Flying Papercraft.com

Flying your Papercraft Plane Photo: Tie Brooks

Flying Papercraft.com THE ABOVE SEA LEVEL DIVISION OF BROOKS BOATS DESIGNS Pg. 1 Flying Papercraft.com A-4

Contents

Flight Characteristics ...... 2 Learning to Fly ...... 2 Forces on a Plane ...... 3 Center of Gravity ...... 4

Control Surfaces ...... 5 Washout Bend ...... 6 Flaps ...... 6 Leading Edge Flaps ...... 6 Elevators ...... 7 Ailerons ...... 7 Rudders ...... 7

First Flight ...... 8 Preflight Check ...... 8 Setting Up for Slow Flight ...... 8 Adjusting the Plane ...... 9 High Speed Flight ...... 10 Scale ...... 10

Fun Things to Do With Your Plane ... 11 Turns ...... 11 Rolls ...... 11 Landing ...... 12 Loops ...... 12 High Flying ...... 12 Flying in Wind ...... 12 A Final Thought ...... 13

All photos are by Leigh, Tie, Hanxiang and Jack Brooks, except where noted. Thanks guys!!

Copyright Ⓒ 2014 John Brooks All rights reserved. Pg. 2 Flying Papercraft.com A-4

Flying your Papercraft plane

Flight Characteristics

You built the plane out of card stock so it is heavy. However, your plane can be thrown quite hard, so it can go fast, high and far. And because it is heavy, your plane can fly in much more wind than many l planes made out of regular paper. In fact, it can be quite fun to fly in some wind.

Here is how your plane can fly: A flying version of a regional jet.

When I first test a plane I am usually inside the house where there are two rooms connected to make a space that is a little over 30 feet (10 meters) long The planes usually hit the opposite wall with a resound thwack at about the same altitude they left my hand. In the back yard‒an average sized back yard‒the plane often ends up on the roof or in the surrounding bushes. So we often fly on the soccer field at school and occasionally can use up nearly all the airspace over half the field! With some adjusting and practice, you can make this little plane really fly!

Learning to fly The model used to illustrate this manual is the A-4 Skyhawk. You have built a sophisticated flying machine. While all planes are influenced by the same forces as they move through the air, and all paper planes can be adjusted for where they go, on this plane you can change the shape of the wings for different speeds you want to fly, and there are many ways to adjust how and where your plane flies.

Along with learning how the plane flies, you will also be learning just how to throw it so it will go where you want.

A gentle take off is a good idea for the first flights.. Pg. 3 Flying Papercraft.com A-4

Forces on a plane How a plane glides takes a little explaining. The wings The first thing to understand is the four primary and the horizontal tails on your plane create an area forces working on a plane as it flies. of lift and somewhere in those areas is the Center of Lift, a point where the amount of lift in front of that The two forces that keep the plane in the air are lift point is the same as the amount of lift behind it. on the wings and thrust when you throw it. The two forces that eventually bring the plane back to the At the same time, the weight of your plane is ground are gravity, and drag, which slows the plane centered around a point called the Center of Gravity as it pushes through the air. The center of lift is the force going up, the center of For a wing to create lift, it has to be moving through gravity is force going down. For a plane to glide, you the air. And the faster the wing is moving, the more need the center of gravity in front of the center of lift that is created. The amount of lift created also lift so the nose tips down and air flows over the depends on amount of section shape in the wing. wings. How far apart or close together the two points are is the balance of the airplane. If you took an airplane and sawed through the wing parallel to the centerline of the plane, then looked at The center of lift is complicated because on a foil the cut end, this is the wing section. The more shape shape (the section of wing) the center of lift is not in there is in the this section, the more lift it creates the middle, but instead is about 1/3 of the way back and the slower the plane can fly. Jet fighters are from the leading edge of the wings and horizontal designed to go fast so their wing sections are pretty tails. flat and thin. Gliders are designed to go slow so their What that tells us is that we want the center of wing sections are thick and well rounded. gravity pretty far forward on the wings, as you will see as we talk about finding the center of gravity of All wing shapes have a point at which the air speed is your plane. too slow to create any lift and the airplane simply falls out of the sky.This point is ominously called the stall speed. A stall in a car means it can’t go. In a plane it means it can’t fly.

I am sure you have flown a paper plane and watched as it goes up, then drops, goes up, then drops again. What is happening is, as the plane rises, it losses speed to drag and gravity, until the wings stall, then the plane’s nose (which is heavy) drops, gravity speeds the plane up, the wings create lift, the nose rises until the wings either stall again or the plane glides to the ground.

Forces on a plane are pretty easy to understand, but how they interact with a plane can get very very complex and you can study it for many years to come.

Let’s get back to flying your new plane.

One thing to understand is the balance of your plane. Your plane is a glider. That means that after Circles under the wings of the A-4 is the location of you throw it, there is no engine to provide thrust and the Center of Gravity. so your plane just . . glides. Pg. 4 Flying Papercraft.com A-4

Center of Gravity

Planes are sensitive to where the center of gravity is located and although your plane has been adjusted for a good flight, you may need to adjust it to make your plane fly better.

To find the center of gravity (CG), use your thumb and middle finger to balance the plane under the wings. Move the plane forward or aft until it sits level. Where your fingers are touching the plane is the center of gravity.

The pictures show a model of the A-4 and it flies best if the CG is at a point within the circles on the underside of the wings. If the CG is forward of this, Balancing the plane to find the center of gravity. the plane needs much more elevator to fly level and it will fly slow and only for a short distance. If it is aft of this point, it will nose up very easily and stall, then it A quick and temporary way to add weight is by putting can nose dive to the ground. small pieces of blue painters masking tape on the nose or tail. If you don’t like the change, take the tape off. If To move the CG aft, glue the tail weights to the you do, replace the tape with card stock weights underside of the tail cone. To move the CG forward, glue nose weights to the bottom of the fuselage and When you have flown the plane for awhile, you may nose cone. find that you want to make small adjustments to the CG to get better glides by moving the CG forward, or Add the weights gradually, one at a time, then try get more maneuverability by moving the CG aft. If you some flights to see how the plane flies. Small changes like to fly in some wind, moving the CG forward can make a big difference. Add more as you need. help make the plane fly better.

Tail weights are glued on the horizontal tail to adjust the CG towards the back of the plane. Gluing on a nose weight to adjust the CG towards the front of the plane. Pg. 5 Flying Papercraft.com A-4

Control Surfaces

There are four control surfaces on your plane, three that make the plane fly where you want it to go, and one that changes the shape of the wings for different flight speeds.

The drawing shows where these control surfaces are on most planes, including your regional jet.

The three steering control surfaces are:

Elevators on the horizontal tails control how much the nose points up or down. You’ll adjust these the most.

Ailerons, the smaller movable tabs on trailing edge Cut the lines for the various control surfaces after the plane is fully assembled. of the wings, at the tips, control the plane’s roll or banking. Control Surface Bends Rudder on the vertical tail is used sparingly for turns. The fold lines for control surfaces are not scored The wing shape control is: because the bends are not permanent‒ we want to be able to change them. A score line weakens the fold Flaps are the larger tabs inboard of the ailerons and and over time the control surfaces will get floppy and right next to the fuselage. the plane won’t go where you want.

A-4 flight control surfaces

Washout bend Flaps

Control surface bends

Rudder

Ailerons Elevators Pg. 6 Flying Papercraft.com A-4

Using the Control Surfaces Wing shape Washout Bend

While the washout bend is not an actual control surface, you will be adjusting it some in the first few flights and periodically afterward to keep the plane more stable and to adjust for straight flights‒no banking left or right‒when the rudder and ailerons are straight.

The purpose of the washout bend is to create a small The front of the wings folded along the washout amount of twist in the wing, (called washout) so that bend line. the tip is angled down from the angle of the rest of the wing. This helps a plane remain stable in a stall.

When a wing stalls, air flow breaks away from the wing to create turbulence and the wing no longer creates lift. If the whole wing stalls, the plane just drops out of the sky, tumbling to the ground. It’s not pretty.

With washout, the portion of the wing near the fuselage will start to stall but the wing tips‒ angled down a few degrees‒ will stay flying and continue creating lift, so although the plane will still drop, usually nosing down, it won’t tumble out of control. Airflow can smooth out again over the whole wing and the plane can level out.

The idea with our plane is to have enough bend in the Washout fold on the finished plane. washout fold that the plane stays stable, but not so much as to create extra drag.

Flaps Flaps change the shape of the wings: flatter (little or no bend to the flaps) for fast flights, more shape (more bend to the flaps) for slower flights and landings. With the flaps down usually the plane will nose down in flight, so you also need more elevator when you use the flaps.

With the regional jets, you will always want a little bit of flap angle, even for fast flights, so the wings develop more lift. Regional jets are not high speed planes like jet fighters.

Making the cuts for the flaps. Pg. 7 Flying Papercraft.com A-4

Steering control

Elevators Since paper planes are gliders, the center of gravity is forward of the center of lift of the wings and the nose tips down. Without some correction, the plane will just arrow into the ground. The plane needs some up elevator to fly level. How much will depend on how fast the plane is flying. You’ll need more elevator for slow flights, less for fast flights. If you put a large amount of elevator when you throw the plane fast, the nose will Making the cuts for the elevators. go up and the plane will do a loop.

Ailerons At first you might need to adjust the ailerons to make the plane fly level as you learn how your new plane flies. For example, if the right wing dips and the plane banks to the right, put the right aileron down, a little, and the left one up, a little. Do the opposite if the plane banks left. The ailerons can have a dramatic effect, so go easy at first. As you fly your plane you will learn how much aileron you need for Adjusting the elevators to lift the nose. various turns and rolls.

Rudder Making the cuts for the ailerons. Unlike cars or boats, planes act in three directions, not just one. So, when you turn, you don’t just activate the rudder, like a boat, you also activate the ailerons so that plane banks as it turns.

But, more disconcerting, the rudders will also act like vertical ailerons, causing the plane to roll as it turns. The effect can be quite dramatic. So go easy with the rudder. Because this is a paper plane, you can’t straighten the rudder half way through the flight. You have to live with that rudder setting a-l-l-l-l the way to the ground, whether it is a smooth landing. Or a crash.

Making the cut for the rudder. Pg. 8 Flying Papercraft.com A-4

First Flight When you are ready to fly, it is likely that your first flights will be indoors. If nothing else, there is no wind and everything is dry. But no matter how big your house or office is, these indoor flights should be slow ones as there are numerous obstacles to hit‒chairs, cabinets, tables, lamps, and all the many other things taking up airspace in a room.

Slow flights for these first ones have another advantage. You don’t know how your plane will fly exactly and if it doesn’t go where you want or does something you didn’t expect, whatever it hits won’t damage the plane. Or knock over a lamp. Preflight Check.

Before a pilot flies, she walks around the plane to check that everything is in good working order and there are no signs of problems. We also need to do a preflight check. Here’s what to look for.

Check that the plane is straight, not twisted. Although you can’t adjust the fuselage or nose and tail cones, you can adjust the wings, and the tails.

Check that the wings are level or angle up‒or down‒ the same amount. The horizontal tails are usually at the same angle as the wings, and the vertical tail is, well, vertical. Make both sides of the plane the same.

Look at the front of the plane to see that the washout fold is the same on both wings. More fold on one side will cause the plane to bank and turn.

Setting Up for Slow Flight

For slow flights, bend the main flaps down a fair amount, and bend the elevators up a fair amount. When I say a fair amount, the flaps and elevators should never be angled more than 45˚ and that is pretty extreme. Angles steeper than this cause more drag than turning effect. Let’s put the flaps and elevators a little less than half way to 45˚.

Take off

Hold the plane by finger tab under the wings and throw the plane gently, in a level attitude. Move your hand in a straight line, not an arc. As your hand moves forward, Pg. 9 Flying Papercraft.com A-4

your elbow will come up to keep your hand level and the plane will be going parallel to the ground.

But how gentle is gently? What if you tossed the plane and it dropped to the ground only a few feet in front of you? The problem is likely that the throw was too gentle. You need to put a little more force into it., Try giving your wrist a little snap at the end of the throw to give the plane just a little more speed.

Every plane has a minimum speed that it will fly, ‒ its stall speed. If the plane goes slower than this speed, the wings don’t develop enough lift and the plane drops to the ground in pretty much the same arc as a wadded up paper ball. Different kinds of planes have different stall speeds. For gliders it is very slow. Bending the flaps for slow speeds. For fighter jets it is fast. Heavier planes, such as yours, also have higher stall speeds since they need more lift than lighter ones.

To give you an idea the kinds of speeds we are talking about, you can take your plane someplace with lots of airspace‒a big (empty) parking lot or a soccer field‒and throw the plane almost as hard as you can. The plane will love the speed and do all sorts of fun things. But when it comes time to perform slow flights, the plane has to be going relatively fast to stay in the air.

So, if the plane plunked to the floor, give it a little more speed when you throw it and the plane should be able to go across a 20 foot room (5 to 7 meters) Move your hand in a straight line to launch the plane. and lose less than 3 feet (1 meter) of altitude to hit Snapping your wrist just before you let the plane go against the far wall. After a few flights you will learn can make the plane go nicely. just how hard you need to throw. Did the plane nose up, then stall? Maybe there is too Adjusting the Plane much elevator, or you need to adjust the CG more forward. It is likely that your plane didn’t fly so great on the first flight. Time to start adjusting things. Maybe it So it goes. You will be adjusting the control surfaces banked right when you wanted it to go straight. On of your plane much of the time. Maybe the plane the wing that went down, set the aileron down a little, didn’t quite do what you hoped for. Or maybe the and on the wing that went up set that aileron up a landing was rough and the control surfaces got little. Or check if the wings or tails are twisted and thrown out of whack. Or maybe you want to try causing the bank. something to see if you get a better flight. You’ll learn a lot about your plane as you adjust it and fly it. Or maybe the plane nosed down, hitting the floor before it hit the wall. Try a little up elevator. If that One of the challenges with paper planes is that you doesn’t work so well, or you need a lot of elevator, can’t adjust the control surfaces in mid-flight. You set think about changing the CG. You may need more tail them before the flight, give the plane a throw and see weight what happens. Have fun! Pg. 10 Flying Papercraft.com A-4

High Speed Flight

For high speed flying, go somewhere with lots of airspace. Straighten the main flaps so they are bent down only a small amount. Straighten the elevators, but make sure you still have them up a little.

In general, the control surfaces have much more effect on the plane at high speeds than at low speeds, so make small adjustments and changes at high speeds.

One trick that I have found is to not actually change the angle of the elevator. Instead, bend it up with your thumb, like a flat spring, and let it flick off. Do this a couple or three times and the the elevator will be changed just enough to make it fly where you want. This trick works well for other control surfaces, too.

Scale How fast is our plane flying? Is it going supersonic? Well, no and maybe yes. In actual speed over the ground your plane does not fly at supersonic speed, which is about 765 mph. You can’t throw it hard enough. However, by scale your plane may be going supersonic when you throw it hard. Let’s see how.

The example plane, the A-4, is 40’-3” long so 131 plane lengths equals a mile.

5,280 divided by 40.25 = 131

The model is 7-1/2 inches long so a mile, by scale, is 82 USFG Photo feet Full size A-4’s

7.5 x 131 = 982.5 inches divided by 12 = 82 feet

At just the speed of sound, a plane is covering a mile every 4.7 seconds.

1 hour = 60 minutes x 60 seconds = 3600 seconds 3600 divided by 765 = 4.7 seconds per mile

For our model, this means it travels 17.5 feet every second or 35 feet every two seconds.

82 feet divided by 4.7 seconds = 17.45 feet/second 17.5 x 2 = 35 feet

For a paper plane, two seconds is a long time. Measure off 35 feet (measure the length of your stride, then pace off the distance) and count (one thousand one, one thousand two) how many seconds it takes the plane to fly that 35 feet. A-4 models built to two scales. Pg. 11 Flying Papercraft.com A-4

But how fast is your plane flying, really? If it covers 35 feet in two seconds, it is flying at just over12 miles an hour.

1 hour = 3600 seconds divided by 2 = 1800 1800 x 35 feet = 63,000 feet (!) 63,000 divided by 5,280 = 11.93 mph

There’s only one catch: The A-4 and our regional jets are not a supersonic planes. The top speed of A-4 is 673 mph, almost 100 mph short of the speed of sound. But now you know about scale.

Fun Things to Do With Your Plane

Turns For gentle turns, give a touch of aileron, up on the inside of the curve, down on the outside, and a tiny bit of rudder. A fun maneuver is to set the plane up this way, then throw it with same banking angle and up, usually across the wind. The plane will turn and climb until speed bleeds off, it will level out and can glide for a long ways in nearly a straight line or in a gentle curve.

For sharp curves, set the ailerons with a little more angle, then angle the elevators up. Keep the rudder straight or nearly straight. Throw the plane with some banking angle to it. The plane will fly in a steep bank, the wings will be nearly vertical, and in this attitude the elevators become the “rudders” that make the plane turn instead of climb.

It is fun to get a plane to turn at just the right rate and angle up that it comes back around to you so you can catch it!

Rolls For rolls the ailerons are set at a fairly sharp angle, depending on how fast you want the roll, and the rudder kept either straight, or even a little in reverse of the roll (if the ailerons are set for a right roll, the rudder is nudged a little left). A little reverse direction on the rudder will speed the roll up. Set the elevators for either level flight, or a little up to make the plane climb.

Rolls are hard because when the plane is upside down in the roll, the elevators that are set up a little, will be steering the nose toward the ground. In the best rolls I have done, the plane climbs a little in altitude in the first half of the roll, then loses some of it as it flies upside down, but will gain again as it comes back upright.

In a real plane a roll is usually once or twice around, then the plane levels out again. Unfortunately our plane will keep rolling because the controls can’t be changed. Make sure the plane has a soft place to come down. It may not be pretty. Pg. 12 Flying Papercraft.com A-4

Landing

When landing, you want your plane to be going as close to stall speed‒as slow as it can‒without actually stalling. This can be challenging with a paper plane.

Set the flaps down and elevators up, as described for the first flight, only a little more, and throw gently. If there is enough flaps and elevators the plane will fly with the nose up attitude of flaring just before a landing.

Loops

Set up the plane for fast flight with some up elevator, then throw the plane pretty vigorously about a 30˚ angle. The plane will nose up, then fly all the way around the loop, losing speed as it climbs, then picking up speed after it has gone over the top and heading down again. Or it may lose so much speed that it nearly stops, it will flip over as the nose suddenly drops, then pick up speed quickly as it heads straight down, then pull out of the dive and glide.

High Flying

A maneuver that I like to do is to set up the plane for a big loop and fast flight, then throw the plane hard nearly straight up. It will do a big loop, topping out at least 30 or 40 feet above the ground then it will level out and glide for a long ways.

Flying in Wind

Nowhere else is scale of your plane more apparent than when you fly it in wind. Think about this: when your plane is flying at scale speeds close to Mach 1 (the speed of sound) it is flying over the ground, in the real world, at only about 10 mph. That means that a wind of 1 or 2 mph is hurricane force, by scale, and a 4 mph breeze is jet stream winds (100 to 200 mph) to the little plane. So when you try to fly in 8 to10 mph don’t be surprised when that little plane goes tumbling! Calm or very light winds are best.

Generally speaking, it’s not a good idea to fly directly into the wind. This increases the speed of the plane through the air and the control surfaces have much more effect on the plane. The plane often shoots up into a loop, but once it goes over the top and is going with the wind, the wind is subtracted from the plane’s speed and the plane often stalls and falls, tumbling out of control in the wind.

So flying across the wind or at an angle to it is better. When things go right, flying in wind can be fun. Having the center of gravity further forward can help the plane fly better in wind. Pg. 13 Flying Papercraft.com A-4

A Final Thought

One thing that I find fascinating with paper planes is that every flight is different. I am continually learning new things about flying these simple yet sophisticated model planes. Don’t be afraid to try things. If it really doesn’t work, you can always make another plane!

Have fun!

Good flights to you!