations of control horns. I used inch-diameter music-wire pushrods inside plastic tubing, supported on both ends and in one location in the middle. Add stringers to the aft fuselage deck or other places where applicable. Install any remaining formers, and sheet the upper fuselage as required with 1/16 balsa. Install all battery and ESC shelves, the landing gear mounting block, and blind nuts before sheeting the bottom of the forward fuselage. You’re close to 50% finished with construction. Build and install the wing before sheeting the bottom aft fuselage, to assure a good fit.
Another good tip for new scratch builders is to choose a straight wing design. That way, multiple ribs can be made simultaneously. Tapered ailerons simulate a more advanced look.
A question I had was, When scaling down a wing, how do you know what size spars to use? The answer is to scale them down too. The original Four-Star 40 has 3/8 x 3/16 spruce spars. Electric power is easier on structure than an engine, so 3/16 square hard balsa should work for the main spars. Four-Stars have five spars, so all but the main spars, top and bottom, could go down to 1/8. I used those sizes on my airplane, and they worked fine. The ribs are 1/16 balsa; 1/32 would work but is extremely fragile. Use the reduced-size rib outlines to determine airfoil and spar placement. I used rib spacing that was close to that of the full-size Four-Star 40 and decreased the number of ribs to save weight. Make two templates from 1/8 plywood for cutting ribs. Drill holes and use 3/ or 1/4-inch-diameter dowels to hold the templates and balsa together. Trace the rib outlines onto balsa, and use an X-Acto knife to cut all ribs a bit oversize. Assemble all of the same-size balsa ribs between the plywood templates, drill, and hold together using the dowels.
Typical cutting implements used for model building include (clockwise from top) an X-Acto razor saw, a hand plane, a bulk pack of #11 X-Acto blades, a hobby knife, a single-edge razor blade, and (center) a balsa stripper. Carelessness with any tools can land you in the emergency room.
Sand all ribs to the exact shape and cut notches for spars at the same time, using the templates as a guide. All W-2 ribs should be identical at this point. The W-1 ribs are 1/8 inch thinner (11/16 on each side), to allow for the 1/ inch center sheeting. Cut a joiner from 3/16 plywood (or the same thickness as the main spars), and cut 1/16 balsa to width for the TE sheeting. Make a scaled-down LE from medium balsa. Cut a TE to size and sand to a slight taper to match the TE sheeting. Glue the ribs and spar parts together with CA. Be sure to make left and right wing panels, and cant the center W-1 ribs, as shown on the full-size plans, to allow for dihedral. Add 1/16 balsa shear webs on each side of the main spars in the area to be sheeted on each panel; shear-web grain should be vertical. They make a box to contain the wing joiner. Cut out the area between the main spars in the center ribs to accommodate a wing joiner. Check the fit and try pushing the wing halves together, with the joiner in place, before gluing. Sand and trim the joiner as necessary to make it fit. Place proper-thickness wood blocks under the tips for dihedral and join the wing halves with minute epoxy, ensuring that the wing tips are in alignment with each other. Determine where the wing-mounting screws will be, and make sure that there is solid balsa in that area. Add balsa blocks if necessary. Add 1/16 sheeting to the center of the wing where shown on the plans. Make ailerons from 3/16 balsa sheet and sand them. Sand a “V” shape on their LEs, to provide clearance for movement when hinged. If the ailerons are significantly larger, for 3-D flying, consider building them using the technique I will describe later when I address the tail surfaces. The easiest way to make tail surfaces is to simply cut them from 3/16 or 1/8 balsa.
The author suggests an excellent tail-surface construction method. The fin and stabilizer are built up using laminated 1/16 balsa. Lightening holes can be cut in the core sheet after assembly, if desired.
Sand them smooth, and sand a “V” shape on the LEs of the elevator and rudder hinged edges. If you want lighter surfaces, an open built-up structure will do the job. I have a slick way to make a light structure. Check (look down the edges) and buy balsa that is unwarped. Cut pieces of 1/16 balsa to the desired shapes for the fin, stabilizer, rudder, and elevator, with the grain running lengthwise. Make doublers for areas where the control horns and tail wheel tiller will be located. Make a doubler for the center of the stabilizer that is approximately 1/4 inch wider on each side than the fuselage at that point. Select proper-thickness balsa strips to make the surfaces the thickness that you want. They’re available in most sizes from your favorite hobby shop. If you cut your own, use a balsa stripper to make the pieces the desired width to make LEs and TEs. With the balsa core on a flat surface, use thin CA to glue the doublers in place. If the edges or tips are curved, sometimes you can use the scrap from cutting the original outline as a doubler, at least on one side. Cut more strips to make ribs, perpendicular to the core grain, and glue in place with CA. How many ribs do you need? I used two on each side for the 60% Four-Star. Space the ribs evenly and use what looks right; it’s noncritical. Repeat all the doublers and ribs on the other side (bottom) of the core. The CA hardens the balsa, making a plywoodlike structure, and, under normal atmospheric conditions, the perpendicular wood grains keep it from warping. Sand the edges to the desired shapes. If a knife edge is desired, install ribs and sand to a taper, but don’t use a doubler on the outer edge. If you want, use a Dremel tool and sanding drum to cut lightening holes in the cores after assembly. Sand the rudder and elevator LEs to a wedge shape and cut slots for hinges. I use the Great Planes Slot Machine for this, but a knife or purpose-made slot cutter can also do the job.
The Great Planes Slot Machine (top) cuts hinge slots, and the Great Planes Power Planer shapes solid-wood parts. Both are useful for the scratch builder and can cause bodily injury if used improperly. Be careful!
If you want a different-thickness surface, use different-size doublers and ribs, but stay with the 1/inch core unless you’re building a much larger aircraft. Sand all surfaces smooth, and cover the mating surfaces to be hinged with strips of covering material that is roughly 1/4 inch wide. Then cover the rest of the surfaces, overlapping the strips and edges. Install CA-type hinge material and you’re finished. This building technique can be used for much bigger airplanes too. It makes a lightweight yet strong and rigid structure, and it is almost as quick to build as it is to describe. Cut and install wing-mounting blocks in the fuselage. Make them large enough to have sufficient wood around the bolt locations, but leave room between them for the aileron control rods and horns. Install the blocks approximately 11//8 inch below the aft wing saddle surface. Cut a piece of dowel rod close to 1 inch long and, chucking it in an electric drill or drill press, sand one end round. A 3/ inch-diameter dowel will work fine for a small electric airplane; you could enlarge the dowel to 1/4 inch for a glow-powered aircraft. Drill and install the wing retaining dowel in the center of the wing LE, with the rounded end out. Fit the wing in the saddle and be sure that it properly fits the contour. Adjust the dowel hole as necessary for a good fit. When you’re satisfied that it’s correct, glue the dowel into the wing. Put the wing in place and align it by measuring from each wingtip to the center of the aft end of the fuselage. Determine the wing-mounting-bolt locations. With the wing properly aligned, with an equal measurement from each wingtip to the center of the fuselage tail end, drill the bolt holes. I used two screws, with flat washers, to hold the wing in place on the little Four-Star. Once the holes are located in the mounting blocks, drill as necessary and install blind nuts. With the wing installed, fit and sheet the aft fuselage bottom with 11/16 balsa, with the grain crossways. Use fine sandpaper to smooth all surfaces, corners, edges, and irregularities in the fuselage and wing. Instructions are included with most covering materials, so I’ll address that part in general.
This is what is called the “bones” shot. The exposed wood is ready for final sanding in preparation for covering.
As with the tail, cover the mating hinge surfaces with narrow strips of your favorite iron-on material. Cover the wingtips, with some overlap around the edges, and iron it smooth. Cover the bottom of the wing, one side at a time, with some material overlapping the edges and roughly 1/2 inch of overlap in the center. Ensure that every edge is tightly sealed before shrinking the center of the material. Pulling edges loose can be a problem if you don’t. Trim any excess with a new #11 X-Acto blade. Cover the top, one side at a time, with some material overlapping the edges and close to ½ inch of overlap in the center. Trim as necessary and iron down all loose edges. Cover the rest of the ailerons, first on the bottom and then on top. Cover the bottom surfaces of the fuselage, with some overlap around the edges. Cover the sides and then the top surfaces.
Building leads to finishing. A small model such as the author’s was covered in Solite to save weight. Models with wingspans longer than 40 inches can be covered with MonoKote or UltraCote.
You should have made slots in the balsa for the stabilizer and fin when you cut out the sides of the fuselage. On the miniaturized Four-Star, the stabilizer is installed on a flat surface on top of the fuselage. Trim away the covering material in areas to be mated with the stabilizer. Horizontally align the stabilizer with the wing by measuring tip to tip. The stabilizer can be held in place with pins or rubber bands while checking alignment. When you are satisfied, use a felt-tip marker to sketch the outlines of the fuselage edges on the stabilizer. Trim the covering on the stabilizer so that the joint to be glued is wood to wood, with just enough covering overlap to hide the joints. Vertically align the stabilizer by sighting from aft of the tail and comparing the stabilizer tips with the wing. Trim or shim the fuselage as necessary to get it right. The better the alignment, the less likely your model will be to have weird flying characteristics. Install the stabilizer using CA or your favorite adhesive. Trim the covering as necessary and install the fin 90° from the surface of the stabilizer. Be sure that the aft fuselage and back of the fin are aligned for rudder hinging. Commercially made aluminum landing gear is available from most hobby shops, but the chances of finding a set that perfectly fits your airplane are slim. You can fabricate landing gear from inchdiameter sheet aluminum cut out on a band saw with a metal-cutting blade. File and sand the edges smooth, and bend it into shape using a drill press vise. If the vise jaws are rough, protect the aluminum with scrap sheet metal to keep from marking it. If a buffer is available, polish the aluminum. You can also make landing gear from music wire.
Drill press vises have many applications in aeromodeling. The author made the one shown in a high school shop class, and it has had many years of hard use. Manufactured drill press vises are available for as little as $ at Harbor Freight.
Look for lightweight wheels in a size that looks appropriate. I fly from an asphalt runway, so 1 1/4-inch-diameter wheels work fine. If you fly off of grass, you will probably need to use bigger wheels. The first two Four-Star replicas I built had open wheels. The most recent version has scratch-built wheel pants. A variety of hobby shops sell canopies for numerous sizes of models. The ones I used on my aircraft were cut from a World War II 9-inch bubble canopy from Sig. You could also use plastic soda or water bottles or various product bubble packs as canopies. From this point forward, assembly is essentially the same as with a kit-built model. Install the motor, ESC, and radio. I’ve used a full-size, full-range Futaba receiver in all three Four-Star replicas I’ve built.
A variety of manufactured and homemade clamps may be used. One-inch-square wood blocks with nails are easy to make and useful for holding structures in place on a building board. Manufactured clamps are available from Harbor Freight and other tool sellers.
My current model has a Rimfire motor, E-flite amp ESC, Hitec HS servos, and 3S volt, mAh battery. This sized-down Four-Star 40 has an all-up weight of 24 ounces and flies similar to the full-size version. Even moderate winds are no problem. Start with the CG in the same relative place as on the airplane you used as the source for your design. Shift the battery fore or aft, if possible, to aid balancing before adding weight. I had to put 1/4 ounce of lead in the tail of my current aircraft. I didn’t have to add weight to the previous versions, but they used lighter batteries and smaller ESCs, and they weighed 20 ounces apiece. When in doubt, go slightly nose-heavy—never-tail-heavy—and your new model will be more likely to survive for a second flight. Scale down the source airplane’s recommended control surface throws. Use an incidence meter or other method to assure that when the trim is centered, the ailerons are in equal positions at the outboard tips before flying. That will reduce the likelihood of unpleasant surprises on the first takeoff. Have fun with your new scratch-built model! It will give you much more pride of accomplishment than any ARF. Once you have completed your first scratch-built airplane, you might want to move on to more elaborate, more original projects. The sky’s the limit! -Walt Wilson [email protected]
Sources:Sig Manufacturing () www.sigmfg.com AMA Plans Service () , extension www.modelaircraft.org/plans/plans.aspx
How to Build an RC Plane from Scratch, ARF or Kit
In this article, we will look into how to make RC planes and the multitude of options there are for the aspiring RC model aircraft builder.
It is easy to assume that building RC airplanes is a difficult task but, in reality, they are actually fairly simple to make at home. It requires a little planning and a few materials but if you give it a few hours you could become an expert at building RC airplanes. All you need are the main components of a plane: the body (fuselage), wings, rudder (or ailerons/elevator), wheels, motor and radio transmitter. Building RC airplanes has become easier recently because of less expensive radio equipment and more efficient batteries and motors.
Building RC Planes Quick Overview
The process of building RC airplanes should always begin with the layout of the plane; you want to make sure all of the parts are attainable and that they will fit on the plane. You can use plastic, balsa wood or foam – the former two are definitely good choices but the most affordable and safest materials would be foam. Building RC airplanes is made easier by foam because you can simply purchase one 1/2’’ foam core board for the entire plane (for a inch plane). Additionally, building RC airplanes out of foam keeps them intact when they crash.
To continue the process of building RC airplanes, use the fuselage and fit your ailerons into a groove in it using packing tape; this type of tape is the best kind for making a plane because it is lightweight and cheap. Then, fit your elevator into a groove in your fuselage or using packing tape. When building RC airplanes from scratch, it is essential to maximize the surface area between the fuselage, ailerons and the elevator and the packing tape. This makes sure none of the pieces fall off while the airplane is in flight. Next, put the wings on the plane. Make sure they are even; when building RC planes, accuracy is essential for a successful flight. After this, put the servos on the plane’s wings. When building RC airplanes, servos are important because they ensure that the plane is easily controlled and that it flies properly.
The next step in building RC airplanes is to assemble the motor. For a beginner, it makes sense to simply purchase a pre-made motor. If you have training, you may craft the motor yourself while you are building RC airplanes. For a plastic or balsa wood plane you can put the motor and radio transmitter inside the plane (with insulation so the motor doesn’t light the plane on fire) but, with a foam plane, you will have to put the motor and radio transmitter on the outside while you’re building RC airplanes.
In the process of building RC airplanes, the last and most important step is to test your airplane out. If it is not flying straight, check the propeller and make sure that you have mounted your motor with at least two degrees of right thrust to ensure that the torque of the plane is counteracted. Hopefully, you find that building RC airplanes is a fun process!
RC Planes Types
RTF RC Airplanes
Nowadays there is a bewildering amount of choices for the budding aero modeller who wants to learn how to make an RC airplane. Recently the emergence of ready to fly or RTF RC airplanes is probably the easiest route into beginner RC airplane flying with no assembly required. You literally unpack, charge the batteries then go flying.
ARTF/ARF RC Airplanes
Almost ready to fly or ARTF/ARF RC airplanes have shortened the time from purchase to the first flight to a few hours with just simple assembly to do before the first flight.
Many people enjoy the build phase as much as flying the aircraft, and they will design and build the whole airplane from scratch.
Kits make building a plan quite easy. There are many diverse types of airplane kits. You simply need to find a design you like, buy it and then put it all together. Kits vary from the simple to the very complicated and come in wood, plastic and metal.
Electric RC Airplanes
Over the last couple of years, electric power for RC airplanes has made enormous gains on the traditional world of the nitro RC airplane. The reason for this is twofold in my opinion. Firstly, advances in both electric motor and battery technology have made electric airplanes performance and practicality extremely attractive to serious RC airplane enthusiasts, where cost is an issue Electric Power for RC Airplanes makes very good sense as you don’t have to keep buying nitro fuel. Secondly, the environmental issues that go with traditional nitro RC airplanes i.e. Noise and pollution are no longer an issue.
Personally, I feel there will always be a place for the internal combustion engine within aero-modelling, especially with large scale RC airplanes, however, these advances in motor and battery performance are blurring the issue.
Just a few years ago electric power for RC Airplanes was reserved for only the cheapest RC Models, indeed the phrase “remote-controlled airplane” would have been synonymous with electric power. The main reason for this increased practicality and performance is the Brushless RC motors and Lithium Polymer batteries also known as Li-Po batteries. Electric motors also work really well with ducted fan RC airplanes, these can be an alternative to real RC Jet Engines, so jet appearance models are now available almost ready to fly without the cost of true jet technology.
So electric power for RC airplanes is now a totally viable alternative to traditional Nitro Power RC Airplanes, I think that it is a great, clean, quiet and thoroughly modern power source.
Nitro RC Airplanes
2 and 4 Cycle Nitro RC Airplanes
Most traditional engines used in radio-controlled airplanes are 2 stroke glow engines, this means that they operate on the 2 cycle principle, just like a chainsaw engine. However, rather than having a spark plug to ignite the fuel/air mixture a small glow plug, which is preheated by a battery at startup, continuously glows and burns the fuel. These engines are simple, light, and inexpensive so this is why Nitro RC Airplanes are so popular. They are fuelled by Nitro-methane/methanol this fuel is mixed with 20% oil for lubrication. Most engines for Nitro RC Airplanes are categorized by their size in cubic inches e.g. 40 size = cu in.
4 Cycle engines are a bit more expensive and complicated, so are more often used in the larger and more expensive airplanes, where their better low down power suits this type of airplane. 4 cycle engines are more suited to the more experienced modeller, as they are more complicated to use and maintain.
Nitro RC Airplanes versus Petrol and Diesel Engines
The much larger petrol engines are for use with the large scale RC airplanes that have become popular lately. These large engines are normally between 32cc to over cc so are clearly serious bits of equipment, with price tags to match. When used with the very large scale RC airplanes they make for a truly stirring sight. Diesel engines used to be quite popular and work by igniting their fuel using very high compression ratios, these engines were available in a large range of sizes and although were less powerful than similar-sized nitro engines they did produce good low down power, they have however become hard to obtain. So Nitro RC Airplanes have become the most popular aircraft for more experienced modelers.
Building RC Planes from Kits
Airplane plans and kits are available in many variations to suit all potential aviation enthusiasts. Theres a great deal of pleasure to be had from piloting your own plane. Its a hobby that can bring hours of fun. Model planes are available for children, adults, and those of all skill abilities.
There are choices for both new and experienced users. Plastic aircraft kits have a flexible selection of uses. Lightweight designs afford a higher flying speed and the ability to fly for a longer distance. Costs are low for basic airplanes and if you dont need your aircraft to fly, theres always model aircraft for display purposes only.
Kit planes made of wood offer similar attributes to the plastic planes, giving choices between models for display only or construction of aircraft that will actually fly. Wooden aircraft kits take longer to put together than their plastic counterparts, but assembly is usually straightforward.
Remote radio-controlled airplane kits, usually called RC airplanes, suit the most fun type of model aircraft. The controller becomes the pilot! RC aircraft models are available to a varied range of beginners right through to the expert level. Moneywise the cost can be quite low but it can also reach thousands of dollars depending upon the superiority, dimensions and detail required.
Model aircraft are hugely popular. Thousands of airplane aircraft kits and plans are available to make replica aircraft Plans are can be bought not just for modern aircraft, but for plans of airplanes since the early days of their invention.
Theres a great deal of interest in aircraft from the World War One and Two eras these represent the highest plan sales. Approximately , model aircraft builders face the same problems in selecting the aircraft they want to construct and then finding the right plan to suit them. Many plan purchasers will build the aircraft from balsa wood which is easy to work with.
Its vital to get full assistance for each aircrafts building method. This will ensure that each piece is exactly correct for both size and weight. This will aid the balancing of the aircraft during its time in the air.
Some plans will include specifics of what types of wire should be used, whether its piano wiring for propeller shafts or electrical wire for motors.
Ready constructed, fully functioning motors can be purchased for your airplane if you intend to fly it. This applies to nearly all plans for aircraft, airplane plans, and kits.
How To Build an RC Plane From Scratch
Many modellers, myself included, get a great deal of pleasure from constructing a model either from a basic kit of parts or building from scratch from plans. Plans are often available for free from magazines all you need to do is to copy them and get the paper blown up to the required size. Often designers will sell the plans on the internet or from magazine classified ads, all you need is the time and raw materials to turn their plans into reality.
This method will obviously take more time to produce your flyable model, but for many people, this is the only way to go. There is a good chance you are going to go through several designs and variations before you come up with your first good working project.
Building your first park trainer out of foam is a great way to get started and most of the other parts you need will be useful in future projects as well. So right from the start, when deciding how to build an RC plane from scratch, think about how you want to get started in the hobby.
If you aren’t quite sure yet, if it is for you, sticking to the lower end parts and electronics is understandable. If you are already planning your second and third projects, you might want to consider investing a little more to get the gear that you will work well for those projects as well.
Things to think about when Building an RC Plane From Scratch
- Start out with the end in mind, if you are going to get into the hobby, you will need your own workspace. So find an area where you can get set up to do some work and keep your tools that will be out of everyone’s way. Having a workbench or table to work at is important. You aren’t going to want to start out on Mom’s dining room table, she won’t be impressed if you nick the table with your Exacto drip some glue on the chairs.
- During assembly, your project will need time for the glue to set up and the last thing you want is to be moving it around or having to stuff it into a closet.
- Once you have your workspace and materials and figured out how to build an RC plane from scratch, all that’s left is to get to it.
- The learning comes from the doing and don’t be scared about things not working out, if it’s your first project, you may end up reworking some of the details…
- My first plane project was all balsa and to be totally honest, it took way too long and as a young guy, my patience was challenged to finish it.
- That’s what makes this foam project such a great first start to flying. You will be able to put it together reasonably quickly and get out there and test your flying skills!
So now’s the time, stop wondering how to build an RC plane from scratch, and let’s get started.
Building the Model
The main difference between this type of project and kit construction is, of course, that you are manufacturing all the components yourself once that has been done you are back in familiar territory of kit building, so this article will simply concentrate on how to go about those operations in preparation for the actual construction.
Having chosen the model and obtained the plans, the first thing to be done is to obtain your raw materials chiefly balsa and lite-ply if your own stocks are not sufficient. Your plans will show what sizes of balsa you are looking for, so draw up your shopping list and head for your local model shop! From what we read in the modelling press, the availability of good quality balsa in your local shop is not what it used to be and specialized direct-mail suppliers are also getting thin on the ground. Basically, though, what you are after in most models is the best combination of lightness and strength, so it can be boiled down to looking for denser weights of balsa for those parts subject most likely to take the knocks or subject to stress and strain and less dense material for the rest! Less dense balsa will have a slightly fluffy feel and appearance, whilst the harder balsa will have a smoother surface. Good savings can be made by buying sheet balsa from which to cut your strip balsa requirements, rather than buying all the strip material ready-cut. A balsa strip-cutter (above) is a great investment, but it can also be done with a steel rule, a steady hand, and a good sharp modelling knife! Matching the weight of parts falling either side of the center line of the model is
Next, take a photocopy of the plans. These can usually be obtained from the more professional stationery suppliers or office bureaux who offer plan copying. You might even have such facilities available through the drawing office at your place of work. If you want to keep your original plan in pristine condition, you might even consider the luxury of having two copies taken, if its not too expensive, since you will be cutting one plan up and building on another.
The first part of construction can be anything you like. The easiest way of doing it is to start with the fuselage (The body of the plane) These can be put together in different ways according to the model. The easiest model to build is an ARTF (Almost ready to fly) model. These come pre-built, covered and decorated. This is the only way of ensuring a perfect result and they can be built and ready to fly in as little as three days. The most common and cheapest way of doing it is a kit. These are basically a box of wood that you have to make a plane out of.
IMPORTANT: Be careful with balsa wood as it damages and snaps very easily. The body of the plane (Known as the fuselage) is fairly daunting when you see the work involved. Dont let this put you off, because it really is worthwhile in the end. First, lay out the plan on your board and pin it down. The first thing to do, before gluing, is to cut out all the necessary parts. You will need a modelling knife and your razor saw. Lay the wood over the plan and draw on to the wood all of the lines that will be cut out. If it is a complex, cut, it would be wise to do this with the modelling knife, not the razor saw. You could even pin the wood to the plan if you are struggling. Once all the parts are cut out you will notice lots of parts that are like squares. These start off large and get smaller and smaller. These are supports. These need to be fitted to the inside of the fuselage to strengthen the structure. Layout the appropriate pieces on to the plan and then mix some epoxy resin/PVA glue. Glue all the pieces and you should have a very good fuselage. It will then need to be shaped to get the airflow right and the model will fly both more stable and it will fly faster when wanted.
To speed things up, Plane off the sharp edges and then sand them down. You will then have extremely smooth edges. The next step is to construct the wing. This is the most difficult part. The wing of a trainer often has an angle like a V in the center so that the tip of the wings are raised up. This makes the model fly stable. Again, cut out the pieces and glue them accordingly. When fitting the wing ribs try to get the heaviest towards the center of the wing.
The leading edge must now be sanded like on the fuselage. This is made easier using a block with sandpaper around it. You have now assembled the wing and when it is sat on the fuselage it starts to look the slightest bit like a plane. Using the same techniques as above, construct the fin, rudder, elevator, and ailerons (These are the flaps used for controlling the plane). Then the model has to be covered. There is a variety of films to use. Some are self-adhesive and some are iron-on. It does not matter what you use. When the model is done you can sit back and relax until it comes to the control hardware. This is the next step.
Installing The Radio Equipment
Installing the radio equipment has to be one of the easiest things to do when you have installed the hardware e.g pushrods etc. Just slot in the servos and screw them tight. Then connect all linkages and connect the servos to the correct ports on the receiver. Now you must switch on the equipment and test it all. If everything works in the correct order then proceed to the next step.
Running The Engine
Running the engine on your model can be dangerous. Please take extreme care when attempting to start the model engine.
The engine has a number of features. The carburetor is a small hole at the front of the engine that can be opened and closed. This is used to control the intake of air and fuel. This speeds up and slows down the engine for takeoff, landing, and aerobatics.
The needle valve is a small knob on the side of the carburetor. On some engines, this is located at the back of the engine to make adjusting safer due to the speed of the rotating propeller. This valve is used to adjust the mixture of fuel and air intake. To open the needle valve it richens the mixture which lets more air than fuel into the engine and lets the engine burn cooler. This gives you less power but there is less chance of going deadstick. (Deadstick is when your engine cuts and the model has to be glided back in) To close the needle valve, it leans the mixture sending less fuel than air into the engine thus the engine burns hotter and you have more power.
The chances of going deadstick are greater. To start the engine, fill the model with fuel either using a bulb or a fuel pump. Then, you must prime the engine. This is when you open the throttle fully, place your thumb over the carburetor and turn the engine over anticlockwise 4 or 5 times. This brings fuel into the engine and makes the engine easier to start. Then take your thumb off the carburetor and move the throttle until it is 1/3 open. Then flick the engine over a few times to let air into the engine. DO NOT DO THIS PROCEDURE WITH THE GLOW PLUG CONNECTED TO A POWER SUPPLY!!! Now open the needle valve 1 and 1/2 turns. It would be wise to remember this position.
Energize the glowplug with a volt power supply and give the engine a flick to the right and it should start running. If you do not feel safe using your finger or a stick use a starter that is a bit like a high torque drill and will turn the engine over for you. When the engine has been running for a couple of minutes, open the throttle fully and hold the model at a steep climbing angle for seconds. If the engine changes in sound at all or cuts, the needle valve needs adjusting again. Repeat this procedure until the engine runs smoothly. This position on the needle valve is the optimum running position. It would be wise to remember this position for future running.
Wing ribs and other multi-copy components. Cut out the shape from the plan and stick it down onto a piece of 1/8 ply or lite-ply, cut it to shape using a hand saw and rasp a flat Permagrit strip is my favorite shaper. Repeat to make a second identical piece (or make both at the same time with two pieces of ply taped together). Clamp the two pieces together and drill three holes through the centerline of these patterns. Next, cut balsa strip into pieces just large enough to cover the shape, cutting as many as required of that particular size. Tape or lightly clamp the balsa pieces into a bundle, topped with one of the patterns, and drill three holes through the bundle, using the pattern as a jig for the holes. Register the second pattern at the bottom of the stack and hold the whole bundle together with suitable bolts. You can now sand and file the balsa down to the shape of the patterns.
Complex shapes. Again, cut out a pattern from the plan, or just photocopy the particular part on the drawing, and stick it on to the balsa or lite-ply required for the part and then cut, file and sand to shape. In the case of the formers shown here for the stringers, the plan just provides the detailed edge which is then stuck down to the balsa. With a shape like F9, to prevent breaking off the very narrow supports, you cut out each alternate slot, then fit stringers into those slots before cutting out the other slots (shown in pink in the picture above right).
Larger, less complex shapes, like fuselage sheeting, doublers, etc., can simply be drawn lightly on to the balsa from dimensions taken from the plan and then cut to shape.
Where a part is repeated for, say, left and right fuselage sides, cut both at once to ensure identical shape. Choose your balsa as carefully as possible to try and ensure the equal weight of such parts as are duplicated either side of the centerline of the fuselage, left and right wings, etc., to maintain uniformity of weight as the plane is built. For lengths of sheeting longer than the 36 length of your stock sheeting, join them together with a diagonal cut, using the good old-fashioned balsa cement before cutting to shape.
Moulded shapes. For contoured shapes like engine cowls (right), glue large pieces of block balsa together or to a frame (the plan will show the suggested method) and then carve, sand, and cut to shape.
Wire bending for undercarriage. A wire bender is a worthwhile investment if you are going to do a fair amount of plan building. This allows you to carefully bend the wire to shape, offering it up to the plan as you go, to accurately replicate the required angles. The picture shows the wire laid through the holding pins of the bender and the wire is bent by pulling the large pivoted lever. The flat plate of the bender is designed to be permanently screwed down to a heavy base or can be firmly held in a vice.
By following these straightforward techniques, it will not be long before you have all the bits that you would normally find in a kit, but at a lot less cost. With the many hundreds of plans available, many as give-aways in modelling magazines, you have a very wide choice of model, many of which you will never find as a kit of any sort. There are also some superb plans available, together with accessory kits for some of the specialists and more complex moldings like canopies, cowls, spats, etc., as well as wheels, undercarriage, and other dedicated fittings.
How to Build an ARTF/ARF RC Plane
If you had paid a visit to any model flying field as recently as seven or eight years ago, you would have been very lucky indeed to have spotted an ARTF model airplane. Today, things are very different and youll probably find yourself perusing a wide variety of ready-built models in the pit area.
Since most of the hard work has already been done for you, the construction of these models is generally a pretty simple affair, but care is still needed if the model is to be straight and true on the occasion of its first flight. The purpose of this section is to point out a few important areas to which particular attention should be made if you wish to attain the best performance from any ARTF model aircraft kit.
Worth the wait!
Having selected your chosen kit, take a trip to your nearest stockist, and purchase the model. Due to the huge number of ARTF kits available, you may find that your favorite retailer simply does not have sufficient space to stock all the kits that he or she would like. But dont be too disappointed if the kit which you selected is not immediately available. For this reason, it may well be worth telephoning the shop before you leave home or work to check that they have the kit you want in stock. If not, simply ask them to phone through to our sales team and, if it is available, we will despatch the model the very same day.
Check it out
Once you get the kit home, take a few minutes to carefully unpack all the main components, and give each part a thorough check-over. Thankfully, major faults are very rare, but as with any mass-produced item, mistakes do slip through from time to time. Nows the time to identify any major problems such as a warped wing or a twisted fuselage not when you have glued it all together and its impossible to replace the affected part!
If you are satisfied with the overall appearance of the model, take a few minutes to check the finer details. One area to pay close attention to is the control hinges. Check whether they are pre-installed and if so, give each control surface a firm pull. If any hinges show any signs of looseness, please cut away the complete control surface and re-hinge as necessary. Now is the time to discover any such problems, not when your model is feet up in the air!
Taped hinges should be stuck firmly to both surfaces. If such a hinge shows signs of lifting, rub it down firmly. If it continues to lift, the adhesive may have become contaminated with dust, etc., from inside the box. Any badly affected areas should be carefully cut away and replaced. Film hinges may also lift, but in most cases, they can simply be ironed back into position using a heat sealing iron in a suitably low setting.
Check each control surface for free and full movement. Any binding should be investigated and resolved. In rare circumstances, you may find that too much glue has been used to fix the hinges in place. The excess will have settled at the hinge line and solidified, causing an obstruction. In most instances, it is easily removed and full control is regained.
Many ARTF kits have pre-installed pushrods and control runs. These must also run free and it is easier to check out and resolve any restrictions before you assemble the model. Recheck them once you have completed the model, just in case connecting them to either the servo arm or control horn has caused a small distortion. The simplest remedy here is often a slight bending of the wire pushrod to realign the linkage. In some cases, you may even need to enlarge the push-rod exits at the rear of the fuselage. Proceed with care, preferably using a small file to gently remove material from the fuselage side. Avoid using a knife as this may set up small splits in the fuselage side that may get bigger when the model is in use.
As with all model aircraft, your ARTF will fly much better if it is assembled straight and true. The wing should sit squarely to the fuselage and likewise, the tail should be level in relation to the wings, with the fin at 90 degrees. With the wing bolted or bonded to the fuselage, insert the tailplane and check its position. If it is out of square by a small amount, then dont be frightened to gently sand away some material from the high side of the tailplane mount. Likewise, small wedges of balsa wood can be glued onto the mount to build up any low points. Of course, if the tailplane mount is way out of square in relation to the wing mount, then you will have detected this during your preliminary inspection and have already acquired a replacement fuselage!!
The same goes for the fin. Dont just glue it into its slot check that it is truly vertical and at 90 degrees to the tailplane. Use postcards or beer mats, etc., as simple set squares for this job, cutting them away where they clash with the fuselage sides. Again, dont be frightened to make good any faults. Even though its an ARTF, its still OK to do a bit of balsa bashing!
Before you glue the tail in place also check that in planform it sits square to the fuselage and wings. The easiest way to do this is to use lengths of thread to measure the distances between wing and tailplane tips, as shown in the accompanying diagram below (click the image for a more detailed view}. Before gluing the tail parts in position, check to make sure that the covering film does not cover up any areas to be glued. If it does, then mark it carefully and remove using a sharp knife. Be careful not to cut into the underlying wood structure as this may weaken the airframe.
Got the gear?
When fixing the undercarriage in position, please make sure that the wheels turn freely and that they do not exhibit any large degree of toe-in or toe-out. If they do, remove the offending leg and tweak it as necessary. Dont try and bend it whilst it is attached to the model since you will most likely rip it away from its wooden mount.
Steerable nose wheels should turn easily in their bearing blocks. Make sure that the control arm is firmly attached to the nose leg otherwise, it will slip and the whole thing may revolve in flight or, in the worst case, it may even drop out altogether! As with other control linkages, the pushrod to the tiller arm should run freely. Pay particular attention here as a binding nose leg can cause lots of battery drain and stress on the poor rudder servo every time that you yaw the model. Remember, the nose leg also turns in flight and not just when the model is on the ground!
Models equipped with spats should be closely examined to make sure that the wheels revolve freely. If the spat rubs against the wheel, simply pare it away using a sharp knife until the wheel is loose, making sure to allow some sideways clearance for the wheel to move slightly along its axle.
Ailerons may either be activated by torque rods or by independent wing-mounted servos. If the latter applies, you may find that the ends of the rods that are connected to the servo are at different angles when the ailerons are neutral. If so, the pushrods will need to be of different length; in most cases, this can be achieved by simply adding a few extra turns to the clevis on one side.
Some ARTFs will have been assembled in countries where the climate is far different from our own. During transit and storage, the wood may have settled and have distorted slightly. This is most likely on unsupported parts like ailerons and elevators but is far less likely where the wood is bonded in position as part of the airframe.
On the control surfaces, such distortions are likely to manifest themselves as a slightly bowed or wavy trailing edge. In most sport flying applications, they will have very minimal effect on flying performance, but attention should be taken to make sure that the controls are lined up more in relation to the wingtips rather than the center section. This is because, generally, the outer sections of the control surfaces have a far greater aerodynamic effect than the sections nearest the fuselage.
Most modern ARTFs have pre-installed engine mounts, with the engine lugs retained by simple metal straps. These have proved to be very effective and secure, provided that care is taken to tighten down the straps evenly and tightly. Such mounts also allow a small amount of thrust line adjustment, which can be of help when you are fine-tuning your model during its early flights.
Again, do check that the control linkage to the throttle servo is free and take any necessary steps to relieve any binding. In most instances, all that will be required is a gentle bend in the wire pushrod.
As with any model, take your time to set up the throttle such that it gives full movement at the carburetor barrel without stalling the servo, and that it also closes fully when the throttle stick AND throttle trim are pulled back. This is very quick and easy using a modern computer radio set, such as any of the JR Propo range of radio control systems.
Hopefully, you will have rectified any control linkage problems during construction, but its never too late to double-check just to make sure. Stalled or binding servos will quickly drain the poor flight battery, leading to shorter available flying times and potential servo failure in the long term. Your R/C system is the heart of your model, so treat it with care. Protect against vibration by wrapping the battery and receiver in suitable high-density foam and make sure that all servos are secured with all screws (normally four), including their rubber mounting grommets and brass anti-crush ferrules.
The switch should be mounted either internally, where it can be operated by a short wire pushrod, or externally, on the side opposite the engine exhaust (if fitted). Take care to protect an external switch from moisture in wet or damp conditions.
How To Build An Electric Model Airplane
Electric remote control airplanes are a popular type of model aircraft among model airplane enthusiasts. In this type of model airplane, the engine is powered by batteries, rather than by fuel. Electric model airplanes can be purchased in line-control or radio-controlled versions.
As with other model airplane kits, electric model airplane kits can also be purchased pre-assembled or as a kit you assemble. In pre-assembled kits, the major components, like the wings and the fuselage come already assembled. Some minor assembly may be required for landing gear, battery installation, and other easy to assemble parts. Electric model airplane kits that you need to assemble can be a little complex and do take some time to build before you can actually fly your model airplane.
Both pre-assembled and assembly required electric model airplane kits come with instructions to guide you through all the assemblies required to get your electric model airplane in the air. Read through and follow these instructions as you put your electric model airplane together.
One of the tools you will need to build your electric model airplane, besides the tools common to all model airplane building, is a circuit tester. A circuit tester will aid you in making the right electrical connections from your electric model airplane’s battery to the engine and to the servos that control flight and landing. Circuit testers are also a great tool to take out to the field with you to perform some pre-flight inspections and /or modifications.
Wire strippers/cutters are another tools that you may find helpful in the assembly and maintenance of your electric model airplane. This tool can strip away the plastic sheath that protects the wire and can also cut the wire to the required lengths. X-acto knives, screwdrivers, and spare parts are also suggested as part of your electric model airplane tool kit.
Make sure to set the control surfaces and center of gravity as shown in the instructions. These will not necessarily be the best positions for optimum performance of your own particular model but will be sufficient to ensure a safe first flight. Depending on your piloting skills, you may wish to change these settings to suit your own flying style, but please do so one at a time so that you can easily assess any changes to flight performance.
Novice pilots are advised to stick with the recommended settings unless advised otherwise by their instructor, who will preferably have been certified by the British Model Flying Association (or its equivalent in your country). If you have never flown an R/C model before, or have limited experience, please do seek help from an experienced instructor. Your model shop will be able to advise you of suitable model flying clubs in your area that can offer flight training.
I hope that this article has given you some positive ideas on how to get the best from your next Almost Ready To Fly kit. Although most ARTF kits can be quickly thrown together and still fly, you will reap even more enjoyment from your new model if you take your time during assembly to make sure that everything is straight and true.
Introduction: Scratch Built RC Airplane
Hi, In this instructable, we'll be building our own RC airplane.
Why this instructable?
Well, I started in RC hobby about 2 years ago. Watching people build and fly their own RC airplane has always been inspiring for me. After reading lots of articles and watching a number of videos covering tutorials (which was the hardest part during the entire build process). Finally, I was able to build my first RC airplane.
So, this instructable covers everything you need to know in order to build your first RC airplane. This is a beginner’s guide. So, even if you have just got into RC hobby you can build and fly this model.
In this instructable, we'll be building a medium-sized RC airplane with a wing span of about 20 inches.
Why scratch build RC airplane?
- Well, it costs a lot less than building it from RC kits or Ready to fly models. And It’s fun
- Flying RC airplanes is always fun. But, when you build something and see that flying it feels incredible.
Step 1: Part list
Step 2: Choosing electronics and parts
Step Preparing the electronics for connection
Step Connecting and testing electronics
Step Building the foam airplane
Step Installing electronics to airplane
Step Flying and Troubleshooting
Step 1: Part List
For building your own RC airplane you’ll need:
- Emax MT KV Brushless motor
- 20 A ESC
- 2 X 9g digital servo
- FlySky FS-T6 ghz transmitter with FlySky R6-B receiver
- mAh 30C 3s li-po battery.
- Li-po battery balance charger
- Li-po battery low voltage alarm
- 2mm Depron Foam / 4mm Adam’s Readi-Board
- mm Hobby grade plywood / Motor mount
- XT60 connectors, Bullet connectors, Heat shrink tube
- Music wires
Tools / Equipment:
- Soldering tools
- Hot glue gun
- X Acto knife or Box cutter
- Scotch tape
- Helping hands
Step 2: Choosing Electronics and Parts
Once you have decided how big your airplane is going to be, start by choosing a proportional propeller. By proportional I mean you don’t want to choose too big or small prop for your airplane.
Now, determining the size of propeller sure requires some maths. But you do not need to worry about determining prop size unless you want to design your own RC airplane. Anyways, you can always use e-calculators.
I used eCalc to determine the size of propeller.
This airplane has a wing span of 20 inches that requires a inch prop. Now, I think 5-inch prop works best. Where 5 inch is the diameter of the propeller. Also, the airplane is for beginners and we do not want a massive amount of thrust. So, we’ll use a inch prop with a inch pitch.
What do the numbers on a propeller mean?
Suppose a propeller is labeled a X b. Here, ‘a’ represents the diameter of the propeller in inches and b represents pitch of the propeller in inches. Where pitch is the distance that the propeller is going to move forward during one revolution (Under perfect conditions).
So for this airplane, we will use a X propeller. Simply, a propeller. Combine this propeller with a powerful motor to meet the thrust to weight ratio.
Thrust to weight ratio?
Well, keeping the weight of the airplane you are building in mind, you need to supply a motor and prop powerful and big enough to pull your airplane into the air. Typically it’s normally to for slow-flyer. For example, if your airplane weighs gm. For, thrust to weight ratio you need a motor and prop producing a minimum thrust of gm.
Once you know the average weight of your airplane, look for a motor and propeller combination that at least meets thrust to weight ratio. If the design of airplane is efficient enough, it flies great even with a small amount of thrust. But, remember this was just a general statement to give an idea of thrust to weight ratio.
Type of motors used on RC airplanes:
We use brushless motors in RC airplanes these motors are highly efficient and are lightweight as compared to brushed motors. Brushless motors are classified on the basis of their size and rotational speed.
What does the numbers on a motor mean?
The first set of number is a 4 digit number or 2 two digit numbers separated by a dash “–“. The first two digits number is diameter (in mm) and the second two digits number is the height of the motor (in mm).
The second set of numbers represents KV. Or, at how many RPMs the motor is going to rotate when powered through 1V. So, if you have a KV motor running at Volts your motor is running at X = RPM.
Choosing the motor:
With the battery and electronics our airplane will weigh about grams. So, we’ll be using a EMAX MT KV brushless motor. This motor produces grams of thrust with prop at Volts. This amount of thrust is good enough for this design. (In the build I’m using the same motor from a local manufacturer.)
Find how much thrust your motor produces:
Motor manufacturers provide datasheets along with the motors. Here you can find how much thrust your motor is going to generate with a particular propeller and battery. Refer to the datasheet of EMAX MT here.
Moving on to powering the motor, Brushless motors require ESCs or, Electronic Speed Controller that converts DC current from your battery to AC current going to your motor because, Brushless motors operates on AC current.
ESC also controls the speed of motor through its servo lead and provides 5V DC power for your receiver that controls all your electronics. Now, ESCs are able to provide 5V DC power for radio receiver using a BEC or a Battery Elimination Circuit . So, that you do not need two separate batteries for your motor and your radio receiver.
ESCs are classified on how many amps. of current they are going to supply to your motor. So, an ESC that’s rated 10 A is going to supply a maximum of 10 A current to your motor (Safely). Once you know which motor and propeller to use, refer to the datasheet of your motor and find out how much current your motor is going to draw.
Now, for safety reasons we always choose an ESC that’s rated amperes more than the requirement of a motor at full throttle. This will make sure that the ESC is running cool and you don’t need to worry about heating inside your airplane.
By referring to the datasheet provided for EMAX MT, I found that the motor will be drawing 8 A of current from the ESC when working with prop and 3s li-po battery at full throttle. Considering safety for ESC and to run it cool we’ll be using a 20 A ESC.
Now, as already mentioned we’ll be using a 3s li-po battery. Also, we do not want to make our airplane heavy. So, use a mAh 30C 3s li-po battery. Li-po batteries are rechargeable batteries that require a special charger for battery’s long life called a Balance Charger. Any other attempts of careless charging can not only damage your battery. But, can even lead to explosion in battery!
What does the numbers on a Li-Po battery mean?
Li-Po batteries are labeled with “mAh”, “S ratings” and “C ratings”.
- mAh stands for milliampere–hour; This represents the capacity of the battery.
- ‘S rating’ shows the number of cells that your battery has. If your battery has 3 cells then you get a voltage of 3 X V across the terminals of a battery (under perfect circumstances).
- 'C rating’ of the battery explains how many amps of current can be drawn continuously from the battery without damaging it.
Moving onto servos, Servos moves the control surfaces on a RC airplane to control altitude or direction of the airplane. For this airplane, we obviously require 2 servos. One to control the altitude and another to control direction. I’m using 2 X 9g digital nylon geared servos.
Transmitter and Receiver
Finally, we need a Transmitter and Receiver for controlling the airplane.
Channels on the Transmitter and receiver:
Channels on the Transmitter and receiver decide how many functions or controls you get. For this airplane, we need 3 channels. That is Throttle, Rudder and Elevator. Where throttle controls the speed of the airplane, Rudder controls the direction and Elevator controls the altitude.
I’m using a FlySky FS-T6 ghz transmitter with FlySky R6-B receiver.
Step 3: Soldering Connectors on Motor and ESC
The electronics that you buy does not come with connectors. For example, you need to connect the ESC to the motor but you are not supposed to solder them directly.
So, we will solder connectors to ESC, motor and battery. So that, if any of the parts is damaged you can easily replace it.
Start by soldering bullet connectors to the ESC. So, we’ll start by soldering female bullet connectors on the ESC.
How to solder female bullet connectors on ESC?
- Hold the bullet connector using helping hands.
- Apply heat to the bullet connector by touching soldering iron to surface of the connector and fill 1/2 of the shallow end with solder.
- Keep applying the heat and dip the stripped end of the wire into it.
- Remove the soldering iron. Do not apply heat for a long time or this could damage your ESC.
Why solder female bullet connectors on the ESC?
Suppose you solder male bullet connectors on your ESC and you connect your ESC to the battery without motors connected to its other end. The male connectors of the ESC are likely to come in contact with each other resulting in short circuiting. And you might end up burning your ESC. So generally, we connect female connectors on electronics that are giving power. While electronics that are receiving power takes male connectors.
Once done with the soldering, apply heat shrink to the bullet connectors. Now, we do not want ESC’s wire to short circuiting by touching each other. So cover it perfectly using heat shrink. Such that end of heat shrink lines with the end of bullet connectors. Use a lighter to shrink the heat shrink.
Similarly, solder male bullet connectors to wires on the motor.
Step 4: Solder XT60 Connectors to ESC and Battery
In order to connect the battery to the ESC, we need to solder male XT60 to the ESC. XT60 is connected to the two wires coming from the ESC. And battery takes the female XT
Before soldering XT60, make sure to put in your heat shrink to the wire of ESC. Because once soldered you won’t be able to do that.
Soldering XT60 is similar to soldering bullet connectors. But, XT60 has polarity for soldering. So, make sure you get it right in the first attempt. Look for a “+” sign at the end of XT60 this is where you connect your red or positive wire from ESC. And the black wire at the “-” end of the XT
If you connect this wrong you can end up burning your electronics. And, trust me you never want that.
Once soldered, shrink the heat shrink tube to cover any exposed part of the wire that can lead to short-circuiting.
Repeat this process to solder female XT60 on battery. Luckily, my battery already had a female XT So, Yay!
Step 5: Connecting Electronics
Finished soldering? Well, now it’s the time to connect everything together and test run for the first time. Connect three wires coming off the ESC to your motor. Since Brushless motors run on AC current. So, it doesn’t matters which wire of the motor connects to which one on ESC. Connect the servo lead coming from your ESC to throttle channel of the receiver. The servo leads have polarity and so does the receiver. So if you are using a FlySky receiver like me, the ground is towards the extreme edge of the receiver in which the black or brown wire of the servo lead goes in. In order to know about throttle channel and polarity of your receiver refer to user’s manual of the Transmitter and Receiver.
Connect the servos to the receiver. One of the servos goes to rudder channel and the other goes to elevator channel. Again, it doesn’t matters which one of the servos goes to rudder or elevator. While connecting, make sure the polarity of servo lead is right.
Here’s the setup that I am using:
- Servos are connected to channel 1 and channel 2.
- ESC’s servo lead goes to channel 3 of the receiver.
Now before connecting battery, always remember this as a rule:
Unless you are ready to fly, never put on your propellers to the motor. I repeat NEVER!!!
Putting on propellers to the motor and running it can be extremely dangerous. You can hurt yourself or anyone around badly.
Now all the electronics are connected we can move forward to Binding Radio Transmitter and Receiver together.
Step 6: Binding Transmitter and Receiver
To bind your transmitter to the receiver, insert the bind plug in your receiver’s bind or battery port. Again, look for bind port of receiver in receiver’s user manual. Now, making sure your radio transmitter is turned off. Plug in the battery to ESC. This will power all the electronics. Look for a flashing light on the receiver, saying it’s ready to be bound.
Now, keep holding the bind key of your transmitter and power it on. Light on the receiver is going to stop flashing, saying it’s bound. Release the bind key. Then remove the bind plug from your receiver. Finally, unplug the li-po battery and plug it again. Your transmitter and receiver are bound. For safety, always power on your transmitter before powering your receiver. (Unless you are binding your transmitter and receiver). Finally, connect all the electronics and test run just to make sure that everything is working.
Step 7: Printing and Cutting the Build Plans
Print the pdf plans for the build.
Make sure to scale the document to % (or as close as possible) while printing.
Once done cut the edges of the paper such that the plans align to one another. Use some scotch tape to stick the pdf plans together.
About the build plans:
So, I’ve designed this RC airplane using SketchUp. It's most basic design with a wing, a vertical and a horizontal stabilizer. With a wing span of 20 inches and wing breadth of about 9 inches, the wing area of this airplane is about sq. inches. That makes it a nice slow flyer.
This design uses most of the traditional ideas for building RC airplanes. Making it super simple to build and fly.
The wing has a small but effective dihedral angle. That provides additional stability to the RC airplane. Which is good for beginners.
Dihedral wings are bent upwards at a particular angle that provides additional stability to the aircraft. Lift of the airplane decreases due to dihedral wings. But, it provides additional stability, resulting in a smooth flight.
Step 8: Cutting Foam Board
Lay out the plans for built on the foam board. Use some scotch tape on the edges to hold them in position. Also, use a straight edge or ruler along with X Acto knife to cut with precision.
Which foam board to use?
I have used 2mm depron foam board. Most people use 4mm Adam’s Readi-Board. But, that’s not available worldwide. But, you can use 4mm Adam’s Readi-Board if it’s available to you. Anyways, 2mm or 4mm depron foam is available in almost every country. So, I’ve used depron foam board.
Score cutting and cutting all the way through it:
The bold line in the build plans shows cutting all the way through it. While dashed lines shows score cutting.
For, score cutting you cut the foam board halfway only. So, that it can be folded easily to form a nice and strong hinge. This hinge is used as a control surface in order to control direction and altitude of the airplane. If you have destroyed the hinge by cutting all the way through foam board, do not worry just use a packing tape above the hinge to make it right.
For control horns and motor mounts:
Use mm thick hobby plywood. Place the plans for the motor mount and control horns on the plywood (Or glue the plans on the plywood). Then, use a drill to make holes according to the plans. Finally, cut the motor mount and control horns.
Step 9: Building the Fuselage
Once you have cut all the foam parts, start by making the fuselage. Take the fuselage part that you cut earlier. Score cut as instructed on the pdf plans. Finally, break the foam board at the scored area to make a hinge. To break the foam, bend the foam board until it breaks. Make sure it breaks at the joint. Remove any excess foam at the joint.
Once done fill hot glue at the joint. Then bend foam surfaces at the joint to form a nice 90° angle. Repeat this process until you get a nice cuboidal fuselage.
Step Build the Wing, Rudder and Elevator
Take the wing part of the foam board. Score cut as instructed in the plans. And make the dihedral shape.
How to form the dihedral shape?
- Bend the wing at the score cut. Such that the edge of the wing is elevated by inches.
- Fill the scored area with hot glue. Such that the wing is able to maintain its shape.
- Keep holding the wing in the same orientation until the glue cools.
Now take the Rudder and Elevator and score cut to form a nice and strong hinge for the control surface. Finally, bevel the edge of control surfaces so that it can move freely in both the directions.
How to bevel control surfaces?
- Fold the control surface at degrees from the hinge.
- Place it on the edge of a table.
- Now, with the help of a straight edge or ruler bevel at 45 degrees using your X-Acto or box cutter.
Use some packing tape on the control surfaces to reinforce the joint.
Step Joining Fuselage and Wings
Using the reference marks on the plans, hot glue the wing to the fuselage. You need to glue the wing about 2 cm behind the leading edge of the fuselage.
Finally hot glue the Elevator and the Rudder. Then hot glue the control horns to the Elevator and Rudder. Make sure you haven't glued your control surfaces and they are free to move.
Now, while gluing Elevator and Rudder make sure that:
- Elevator is centered and perfectly horizontal
- Rudder is centered and makes a 90 degree with the elevator
- Control surfaces are free to move
Once done, move on to installing electronics.
Step Installing Electronics to Airplane
Place motor on your plywood motor mount and tighten it using screws. For safety use the screws that come with your motor. So that, screws do not touch the wires inside the motor. Hot glue your motor mount to the front of the fuselage making sure that it’s centered. Make sure your motor is spinning and you haven’t glued outer can of the motor.
Put on the servos in the servo port on the fuselage. Insert servo arms to the servo making sure that the servo is centered. Again, connect everything to the receiver as earlier.
Step Link Servo to Control Surfaces
For push rods, I am using thin music wire. These wires are flexible and are easy to bend. Before linking control horns with servos, make sure control surfaces are perfectly horizontal with the wing. Any deflection can produce unnecessary upward or downward force making it hard to fly. Take help of a ruler to make sure it’s straight.
Put a Z bend at one of the ends of the wire, Insert it in the servo arm and measure the length of wire such that it reaches the control horn put a Z bend at the other end and link it to the control horn.
How to make Z bends?
- Take your pliers and bend wire making a 90 degrees angle. Now, bend it again in the opposite direction to make another 90 degrees.
Repeat this process with both the servos.
Once done, all you need is to program your radio and balance the Centre of Gravity of your airplane to fly.
Step Flying and Troubleshooting
Once you are all done, check that your sticks on the transmitter are functioning correctly. I’m using right stick of transmitter for controlling directions. And left stick as throttle only.
Make sure your airplane is responding correctly to your commands. Here’s how to do it:
Keep the airplane facing away from you and plug in the battery. Move the sticks and watch your airplane’s response.
For right stick,
- Pull the stick down: Elevator should go up.
- Push the stick up: Elevator should come down.
- Move the stick to right: Rudder should move right.
- Move the stick to left: Rudder should move left.
For left stick,
- Push the stick up: Motor starts rotating
- Pull the stick down: Motor slows down and finally stops.
If any one of these doesn’t respond correctly go to functions setup on your transmitter and opt for reversing. Finally, select the channel that is not functioning correctly and reverse it. Now, if your elevator is responding instead of the rudder and rudder instead of the elevator. Simply switch the servo lead going to the receiver.
If you power on your motor and it’s running the opposite way switch any two of its wire going to the ESC, this will reverse the direction of rotation of the motor.
Throws decide how much your control surfaces are going to move. If you have your throws set to %; your airplane is going to react a lot even for very small movement on the sticks of your transmitter. So, make sure to set your throws to about % while programming the radio. A lot of movement of the control surfaces is just not good, especially for beginners.
Balancing the Airplane:
Now all you need is to place the battery on the airplane using a velcro or double sided tape. Generally, the battery is the heaviest part on an RC airplane. So, we use the battery for balancing the airplane. Now for balancing we make sure that the entire weight of the airplane is concentrated near the Center of gravity of the airplane. This is a very crucial step and cannot be ignored.
I've added a reference line for Center of gravity (or CG) in the plans. Anyways, the Center of gravity for this airplane is about 11 cm behind the motor mount. So, move your li-po battery back and forward unless the weight of the airplane is roughly concentrated near CG. Here's a nice article on how to balance your airplane by FliteTest. Once you have balanced your airplane it's time to fly.
Here's a quick first flight check list:
- Make sure that your airplane's control surfaces are responding correctly.
- Everything is plugged in right.
- You have your airplane balanced.
- Your battery is charged.
Here's a nice article by FlightTest for first successful flight.
Li-po battery charging and safety:
Li-po batteries can prove dangerous if not used and handled with care. Always charge a lipo battery using a balance charger. Balance charger is important for a long life of lipo batteries. Balance charger makes sure that your lipo is not over charged and each cell of the lipo is at the same voltage.
Never over discharge your lipo batteries. Over discharging lipo batteries can damage your batteries. Use lipo battery voltage alarm that will beep when your battery is discharged. Here's a nice lipo safety guide by The Drone Girl.
For 3s lipo battery:
- Fully charged voltage: V
- Fully discharged voltage: V
If you follow each step with precision you should not encounter any problems. Anyways If you still face problems and you are unable to get your airplane into air write in the comments below or refer to a good RC forum around the internet. I think RCGroups is a good place to get your answers.
Thanks for viewing. Further questions and suggestions are welcome.
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