Chapter Two -- Building Your First Plane
Getting Started
Well, you've done the most important thing before selecting and purchasing your first plane and joined your local club. Your club will give you lots of good advice. Take it. Our club is supported by a couple of pretty good local modeling stores who will give you good advice too. You may want to buy through a mail order company, but they may not always give you the right advice you are looking for. Your choice of equipment can depend on local conditions - runway, weather, TV interference, etc.. Mail order companies can't be expected to know about your locality. Also, you will be needing the services of a flight instructor (this is a free service in our club, as it is in most clubs) and the instructors often have preferences that will speed up your learning process if followed.
In Chapter One, you learned about some of the choices available in starting up in this hobby. I will brush up against some of these choices in this chapter too. I strongly urge you to read Chapter One and talk to members of your club before you buy. The remainder of this chapter assumes that you have chosen to purchase one of the many Almost Ready to Fly (ARF) kits on the market and it continues to describe the general process of assembling your first ARF aircraft.
Check List:
Read Chapter One.
Joined your local club and talked to some of its members about what equipment to buy.
; Join the recommended affiliation of you local club (AMA).
Purchased your ARF kit
; Purchased our recommended radio and extra servos (if needed). You will require a total of 4 servos.
; Purchased the engine
; Purchased all the ancillary construction materials and tools (often recommended by the manufacturer of the ARF kit)
Glue
Spinner
Wheels
Xacto knife
; Pins
Sandpaper
etc.
Purchased you field box stuff (This could wait a while if you are not planning on running up you engine just yet)
Hooked up with a club instructor.
ONLY PROCEED IF ALL THE ABOVE LIST IS DONE
Open the box
If you haven't already done it, open up all the boxes and check for signs of damage. Individually, check the contents of each box (Kit, Engine, Radio, etc.) and check for missed items. Identify each item and if you can't, check the documentation that came with it. If that doesn't help STOP. Call your instructor or local hobby store (The one where you purchased the item) and ask for help.
Put your Transmitter (TX) and Receiver (RX) batteries and you field box battery on charge.
TIP: Buy a simple domestic light timer and set it up to come on once a day for about one hour. Rotate the time through the On time until it just switches off then turn the timer on manually. This will keep the chargers on for 23 or so hours to give then a full charge. Once the batteries have been on charge for their full time the timer will allow a one hour top-up charge every day until you need the batteries next. Do this after each time you have used the batteries. Also, make sure that you do this during the night before flying.
Clear an adequately large working space that has a large flat surface, preferable that you can stick pins in to and that doesn?t mind getting dusty. (Laundry rooms, for instance are a definite No No). Make sure that you work place has space to store things like finished wings, fuselages, etc. so they are easily accessible and are not in the way and get damaged.
If you will be running-in your engine off the plane find a suitable outdoor location to set up the engine test stand. Read the documentation that came with your engine?.twice or more. If there is anything you don't understand You guessed it - call your instructor. Many folks run-in their engine on the plane - its a question of personal choice (Me? Small engines I run-in on the plane, big ones I do on a test stand. If you have a .40 or .46, thats small. For the purposes on this article I will assume that you will be running-in your engine ON the plane
Check List:
You can stand in you workshop and find everything you need
You know that you have everything you need
You know what everything is
You have the assembly documentation on the workbench
; Your significant other has buy-in on all this
Assembling Your ARF
No, don't worry, I'm not going to tell you how to build your ARF. One, I don't know what ARF you have, and two, I bet the manufactures have done a better job of it than I could. What I will do is emphasize some of the things to watch out for and give you some hints and tips for success.
Essentially the whole process can be broken down into several areas. One manufacturer may recommend doing the wing before the fuselage, another will recommend doing the fuselage before the wing. Always follow the recommendations of the manufacturer regardless of the order of things in this article.
Tail Feathers:
This refers to the Horizontal Stabilizer and Vertical Stabilizer that sit at the tail end of the fuselage.
Horizontal Stabilizer. the rear wing acts like a weather vane and keep the fuselage level. This keeps the main wings level. Mounted on the horizontal stabilizer is a movable flap (up and down) called the Elevator. The elevator is controlled by one of the radio servos and by the right hand TX stick (moving forward and back). As the Elevator Stick is moved forward, the elevator flap moves down and increases the Lift on the horizontal stabilizer. The horizontal stabilizer moves upward, rotating the fuselage around its center of gravity to point the nose down. You are in a dive. When the elevator stick is pulled back, the elevator moves upwards and decreases the lift on the horizontal stabilizer. The fuselage now rotates in the opposite direction causing the nose to point up. You are now in a climb.
Vertical Stabilizer. The fin also acts like a weather vane but in a different plane. It also has a movable flap on it?s rear edge called the Rudder. The rudder is operated by another servo and the left hand TX stick (moving left and right). The rudder's direction, as viewed from behind the aircraft, follows the direction of the rudder stick. When the rudder moves to the right, the tail is forced to the left and the fuselage rotates pointing the nose to the right. You are in a right yaw. Moving the rudder stick to the left gives the opposite yaw.
Hinges
Often the elevator and rudder are assembled into the tail feathers, but the hinges are not glued in. Follow the manufacturers direction on gluing the hinges in place.
TIP: The horizontal stabilizer must be set square or perpendicular with the center of the fuselage and set exactly horizontal. Make sure the seat where the horizontal stabilizer will be glued is horizontal. Use 12 minute or 30 minute epoxy to glue in the tail feathers. Set the horizontal stabilizer on the fuselage and before the glue has set measure the distance between the left tip of the horizontal stabilizer to a point on the fuselage along its center line near the front. Make a similar measurement from the right tip of the horizontal stabilizer to the same point on the fuselage. Adjust the horizontal stabilizer until it sits centrally in the fuselage and both measurements are equal.
TIP: When gluing the vertical stabilizer in place, use a line (it can be an imaginary line) that runs along the top of the fuselage along its center and align the vertical stabilizer to it by viewing from behind in a manner similar to aligning the sights of a rifle or aiming a pool cue (What does this tell you about my misspent youth)
TIP: When gluing in the hinges you must observe a compromise. The control surfaces (Rudder and elevator) must be free to move easily without any tendency to spring to a particular position and with no binding, but the gap between the control surface and the stabilizer trailing edge must be as small as possible. An additional idea is to use some self adhesive tape to seal the gaps. Be careful, the tape must start on the rear edge of the stabilizer go halfway down the trailing edge all the way to the hinge, then up the leading edge of the control surface up on to the top surface. If you just tape across the gap, the control surface will not be able to move in at least one direction.
Installing the Pushrods
The pushrods are the mechanism that transfers movement on the servo horn to movement on the control surface. There are two types of pushrod and its a matter of personal choice which one to use. The non-flexible type is the cheapest form and they comprise of a wooden dowel (usually about ¼" diameter) onto which a threaded metal rod is attached at both ends. The metal rods screw into a variety of servo horn or control horn devices, usually supplied in the kit. These types of pushrods are only suitable when they have a straight run with no bends or corners. The second type are flexible coaxial rods that act like the brake cables on a bike. In this case the outer tube must be fixed solidly to the frame of the model at least at each end and preferably several places along its run. The center rod then moves within the outer tube. Each end of the inner rod has a threaded metal rod attached to connect to the servo and control surface. These rods are flexible so they can be routed around obstructions. Some rods are more flexible than others.
The threaded rods at the ends of the push rods must be long enough to have at least ¼" of thread screwed into the linkage unit.
TIP: When attaching the control surface horns, care must be taken to ensure correct positioning. The horn should be installed on the control surface so that no undue stress and bending is done to the exiting pushrod. It must also be in a position so that the actual connection between it and the linkage on the end of the pushrod is exactly over the control surface hinge line.
TIP: Make sure if the linkages are clevises (looks like a tuning fork) that you use any locking device that is supplied. If no locking device is supplied make some from a ¼" piece of fuel tubing. Place the fuel tubing over the metal rod before screwing on the clevise. Once the clevise has been attached to the control surface or servo horn push the fuel tubing up and over the two blades of the clevise so that they cannot inadvertently spring apart.
Check List:
; The tail feathers are square and true to the centerline of the fuselage
· The hinges are secure and can not be pulled out or otherwise moved
The pushrods are installed and connected to the rear control surfaces (rudder & elevator)
The rear control surfaces move easily when the pushrods are operated from the servo area of the fuselage.
; No binding of any moving part can be seen or heard
Installing The Servos
The servo tray sits in the center section of the fuselage. It will hold three servos - one for the elevator, one for the rudder and nose-wheel steering and one for the engine throttle. Connection to the servo horns: Pushrod connection to the servo horn is done with one of the following methods. Servos must have adequate suspension at their attachment to the servo tray. The manufacturer of your radio will supply suitable rubber/metal mounts. Use them.
Clevise: Follow the details described above
EZ Link: This is a brass collet that is secured to the servo horn by pushing its spigot through an appropriate hole in the servo horn and fixed in place with a plastic washer. The metal rod on the end of the pushrod is fed through the hole in the EZ Link and secured by tightening a screw. This is a very simple, easy and quick way of connecting a pushrod to a servo horn. It also allows easy adjustments. However, if not inspected regularly, it can work loose and fail - usually in the air causing a crash.
?Z? bend: Probably the simplest method. Simply bend the metal rod one way at 90 degrees the back 90 degrees making it look like a step. Once in the servo horn it is the most reliable connection. However, it is not adjustable.
How to Choose the Appropriate Hole in a Control Horn
Assume we are fitting the linkage to the elevator. Attach the pushrod to one of the holes in the elevator control horn. I usually pick one away from the furthest hole from the surface. Establish what is the recommended throw (up and down movement) of the elevator. This will be on the plans or in the building instructions. Measure the full travel of the selected hole on the horn for the maximum throw of the elevator. Connect the elevator servo to the appropriate channel of you radio and turn on the RX and TX. Operate the elevator servos from maximum up to maximum down. Establish which hole on the servo moves the same distance as the selected hole on the control horn. That is the hole you need to use. When you attach the pushrod to the servo operate the servo to its maximum throw. Watch for the servos stalling (Stopping because of mechanical limitations). If you fly in this configuration you will run the receiver batteries down faster than normal. If the servos stalls, try a different combination of horn holes. This can be a bit tedious. But it?s worth getting this right. Repeat for the rudder.
Check List:
With you radio turned on:
Push the right stick away from you the elevator should go down
PULL the right stick back the elevator should go up
Move the left stick to the left the rudder should move to the left
Move the left stick to the right the rudder should move to the right
None of the servos should stall and no binding should be seen or heard
Installing the Engine
Before doing anything else in this area, make sure of three things: All the wood to wood joints are well glued, the whole engine compartment is coated with a fuel proofing agent (epoxy glue is good for this), there is an appropriate sized hole in the firewall to allow the throttle linkage through. If you are in doubt about any of these, then fix it now as follows.
TIP: Use epoxy glue to make a filet where the firewall meets the fuselage sides
TIP: To coat the engine compartment, mix up some epoxy then thin it with denatured/rubbing alcohol.. Then use a stiff brush to paint the solution to all exposed surfaces inside the engine compartment.
TIP: Temporarily hold the engine in its final location. Then drill a 1/8 inch (Or the appropriate size for the pushrod outer tube) hole in the firewall immediately behind the throttle control horn (or as close to it as possible). Make sure to read the manufacturers instructions if available and follow their advice. Always!
Install the engine mount. Here?s what to look for. Some planes require the engine to point downwards and/or slightly to the right (usually not more than a couple of degrees) These offsets are called ?Down-thrust? and ?Side-thrust?. These offsets can make the engine installation look a bit sloppy. But they are essential if the manufacturer calls for it. Usually the firewall will be already installed to accommodate this. If not follow the manufacturer?s instructions. The main point is:- don?t try to correct it by placing the engine straight. The offsets are needed if called for.
You may have to drill holes in the engine mount to align with the mounting holes on the engine. To do this, place some chalk or similar material on the bottoms of the engine?s mounting lugs. Hold the engine on the engine mounts where you want the engine to be (Watch out for clearance between the engine spinner/propeller and the fuselage). When you carefully lift off the engine you should see a clear outline of the mounting lugs, with the holes, on the top surface of the mount. Carefully drill the holes. In a metal mount, these holes will be drilled and threaded, in a plastic mount the screws may be used to self-tap the threads. Your manufacturer?s recommendations should be followed.
When you install the throttle pushrod, rough-up the surface of the outer tube where it will pass though the firewall. Use epoxy to thoroughly secure the pushrod to the firewall. Follow the manufacturer's instructions on running the flexible inner wire to the throttle control horn. Don't forget, this pushrod, like all pushrods, must have both ends of its outer tube secured to the structure (preferably, it should be secured at more than two points).
When the engine is mounted, use the suggested method of connecting the throttle cable to the control horn and to the throttle servo. Use Loctite on the engine mounting screws.
Checklist:
Mounts are tightly secured to the firewall
· Engine is tightly installed in the mounts and the screws are Loctited down. Washers are in place
down-thrust and side-thrust is observed (if called for)
throttle cable is securely fastened to the engine and servo control horns
· The throttle servo operates without binding and stalling
Installing the Nose Wheel
Most ARF kits either have the landing gear mechanism partially installed or not at all. But whatever is the case, follow the manufacturer's instructions.
TIP: Make sure that the mechanism is tightly fitted to the firewall.
TIP: Connect the push rod in a similar way as the throttle pushrod. The servos end connects to the rudder servo.
TIP: Make sure that when you operate the servo to check for binding and stall, that the rudder and nose-wheel turn in the same direction.
Installing the Landing Gear
Once again, use the manufacturer's instructions and don't skimp on strength.
TIP: If the kit comes with foam rubber wheels - trash them and replace them with rubber wheels such as the Du-Bro wheels of the same size.
TIP: If you will be flying off grass, you may want to think about sizing your wheels up by a ¼ or ½ inch.
Installing the Fuel Tank
TIP: Even if the manufacturer doesn't tell you, you should try to wrap foam rubber (model shops can sell you special high density foam sheets made just for this purpose). This stops vibrations foaming up the fuel.
TIP: There will be two fuel lines coming from the tank to the engine compartment. Use different colors to distinguish between them. Red (hot) for the pressure line (on the muffler) and blue (cool) on the carburetor feed.
TIP: Use the pre-made spring clips to hold the fuel tubing onto the various fuel nipples. Normal wire bent round and twisted tight will cut through the silicon tubing and cause leaks.
TIP: If possible, modify the fuselage so that the fuel tank can be removed at a later date. This may mean cutting a hatch either above or below the tank and fitting it with retainers and screws. If you have any doubts about doing this - either don?t or ask an accomplished builder in your club for help and advice.
Assembling the Wings
The wings will be in two parts, often referred to as the ?Wing Panels?. The manufacturer will describe how to join the two halves. The most important part of this operation is to install the ?Dihedral brace?. Most likely, this will be a single or built-up laminate piece of ply wood that is about 6 - 8 inches long and is cut to form a very shallow ?V?. This brace in the strength element that glues between the two wing panels. It also governs the angle of the dihedral. In addition to this, the manufacturer may require you to wrap fiber-glass cloth around the center join. DO NOT SKIP EITHER OF THESE STEPS.
TIP: In fact, even if the manufacturer of your plane doesn?t suggest the use of a dihedral brace, you should ask a club member?s advice on how the modify the wing to accept one.
The ailerons will most probably be operated by a torque rod. The torque rod will run through a sleeve that is attached to or near the rear edge of the wing root. Make sure that this assembly is installed correctly and that glue does not penetrate the sleeve.
TIP: Apply Vaseline inside the sleeve to avoid any glue seizing-up the torque rod. This can be done by gently heating some Vaseline so that it runs down inside the sleeving.
TIP: Balance the wing by holding the wing inverted so that it straddles a dowel that runs along the wing joint. The wing should act like a see-saw and come to rest with neither wing panel lower than the other. If it is not balanced, find a suitable spot on or near the wing tip of the LIGHTER wing panel where there is solid wood. Make a suitable size blind hole and fill it with lead shot or other heavy material, until the wing balances OK.
Check List:
· The dihedral brace is glued in well
· The joining tape is firmly installed and completely encased in glue
· The wing balances OK
· The ailerons move freely with no binding
· The aileron servo operates without stalling
Checking the Balance
· Now all the parts are built.
· Assemble the plane including the receiver battery and engine. DO NOT fill with fuel.
· Position yourself to face the plane and place your hands beneath the wing - one hand each side of the fuselage.
· Lift the plane of the surface by place the index finger of each hand on the underside of each wing panel at a position approximately 1/3 back from the wing?s leading edge. (The manufacturer may show this point as the ?Center of Gravity? (CG). The plane should ?hang? in a level state with neither the nose or the tail tending to be lower than the other.
TIP: A slightly nose heavy plane is OK. A tail heavy plane will crash.
TIP: If the plane doesn?t balance - see if you can reposition the receiver battery and the receiver itself to correct or partially correct the condition.
TIP: Add weight to the lighter end of the plane. Model stores sell self adhesive lead weights that do the job very well.
Checking the Control Surfaces
The manufacturer will probably tell you how to set the throws on each control surface. Keep to the manufacturer?s recommendations. Too little throw and you may not have all the control you need, too much throw and the plane will be too sensitive and difficult to fly.
TIP: Make sure that both ailerons operate the same amount.
Running the Antenna
The receiver antenna must be run in as straight a line as possible. If the manufacturer suggests a routing for it then follow the instructions. Usually the antenna will be attached to the top of the vertical stab.
TIP: Do not tie knots in the antenna wire.
TIP: Place a securing device inside the fuselage just before the antenna exits the fuselage and one to secure the end of the antenna to the vertical stab.
TIP: A good securing device can be made from a two inch length of fuel tubing. With a modeling knife, cut slices across the tubing in four evenly spaced intervals. The slices should go about half way through the tube. Now thread the end of the antenna wire into one end of the tube and out through the first slice (bend the tube to open up the slice). Thread the end of the wire back into the tube through the second slice. Continue this for the length of the tubing. This device can be slid into place and it will hold the wire secure but it will slip if sufficient force is applied thus saving damage to the antenna wire in the event of a crash.
Taxi Tests
Landing is probably the most difficult skill to master. Take off is essentially a high speed taxi with a rotation at the end. Taxiing is probably the second most difficult skill to master. So, before you get too far in your flying lessons do some serious taxiing practice. Try fast and slow - they?re different.
TIP: If you are finding it difficult to keep the plane in a straight line it could be that the nose wheel steering is too sensitive (it turns too much for a given stick input). In this case either move the linkage farther out on the nose wheel horn or farther in on the servo horn.
TIP: As a goal when you are taxiing, try to taxi the plane down one edge of the runway, cross the runway and then down the opposite side. Then pick a spot on the runway a taxi the plane to that spot. First taxi to the spot going away from you, then do it with the plane coming towards you. This will give you an idea of the ?Reverse control? experienced when a remotely controlled plane is flying towards you.
First Flight
TIP: DON?T DO THIS WITHOUT AN INSTRUCTOR BY YOUR SIDE.
Well, I hope this has helped you construct your first plane. Flying radio controlled miniature aircraft is not difficult to learn. It?s a bit like riding a bike. The first time you tried you thought you?d never get the hang of it. Now you can?t understand why the kid next door keeps falling off his bike. The secret is to join a club and use one of the club instructors.
How long does it take to learn. Well that?s impossible to say. I?ve known some folks take all season, and others who did it in two days. It depends on how much time you can put into it, what your eye to hand coordination is like and a variety of other factors. But, what ever is the case, you will learn to fly faster and better with the help of a club instructor.
Good luck and happy flying.
New Plane Checkout Sheet
FUSELAGE & WINGS Check
· Check for any loose glue joints ---------
· Check incidence, alignment, wash-in/wash-out, for warps ---------
· Landing Gear properly placed and secured ---------
· Wheels rotate freely ---------
· Control surfaces properly secured ---------
· Linkages free from binding and slop ---------
· Wing bolts/bands securely fastened and in good condition ---------
· Clevises properly fastened and secured ---------
· Fore/aft balance correct ---------
· Name and Address and AMA number on/in plane ---------
ENGINE
· Engine is correct size for plane ---------
· Engine properly fastened to plane ---------
· Propeller is correct size for engine and is undamaged ---------
· Fuel tank in proper location, size and hookup ---------
· Spinner or rounded prop nut securely fastened ---------
· Acceptable muffler with acceptable noise level ---------
RADIO INSTALLATION
· Frequency flag with proper channel on transmitter ---------
· Receiver and battery pack properly wrapped and installed ---------
· Servo grommets not too tight, all screws secure ---------
· Push rods secure and functioning properly ---------
· Antenna properly mounted, fully extended ---------
AFTER FREQUENCY IS CLEARED
· Proper control movement with no binding ---------
· Control surfaces correspond with stick movement ---------
· Control surfaces in neutral position with trims in NEUTRAL ---------
· Radio range checked ---------
· Engine idle setting checked ---------
GENERAL
· Frequency control understood ---------
· Proper frequency pin in use ---------
· Field rules understood ---------
· Safety issues understood and discussed ---------
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