Sig Mfg. Co., Inc....401-7 South Front Street....Montezuma, Iowa 50171



Introduction

Congratulations on your purchase of the 1/5-scale SIG PIPER J-3 CUB kit. This is a computer engineered laser-cut kit of America’s favorite lightplane. Laser cutting is more expensive than the older methods of kit production, but it provides incredible accuracy and perfect parts fit. We believe that you will enjoy putting this kit together just as much as you’ll enjoy its legendary flying characteristics.

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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 Piper Cub was the most commonly seen lightplane 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. The J-3's charm and legendary flying abilities have made it one of the most famous, best loved airplanes of all time.

To understand the Cub's appeal, look back at aviation as it was in 1930. Lindbergh had crossed the Atlantic 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 Jennys 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 fledgling company in Pennsylvania headed by designer C.G. Taylor and businessman 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.

Piper J-3 Cub owned by Les Gaskill/Ottumwa, Iowa

In 1937 a further improved version of the Cub was introduced, the legendary J-3. The Piper factory produced 14,125 model J-3 Cubs between 1937 and 1947. That made it the single most successful civilian airplane design up to that time. The popularity of the J-3 Cub was easy to understand. It provided airport operators with a low-maintenance, economical trainer that could survive most bad landings. America's weekend pilots found an affordable basic stick and rudder machine that set a new standard for fun and economical flying. The J-3 Cub was equally at home on wheels, floats, or skis, and it could be flown in and out of places the larger civilian airplanes couldn't get close to. Cubs also found work towing gliders and banners, doing small-field crop dusting, and even in air shows. Crazy "drunken" Cub acts, landing on moving automobiles and aerobatics in "Clipped Wing Cubs" are just a few of the things the J-3 could do to entertain the crowds.

Like Henry Ford and his Model T car, William Piper had a standard for factory paint jobs for the J-3 -- "You can have any color you like as long as it’s 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 Piper L-4 "Grasshopper" was little more than an olive drab J-3 with a greenhouse style cabin. Piper produced 5,673 L-4s between 1942-1945. They were used for observation, aerial photography, artillery spotting, as transports, and as ambulances.

Even though the Piper J-3 Cub 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 and dials, there will always be yellow Piper Cubs!

Hazel Sig's Clipped Wing Cub

In 1953, an aerobatic pilot named Earl C. Reed got FAA approval to shorten the wings of his Piper J-3 Cub for better aerobatic performance. Reed’s modification was to take 40-1/2 inches (about 2-1/2 rib bays) off the inboard end of both the left and right wing panels. That shortened the standard J-3 wingspan of 35’-1-1/2" to 28’-5-1/2" and gave the airplane a faster roll rate.

Hazel Sig, co-founder of SIG MFG. CO., bought a well-used Piper J-3 Cub for pleasure flying in January of 1968. Carrying registration number N32629, Hazel’s Cub had been manufactured in 1941 at the Piper factory in Lock Haven, Pennsylvania as a standard Piper J-3C-65 Cub, serial number 5498. The log book showed that the Cub had been covered with ceconite and painted with enamel in 1965, just three years before Hazel bought it. The ceconite and enamel turned out to be a bad combination. After the simplest aerobatics, the enamel began to crack and loosen from the fabric in several places.

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It quickly became obvious to Hazel that the Cub was going to need recovering again in the near future, much sooner than should have been the case.

As it turned out, a late-summer 1968 wind storm brought the Cub's covering problems to a head. With the storm fast approaching and no hangar space available, Hazel quickly tied the Cub down outside. To keep the rudder from slamming from side to side in the gusty wind, she grabbed a roll of duct tape and taped the rudder to the fin. Needless to say the tape held perfectly during the storm, but when she tried to take it off later, huge chunks of enamel came off with it. The recovering project couldn't be put off any longer!
Hazel’s Cub in 1968

After retaping over the bare fabric spots, Hazel flew the wounded Cub to the Ottumwa, Iowa airport. There the entire airplane was stripped of its covering and inspected. It turned out to be in worse shape than originally thought. The wooden wing spar had been damaged by mice and hastily varnished over in '65. The control cables were brittle. The engine needed an overhaul. And the list kept growing. The Cub needed to be completely rebuilt!

Hazel’s Cub in 1968


Hazel, assisted by her husband Glen and SIG factory superintendent Maxey Hester, completely disassembled the J-3 and trucked it back to the SIG factory, where they worked on it through the winter. Since the airplane needed a complete overhaul, they decided to make it a Clipped Wing Cub using Earl Reed’s FAA-approved plans and instructions. In addition to shortening the wings and struts, the steel tube fuselage was sandblasted and primed with zinc chromate. The wooden parts were repaired or replaced as needed. The airframe was then recovered with grade "A" cotton and painted with SIG SUPERCOAT MODEL AIRPLANE DOPE. When it came time for the color painting Hazel, Glen, and Maxey all had different ideas.

They had agreed on the sunburst pattern, but according to Hazel; "Glen wanted it to be red and white, Maxey like blue and white, and I thought yellow and white would look best. As you can see, Maxey is the one who actually loaded the spray gun." The Cub’s Continental A65-8F engine was given a complete overhaul and modified to produce 75 h.p. instead of its normal 65. New cowlings, windshield, side windows, tailwheel, and metal prop were installed. Added "extras" like chromed cylinder heads and top shrouds, streamlined bungee covers, a personalized Cub bear emblem, radio gear, and a new interior made Hazel's Clipped Wing Cub one of a kind.

In the spring of 1969, the Cub was trucked back to Ottumwa airport for final assembly. Hazel made the first test flight herself and then flew the Cub back to it’s home at SIG FIELD. Pilots who’ve had a chance at the controls of Hazel’s Clipped Wing say it is the sweetest flying Cub they’ve ever flown. Most modelers feel the same way! Over the years, Hazel moved on to snappier and more powerful aircraft for her aerobatic flying, but none has captured the attention and affections of modelers worldwide as much as the little blue and white Cub. It's a very special example of America's favorite airplane!

Build A Standard J-3 Or A Clipped Wing Cub

You can build either a standard PIPER J-3 CUB (84-1/2" wingspan) or a CLIPPED WING CUB (68-1/4" wingspan) from this kit. All of the parts to build either version are included in the kit. The differences between the J-3 and the CLIPPED WING are clearly shown on the full-size plans and are noted in the building instructions. Decide which version you want to build and pay close attention to the instruction sequence as you proceed.

Engine Selection

Engine choices for the 1/5-scale Piper J-3 Cub are many. When selecting an engine, please keep in mind that the Cub is by nature a lightly loaded airplane meant to be flown slow. Over-powering this model is totally unnecessary and not at all recommended.

We’ve found that 4-stroke engines in the .45 - .65 displacement range give the Cub outstanding flight performance. It just looks and sounds "right" with a 4-stroke in the nose. Our preferred installation is to side-mount the engine.

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Typically 4-strokes have an exhaust stack/muffler which is adjustable in direction, so there shouldn't be any special installation problems. The exhaust can be easily directed outside the cowling.


2-stroke engines also fly this airplane very nicely. Any plainbearing or bearing equipped .40 - .46 cu. in. sport engine would be a good choice. For example, a great choice would be the Irvine .46 engine. Like all Irvine engines, the .46 is powerful, reliable, and quiet.

Our preferred installation is to side-mount the engine. You can use the engine’s stock muffler, but in most cases that will necessitate cutting away a large portion of the side of the cowling to clear the muffler. A better alternative is to use an "after market" muffler, such as the J’TEC #JTC605 Universal In-Cowl Muffler shown here. This type of muffler will be completely enclosed inside the cowling. Use rubber extensions on the exhaust tubes to extend them out the bottom of the cowl.

Whatever engine you choose, take the time to carefully break it in according to the manufacturer's instructions. A good running, reliable engine is a minimum requirement for the enjoyment of this or any R/C model aircraft.


Radio Equipment

The Piper J-3 Cub requires a standard 4-channel radio system and five standard servos. We have used and can highly recommend both the Airtronics and Hitec radio systems. For reference, this assembly manual shows the installation of an Airtronics radio system with standard servos. In addition, you will need two aileron 24" servo lead extensions and an aileron servo Y-harness for connection to the receiver.


Required Tools

For proper assembly, we suggest you have the following tools and materials available:

Razor SawHobby Knife with sharp #11 Blades
ScissorsDiagonal Wire Cutters
Masking TapeSandpaper and Sanding Blocks
Paper TowelsHeat Iron and Trim Seal Tool
Small Allen Wrench AssortmentPin Vise for Small Dia. Drill Bits
Screwdriver AssortmentPliers - Regular & Needle Nose
Power Drill With Selection of BitsSoldering Iron, Solder and Soldering Paste Flux
A selection of glues - SIG Thin and Thick CA and SIG Kwik-Set 5-Minute Epoxy
Clear Dope For Fuel-Proofing Engine Compartment
Threadlock Compound, Such as Loctite® Non-Permanent Blue
Dremel® Tool With Selection of Sanding and Grinding Bits


It has been correctly said that the difference between a good model and a great one is sandpaper and the knowledge of how to use it. In these instructions you will note that we often mention "sanding blocks". An assortment of different size sanding blocks are indispensable tools for all model construction. A sanding block will give you a much flatter, truer result than you would get with an unbacked, limp piece of sandpaper held in your fingertips. There are many styles of commercially made sanding blocks available in hobby shops, or you can make your own.

We suggest using 80 grit sandpaper during general construction, then switching to 220 or 360 grit for final sanding, before covering.

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The following is a complete list of all parts contained in this kit. Before beginning assembly, we suggest that you take the time to inventory the parts in your kit.

COMPLETE KIT PARTS LIST
Laser-Cut Balsa Sheets
13/32" thick Sheet #3: W-2 33/32" thick Sheet #4: W-4 23/32" thick Sheet #5: W-5, TB2 13/32" thick Sheet #6: J-3 Cub - Front Spar Web, Rear Spar Web
23/32" thick Sheet #8: Aileron Top sheet 23/32" thick Sheet #9: Aileron Bottom Sheet 13/32" thick Sheet #10: Cabin Top Sheeting, F-1A , F-2, F-5A, Rear Center Web, Top Front, Top Rear, Window Frame, Window Front, Window Rear 13/32" thick Sheet #11: Aileron Ribs, TB-1, TR-1, TR-2, TS-1, TS-2, TS-3, W-6
23/32" thick Sheet #12: J-3 Cub - Bottom Leading Edge Sheet 15/16" thick Sheet #13: E-1, E-3, E-4, E-5, E-6, FN-1, FN-3, FN-4, S-1, S-4, S-5, S-6, R-9 15/16" thick Sheet #14: E-2, FN-2, FN-5, R-1, R-2, R-3, R-4, R-5, R-6, R-7, R-8, S-2, S-3 11/8" thick Sheet #16: Right Fuselage Side, Tail Mount
11/8" thick Sheet #17: Left Fuselage Side, Tail Mount 13/32" thick Sheet #18: Fuselage Doublers 11/8" thick Sheet #19: F-5, F-6, Fuselage Bottom Rear 11/8" thick Sheet #20: F-2 Angle Guide, Fuselage Top Rear, Tail Fairing
13/32" thick Sheet #23: Cabin Window Doublers, Elevator Exit, F-6A, Rudder Exits 23/32" thick Sheet #24: C.W. Cub - Bottom Leading Edge Sheet 13/32" thick Sheet #25: C.W. Cub - Front Spar Web, Rear Spar Web, Triangle
Laser-Cut Plywood
11/8" Lite-Ply Sheet #1: W-1,W-3, CR-2 11/8" Lite-Ply Sheet #2: Cabin Floor Front, Cabin Floor Rear, F-4A, F4-B, Nose Top, Tank Floor, Window Braces 11/8" Lite-Ply Sheet #21: Cabin Widows 11/8" Lite-Ply Sheet #26: F-3, Hatch Dowel Support, Hatch Mount, Nose Bottom, Latch Pivot, Stab Mount, Tailwheel Mount
11/8" Lite-Ply Sheet #27: Aileron Horn Mount, Center Section Web, F-7, Main Gear Doublers, Servo Tray, Servo Tray Doublers, Wing Tip 11/16" Birch Ply Sheet #7: Servo Hatch, and Cabin Hatch Hard Points 13/32" Birch Ply Sheet #15: CR-1A, Strut Mounts, W-1A 11/4" Birch Ply Sheet #22: F-1
Balsa Wood Sticks
133/32"x1/4"x36" Cap Strips, Fuselage Side Stringers 51/4"x1/4"x36" Main Spars, Fuselage 53/16"x3/16"x36" Rear Spars, Fuselage 51/8"x1/4"x36" Wing Spars
31/8"x1/4"x48" Aileron Spars & Fuselage Stringers 41/8"x1"x24" Wing T.E. Cap & Aileron Cap 25/16"x5/16"x36" Fin, Rudder, Stabilizer & Elevator 23/32"x3/32"x36" Fuselage Corner Stringer
11/2"x1/2"x36" Balsa Triangle: Firewall & Main Gear Braces 236" long Pre-Shaped Leading Edges
Balsa Wood Sheets
23/32"x1"x36" Wing T.E. Sheeting 43/32"x3/4"x24" Wing Aileron Bay Sheeting 43/32x3"x36" Wing & Nose Sheeting 13/16"x6"x8" Main Gear Fairing
Balsa Wood Blocks
21/2"x1"x2" Wing Tip Block
Hardwood
13/16"odx6" Dowel 31/8"odx6" Dowels 15/16"odx1-1/2" Dowel with 5/64" id hole thru center 41/4"x3/4"x7/8" Basswood Aileron Servo Mounts
13/8"x3/8"x3" Basswood Cowl Mount Blocks 11/4"x1/2"x16" Basswood Grooved Hatch Rails 23/8"x3/4"x4-15/16" Basswood Grooved Landing Gear Blocks 11/8"x1/4"x24 Spruce Fuselage Top Stringer
41/4"x1/2"x24-1/4" Spruce Front Struts 21/4"x3/8"x24-1/4" Spruce Rear Struts
Molded Parts
1 .030" clear Molded Windshield 1.015" clear Molded Right Side Window 1.015" clear Molded Left Side Window 1set Molded ABS Plastic: Dummy Engines
1set Molded ABS Plastic: Dummy Engine Shrouds 1Molded Fiberglass Cowling
Wire Parts
15/32" dia.x18-3/8" Formed Main Landing Gear 15/32" dia.x20" Formed Landing Gear Brace 11/8" dia.x7" Formed Top Shock Strut 11/8" dia.x13" Formed Bottom Shock Strut
13/32" dia.x9" Formed Elevator Joiner 11/16" dia.x3-7/8" Formed Front Door Lock 11/16" dia.x4-7/8" Formed Rear Door Lock 120' roll Soft Copper Wire
910" long 2-56 Threaded Steel Rods

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Hardware Bag
31-72x1/2" Brass Bolts (Slotted Rd. Hd.) 31-72 Brass Hex Nuts 26#2x3/8" Sheet Metal Screws 2#2x1/2" Sheet Metal Screws
42-56x3/8" Bolts (Slotted Rd. Hd.) 42-56x3/8" Bolts (Flat Head) 112-56 Hex Nuts 42-56 Blind Nuts
6#2 Flat Metal Washers 84-40x3/8" Bolts (Slotted Rd. Hd.) 24-40x3/8" Bolts (Socket-Head) 24-40 Hex Nuts
104-40 Blind Nuts 46-32x3/4" Bolts (Slotted Rd. Hd.) 46-32 Blind Nuts 2#6 Flat Metal Washers
28-32x1/2" Bolts (Socket-Head) 19/64" Allen “L" Wrench: for 8-32 bolts 28-32 Blind Nuts 2#8 Flat Metal Washers
25/32" id Wheel Collars 26-32x1/8" Headless Set Screws: for wheel collars 11/16" Allen “L" Wrench: for wheel collars 24-40x3/8" Nylon Bolts (Socket-Head)
2Small Nylon Control Horns 1Medium Nylon Control Horn 4Nylon Landing Gear Straps 32-56 Nylon R/C Links: Ailerons(2), Elevator(1)
62-56 Metal R/C Links: Rudder(2), Tail Brace Wires(4) 72-56 Solder Links: Elevator(1), Ailerons(2), Tail Brace Wires(4) 2brass Pushrod Connector Bodies 24-40x1/8" Socket-Head Bolt: set screw for pushrod connector
41/4" od Nylon Retainers: pushrod connectors(2), door latch(2)
Easy Hinge Bag
173/4"x1" SIG Easy Hinges
Nylon Hinge Bag
2Molded Nylon Hinges 4Straight Pins
Rudder Pull-Pull Bag
1.021" dia.x6 ft. Steel Cable 43/32" odx1/2" Aluminum Tubes 22-56 Rigging Couplers 22-56 Hex Nuts
11/8" dia.x2" Heat-Shrink Tubing
Tail Wheel Assembly Bag
13/32" id Wheel Collar 14-40x3/16" Mounting Bolt (Slotted Rd. Hd.) 24-40x3/8" Mounting Bolts (Slotted Rd. Hd.) 24-40 Lock Nuts
26-32x1/2" Mounting Bolts (Slotted Rd. Hd.) 26-32 Square Anchor Nuts 1Nylon Tailwheel Bearing 1Nylon Rudder Horn
1Nylon Tiller Bar 1Formed Leaf-Spring 1Formed Tailwheel Wire 2Steering Springs
Miscellaneous
2Glass-Filled Engine Mounts 2.130" od x36" Nylon Tubes: Elevator Pusrod, Throttle Pushrod 1.190" od x36" Nylon Tube: Elevator Pushrod Sleeve 11/16" od x24" Steel Cable: Throttle Pushrod
1Aluminum Fueler Mount 2.060" thick Aluminum: Lower Strut Fittings 6.060" thick Aluminum: Upper Strut Fittings, Fuselage Strut Fittings 17/8" od x17-1/2" Aluminum Wing Joiner Tube
1.880 id x17-1/2" Phenolic Wing Joiner Tube 35/32" od x12" Brass Tube for Jury Struts 12"x20" Glass Cloth Tape 1SIGDKM282A J-3 Cub Wing Decal
1SIGDKM282B J-3 Cub Fuselage Decal 1SIGDKM282C J-3 Cub Bear Decal 1SIGDKM283A Clipped Wing Cub Fuselage Decal 1SIGDKM283B Clipped Wing Cub Bear Decal
1Printed Instrument Panel 1Plan Sheet 1 1Plan Sheet 2 1Plan Sheet 3
1Plan Sheet 4 1Assembly Manual


Wood Parts Identification

Dimensioned balsa and hardwood parts are easily identifiable by comparing their shape and dimensions to the plans and to the COMPLETE KIT PARTS LIST. On the other hand, proper identification of the different wing ribs, wing sheeting, fuselage formers, etc., can be confusing because some of them are very similar looking, when in fact they are quite different.

Use the following KEY TO LASER-CUT PARTS diagrams to correctly identify each part. Use a pencil to label each part with its name or number, before removing the parts from the laser-cut sheets.

IMPORTANT:
The laser cut parts contained in this kit are extremely accurate in outline and fit. They are meant to be used directly out of their sheets, without any trimming or sanding unless specifically called for in the instructions. The laser cutting process produces a brownish edge to the parts and, in some cases, a blackout edge may result when cutting harder plywood parts.

CA adhesives work perfectly on these parts and they do not need to be sanded to remove the discolored edges. In fact, sanding the edges of laser cut parts can change their shape and/or dimensions, resulting in a poor fit. DO NOT edge sand the laser cut parts in this kit.

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