Great Planes GPMA0235 User Manual

WARRANTY

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 buyers are not prepared to accept the liability associated with the use of this product, they are advised
to return this kit immediately in new and unused condition to the place of purchase.

READ THROUGH THIS INSTRUCTION MANUAL
FIRST. IT CONTAINS IMPORTANT INSTRUCTIONS
AND WARNINGS CONCERNING THE ASSEMBLY
AND USE OF THIS MODEL.

EXT4P03 V1.1 Entire Contents © Copyright 1997

P.O.Box 788 Urbana, IL 61801 [phone]

INSTRUCTION MANUAL

INTRODUCTION ...............................................................2

PRECAUTIONS.................................................................2

DECISIONS YOU MUST MAKE........................................3

Engine Selection............................................................3

Exhaust System.............................................................3

PREPARATIONS ...............................................................3

Required Accessories ...................................................3

DIE-CUT PATTERNS .....................................................4,5

Building Supplies and Tools ...........................................6

Optional Supplies and Tools ..........................................6

Types of Wood................................................................6

Common Abbreviations..................................................6

Building Notes................................................................7

Get Ready to Build.........................................................7

BUILD THE T AIL SURF ACES............................................7

Make the Stab Leading Edge Doubler...........................7

Build the Stab.................................................................7

Recommended Elevator Building Sequence..................9

Recommended Fin Building Sequence..........................9

Recommended Ruder Building Sequence.....................9

Hinge the Tail Surfaces ..................................................9

Finish the Tail Surfaces................................................10

BUILD THE WING............................................................12

Build the Wing Panels..................................................12

Join the Wing Panels....................................................15

Sheet the Wing.............................................................15

Build the Ailerons.........................................................17

BUILD THE FUSELA GE..................................................20

Assemble the Fuselage Sides......................................20

Mount the Wing to the Fuselage..................................23

Finish the Bottom of the Fuselage ...............................26

Build the Front Fuselage Deck.....................................27

Mount the Stab and Fin to the Fuselage......................28

Build the Turtle Deck ....................................................29

Mount the Engine.........................................................31

Install the Servos and Make the Pushrods...................31

Assemble the Wheel Pants..........................................34

Assemble the Cowl ......................................................35

PREPARE THE MODEL FOR COVERING .....................37

COVER ING.....................................................................38

Covering Technique......................................................38

Suggested Covering Sequence ...................................38

PAINTING........................................................................39

FINAL HOOK-UPS AND CHECKS.................................39

Join the Control Surfaces.............................................39

Install the Hardware.....................................................40

Attach the Canopy........................................................41

Set the Control Throws.................................................41

Balance Y our Model......................................................42

PREFLIGHT.....................................................................42

Charge the Batteries....................................................42

Balance the Propeller...................................................43

Find a Safe Place to Fly...............................................43

Ground Check the Model.............................................43

Range Check the Radio...............................................43

Engine Safety Precautions...........................................43

AMA Safety Code...........................................................44

General ........................................................................44

Radio Control...............................................................44

FLYING ............................................................................44

Takeoff..........................................................................44

Flight ............................................................................45

Landing ........................................................................45

APPENDIX.......................................................................45

TRIM CHART...................................................................45

TWO VIEW DRAWING.................................BACK COVER

Your Extra 300 is not a toy, but rather a sophisticated,
working model that functions very much like an actual
airplane. Because of its realistic performance, the Extra, if
not assembled and operated correctly, could possibly cause
injury to yourself or spectators and damage property.

If this is your first low wing sport model we
recommend that you get help from an experienced,
knowledgeable modeler with your first flights. You'll

learn faster and avoid risking your model before you're truly
ready to solo.Your local hobby shop has information about
flying clubs in your area whose membership includes
qualified instructors.

You may also contact the national Academy of Model
Aeronautics (AMA), which has more than 2,300 chartered
clubs across the country.

Academy of Model Aeronautics

5151 East Memorial Drive

Muncie, IN 47302-9252

Tele. [phone]

Fax [phone]

Congratulations and thank you for purchasing the Great
Planes Extra 300. For the record, the model we have chosen
to replicate is the Extra 300S.

The Extra is a rather "square" airplane with well defined
lines. Coincidentally, this makes it exceptionally easy to
build and cover–especially for a semi-scale sport model.
Framing the model is very straightforward as most of the
structure features interlocking balsa and lite-ply. The Tur tle
deck sheeting may look a little intimidating but in actuality it
is quite easy to apply if you follow the instructions and use
the template provided to cut the sheeting.

Flying the Extra 300 is a thrilling experience–as it should be
for such an aerobatic model! It doesn't take much elevator

INTRODUCTION

PROTECT Y OUR MODEL,YOURSELF

& OTHERS...FOLLOW THIS

IMPORTANT SAFETY PRECAUTION

TABLE OF CONTENTS

2

or aileron throw to put the Extra through its paces. Of
course, the throws can be decreased to low rates
(illustrated in the instructions) if you'd just like to take it
easy and poke holes in the sky. The Extra performs
surprisingly well on a ball bearing schnurle por ted .40
2-stroke but seasoned experts will surely want to get the
most out of the Extra by strapping on a .46 2-stroke or a
.70 4-stroke.

We hope you enjoy building and flying your Great Planes
Extra 300S as much as we did the prototypes.

Please inspect all parts carefully before starting to
build! If any parts are missing, broken or defective, or if
you have any questions about building or flying this
airplane, please call us at [phone]. If you are
calling for replacement parts, please reference the part
numbers and the kit identification number (stamped on
the end of the carton) and have them ready when calling.

1. Build the plane according to the plans and instructions.
Do not alter or modify the model, as doing so may result in
an unsafe or unflyable model. In a few cases the plans and
instructions may differ slightly from the photos. In those
instances the plans and written instructions are correct.

2.Take time to build straight, true and strong.

3. Use an R/C radio system that is in first-class condition,
and a correctly-sized engine and components (fuel tank,
wheels, etc.) throughout your building process.

4. You must properly install all components so that the
model operates properly on the ground and in the air.

5.You must check the operation of the model before every
flight to ensure that all equipment is operating, and that the
model has remained structurally sound. Be sure to check
nylon clevises or other connectors often and replace them if
they show signs of wear or fatigue.

6. If you are not already an experienced R/C pilot you must
fly the model only with the help of a competent, well
experienced R/C pilot.

Remember:Take your time and follow directions to end
up with a well-built model that is straight and true.

Items in parenthesis (OSMG2691) are suggested part
numbers recognized by distributors and hobby shops and
are listed for your ordering convenience. GPM is the Great
Planes brand, TOP is the Top Flite brand, and HCA is the
Hobbico brand.

❏ 4 Channel Radio with 4 Servos
❏ Engine -

See

Engine Selection above

❏ Muffler -

See

Exhaust System above

❏ Spare Glow Plugs (O.S. #8 for most 2-stroke engines,

OSMG2691)

❏ Propeller (Top Flite

®

Power Point™);

Refer to your

engine's instructions for proper size

❏ Top Flite MonoKote

®

covering

(Approximately 2 rolls)

❏ Fuelproof paint -

See

Painting (page 39)

❏ Medium Fuel Tubing (GPMQ4131)
❏ 1/4" Latex Foam Rubber Padding (HCAQ1000)
❏ 1/16" Foam Wing Seating Tape (GPMQ4422)
❏ 10 oz.Fuel Tank (GPMQ4104)
❏ (2) 2-1/2" Wheels (GPMQ4223)
❏ (1) 3/32" Wheel Collar (GPMQ4302)
❏ 2-1/4" Spinner (GPMQ4517 – red)
❏ Pilot (Williams Bros.1/5 Scale Sportsman Pilot used

in prototype, WBRQ2485)

❏ Fueling System (Top Fueler, GPMQ4160)
❏ (1) 1" Tail wheel (GPMQ4241)

Required Accessories

PREPARATIONS

Engine Selection

There are several engines that will work well in your Extra
300, but for unlimited performance we recommend a

hot

2-stroke such as an O.S.®.46FX or SuperTigre™G45. If
you prefer a 4-stroke, an O.S. .70 Sur pass is the ticket.
Your choice of 2-stroke or 4-stroke will determine the
location of the throttle servo and throttle pushrod exit on
the firewall so plan ahead.

Exhaust System

If you choose to use a 2-stroke engine we suggest an
in-cowl muffler for the best appearance. On our prototype
Extra 300 with the O.S. .46SF we used the Slimline
#3218 Pitts Muffler (SLIG2218) without the exhaust
extension kit. If you prefer to use the exhaust extension
kit purchase #8012 (SLIG5012).

DECISIONS YOU MUST MAKE

NOTE: We, as the kit manufacturer, provide you with a

top quality kit and great instructions, but ultimately the
quality of your finished model depends on how you build
it; therefore, we cannot in any way guarantee the
performance of your completed model, and no
representations are expressed or implied as to the
performance or safety of your completed model.

PRECAUTIONS

3

4

DIE-CUT PATTERNS

5

DIE-CUT PATTERNS

These are the building tools, glue, etc. that we recommend
and mention in the manual.

We recommended Great

Planes Pro™CA and Epoxy

❏ 2 oz.Thin CA (GPMR6003)
❏ 2 oz. Medium CA+ (GPMR6009)
❏ CA Accelerator (GPMR6035)
❏ 30-Minute Pro Epoxy (GPMR6047)
❏ Pacer Formula 560 Canopy Glue
❏ #1 Hobby Knife Handle (XACR4305)
❏ #11 Blades (HCAR0311, 100 qty.)
❏ Razor Saw
❏ X-Acto

®

(or similar) Building Square (XACR7726)

or Building Triangle (XACR7725)

❏ Small T -pins (HCAR5100)
❏ Medium T -pins (HCAR5150)
❏ Waxed Paper
❏ Masking T ape
❏ Electric Power Drill
❏ 1/4-20 Tap (GPMR8105, drill bit included)
❏ Drill Bits: 1/16", 3/32", 7/64", 1/8", 5/32", #18 or

11/64", 3/16", #10 or 13/64" (unless purchased with
1/4-20 Tap listed above), 7/32", 1/4"

❏ Pliers
❏ Monofilament String for aligning wing and stabilizer
❏ Screwdrivers (Phillips and Flat Blade)
❏ HobbyLite Balsa Filler (HCAR3401)
❏ Sealing Iron (TOPR2100)
❏ Bar Sander or Sanding Block and Sandpaper (coarse,

medium, fine grit)*

In our busy work shop we use the Great Planes
Easy-Touch Bar Sanders equipped with Great Planes
#80, #150 and #220-grit Easy-Touch Adhesive-Backed
Sandpaper. Great Planes Easy-Touch Bar Sanders are
made from lightweight, rigid, extruded aluminum and can
be found at most hobby shops.

They are available in three sizes–5-1/2" (GPMR6169) and
11" (GPMR6170) for most general purpose sanding and
22" (GPMR6172) for long surfaces such as wing leading
edges. The Easy–Touch Adhesive-Backed Sandpaper
comes in 2" x 12' rolls of 80-grit (GPMR6180), 150-grit
(GPMR6183), 220-grit (GPMR6185) and an assortment

pack of 5-1/2" long strips (GPMR6189) for the short Bar
Sander. The adhesive backed sandpaper is easy to apply
and remove from your sanding bar when it's time
for replacement.

This setup is all that is required for almost any sanding
task. Custom sanders can be made from balsa or
hardwood blocks and sticks for sanding difficult to reach
spots. We also keep some #320-grit wet-or-dry sandpaper
for finish sanding just before covering.

❏ 1 oz.Thick CA- (GPMR6014)
❏ 6-Minute Pro Epoxy (GPMR6045)
❏ CA Applicator Tips (HCAR3780)
❏ Epoxy Brushes (GPMR8060)
❏ Epoxy Mixing Sticks (GPMR8055, qty. 50)
❏ CA Debonder (GPMR6039)
❏ Hot Sock (TOPR2175)
❏ Trim Seal Tool (TOPR2200)
❏ Heat Gun (TOPR2000)
❏ Single Edge Razor Blades (HCAR0312, 100 qty.)
❏ Razor Plane (MASR1510)
❏ Straightedge (Fourmost Non Slip, FORR2149)
❏ 1/8" Brass Tube, see page 11, step 7
❏ 5/32" Brass Tube, see page 33, step 18
❏ Denatured or Isopropyl Alcohol (for epoxy clean-up)
❏ Dremel MultiPro™ or similar w/Sanding Dr um, Cutting

Burr, Cut-off Wheel

❏ Kyosho Curved Scissors for trimming Cowl, Wheel

Pants, and Canopy (KYOR1010)

Elev = Elevator Fuse = Fuselage
LE = Leading Edge (front) LG = Landing Gear
Lt = Left Ply = Plywood
Rt = Right Stab = Stabilizer
TE = Trailing Edge (rear) " = Inches

Common Abbreviations

Balsa Basswood Plywood

Types of Wood

Optional Supplies and Tools

Building Supplies and Tools

6

7

There are two types of screws used in this kit:
Sheet metal screws are designated by a number and
a length.

For example #6 x 3/4"

Machine screws are designated by a number, threads per
inch and a length.

For example 4-40 x 3/4"

When you see the term “test fit” in the instructions, it
means you should first position the part on the assembly
without using any glue, then slightly modify the part as
necessary for the best fit.

Whenever just “epoxy” is specified you may use

either

30-minute epoxy or6-minute epoxy. When 30-minute epoxy
is specified it is highly recommended that you use only
30-minute (or slower) epoxy because you will need either
the working time and/or the additional strength.

Several times during construction we refer to the “top” or
“bottom” of the model or a part of the model. For example,
during wing construction we tell you to “glue the top main
spar” or “trim the bottom of the former.” It is understood that
the “top” or “bottom” of the model is as it would be when the
airplane is right side up and will be referred to as the “top”
even if the model is being worked on upside down. I.E. the
“top” main spar is always the “top”main spar even when the
wing is being built upside down.

1. Unroll the plan sheets. Reroll the plans inside out to
make them lie flat.

2. Remove all parts from the box. As you do, figure out the
name of each part by comparing it with the plans and the
parts list included with this kit. Using a felt-tip or ballpoint
pen, lightly write the part name or size on each piece to
avoid confusion later. Use the die-cut patterns shown on
pages 4 and 5 to identify the die-cut parts and mark them
before removing them from the sheet. Save all scraps. If
any of the die-cut parts are difficult to punch out, do not
force them! Instead, cut around the parts with a hobby
knife. After punching out the die-cut parts, use your bar
sander or sanding block to lightly sand the edges to
remove any die-cutting irregularities or slivers.

3. As you identify and mark the par ts, separate them into
groups, such as fuse (fuselage), wing, fin, stab (stabilizer)
and hardware.

You may remove the stabilizer and elevator drawing from
the wing plan by cutting along the dotted line. Don't forget
to cover the plans with waxed paper so the glue won't stick
to them.

❏ 1. Begin making the stab leading edg e doubler by

accurately

cutting the 1/4" x 1-1/2" x 15" balsa sheet so it is

13-3/4" long.

❏ 2. Use a ballpoint pen and a drafting square to

accurately

mark the centerline of the stab doubler (6-7/8"
from the end). Use your pen to mark another line on both
ends of the doubler 7/8" from one edge. The following
photo shows the locations of these marks.

❏ 3. Use a straightedge to draw a line connecting the

centerline of the stab doubler with the marks on the ends
as shown in the photo.

❏ 4. Use a hobby knife with a sharp #11 blade to cut along

the lines you drew. If necessary, use a bar sander to true
the leading edges you just cut. Use the plan as a guide to
mark and cut the bevel on both ends of the stab doubler.

❏ 1. Pin the stab LE doubler in position over the plan. Cut

the stab center from the 1/4" x 2" x 6" balsa sheet and
save the small piece you cut off. Add a bead of medium CA
to the front of the stab center, then glue it to the LE doubler
and pin it in position.Wipe away excess CA before it cures.

Build the Stab

Make the Stab Leading Edge Doubler

BUILD THE T AIL SURF ACES

Get Ready to Build

Building Notes

8

❏ 2. Cut a 1/4" x 1/2" x 24" balsa stick (do not use the

30" long stick–it's for the fuse turtle deck) into two 12" long

pieces to make the stab leading edges. Use the
die-cut 1/8" plywood stab bevel gauge (SBG) to mark,
then cut one end of both sticks. Don't cut the tips of the
LE's yet. Cut and “square them up” with the end of the stab
after you remove it from the plan at step 7. Glue the stab
LE's to the LE doubler with medium CA and pin them in
position over the plan.

❏ 3. Glue a 1/4" x 1/2" x 24" balsa stick to the stab center

and pin it in position over the plan for the stab trailing edge.
Use the plans or a straightedge as a guide to make sure the
stab trailing edge is straight as you pin it in position.

Hint: If possible, choose one of the softer pieces of wood for
the stab trailing edge. This will make cutting the hinge slots
easier than if you were to use a harder piece of wood.

❏ 4. Cut the ends of the stab from another 1/4" x 1/2" x 24"

balsa stick using the stab bevel gauge to cut them at the
correct angle. Glue the ends of the stab to the leading and
trailing edges and pin them in position. Make the gussets
from the 1/4" x 1/2" stick and glue them in position (you can
use the stab bevel gauge to mak e the gussets too).

❏ 5. Make the 1/4" tail ribs from a 1/4" x 1/4" x 24" balsa

stick, then glue them in position.You can use the stab bevel
gauge for two of the ribs and the 2" wide piece you cut off
the stab center as a gauge to cut the remaining four 1/4"
ribs to exact length.

Hint: Use a sharp single edge razor blade to cut the tail ribs.

❏ 6. Make the 1/8" tail ribs from a 1/8" x 1/4" x 24" balsa

stick, then glue them in position. We recommend cutting
these tail ribs with a single edge razor blade too.

Sorry, no

gauges for these.You'll just have to rely on pure skill!

❏ 7. Remove the stab from your building board. Inspect all

the glue joints and add CA to any joints that don't look
strong. Cut the ends of the leading and trailing edges so
they extend past the end of the stab by about 1/16". Use
your bar sander to finish the job by sanding the ends of the
LE's and TE so they are flush with the end of the stab. Cut
the 1/8" x 1/4" tips, then glue them to the end of the stab.

❏ 8. Use your bar sander or a large sanding block and

220-grit sandpaper to sand the entire top and bottom
surface of the stab until it is flat and even. Be careful while
sanding so you do not over-thin any one particular area of
the stab or gouge the stab ribs by snagging the sandpaper
on them.

There, that was kind of fun wasn't it? Let's continue to build
the elevators, fin and rudder.

❏ 9. Follow the recommended building sequence that follows

to build the elevators, fin and rudder from the same sizes of
balsa sticks you used for the stab. Use the die-cut 1/8"
plywood elevator bevel gauge (EBG) where appropriate.The
elevator root ends are made from the leftover piece you cut
from the 1/4" x 2" x 6" balsa sheet at step 1.

Hint: Cut one of the elevator root ends from the plan and
use it as a template to make the balsa part. The rudder
balance tab, rudder bottom and fin base are made from
the 1/4" x 2" x 10" balsa sheet.

Note: Refrain from using excessive accelerator. Even hours
after it's sprayed on, residual accelerator can prematurely
and unexpectedly cure the CA you use later on nearby glue
joints. Unless you must handle or remove the part from your
building board right away, we recommend using no
accelerator at all.

9

A. LE (leave 1/16" long at both ends)
B.Root end
C.TE (cut 1/16" long at both ends)
D. 1/4" x 1/2" tip
E. 1/4" ribs

F. 1/8" diagonal ribs

G. Remove the elevator from the plan and inspect all the

glue joints. Add CA where necessar y. Sand the LE
and TE flush with ends

H. Add 1/8" tips, sand flat and smooth with bar sander

and 220-grit sandpaper.

I. Build the other elevator the same as the first.

A. LE (cut 1/16" long at both ends)
B. Fin tip (use 1/4" x 3/4" x 24" balsa stick, remainder is

saved for front fuse deck sides)
C.Fin base
D.TE (cut 1/16" long at both ends)
E. 1/8" tail ribs

F. Remove the fin from your building board and inspect all

the glue joints. Add CA where necessary. Use your bar

sander to sand the top of the leading and trailing edges

even with the tip of the fin.Sand the bottom of the leading

edge even with the base. Sand the entire fin flat and

smooth with your bar sander and 220-grit sandpaper.

A. LE (cut 1/16" long at both ends)
B.Rudder tip

C.Rudder bottom
D. TE
E. 1/8" tail r ibs (glue the two “straight” ribs before the

diagonal ribs)

G. Inspect all the glue joints and add CA where necessary.

Shape the bottom of the rudder as shown on the plan.
Sand the entire rudder flat and smooth with your
bar sander.

Note: The Balance Tab will be made later.

❏ 1. Place the stab over its location on the plan and

lightly

mark the hinge locations on the trailing edge with a
ballpoint pen. Mark the hinge locations on the elevators in
the same manner.

❏ 2. See the Exper t Tip that follows, then mark the

locations of the hinge slots on the stab and elevators.

HOW TO MARK THE HINGE SLOTS

It's important that the hinge slots are centered and parallel to
the part you are hinging. The best way to start is by accurately
marking the hinge slots.We'll start with the stabilizer.

A. Lay the stabilizer and a ballpoint pen on a flat surface.
Mark a “test line” on the trailing edge of the stab away from
the hinge locations you marked earlier.

Hinge the Tail Surfaces

Recommended Rudder

Building Sequence

Recommended Fin
Building Sequence

Recommended Elevator

Building Sequence

B.Flip the stab over and mark another line in the same location
as the first.If you see only one line, then it is on center.Proceed
and mark the hinge slots at each hinge location. If you see two
lines (as in the photo) you will have to adjust the height of the
stab until you can mark the centerline.

C. Use playing cards or business cards to adjust the height
of the stabilizer until you can mark the centerline. Mark the
hinge slots at each hinge location.

D. Use the same technique to mark the centerline along the
entire length of both elevators.

❏ 3. Cut the hinge slots in the elevator and stabilizer using

a #11 blade.Begin by carefully cutting a ver y shallow slit at
the hinge location to accurately establish the hinge slot.

Make three or four more cuts going a little deeper each
time. As you cut, slide the knife from side to side until the
slot has reached the proper depth and width for the hinge.

❏ 4. Cut the hinges for the elevators and rudder

from the supplied 2" x 9" hinge material, then
snip off the corners. Temporarily join the
elevators to the stab with the hinges adjusting
any hinge slots if necessary so they all align.

Do not glue in the hinges until you are
instructed to do so.

❏ 5. Return to step 1 and use the same procedures to

hinge the rudder and fin.

❏ 1. Refer to the Expert Tip that follows and shape the

leading edge of the elevators to a “V” as shown on the plans.

HOW TO BEVEL THE LEADING EDGES

A. Place the leading edge of one of the elevators on your
work surface and use your ballpoint pen to mark a “bevel
to” line on both sides about 3/32" high.
Note: You will probably have to adjust the height of the
elevator with card stock (as you did while marking the hinge
slots) so your “bevel to” line is not too high – making too
sharp of a “V.”

B. Using the bevel to lines and the center line as a guide,
make the “V” on the leading edge of the elevators with a
razor plane or your bar sander with 150-grit sandpaper.

Finish the Tail Surfaces

10

CUT HINGE SLOT

WITH HOBBY KNIFE

AND #11 BLADE

❏ 2. Use the same procedure to bevel the leading edge of

the rudder.

❏ 3. Cut a notch in the leading edge of the rudder for the

balance tab. The notch should be the same height as the
balance tab (1-3/8") and approximately 1/8" deep or, as
deep as the “V” on the leading edge. Make the balance tab
from the remaining piece of balsa left over from the
1/4" x 2" x 10" sheet. Glue the balance tab to the r udder
with medium CA, then glue the 1/8" balsa tip to the top of
the rudder.

Let's get back to the elevators.

❏ 4. Make sure the tips of the elevators are even with the

tips of the stab, then lay the elevator joiner wire on top of
the elevators in the position shown on the plan. Use your
ballpoint pen to lightly mark the centerline of the ends of
the joiner wire on the stab.

❏ 5. Remove the elevators from the stab and use a

draftsman's square to extend the line you marked on both
elevators to the leading edge.

❏ 6. Drill a 3/32" pilot hole into the leading edge of the

elevators. As you drill each hole keep the drill aligned with
the top and bottom surface of the elevator and the
reference line you made in the previous step. Redrill the
holes with a 1/8" drill bit.

❏ 7. Refer to the Exper t Tip that follows, then cut a 1/8"

groove in the leading edge of both elevators to recess the
joiner wire.

HOW TO CUT A GROOVE FOR THE ELEVATOR

JOINER WIRE

A. Use a #11 knife blade to sharpen the end of a piece of
1/8" brass tube. Roll the tube as you

carve

the end. If you
have a file or a cut-off wheel it helps to sharpen the outside
of the end of the tube as well.

B. Use the shar pened tube to

carefully

gouge the leading
edge of the elevators. You'll have to make a few cuts to
make the recess deep enough for the joiner wire.

11

❏ 8. Temporarily join the elevators with the joiner wire.The

joiner wire will be easier to install if you chamfer (bevel) the
ends a little. If necessar y, “tweak” the joiner wire so the
elevators are parallel and lay flat on your building table
when the joiner wire is installed. If you found it necessary to
“tweak” the joiner wire use a felt-tip pen to mark it so you
can install the joiner wire in the same orientation when you
permanently join the elevators.

❏ 9. Use your bar sander and 150-grit sandpaper to round

the tail surfaces as shown on the fuse plan. Keep the ends
of the tail surfaces squared off just like the full size
Extra 300.

That's about it for the tail surfaces. They're a little more
work than sheet surfaces but they are much lighter, just
about as strong and add a nice piece of craftsmanship.
Clean off your work bench and get out the wing plan!

Start by building the right wing panel upside down over the
left wing panel plan so your progress matches the photos.

❏❏1. Use one T-pin to pin the root end of a 5/16" x 5/16"

x 30" balsa main spar over its location on the plan so
approximately 1/2" extends past the wing centerline.This is
the top spar. Place a piece of 3/32" leftover balsa under
the tip of the spar past the location of rib R-10, then pin the
tip of the spar to the plan. Inser t the T-pin at an angle so it
does not interfere with the bottom spar when it is added to
the assembly at step 5.

❏❏2. Place the die-cut 3/32" balsa wing ribs R-2 through

R-10 on the top spar over their locations on the plan.
Note: The short jig tabs, the ones on every rib, should be

contacting the plan.

❏❏3. Using small T-pins, pin the aft jig tab of ribs R-2

through R-10 to your building board over their location on
the plan.

Note: Inser t the T-pins at an angle from the rear so they
can be removed after the trailing edge and bottom sheeting
are glued in position.

❏❏4. Use small T-pins to pin the front jig tabs of r ibs

R-2 through R-10 to the building board. You may insert the
pins into the front jig tabs any way you like because they will
be removed before the bottom leading sheeting is added.

Note: Due to the decreasing thickness in the wing towards
the tip, the top

main spar

is not pinned directly to the

building board. Instead, the

ribs

are securely pinned to the
building board.This is done so the ribs of both wing halves
will be vertical. You must follow the instructions closely on
where to insert the T-pins in the ribs so you do not conceal
them under the sheeting therefore making it difficult to
remove the wing from the building board.

Build the Wing Panels

BUILD THE WING

12

❏❏5. Place a 5/16" x 5/16" x 30" bottom spar in the

notches of the ribs. Approximately 1/2" of the bottom spar
should extend past the wing centerline.

❏❏6. Glue the main spars to the ribs with thin CA. As

you glue each rib to the spars, simultaneously

pull

the top

spar up into the rib and

push

the bottom spar down into the
rib to make sure the spars are fully seated in the notches.
Make sure all the jig tabs are contacting the work surface.

❏❏7. Position the 27" shaped balsa leading edge (LE)

on the front of the ribs. The LE should be centered on all
the ribs and the root end should extend past rib R-2 by
about 1/16". Make sure all the jig tabs are contacting the
work surface, then use thin CA to glue the LE to the front of
the ribs.

❏❏8. Use thin CA to glue the shaped 30" balsa trailing

edge (TE) to the ends of the ribs so approximately 1/2"

extends past the centerline of the wing.

❏❏9. Use medium CA to glue the 3/32" x 7/8" x 30" balsa

trailing edge sheeting to the TE and wing ribs so the end
extends past the wing centerline by approximately 1/2".

❏❏10. Star ting at ribs R-8 & R-7 test fit, then glue the

die-cut 3/32" cross grain balsa shear webs to the front of
the spars. Note that the shear webs increase in height as
they get closer to the root and there are two shear webs
that are the same height between ribs 2 & 3 and 3 & 4.

❏❏11. See the Exper t Tip that follows, then glue two

3/32" x 3" x 30" balsa sheets together to make one 6" wide
sheet for the top and bottom leading edge wing sheeting.

HOW TO MAKE WING SHEETS

A. Use a metal straightedge as a guide to trim one edge of
both sheets.

13

B. Use masking tape to tightly tape the two sheets together
joining the trimmed edges.

C. Turn the sheet over and place weights on top of the
sheet to hold it flat. Apply thin CA spar ingly to the seam
between the two pieces quickly wiping away excess CA
with a paper towel as you proceed.

D. Turn the sheet over and remove the masking tape, then
apply thin CA to the seam the same way you did for the
other side.

E. Sand the sheet flat and smooth with your bar sander and
150-grit sandpaper.

❏❏12. Cut the sheet as shown in the photo to make a

top and a bottom LE wing sheet.

❏❏13. Fit one of the leading edge sheets to the bottom

of the wing panel by first sanding a bevel on the front edge

of the sheet so it matches the leading edge of the wing,
then trim the aft edge of the sheet so it “ends” at about the
middle of the main spar.

❏❏14. Before you glue the LE sheeting in position,

remove the T-pins from the front jig tabs in the wing ribs.
Reinstall the T-pins through the top main spar and into your
building board.

❏❏15.Wet the outside of the leading edge so it will bend

easier.
Hint: a 50/50 mix of water and alcohol or ammonia helps

soften the wood fibers so the sheet is even easier to bend.
Position the front of the sheet against the LE and glue it in
position with thin CA.Wet the sheet once more.

❏❏16. Carefully lift the sheeting away from the ribs, then

apply a bead of medium or thick CA to the top of each rib.

14

Working quickly,

pull

the sheeting back toward the main

spar as you

press

it down to the ribs and spar, then glue
the aft edge of the sheeting to the main spar with thin CA.
Use masking tape, T-pins or weights to hold the sheeting to
the ribs until the CA cures.

❏❏17. Use the die-cut 1/8" plywood dihedral gauge

and a ballpoint pen to accurately mark the wing centerline
on the spars, TE and bottom TE sheet.

❏❏18. Remove the T-pins, then take the wing off your

building board.
Repeat steps 1 through 18 to build the left wing panel over

the right wing panel drawing on the plan.

❏ 1. Use a razor saw to accurately cut the spars, TE and

bottom TE sheeting of both wing halves along the lines you
marked at the wing centerline. At the wing tips, trim the spars,
LE and bottom sheeting so they are ev en with rib R-10.

❏ 2. Trim the bottom LE sheeting and the LE so they are

even with rib R-2.

❏ 3. Without using any glue, test join the wing panels by

laying them upright (on the tall jig tabs on the bottoms of
the ribs) on your flat building table and join the ends of the
spars and TE.

❏ 4. Test fit the 1/8" x 1-3/8" x 5-3/8" ply spar joiners on

the front and rear of the spars and temporarily clamp them
in position.

❏ 5. Make sure the ends of the spars and TE's join without

any gaps. If there are any gaps, use your bar sander to
make small adjustments to the ends of the spars.Whatever
adjustments you make, the lengths of the spars and TE's
must be identical so you do not build any “sweep” into the
wing. In other words, when you temporarily clamp the spar
joiners to the spars, you should not have to pull the TE's
together, nor should they be pushing against each other.

❏ 6. Glue the spar joiners to the spars with 30-minute

epoxy by spreading a film of epoxy on both the spars and
the spar joiners. Once the C-clamps are tightened wipe
away excess epoxy. Place waxed paper under the center of
the wing to catch excess epoxy and place weights on top of
your wing to hold the jig tabs down. Glue the TE's together
with thin or medium CA. Do not disturb the wing until the
epoxy cures.

❏ 1. Glue the two R-1 ribs together with medium CA. Fit

the laminated R-1 rib between the aft spar joiner and the

Sheet the Wing

Join the Wing Panels

15