Sig Mfg. Co., Inc...401-7 S Front St ...PO Box 520....Montezuma IA 50171-0520

Welcome to the sport of Radio Control flying, and thank you for choosing the SIG KADET LT-40.

We understand how anxious you are to get started building and flying your KADET LT-40, but please take a few minutes right now to study the full-size plans while you page through these instructions. This will familiarize you with the general layout of the airplane and the building sequence, making the entire project easier in the long run.


In order for your KADET LT-40 to fly as well as it was designed to, it must be carefully assembled. A model airplane that is not built properly will not fly properly! Remember to work slowly and follow the instructions exactly. SIG, as the kit manufacturer, can provide you with a proven aerodynamic design, quality materials, and detailed instructions, but ultimately the flyability of your finished model depends on how well YOU put it all together.

Customer Service

SIG Mfg. Co., Inc. is totally committed to your success in building and flying the KADET LT-40. Should you encounter any problem building this kit, or find any missing or damaged parts, feel free to contact us by mail or phone.

401-7 S Front St
P.O. Box 520
Montezuma, IA 50171-0520

SIG MODELERíS HOTLINE: 1-641-623-0215 Weekdays, 7:00am - 4:30pm Central


Flying machines of any form, either model-size or full-size, are not toys! Because of the speeds that airplanes must achieve in order to fly, they are capable of causing serious bodily harm and property damage if they crash. IT IS YOUR RESPONSIBILITY AND YOURS ALONE to assemble this model airplane correctly according to the plans and instructions, to ground test the finished model before each flight to make sure it is completely airworthy, and to always fly your model in a safe location and in a safe manner. The first test flights should be made only with the assistance of an experienced R/C flyer.

The governing body for radio-control model airplanes in the United States is the ACADEMY OF MODEL AERONAUTICS, sometimes referred to as the AMA. The AMA SAFETY CODE provides guidelines for the safe operation of R/C model airplanes. While AMA membership is not mandatory, it is a good idea and we encourage all new R/C fliers to join the AMA. Membership in the AMA provides you with important liability insurance protection in case your R/C model should ever cause serious property damage or personal injury to someone else.
For more information, contact:
5161 East Memorial Drive
Muncie, IN 47302
Phone: 765-287-1256

Limit of Liability

The craftsmanship, attention to detail, and actions of the builder/flyer of this model airplane kit will ultimately determine the flight performance and safety of the finished model. SIG MFG. CO.ís only obligation shall be to replace those parts of the kit proven to be defective or missing. The user shall determine the suitability of the product for his or her intended use and shall assume all risk and liability in connection therewith.

Die-Cut Balsa Wood Sheets
2Sheet No. 1: wing ribs W1, W2 2Sheet No. 2: wing ribs W3, W4 8Sheet No. 3: wing ribs W5 2Sheet No. 4: wing sheeting WS-T1, WS-B1
1Sheet No. 5: wing sheeting WS-T2, WS-B2 1Sheet No. 6: wing sheeting WS-T3, WS-B3
Die-Cut Plywood Sheets
2Sheet No. 7: FS-R fuselage side rear, F8 fuselage former 2Sheet No. 8: FD fuselage doubler, HATCH TONGUE 1Sheet No. 9: FB-F fuselage bottom front, FB-R fuselage bottom rear 1Sheet No.10: FT-R fuselage top rear, HATCH, WINDSHIELD
1Sheet No.11: F4 fuselage former, F5 fuselage former, DTG dihedral tip gauge, DRG dihedral root gauge 1Sheet No.12: F7 fuselage former, TANK FLOOR 2Sheet No.13: FS-F fuselage side front, WTP wing tip plate 1Sheet No.14: ASM aileron servo mount, FSM fuselage servo mount
Sawn Balsa Wood Parts
Sawn Plywood Parts
Laser-Cut Parts
21/8" thick balsa wood SW-1, SW-2, SW-3 shear webs 15/16" thick balsa wood STAB L.E. JOINER 21/8" thick birch plywood MADB main dihedral brace 11/4" thick birch plywood F1 firewall
11/8" thick lite-ply F2 fuselage former 11/8" thick lite-ply F3 fuselage former 11/8" thick lite-ply F6 fuselage former
Balsa Wood Sticks
41/4"x3/8"x36" REAR SPARS, TOP & BOTTOM 41/4"x1/2"x10-1/8" SPAR DOUBLERS, TOP & BOTTOM 25/16"x5/16"x36" STABILIZER PARTS, FIN PARTS 35/16"x1/2"x36" STABILIZER PARTS, FIN PARTS
23/8"x3-13/16" BALSA TRIANGLES for firewall support
Special Pre-Shaped Balsa Wood Parts


Hardwood Parts
41/4"x1/2"x36" MAIN WING SPARS, TOP & BOTTOM 13/8"x1"x3-1/2" GROOVED LANDING GEAR BLOCK 21/2"x1"x1" L.G. ANCHOR BLOCKS (in Hardware Pack #1) 25/16" dia. x5-1/2" DOWELS (in Wire Parts Pack)
Wire Parts Pack
21/16" dia. x18" STRAIGHT MUSIC WIRE 610" THREADED STEEL RODS (threaded one end)
Hardware Pack #1
44-40 x1/2 MOUNTING BOLTS (Slotted Round Head) 44-40 x1 MOUNTING BOLTS (Slotted Round Head) 46-32 x3/4 MOUNTING BOLTS (Slotted Round Head) 44-40 AIRCRAFT LOCK NUTS
44-40 BLIND NUTS 46-32 BLIND NUTS 16-32 x1/4 SELF-TAPPING SCREW (Slotted Panhead) 5#2 x1/2 SHEET METAL SCREWS (Slotted Panhead)
Hardware Pack #2
Miscellaneous Parts
2LARGE DIA. NYLON PUSHROD TUBING, 3/16" O.D. x26-5/8" long 12" dia. SIG SPINNER, complete 18 ounce DU-BRO FUEL TANK, complete 23" dia. KAVAN MAIN WHEELS

Wood Parts Identification

Wood parts such as standard stick and sheet stock, leading edges, trailing edges, ailerons, elevator, etc., are all easily identifiable by comparing their shape and dimensions to the plans and the KADET LT-40 COMPLETE PARTS LIST; therefore we did not feel that there was any need to label these parts. 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, but in fact they are quite different. Wherever possible, we have labeled (printed) these parts. The die-cut plywood parts are not labeled. They can be identified using the plans and the KEY TO DIE-CUT PLYWOOD PARTS.

Use a pencil to label each part with its name or number, before removing the parts from the die-cut sheets. Use the KEY TO LASER-CUT PARTS to identify and label the following laser-cut parts: STAB L.E. JOINER, MADB, F1, F2, F3, and F6. Use the SHEAR WEB IDENTIFICATION DIAGRAM to identify and label the sawn balsa wood SHEAR WEBS SW-1, SW-2, and SW-3.

Be careful when removing parts from die-cut sheets. If difficulty is encountered, do not force the part from the sheet - use a modeling knife to cut it free. Handle the removed parts carefully, as long parts (such as the fuselage sides) are fragile until glued into a structural unit. Sort the different parts into individual piles to avoid confusion during building. Save all scrap wood until the model is finished. You never know where a small piece of scrap wood may come in handy during construction.


NOTE: The edges of all the laser-cut parts have a "burnt" appearance varying from light brown to dark black, depending upon the thickness and type of material the part is made of. Our tests indicate that a slight discoloration of the edges does not significantly affect the bonding ability of these parts. The lightly discolored parts F2, F3, F6, MADB, and Stab L.E. Joiner can be installed as is, without any need to try to clean the edges. However we recommend that the black edges of former F1, made of 1/4" thick plywood, be lightly sanded with an 80 grit sanding block to remove the loose black soot. It's not necessary to sand every bit of black off (you don't want to change the size of the part). Sand until you can run your finger lightly over the edge without picking up any black color (see photos of sanded F1 in the fuselage section).


About The Wood In The Kit

We strive to supply good quality materials in all SIG kits. However wood is a highly variable material (unlike man-made plastic or metal), so every single wood part in a kit will probably not have flawless appearance. Often things that look like an imperfection are actually quite acceptable when you consider the function the part will serve. Mineral stains and tiny knots do not seriously affect balsa wood strength. Also, there is a natural tendency for some balsa sticks and sheets to immediately bow upon being cut off from a perfectly square block due to internal stresses in the wood. In most cases, bows in wood parts (such as leading edges) readily straighten out as they are glued into a structural unit. Likewise Lite-Ply fuselage sides, formers, and doublers that are warped will usually straighten right out when they are glued in place. If you are in doubt about the suitability of any part in your kit for itís intended purpose, call or write to us for assistance and/or a replacement part.

Additional Components Needed

The following items are not supplied in this kit but are needed to complete the KADET LT-40. Because of the wide variety of brands available and the influence of personal preferences, the choice of these items is left to the builder to select.


.30 to .40 cu. in. 2-Stroke Glow R/C Engine w/Muffler, or .40 to .50 cu. in. 4-Stroke Glow R/C Engine w/Muffler

Engines larger than those listed are not recommended! Use of oversize engines will cause balance problems and may overload the structure of the airplane. The KADET LT-40 has a light wing loading and does not need a super "hot" engine to fly well! Any normally ported .40 2-stroke glow R/C engine will provide adequate power to fly the KADET LT-40. We believe that the .40 2-stroke glow R/C engine will be the most commonly used engine in the KADET LT-40, so that is what weíve shown on the full-size plans and in this instruction book.



Propellers are a subject that can fill a book all by themselves! There are a large variety of propeller sizes available, and selecting the best one to use on your KADET LT-40 will depend mostly on which engine you end up buying. Refer to the instruction sheet that comes with your engine for a recommended propeller size. If the engine manufacturer lists several possible sizes, pick the one that sounds like it is for a slower flying model - choose "sport or scale" instead of "pattern or racing". Also, be sure to read "THE BASICS OF RADIO CONTROL" book for more tips on propellers. As a general rule, if you are going to use a normal .40 2-stroke glow R/C engine in your KADET LT-40, you will undoubtedly use a 10-6 propeller, as noted on Plan Sheet 1.


Radio Control System

You will need a (minimum) 4-channel radio control system with 4 servos to operate the ailerons, elevator, rudder, and engine throttle of your KADET LT-40. The KADETís fuselage is spacious enough that any common brand of radio equipment with standard size servos and battery pack can be used. Be certain that your radio system transmits on one of the FCC-approved frequencies for R/C model aircraft. See "THE BASICS OF RADIO CONTROL" book for more information on radio equipment and frequencies.


1/2"x8"x12" Soft Foam Rubber (such as SIGRF-240)

Used to protect your radio receiver and battery pack from damaging engine vibration. Also used as packing around the fuel tank and radio components to keep them from shifting around in flight.


#67 Rubber Bands (such as SIGSH-747)

Used to hold the wing on the fuselage. Always use at least 12 rubber bands when flying. Replace any bands that have stretched out or have become oil soaked.


3 Rolls of Covering Material (such as SIG AEROKOTE COVERING)

Although the KADET LT-40 can be finished with a wide variety of covering materials (some which need to be painted and some which donít), this instruction book assumes that the beginner will use one of the popular pre-finished iron-on plastic film coverings. In the Covering and Finishing section of these instructions you will find a "COVERING CUTTING DIAGRAM" which shows how to cut 3 standard (26" wide x 6 ft. long) rolls of iron-on film covering to fit the KADET LT-40.


4 oz. of Fuel-Proof Paint (such as SIG SUPERCOAT DOPE)

For fuel-proofing the engine compartment, tank area, wing saddle, and ends of the wing dowels.


- Light-Weight Wood Filler

For filling holes, nicks, and dents after assembly of the model, but before covering. Regular household "wall repair" or "spackling" compound (3M, Red Devil, DAP, etc.) works well for this. There are also several excellent "model fillers" available at the hobby shop. Just make sure whatever you use is light weight and sands easily. Do not use household patching plaster - itís way too heavy!



There are so many different types of glue available today for model airplane construction that it can be confusing to even the experienced modeler. To simplify matters, most model airplane glues can be classified as one of four basic types:

  1. Cyanoacrylate Adhesives, such as SIG CA, are very strong and bond in just seconds. Dramatically speeds up building time! Different vicosityís and cure times are available to suit all areas of model construction.

  2. Two-Part Epoxy Glues, such as SIG-KWIK-SET (5-minute cure) and SIG EPOXY (3-hour cure), are super strong but too heavy for general construction. Often used in high stress areas such as the firewall, landing gear, and wing joiners.

  3. Water-Based Glues, such as SIG-BOND (aliphatic resin), are very safe and easy to use. Excellent for general construction, although somewhat slow drying.

  4. Solvent-Based Model Cement, such as SIG-MENT, is the oldest form of traditional model airplane glue. Still used for general construction by some modelers - especially when building super light weight free flight models.

You could build the KADET LT-40 using any of these four basic types of glue. Each type has different characteristics and advantages, and all of them will result in a bond that is stronger than the wood materials being glued together. Often times the choice of which type to use boils down to a matter of personal preference based on past experience. However, if you want to get your KADET LT-40 into the air as quickly as possible, we recommend that you use CA glue for the majority of the assembly of this kit. CA glue is not only fast and strong, but it also makes it possible to do some unique things in the construction sequence. For instance, since CA glue has the ability to penetrate into an already assembled joint, we can first assemble the interlocking fuselage parts "dry" (without glue), then check and adjust the alignment, and finally apply CA to the pre-assembled joints. This makes it very easy to build a straight and true fuselage in a very short time. If the use of CA glues is new to you, please read "TIPS ON USING SIG CA", included in this kit.

The instructions in this book are written assuming the use of MEDIUM CA glue for all steps, unless otherwise noted. In other words, if an instruction simply says "glue" part A to part B - use MEDIUM CA! If THIN CA, SLOW CA, EPOXY GLUE, or SIG-BOND GLUE would work better in a specific instance, we will call for it.

Workshop Tools And Supplies

As the old saying goes, "Having the right tool makes the job easy". That certainly holds true with building model airplanes as well as anything else. Below is a list of the tools we feel are the minimum required to speedily and accurately assembly this kit, and to build other model airplanes in the future. Some of them are common household tools that you probably already have, while some are special "modeling" tools that you will have to purchase at the hobby shop. While there are many more special modeling tools available, and they all do a wonderful job in certain areas, these are the basics with which to get started in the hobby. Like the rest of us, eventually you will add others to your workshop as the need arises.

- Building Board - 12"x36" minimum size- This can be any flat surface that will accept and hold pins - such as insulation board, foam board (cardboard laminated to both sides of a foam sheet), cork bulletin board, soft plywood, a reject "door core" from the lumber yard, etc. The most important thing is that the board must be perfectly flat and untwisted! Your wings and tail surfaces will be built on this board, and if the board is twisted or bowed, the parts you build on it will assume the same shape and your model will not fly properly.

The building board youíll see us using in the photos in this book is an 18" x 48" piece of 3/4" thick plywood (perfectly flat!), with a same sized piece of 1/4" thick foam board stuck down on top of the plywood with double-sided sticky tape. The plywood provides the rigidity and flatness we need, and the semi-flexible foam board lays flat on the plywood and gives us a surface to push pins into. All materials were obtained from the local lumber yard. Insulation board or cork sheet would make a good substitute for the foam board, if that is not available.


- Wax Paper
Used to cover the plans so that parts are not accidentally glued to them.


A Few Dozen T-Pins (such as SIGSH-310)
For holding parts together during construction.


Masking Tape or Scotch Tape
For holding parts together during construction.


#32 or #64 Rubber Bands (such as SIG #SH-364 or SIG #SH-366)
Used to hold the fuselage parts together during initial assembly.




Ruler or Tape Measure


Do not use a ball-point or felt-tip pen for making marks on the model during construction. If not sanded off, ink marks may show through the modelís final finish. Use a pencil instead of a pen.


Modeling Knife (such as X-Acto #1 knife with extra #11 blades)
For general cutting.


Razor Saw (such as X-Acto #75300 or Zona #500)
For cutting thicker wood pieces.


1/2-Dozen Single-Edge Razor Blades (such as SIG #SH-283)
For cutting and trimming covering material.


Long Metal Straight Edge (such as SIG #SE-236)
To aid in making long straight cuts in wood and covering material.


Triangle (such as metal SIG #TR-036 or plastic draftsmanís triangle)
For squaring up parts during assembly and to aid in making short straight cuts in wood and covering material.


Assorted Screwdrivers


Assorted Hex "Allen" Wrenches


Regular Pliers


Drill and 1/16", 3/32", 1/8", 5/32", 5/16" Drill Bits


Needle-Nose Pliers with cutting jaws


Flat File
For cutting, bending, and shaping pushrod wires. For removing burrs and sharp edges from wire parts.


Soldering Iron, Rosin Core Solder, and Soldering Paste Flux
There is one part in this kit that needs to be soldered. (If you donít have a soldering iron, perhaps you can borrow one for this part of the construction.)


Covering Iron
For applying iron-on covering material. Although a household iron can be used to apply covering, smaller easier-to-use irons specifically designed for model covering are available at the hobby shop. (Like the soldering iron, perhaps you can borrow one from another modeler if you are covering your first airplane.)


80 and 220 Grit Sandpaper
We prefer either garnet or silicone carbide type open-coat sandpaper. Use the 80 grit to rough sand and shape parts. Use the 220 grit to fine sand the entire model prior to covering. Sand with the grain of the wood whenever possible. Always use fresh, sharp sandpaper. Sharp sandpaper will cut through glue and hard materials easily, giving an even surface. Dull sandpaper will require more pressure and may gouge the surface.


- Sanding Blocks
The instructions will call for you to sand some parts of the model using a "sanding block", which is simply a piece of sandpaper backed up by a solid, flat block of wood, plastic, or whatever. 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. An assortment of different size sanding blocks are indispensable tools for all model construction. There are many styles of commercially made sanding blocks available in hobby shops, or you can make your own.

A good general purpose sanding block can be made by wrapping a full-size standard 9"x11" sheet of sandpaper around a piece of hardwood or plywood, as shown below. This is the most commonly used sanding block in our workshop! Use screws or thumbtacks along one edge to hold the overlapped ends of the sandpaper in place. Put 80 grit sandpaper on the block during general construction, and then switch to 220 grit sandpaper for final sanding just before covering (or make yourself two of these blocks, one for each grit sandpaper). There will be other times when a slightly smaller sanding block is easier to manage. Also, you can make a small sandpaper "file" by simply gluing a strip of 80 grit sandpaper onto a scrap plywood stick. Sandpaper glued or taped to different size hardwood dowels are great for sanding inside curves and holes.

Last but not least, for sanding really large areas, glue 80 grit sandpaper onto a 24" or 36" long piece of aluminum "channel" or "T-Bar" stock (most hardware stores carry a rack of aluminum extrusions in various sizes and shapes).

How To Use These Instructions

Like a full-size airplane, the KADET LT-40 is built by first constructing several basic structures - the FUSELAGE, WINGS, STABILIZER, FIN, etc. - which are then assembled into a completed airplane. These instructions will take you step-by-step through the construction of each basic structure and then the final assembly.

How To Use The Plans

There are two sheets of Plans included in this kit. The plans will be used in several ways. They will help you identify all the parts and determine the relationship of all the parts to each other. They will also be used as a building pattern for the Wing Panels, Stabilizer, and Fin - which will be assembled directly on top of the plans. The plans also show how we would install a typical radio and engine in the KADET LT-40. By referring to the examples shown on the plan, you should be able to properly install your radio and engine, even if they are not exactly the same as what is shown on the plan.

Everything on the plans is drawn FULL-SCALE, or ACTUAL SIZE (except for the Wing Front view which is half-size) to show the correct size, shape, and relationship of all the parts to each other.

The plans show the model completely assembled. Unfortunately this often covers up the important parts inside the model, making it hard to understand how things fit together. In normal drafting practice, parts hidden inside the model would be shown with dashed lines, and you will find many areas of the plan that do use this method. However in areas where there are so many hidden parts that it would be confusing to use so many dashed lines, we have elected to use "cutaway views". Cutaway views make it appear as if a portion of a part has been cut out and removed. This is done to clearly show the parts that are immediately under the cutaway part. For instance, on Plan Sheet 1 we have used a cutaway to completely remove almost all of the left fuselage side (starting between Formers F4/F5 and going forward) so that the details inside the fuselage could be clearly seen. On Plan Sheet 2 there are several small cutaways in the wing sheeting to allow details underneath to be clearly seen.

NOTE: The cutaways on the plan do not mean that the parts should actually be shaped that way!

Whenever building a structure directly on top of the plans (like the Wing Panels, Stabilizer, or Fin), you must first tape or pin the plan onto your building board and then cover it with a layer of wax paper. The wax paper will keep excess glue from sticking the model parts to the plans. As you add parts to the structure, any parts which naturally come in contact with the plans should be firmly pinned to the plan/building board with T-Pins. Take a look at the photos in these instructions of the wing construction and you will see what we mean. In the pictures you will see that lots of T-Pins have been used to anchor the parts firmly in position on the plans.