THE PIPER J-3 CUB STORY
The yellow Piper J-3 Cub is one of aviation's genuine classics. In the decades right before and after World War II, the cub was the most commonly seen fightplane at airports all over the country. It's been said that back then most people thought that every airplane flying was either a DC-3 or a Piper Cub. Today if you mention the word Cub to a person who has flown in one, he'll undoubtably become lighthearted, his eyes will start to sparkle and the whimsical hanger flying tales will begin. The J-3's charm and legendary flying abilities have made it one of the most famous, best loved airplanes of all times.
Ken Breiting, left, explains the radio control system in his Sig prototype Cub to Larry Frost, the owner of the mint full-size J-3 in the background. Larry actually rebuilt NC5793N from the mangled remains of a wrecked Army L-4 Grasshopper.
To understand the Cub's appeal, look back at aviation as it was in 1930. Lindbergh had crossed the altlantic just three years earlier and made the world "air conscious". Airplanes were getting faster and more powerful every day. Air racing and distance records were front page news. But while the major aircraft manufacturers were busy pushing ahead the state of the flying art, thousands of prospective pilots with limited pocketbooks were being left behind. The cheap barnstorming Curtiss Jenny's were gone, replaced by impressive, but expensive airplanes of the Stearman and Stinson class. With the Depression on, many people wanted to fly but couldn't afford to. What general aviation needed was a simple economical two-seat trainer!
|The basic Cub design emerged in 1930 as the open cockpit Taylor E-2 Cub. It was the product of a fledging company in Pennsylvania headed by designer
C.G. Taylor and buinessman William T. Piper. Taylor left the partnership in 1935 to start his own Taylorcraft company, but his self-taught design genius had made the E-2 a perfect foundation for Piper's
business talents to expand on. In 1936 the J-2 Cub was introduced with an enclosed cabin and 40 h.p. engine. Sales picked up impressively over the E-2.|
In 1937 a further improved version of the Cub was introduced, the legendary J-3. It became the first really successful commercial lightplane - 14,125 were produced between 1937 and 1947. At last fixed base operators had a simple economical trainer that could take all of the abuse students gave it. America's weekend pilots found an affordable basic stick and rudder machine that set a new standard for fun and docility. Being equally at home on wheels, floats or skis, the J-3 could be flown in and out of places other airplanes couldn't get close to. The Cub also found work towing gliders and banners, and even doing small-time crop dusting. J-3s have always been at home at airshows too. Crazy "drunken" Cub acts, landing and taking off from moving automobiles, and aerobatics in clipped wing versions are just a few of the things the J-3 could do to entertain.
Piper seemed to follow Henry Ford's lead when it came to factory paint jobs for the J-3. "You can have any color you like as long as its yellow!" Standard factory markings were black lightning bolts down the fuselage sides, black registration numbers, and the Cub bear emblem. Today, it's hard to imagine a Cub painted any other way.
The Army used a version of the Cub, the L-4, for utility work during World War II. The L-4 was little more than an olive drab J-3 with a greenhouse style cabin. 5,673 L-4s were produced between 1942-1945. Nicknamed the "Grasshopper", they were used for observation, aerial photography, artillery spotting, as transports, and as ambulances.
Even though the J-3 has been out of production since 1947, they are still in great demand by pilots who want a superior, no frills, fun flying machine. As long as there are pilots around who still fly purely for the adventure of flight, and who don't care about all the latest gadgets, dials, horns, and whistles, there will always be yellow Piper Cubs!
The 1/4 scale Piper J-3 Cub can be flown with a wide variey of engines. In fact, there is such a vast number of good quality motors available on the market today for a model of this size and type that it is impossible for us to recommend one particular motor over all others. The engines shown here are just a few that we have tried in the Cub. Generally speaking, we've found that any glow model engine, either a .60-.90 size 2-stroke or a .90-1.60 size 4-stroke, can be recommended for the 1/4 scale Cub. Any brand glow engine that you choose, within these limits, should provide your Cub with good flight performance.
2-Stroke or 4-Stroke?
The first choice you must make in selecting an engine for your Cub is to decide whether you want to use a 2-stroke or 4-stroke motor. From the reports that we have received from our customers, 4-stroke engines have proven to be much more popular for the Cub than 2-strokes. In fact, a 4-stroke engine seems to bring out the best in a slow flying airplane like the Cub. That's because a 4-stroke model engine produces its maximum power at a relatively low r.p.m., just like the full-scale Cub's engine. In other words, it more closely duplicates the power curve of the full-scale motor. While a typical 2-stroke R/C sport engine will normally run at between 10,000 to 13,000 r.p.m. in high throttle, a 4-stroke model engine runs about 7,000 to 9,000 r.p.m. in high. That enables the 4-stroke to turn a larger, more scale size propellor than the 2-stroke model engine could. The large, slow turning prop provides more pulling power for a slow flying airplane like the Cub, giving it an excellent rate of climb without having excessive airspeed in level flight. A 4-stroke engine is the best choice if you want your Cub to have super realistic flight performance.
In testing 2-stroke engines in the Cub, we found that a .78-.90 size 2-stroke provided the best all round performance. Fly it throttled back for realistic speed in level flight and go to full power for aerobatics. We also tried a schneurle-ported .60 2-stroke in one of our Cubs. While it provided very realistic airspeed, most modelers would feel it was underpowered. Even though it would loop out of level flight with no preliminary dive needed, and would cruise in level flight at near scale speed with 3/4 throttle, the climbouts and turns had to be kept very gentle to avoid a stall. A .78-.90 size 2-stroke provides an extra margin of safety. In conclusion, while a 2-stroke engine can fly the 1/4-scale Cub very well, they do tend to fly the model faster in level flight than a 4-stroke would. You have to run them fast in level flight in order to have good climb performance.
We do not recommend converted "chain saw type" gas engines for this model. They tend to vibrate more than a precision made glow engine and are usually too bulky to fit inside the cowling.
Regardless of what size and type of engine you decide to use, strive to keep your Cub as light as possible for best flight performance.
|ENYA .90 4-stroke represents typical installation of a single-cylinder 4-stroke engine in the Cub. Motor is sidemounted for easy starting and dependable Idle. Uses a J'Tee #JT-64 Aluminum Engine Mount, J'Tee #JT-ENS Muffler, and 15-6 prop. No dummy engine needed on this side of the cowling.||O.S. GEMINI 1.20 twin-cylinder 4-stroke engine mounted in the Cub. Note 3/8" thick spacer between back of engine mount and firewall, to provide correct firewall-to-prop distance. Cowl is modified to come apart In two pieces, ala the full-scale Cub (upper section is removed in pboto).||Webra .91 2-stroke engine mounted inverted in the Cub. C.B. Associates 15310 Aluminum Engine Mount, Slimline #3401 Sport Scale Muffler with homemade copper tubing exhaust extensions (plumbing variety copper tubing from hardware store). Inverted engines can be difficult to start.|
No motor mounts are supplied in this kit because of the wide range of engines that can be used. A suitable radial firewall-type mount (such as Tatone, Fox, CB, Hayes,etc.) should be available for just about any mass produced engine. The distance from the front of the cowl to the firewall is adequate for most all .60 to .90 glow engines. Less common engines may require some preplanning and modification in this area.
There is no one type of muffler that is best suited for the Cub. It all depends on the particular engine that you've elected to use. You will have to figure out your own muffler installation. We have had good luck adapting the "exhaust manifold" type mufflers (such as made by Tatone and Slimline) to most .60 to .90 glow engines. Usually they can be made to fit with just slight alterations. Use copper or heat-proof rubber tubing to extend the exhaust pipes to the outside of the cowling.
Sig-Bond (alphatic resin type) glue works best for the majority of the general framework construction. Areas subjected to unusual strain, or including metal pieces, should be epoxied with Sig Epoxy Glue (slow drying) or Sig Kwik-Set (5-minute) Epoxy Glue. You will also find that the cyanoacrylate type adhesives (Hot Stuff, Jet, etc.) can be extremely quick and handy for some applications. Some of the steps in this instruction sequence call out the specific type of glue to use for that particular assembly. In other areas you can use your own judgement as to which type is best suited to the purpose and your building schedule.
About The Building Sequence
The quickest and most efficient way to complete a model is to work on several pieces at the same time. While the glue is drying on one section you can start on or proceed with another part. The numbering sequence used in this book was chosen as the best way of explaining the building of each major assembly and is not intended to be followed in exact one-two-three fashion. It may be desirable, for example, to start building the wing or tail while the preliminary parts of the fuselage are drying. It is suggested that you read the instruction book and study the plan carefully before beginning to build. That will help make it clear where construction out of the descriptive sequence can be done.
Notes Before Beginning Construction
Any reference to right or left refers to right or left as if you were seated in the cockpit.
Building large airplanes requires a large building board! For this Cub, you will need a board that is at least 18" wide x 72" long. It must be perfectly flat and untwisted. If you don't have one that big, go to the local lumber yard and purchase a "door core" of at least these dimensions. Door cores are normally very straight and true (be sure to inspect it before buying), and they are not too expensive.
A piece of thin foam board or celotex-type wallboard makes a handy top surface for your building board, into which pins can be easily pushed. Don't be afraid to use plenty of pins while building, particularily when gluing planking on the top curve of the wing or the round top of the nose.
Due to their large size, the full-size fuselage and wing plans had to be drawn in two pieces. Cut out the adjoining pieces and carefully tape them together along the break lines. Wax paper should be used to protect the plans during building.
Be careful where you use a ball point pen for making marks on the model during construction. If not sanded off, these marks may bleed through many coats of dope and show on the finished model.
Cut all long pieces of balsa first, followed by medium lengths, before cutting up any full length strips into short pieces. Leave the die-cut parts in the sheets until needed in construction. Remove pieces from the sheets carefully. If difficulty is encountered, do not force the part from the sheet. Use a modeling knife to cut it free.
A jig saw is best for cutting out the printed balsa parts. Cut just outside the lines, leaving all of the line on the part. When fitting the piece into the structure, use a sanding block to bring the edges to an exact fit.