GREAT PLANES PT-20 Instruction Manual
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GREAT PLANES PT-20 Instruction Manual

Pt-20; pt-40 great planes
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Instruction Manual

Great Planes
®
Model Manufacturing Co. guarantees this kit to be free from defects in both material and workmanship at the date of
purchase. This warranty does not cover any component parts damaged by use or modification. In no case shall Great Planes' liability
exceed the original cost of the purchased kit. Further, Great Planes reserves the right to change or modify this warranty without
notice.
In that Great Planes has no control over the final assembly or material used for final assembly, no liability shall be assumed nor
accepted for any damage resulting from the use by the user of the final user-assembled product. By the act of using the user-
assembled product, the user accepts all resulting liability.
If the buyer is not prepared to accept the liability associated with the use of this product, the buyer is advised to return this
kit immediately in new and unused condition to the place of purchase.
To make a warranty claim send the defective part or item to Hobby Services at the address below:
Include a letter stating your name, return shipping address, as much contact information as possible (daytime telephone number, fax
number, e-mail address), a detailed description of the problem and a photocopy of the purchase receipt. Upon receipt of the package
the problem will be evaluated as quickly as possible.
READ THROUGH THIS MANUAL BEFORE STARTING
CONSTRUCTION. IT CONTAINS IMPORTANT INSTRUCTIONS
AND WARNINGS CONCERNING THE ASSEMBLY AND
USE OF THIS MODEL.
PT24P03 V1.2 Printed in USA
™
WARRANTY
Hobby Services
3002 N. Apollo Dr. Suite 1
Champaign, IL 61822
USA
™
Champaign, IL
(217) 398-8970, Ext. 5
Fax: (217) 398-7721
airsupport@greatplanes.com
Entire Contents © Copyright 2004

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Summary of Contents for GREAT PLANES PT-20

  • Page 1: Instruction Manual

    In that Great Planes has no control over the final assembly or material used for final assembly, no liability shall be assumed nor accepted for any damage resulting from the use by the user of the final user-assembled product. By the act of using the user- assembled product, the user accepts all resulting liability.

  • Page 2: Table Of Contents

    Engine Selection ............4 Taxiing ................56 Wing Configuration ............4 Takeoff................56 PREPARATIONS ..............4 Flying ................56 Accessories Required to Complete Your PT-20....4 Landing ................57 Accessories Required to Complete Your PT-40....5 SOME MODELING TERMS & TRIVIA ......57 Suggested Supplies and Tools........5 FLIGHT TRIMMING ............61 Optional Supplies and Tools...........5...

  • Page 3: Introduction

    After all, an airplane so easy to takeoff, fly and land is a real confidence booster! Both the PT-20 and 40 are built from this manual. The PT family of trainers has been around for more than a Nearly all the parts in the PT series are identical so most decade.

  • Page 4: Decisions You Must Make

    There are many engines that will work well in your PT. (this is the important one), rubber bands allow the wing to For the PT-20 we recommend a 2-stroke sport engine shift if your wing tip contacts the ground (or an obstacle) such as the O.S.

  • Page 5: Accessories Required To Complete Your Pt-40

    (2) 2-1/2" Main Wheels (GPMQ4223) (4) 3/16" Wheel Collars (GPMQ4308) (2) 5/32" Wheel Collars (GPMQ4306) 2-1/4" Spinner (GPMQ4515 - white) In our busy workshop we use the Great Planes #64 Rubber bands - optional (HCAQ2020); Easy-Touch ™ Bar Sanders equipped with Great Planes...

  • Page 6: Setting Up Shop

    they'll need to do the best job possible. In some instances it Here is a suggested approach for building an inexpensive may not be clear exactly what the optional item is used for workbench. You will need (7) 6' - two-by-fours of good so, where appropriate, we’ve listed the page number and/or quality pine or fir, a 30"...

  • Page 7: Building Notes

    Building Notes The What and How of Adhesives • There are two types of screws used in this kit: Cyanoacrylate or CA glue has changed the way models are built more than any other advance in modeling Sheet metal screws are designated by a number and technology.

  • Page 8: Metric Conversion

    CA. The CA will cure “on the spot” before it has a chance to be Great Planes has several Epoxy formulations available for drawn away from the joint. the modeler. The two most often used epoxies are 6-minute and 30-minute.

  • Page 9: Get Ready To Build

    15 minutes and it's fully cured in about 1 hour. Great Planes Pro Wood Glue is an Aliphatic resin glue that works well on all types of wood. It is non-toxic, virtually odorless and dries clear. Some people are sensitive to the fumes and sanding dust derived from CA, so this is a good alternative for general modeling use.

  • Page 10: Die-Cut Patterns

    DIE-CUT PATTERNS FOR PT-20...
  • Page 11 DIE-CUT PATTERNS FOR PT-40...

  • Page 12: Build The Tail Surfaces

    – otherwise that area of the stab or fin will their locations. become thinner than the rest. This is a little more important on the PT-20. Hinge The Elevator and Rudder Note: One of the best ways to enhance the finish and appearance of your model is to do a good hinging job.
  • Page 13 B. Confirm that the line you have drawn is on center by flipping the part over and drawing a second line over the first. If the line is on center, you will see only one line. Draw a centerline at each hinge location. If you see two lines (as in the photo) go to step C.

  • Page 14: Build The Fuselage

    2" x 9" hinge material, then snip off the corners so they go into the slot easier. Note: If you are building the PT-20, make the hinge for the bottom of the rudder 3/8" wide. 8. Temporarily join the elevator to the stab with the hinges and widen any slots if required so they all match up.
  • Page 15 2. Examine the two fuse sides for blemishes, then 6. Repeat steps 4 and 5 to glue the doublers to the position them on your workbench exactly as shown in the inside of left fuse side. Be sure you are building a right photo with the best-looking sides facing down.
  • Page 16 15. Press a 6-32 blind nut (4-40 if you’re building the PT-20) into one of the holes in the back of the firewall (F-1C), then tap it gently with a hammer until it is fully seated. Put a few drops of thin CA on the outer edge of the 12.

  • Page 17: Join The Fuselage Sides

    3. Test fit, but do not glue, the die-cut 1/8" plywood tank floor and the firewall assembly between the fuse sides. The tab at the rear end of the tank floor should fit into the notch at the bottom of F-2 and the front of the tank floor should fit under F-1C on the back of the firewall assembly.
  • Page 18 6. Test fit the die-cut 3/32" balsa rear fuse bottom 11. Use HobbyLite filler to fill the gap around the between the fuse sides. Temporarily hold the bottom in pushrod tubes on the outside of the fuselage. position with a few strips of masking tape. 12.
  • Page 19 F-2. between the lines you marked. Note: If building the PT-20, the 3/32" balsa strips must be shorter than the ones shown in the photo to fit between the fuselage doublers.

  • Page 20: Install The Main Landing Gear

    Trim to fit bottom of fuselage 22. Locate the die-cut 1/8" plywood hatch retainer (HR). Center the hatch retainer on the bottom (unpunched surface) of the die-cut 1/8" plywood tank compartment hatch with approximately 3/8" protruding from the rear, then glue it in position. 25.

  • Page 21: Install The Engine

    6-32 x 1" screws with #6 flat washers (use 4-40 x 1" angular adjustments if necessary. Hint: If you have a screws with #4 washers if you are building the PT-20). Don’t numbered drill set, you may drill the holes with a #12 drill bit tighten the screws completely until after the engine has (#22 for the PT-20) for easier installation of the landing gear.
  • Page 22 Some modelers prefer to secure the engine to the mount with machine screws (not supplied) because they are easier to screw in. For both the PT-20 and 40, 4-40 x 3/4" screws are recommended. Use a #48 drill bit to drill the 4.

  • Page 23: Install The Nose Gear

    11. From the other piece of outer pushrod tube, cut the nose steering guide tube. It should be flush with the front of the firewall and extend 1/2" aft of F-2. Temporarily install the nose steering guide tube in the firewall and F-2. HOW TO MAKE A Z-BEND WITH REGULAR PLIERS.

  • Page 24: Attach The Stab And Fin To The Fuse

    Attach the Stab and Fin to the Fuse 4. Place a 5/32" wheel collar inside the nylon steering arm and start a 6-32 x 1/4" screw into the arm and the wheel collar (see the following sketch). Carefully cut the end off the steering arm so there are only two holes left.
  • Page 25 8. Remove the stab from the fuse. Mix up a batch of 30-minute epoxy and apply it to both the stab base and the stab between the reference marks. Reposition the stab on the fuse using the reference marks. Use T-pins to clamp the stab in position and recheck the stab alignment.

  • Page 26: Build The Wing

    Sand Reattach the rudder to check the hinge alignment. the fin, dorsal fin and the dorsal fin tab flat and smooth with Remember, the bottom hinge for the rudder on the PT-20 your bar sander and 150-grit sandpaper. is 3/8".

  • Page 27: Build The Wing Panels

    4. Add the 3/16" x 3/16" x 30" top forward spar. 5. Slide a scrap piece of 3/32" balsa under each R2 rib near the trailing edge (use 1/16" balsa for the PT-20). Fit the notched TE to the assembly with the ribs fully seated in the notches.

  • Page 28: Join The Wing Panels

    11. Use a razor saw to cut the TE, main spar assembly and LE about 1/16" longer than the lines you drew with the dihedral gauge. 7. Use thin CA for all points of contact starting with the notches along the TE (the Hobbico applicator tips really help for this step) .
  • Page 29 B. Temporarily install a 3/16" x 3/16" bottom forward spar in the right wing panel. Fit the 1A forward center rib assembly on the spar, then fit the FJ between the rib and the main spars. This should temporarily hold the rib in position for the next step.
  • Page 30 Clamp the joiners in position. Proceed immediately to the next step. PT-20 PT-40 A-wing 7" (178mm) 8" (204mm) B-wing 4-3/8"...

  • Page 31: Prepare The Wing For Sheeting

    C. Remove the dowel and rib doublers. Lightly coat both Prepare the Wing for Sheeting sides of the center rib and only one side of each rib doubler with epoxy. Reposition the doublers on the center ribs and clamp them until the epoxy cures. You will be instructed to glue the dowel in after the wing is sheeted.
  • Page 32 Do not attempt to cut the sheet with only one pass of the knife but make several passes, deepening each cut as you go. This will enable you to actually strip the wood by cutting, not splitting, the wood. This provides a smooth, straight edge instead of a jagged edge.
  • Page 33 plywood washout jigs directly under each tip rib – the jigs should stand vertically. Be certain the jigs are positioned correctly as noted in the photo at step 8. Hint: It helps if you can pin the TE and rear center rib to the work bench. This will keep the wing from sliding from side to side while you position the washout jigs.
  • Page 34 – to cut one more 2-5/8" wide strip and one 4-7/8" wide strip. STEP 23 & 24 FOR PT-20 MK II ONLY 23. Use your ballpoint pen and a drafting triangle to accurately mark and cut the last 1/16" x 3" x 30" balsa sheet into four 2-5/8"...

  • Page 35: Fit The Aileron Servo Tray

    4. Make a left and a right bottom center section sheet by gluing two pairs of previously cut sheets together along one edge. Trim and test fit each sheet to the bottom of the wing (you know the routine) but do not glue them in position yet.

  • Page 36: Wing Completion

    Wing Completion 4. Use a pliers to bend the wire torque rods so the threaded “arm” is ver tical when the torque rods are positioned on the trailing edge of the wing. 5. With the torque rods in the wing center TE’s, position the nylon bearing tubes so they do not restrict movement of the torque rods.
  • Page 37 12. While you’re working on the end of the wing, glue the 3/8" x 11-7/8" tapered balsa wing tips to each end of the wing with medium CA (the wing tips for the PT-20 are 5/16" x 10"). The wide part of the tapered tip goes on top.
  • Page 38 24. If you are building the PT-40, glue each 1/32" plywood wing protector to the top of the wing 1" from the center. If you are building the PT-20, the wing protectors should each be 7/8" from the center. Align the aft edge of the wing protector with the aft edge of the wing center TE.

  • Page 39: Reinforce The Wing

    3. Use your bar sander and 220-grit sandpaper to bevel the sides and front of the top edges of the die-cut 1/16" plywood wing bolt plate (see the photo at step 4). The side of the plate with the scored centerline is the bottom.

  • Page 40: Finishing

    the top of the wing at the front of the wing bolt plate (start at C. You must use a flat sanding block of some type when the trailing edge of the wing if you are building the rubber sanding flat areas such as fuselage sides/top/bottom, tail band-on wing).

  • Page 41: Cover The Structure

    Work out any wrinkles and air Great Planes model shop: pockets as you proceed with a back and forth motion. A. Cover your sealing iron with a Top Flite Hot Sock and E.

  • Page 42: Recommended Covering Sequence

    need to. Trim off the excess, then follow-up with your sealing iron to secure the bond. The idea behind this approach (which can be applied to any part of the model) is to pre-stretch the MonoKote film as it’s applied, removing the air pockets that can expand later causing sags and wrinkles.

  • Page 43: Final Hookups And Checks

    F. Perform the same operation for the other side of the TEMPORARY PIN stab and fin. TO KEEP HINGE CENTERED Applying windows. Use the patterns on the fuse plan (or make your own templates) to cut the window shapes from MonoKote film or self-adhesive MonoKote Trim Sheet.

  • Page 44: Install The Landing Gear

    Install the Landing Gear 5. Seat the landing gear wire in the landing gear rail on Skip step #1 if you are building the PT-20 the fuselage. Use a nylon landing gear strap as a guide to drill 1/16" pilot holes for the screws. Secure the landing 1.
  • Page 45 B. Insert the metal eyelets up from the bottom of the rubber grommets. This way the “lip” of the eyelet will be in contact with the servo tray when mounted. The rubber grommets will isolate the servo from vibration. C. Position the servo in the servo tray, then mark the location of the mounting holes.
  • Page 46 All standard servo horns should fit in the PT-40. If you are building the PT-20 some servo horns may interfere with each other or the side of the fuselage. To avoid this, shorten...

  • Page 47: Balance Your Model

    The balance point (CG) is shown on the plan and on the PT-40 is located 4-7/64" (104mm) back from the leading edge. For the PT-20 the balance If, at any point during the radio installation and hook up point is located 3-1/2"...

  • Page 48: Final Radio Hook Up

    slow down for landing. Moving the balance aft makes the model more agile, providing it with a lighter and snappier feel. Please start at the location we recommend and do not at any time balance your model outside the recommended range. 2.
  • Page 49 7. Once you have finished setting up the nose wheel steering, snap the nylon retainer on the connector under the servo horn. Remove the 4-40 screw, then reinstall it with thread locking compound and tighten it down. Cut off the excess wire, leaving about 1/2" sticking out of the connector.
  • Page 50 15. Mount the receiver switch and charging jack through the fuselage on the opposite side of the muffler exhaust with a Great Planes Switch and Charge Jack Mounting Set (GPMM1000). Make sure the switch and switch mount will not interfere with the aileron servo and pushrods or any of the other components.

  • Page 51: Aileron Lock For 3-Channel Operation

    3. If you are building the PT-40, mark the wire pushrods 4-1/2" from the back end of both clevises (3-7/8" for the PT-20). Make Z-bends at the mark on both pushrods. 4. Drill two 5/64" holes through the punch marks on the die-cut 1/8"...

  • Page 52: Control Surface Throws

    4-CHANNEL TRANSMITTER SINGLE RATE TRANSMITTER The following throws are for a transmitter that does not have Dual Rates. 4-CHANNEL RADIO SETUP (STANDARD MODE 2) PT-20 ELEVATOR 1/4" up 1/4" down ELEVATOR MOVES UP RUDDER 1/4" right 1/4" left...

  • Page 53: Ground Stance

    The following throws are for a transmitter equipped for runway. Dual Rate servo control. Tends to lift-off PT-20 automatically on ELEVATOR takeoff. (High Rate) (Low Rate) 3/8"(10mm) up...

  • Page 54: Preflight

    We use a Top Flite Precision Magnetic Prop Balancer Engine Safety Precautions (#TOPQ5700) in the workshop and keep a Great Planes Fingertip Balancer (#GPMQ5000) in our flight box. Note: Failure to follow these safety precautions may result in severe injury to yourself and others.

  • Page 55: Ama Safety Code

    Get help from an experienced pilot when learning to 2. I will not fly my model aircraft in the presence of operate engines. Use safety glasses when starting or spectators until I become a qualified flier, unless assisted running engines. Do not run the engine in an area of loose by an experienced helper.

  • Page 56: Taxiing

    Takeoff Your first flights should be made in little or no wind. If you have dual rates on your transmitter, set the switches to USING RUBBER BANDS “low rate” for takeoff. Taxi into position, pointing directly into If you are using rubber bands to attach your wing, the the wind.

  • Page 57: Landing

    The most common mistake when learning to fly is “over control.” Think of pressure instead of large movements of the control sticks. Remember all PT’s will recover from almost any over control situation within 50 - 100 feet if you Apply up elevator.
  • Page 58 Buddy Box – Two similar transmitters that are wired Ding – Minor dent or damage to the structure. Also, a nick together with a “trainer cord.” This is most useful when in a prop. Dinged props must be replaced. learning to fly – it’s the same as having dual controls. The instructor can take control by using the “trainer switch”...
  • Page 59 Frequency Control – The FCC has allowed the 72MHz Muffler – A device attached to the exhaust stack of the band to be used for R/C aircraft operations. This band is engine to reduce noise and increase back-pressure which divided up into many different channels in which you can helps low speed performance.
  • Page 60 Roll Axis – The airplane axis controlled by the ailerons. direction of the stalled wing. This situation is not fun when Roll is illustrated by holding the airplane by the nose and you are only a few feet off the runway trying to land. tail.

  • Page 61: Flight Trimming

    If further information is required, settings are made. please contact your local hobby dealer, local flying club or call Great Planes at Also, while you have landed, take the time to crank the clevises until (217) 398-8970 the transmitter trims are at neutral.
  • Page 62 TRIM FEATURE MANEUVERS OBSERVATIONS CORRECTIONS CONTROL Fly general circles and Try for hands off straight Readjust linkages so that CENTERING random maneuvers. and level flight. Tx trims are centered. CONTROL Random maneuvers A. Too sensitive, jerky If A, change linkages to THROWS controls.
  • Page 63 PLANE KITS & ACCESSORIES FROM GREAT PLANES Easy Sport ™ 40............GPMA0150 Super Sportster 40 MK II ...........GPMA0205 Move up from trainers with confidence – and the 59.2" span Easy Reduce throws, and it floats like a trainer. But advance throttle Sport 40.

  • Page 64: Two-View Drawing

    TWO-VIEW DRAWING Photocopy this two-view drawing and use the copy to plan your trim scheme...

This manual is also suitable for:

Pt-40

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