aeroclub-module 2 – make your own powered glider

Aero Club

Presents

Introduction to RC Modeling

Module 2

Powered Glider

Centre for Innovation IIT Madras

Aero Club - Intro To RC Modelling – Module 2 - Powered Glider.

Centre For Innovation – cfi-iitm.org Indian Institute of Technology Madras

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Table of Contents

Prerequisites: .................................................................................................................................................................... 3

Introduction: ..................................................................................................................................................................... 3

What is a glider? ........................................................................................................................................................... 3

Aspect Ratio: ................................................................................................................................................................. 3

RC Modelling & Gliders: ................................................................................................................................................ 3

Balsa: ................................................................................................................................................................................. 4

Grain: ............................................................................................................................................................................. 4

Propellers: ......................................................................................................................................................................... 5

Materials Required: .......................................................................................................................................................... 6

Dimensions: ....................................................................................................................................................................... 7

Cutting Balsa: .................................................................................................................................................................... 8

Assembly: .......................................................................................................................................................................... 9

The Propeller: ................................................................................................................................................................ 9

The Plane:.................................................................................................................................................................... 10

Exercises: ......................................................................................................................................................................... 12

Acknowledgements: ........................................................................................................................................................ 12



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Prerequisites: It is highly recommended that beginners read the introduction to flight module beforehand.

Introduction:

What is a glider?

“A glider is a heavier-than-air aircraft that is supported in flight by the dynamic reaction of the air against

its lifting surfaces, and whose free flight does not depend on an engine.“

Heavier-than-air: An important classification for aircraft. Refers to aircraft in which lift is not produced due

to buoyancy. Examples of lighter than air aircraft would be Zeppelins, Hot Air Balloons.

Does not depend on an engine:This is contrast to most “everyday” airplanes which cannot sustain free

flight without thrust. However commercial airplanes do have some gliding ability due to their relatively

high wing aspect ratio. This also does not mean a glider cannot be equipped with an engine. Or that an

aircraft with an engine cannot be classified as a glider. Powered gliders in fact, have a very good fuel

efficiency.

Powered Glider

Aspect Ratio:

Gliders are designed with high aspect ratio wings. This allows for a higher lift-drag ration which is essential

for unpowered free flight.This can be considered as the defining feature of a glider. Most gliders have an

aspect ratio of 7-9.

RC Modelling & Gliders:

Small hand launched gliders are the first step in RC Modelling. Relatively cheap and easy to make, they give

a first-hand experience of working with many of the standard materials used (Ex: Balsa) in RC Modelling



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Balsa: One of the most widely used material in RC modelling. Preferred due to its low density, balsa can prove to

be a difficult material to work with for beginners. However developing the skills required to work with

balsa will prove advantageous in the long run.

It is usually sold in sheets, with thickness varying from 1 mm to 10 mm.

Grain:

The keen eyed observer will notice tiny indentations on the balsa sheet, this is called grain. It is an

important feature of the wood to keep in mind while cutting. More on this will be discussed in the coming

pages.

Balsa wood is only stiff perpendicular to the grain. Gently try bending the sheet parallel to its grain, it will

bend (and break, don’t break it) very easily. Try bending it perpendicular to the grain however, and you will

be surprised by its stiffness.

This flexible property of Balsa is one of the main reasons it’s used in modelling. This comes in handy when

covering the outer surface of the aircraft/wing.



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Propellers: The propellers used in RC Planes come with a standard numbering convention: - a X b (Ex: 12 X 4.5, 10 X

4.5, 9X6).

The first number is the propeller diameter in inches. The second is the propeller pitch again in inches. So 12

X 4.5 stands for a 12 inch diameter prop with a pitch of 4.5 inches.

In general greater the prop diameter and pitch =>more thrust per revolution => greater the load on the

motor.

Usually plastic propellers are used. Wooden props are paired with IC engines. We will use a plastic prop.



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Materials Required: It’s finally time to get started on our glider. But before that,

WARNING: SOME OF THESE MATERIALS ARE NOT SUITABLE FOR USE BY CHILDREN AND MUST BE USED UNDER ADULT

SUPERVISION.

The materials you will require are:

1. Balsa Sheets: One 3 mm thick sheet and one 10 mm thick sheet.

2. Glue: Fevitite or Anabond. Fevitite is preferable since it sets (hardens) quickly. Buy the one which

sets in 5 minutes.

3. Paper Cutter: Your average everyday paper cutter will do.

4. Ruler: 30 cm long.

5. Pencil: Do not sharpen it. You will need a blunt pencil.

6. Tiny rubber washer. About 1 cm in diameter. Or anything equivalent.

7. Protractor.

8. Cello tape.

9. Paper Clips. Remove the outer plastic covering (if present) and straighten them out.

10. Used ball point pen refills. Make sure the wire of the paper clip can slide into the refill.

11. Butter paper: This should be available in your local stationery shop. Yes it is the same paper butter

comes wrapped in. You will need about half a chart sized sheet.

12. Rubber Band: The most important part of the glider.

13. Propeller. One 6X4.5 prop.

14. Pliers.



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Dimensions:

All the dimensions are in centimeters.

The rudder, horizontal stabilizer and wing are cut from 3mm thick balsa sheets. Hence their depth will be

3mm.

The fuselage is cut from 10 mm thick balsa sheet.

You will also need to cut butter paper of the same outer dimensions as the wing, rudder and horizontal

stabilizer. The butter paper will cover only on one face of each of the structures as will act as the skin of

the glider..



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Cutting Balsa:

This is not as easy as it sounds. First mark the dimensions of the required parts (see below) on the balsa

sheets using a ruler and pencil, in a fairly compact manner. Try to avoid wasting balsa.

IMPORTANT: The direction of grain should be in the same dir ection as indicated by the red

arrows in the above figures.

Then retrace these lines once using the paper cutter. This is to make sure you cut in a straight line.

Now you need to start cutting. Do not try to cut the entire depth in one go. This will lead to the balsa

chipping off leading to a rough cut. Instead cut a few mm at a time, and retrace the cut going deeper each

time until you cut to the other side of the sheet.

It needs to be done extremely carefully. The parts you will need to cut are:

1. One 23.1 cm X 1 cm rectangle from the 10 mm thick balsa sheet.

FOR THE WING:

2. Two 37.5 cm X 0.5 cm rectangles from 3 mm thick balsa sheet.


FOR THE HORIZONTAL STABILIZER:



6. One 3.2 cm X 0.5 cm rectangle form 3 mm thick balsa sheet.

FOR THE RUDDER:

7. One 4.2 cm X 0.5 cm rectangles from 3 mm thick balsa sheet.

8. Two 5.3 cm X 0.5 cm rectangles form 3 mm thick balsa sheet.

Once you have finished cutting all the parts use fevitite to stick them accordingly. (Refer the above figures)

Fevitite needs to be handled carefully. Read the instructions on the box before using. Use a small piece of

butter paper and balsa to mix the fevitite.

For the horizontal stabilizer first stick the outer pieces and let the glue dry before fixing the center piece.

Once you have stuck all the pieces, stick the butter paper onto the respective pieces using fevicol. Apply a

thin layer of fevicol (use as little as possible), You don’t want to unnecessarily increase the weight of the

glider.

Note: Fevitite is used to stick all the balsa pieces together and fevicol is used to stick the butter paper onto

the balsa sheets, which will act as the skin of the glider.



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Assembly:

The Propeller:

Getting this right is critical for your glider to be successful. Take your time in making this and don’t rush

through.

1. First you need to straighten out the paperclips. Use pliers and a hard surface to do this. This will

form your “axel”.

2. Now cut a 1 cm piece of the refill. Now take another paper clip and loop a portion of it around the

refill. You should have a two cm length of paper clip sticking out from the loop once you are done.

Use the pliers to tighten the loop around the refill. Paste a glob of fevitite to make sure the refill

cannot move relative to the loop. Let it dry.

3. Now take the “axel” and pass it through the piece of refill. Make a small hook on one side.

4. Here comes the tricky part. The other end of the axel needs to pass through the center of the

rubber washer and the propeller. Then you need to wind it around the propeller (only) so that the

propeller does not slip.



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The Plane:

5. Now it is time to assemble the plane. First attach the rudder to the horizontal stabilizer using

fevitite. This forms your tail. Now attach the tail to one end of your fuselage using fevitite. This is

the back end of your plane.

6. Next use another paper clip to make another hook. Now insert this hook into the fuselage at about

12 cm from the front end. The paper clip should stick out form the opposite face. Loop this end to

make sure the hook cannot come out. Add a glob of fevitite to secure it in place.

The hook should toward the tail.

7. Fix the propeller to the fuselage in the same way. Insert the 2 cm piece of pape clip which was

sticking out into the front face of the fuselage. The bend it into an L shape to get the prop pointing

in the right direction.

A small piece of balsa should be wedged into any gap between the fuselage and paper clip

wire.Apply fevitite generously.

8. After the fevitite has dried, you need to start fixing the wing. The wing needs to be fixed such that

the center of mass of the entire plane is at the quarter chord of the wing. Quarter chord= ¼ the

wing width (in this case roughly 1.4 cm). So the center of mass should be at 1.4 cm from the leading

edge of the wing. To do this first fix the wing temporarily using the cello tape. Balance the plane at

quarter chord using your fingertips. Check if the plane tilts forward or backward. Accordingly move

the wing forward or backward until the center of mass is just at the quarter chord.

9. Now test if the plane glides by launching it with your hand. Hold the plane just below the wing and

throw it flat, don’t pitch the plane up or down while throwing. Throw it like you would throw a dart.

If you have the mass balance and throw right the plane should glide and land flat, not on its nose or

tail.

10. Now fix the wing using fevitite. Let it dry. This is what it should look like.



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11. Now attach the loop of rubber band to the plane using the hooks. Now wind the prop. Make sure to

rotate/wind the prop in the right direction. When you release the propeller, it should push air

toward the tail off the plane i.e., backwards.

12. Once you are ready to launch, hold the plane as before. Release the prop first and then throw the

plane, as you did above, and watch it soar away!

If there are certain issues with its gliding properties, or if it is not gliding properly, try adding some small

weight to the glider. For ex. If it is pitching nose downward, it means it is heavier near the nose. So attach

some small weight near the tail. And if it is stalling (tail heavy), attach some weight near the nose.

We hope you have enjoyed your experience in making the glider.

Want to know how we came up with the dimensions of the glider? Do spend some time to answer the

exercises in the next page, and also checkout the next module to learn and make your own design.



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Exercises:

1. What is the usual range of aspect ratio for a glider?

2. Why is balsa used for making the glider? What is the importance of “grain” when working with

balsa?

3. What other materials do you think can be used instead of balsa?

4. A propeller has a specification of 10X4.5. What is the volume of air in cubic inches the prop will

push in 1 revolution?

5. What is the setting time of the fevitite you used?

6. Why was butter paper used? What purpose did it solve?

7. How does the propeller generate thrust in the required direction? Is the direction of thrust

reversed, if you rotate it in the other direction?

8. What purpose does the rudder/vertical stabilizer solve?

9. How many parts do you need to cut from the 10mm balsa sheet?

10. How do you launch the glider? Where do you think the CG of the glider must lie and why?

Once you are done with making the glider, you can send the images of the glider and answers to the above

exercises to one of the following mail id’s – [email protected] , [email protected] .

For any queries/feedback on the procedure of making the glider, materials procurement you can write an

email to any one of the above mentioned addresses.

To join aero club, go to the Clubs tab -> Aero Club on the CFI website, and click on Join Aero Club.

Acknowledgements: This course on Intro to RC Modeling was formulated, prepared and compiled by the following members of

Aero Club:

(In the order of the module of the courses)

1. Anil Kumar

2. Hanut Vemulapalli

3. Dheepak N Khatri

4. Sanjesh Hoskopple

5. Nikhil Gupta

6. GuruPrasad Kallanje

mailto:[email protected]

mailto:[email protected]

https://plus.google.com/u/0/101736879033096320463?prsrc=4

aeroclub-module 2 – make your own powered glider

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