Here's a quadcopter build that we did in under an hour to win a bet. We've got some experience building and took some shortcuts (such as using a flight controller from another unit, saving us the time of having to configure it), but I think it's reasonable to say that most makers could build this frame and get everything installed in a day, and still have some time left over to start flying it.

The frame is made from wood... 3/4" x 3/4" fir for the arms, and 1/4" plywood for the body. It's cheap and sturdy... It will take some pretty serious abuse, and if you break it it's easy to repair. The power system (motors, motor controllers, battery) is pretty standard, and uses easily obtainable parts. The flight controller board is an Ardupilot Mega.

About us: We're Mark Harrison and Andreas Oesterer. We've been flying planes, multicopters, and assorted drones for a couple of years. If you like this instructable, come visit us and see what else we're up to!

eastbay-rc.blogspot.com

and
diydrones.com.

(photo note)
Almost all the images here have interesting and laboriously typed "image notes" -- mousing over them gives details about what is being shown. The default view of little pictures don't show the image notes, but you can see them if you embiggen them by clicking on the first image of each set.
tl;dr: click on the first image of each set to see photo commentary.)
(end photo note)

Step 1: Parts

You've got some flexibility in ordering parts. You can pay more or less for things like the radio and flight controller. There's a lot of flexibility in these specs, so if you can get some motors, etc, in the same ball park they will probably work well for you.

Frame

arms: 3/4" x 3/4" fir stick (approx 5 ft)
center plates: 1/4'' or 5mm Plywood (approx 6"x18”)
Machine screws & bolts, and washers
landing gear: 4 wiffle balls
zip ties
battery mount: 3/8" x 3/8" stick (approx 1 ft)
Bamboo Skewers
Piece of soft foam about 1/2'' thick, slightly bigger than your flight control board
velcro, double-sided(approx 8'')
velcro, single-sided, sticky, soft side (approx 6'')

Power System

battery: LiPo 3S 3000-4000mAh (we like this one: 3S 3000 mAh 25-50C)
4 x 40A Turnigy Plush ESC (motor controller)
4 x NTM 35 1100 KV motors
2 10"x3.8" APC SF Props
2 10"x3.8" APC SFP (counter clockwise) props (buy some extras of each prop for when you crash)
power distribution board, presoldered or homemade power distributor

Radio System (remote controller)

This is what we use regularly. Our preference is for FrSky gear. We have found it to be highest quality, and quite reasonably priced.

HobbyKing 9xr
FrSky module and receiver

or

TFrSky Taranis

Here's a cheaper entry-level system.

Flight Control Board

There are quite a few options available. Here are two options that I've used and can vouch for:

3D Robotics Ardupilot Mega ($234). full featured autopilot, full autonomous operation, ground control capabilities.

HobbyKing KK2 ($30). basic quadcopter flight, acrobatic and stabilized modes.

Equipment

saw, drill, hot glue gun

Step 2: Center Plates

First we need to make the center plates, which perform two functions:

- hold the arms securely in place.
- platform to hold the electronics.

Print out 3 copies of the template, superglue them onto the plywood, and cut out the three center plates. Two of the plates will sandwich the arms to hold them in place, and one plate will go on top to provide a flat base for mounting the electronics.

To follow this instructable exactly, use the quad template. You can make a hexacopter or octocopter by using one of the other templates and adding more arms.

Step 3: Arms and Frame Assembly

Cut the arms

Cut the arms to length and mark the center of the long arm.

- 2 arms, 12 inches
- 1 arm, 24-3/4 inches

Attach the arms

Put the arms in place over the template on the center plate. Make sure everything aligns well and superglue into place.

Superglue the top center plate over the arms, paper-side up, aligned with the bottom center plate.

Drill holes through the plates and arms as marked. Bolt the arms to the center plates.

Drill motor mount and landing gear fitting

Now we're ready to drill the motor mount holes. Leave a 3/8'' gap from the end of the arm (we measured this with a scrap of wood), and mark the two motor mount holes, using a motor mount as a template. Drill these through the arm.

Drill horizontally through each arm, centered halfway between the motor mount holes. This will be for the landing gear.

Step 4: Battery Mount, Landing Gear, Motors, and Top

Battery Mount

The battery mount serves two purposes:

- holds the battery away from the protruding bolt
- provides a place to attach the velcro which will hold the battery in place

You can use any sized scrap of wood for this, so long as it keeps the battery from touching the bolt. We had some scraps about 3/8'' high and 1/2'' wide.

Cut 6 pieces about 1'' inch long each, and 2 pieces as long as the center plate.

Line the small pieces up with one of the arms, place the long pieces on top of them, and align them so that they fit your battery nicely. Be sure the gap between the small pieces is big enough for your velcro straps.

Superglue the 6 small pieces into position, and then superglue the large pieces on top of them. Clamp for a minute or two to make sure you've got a good bond.

When you attach the battery, it will be slippery against the wood. In order to prevent this, put a strip of hot glue on the wood. You're not gluing the battery on, you're just giving the battery mount more friction so the battery doesn't slide in the mount.

Motors and Landing Gear

For each arm, bolt the motor onto the motor mount and bolt the motor mount onto the arm. Use zip ties to attach the landing gear.

One nice feature of the whiffle balls is that, unlike pointed landing gear, they don't stick in the grass or earth when you take off.

Top Center Plate

Cut a couple of spacer strips and superglue them to the top center place which is already attached to the body. At a minimum the spacing should be enough to clear the bolt heads. Optionally, you can leave more room if you want to put some extra gear inside there (for example, the optional power distribution board discussed below).

Superglue the top center plate onto the spacers, and clamp for a few minutes to ensure a tight bond.

Step 5: ESC, Motors, Orientation, Props

ESCs

The ESC has several wires. Three of them stick out of one end and attach to the three motor wires.

For each arm, attach the ESC to the motor. The order doesn't matter at this time, but you may have to switch them when you're setting up the flight controller. Attach the ESCs to the arm with zip ties.

Orientation

Look at your flight controller documentation. It will tell you three things important at this time:

- each arm will have a number. Different flight controllers use different numbering schemes, so be careful.
- each motor will have a direction, clockwise or counter-clockwise.
- which way is front.

Mark all of these on your arms and body.

Props

Attach the props to the motor. Note that you have two props that rotate clockwise, and two that rotate counter-clockwise. Try and get this right, or your first flight experience will be flipping upside down into the ground.

Props have the sizes (and usually orientation) molded on their front edge. For multicopters, the numbers face up[*]. We recommend using genuine APC (not "APC compatible") because they're strong and generally come from the factory properly balanced.

To balance the props, put them on a screwdriver so they can spin freely. Bring them level horizontally, and they should maintain that position. If one end droops down, it is heavier than the other end. Put a small piece of scotch tape on the back end of the light side, and repeat until the prop is balanced.

[*] oldtimers, I know that back in 1806 you had a pair of props with the numbers on the other side, but let's not confuse things. Any props that are being sold for multirotors will be as described.

To attach the props, put the washer on the motor with flat end up, attach one of the prop sizers (the little round things in the package) to the prop so that it fits snugly on the prop shaft, and screw down the prop collet. Snug it down firmly, it will be uninteresting to you if it flies off loose in the air.

Prop Safety Note

These props spin with enough speed and power to easily cut flesh. Whenever you see safety instructions to remove the props, REMOVE THEM!!!! It's not some legal blah blah, it's a legit thing right up there with warnings about not sticking your tongue into lamp sockets. If you fail to do so, be sure and upload a picture of your injury as you're waiting in the emergency room for stitches as a warning to others. And if you've got a reasonably strong stomach, google "prop strike" to see other people's uploaded pictures and their pleas to learn from their mistakes!

Step 6: Power Distribution

The purpose of the power distribution system is to attach the positive and negative battery leads to the positive and negative power leads on each of the ESC's ("electronic speed controllers") which control the motors.

We built a WAGO-based power distribution system, but now you can buy a power distribution board for about $4, so that might be a bit easier for this build.

If you buy one of the power distribution boards, you may find it fits nicely in the gap between the top and middle center plates. If you go this route, leave enough room to fit it in and be sure there's room between your spacers. If you've determined that your electronics are all properly fitting, you can even place the power distribution board as you're attaching the center plates to each other. If you do this, you might use small flathead wood screws rather than superglue so that if you need to readjust you can remove the power distribution board easily.

Update: Hobby King is now selling a pre-soldered equivalent of this here. I would recommend buying this as it's probably cheaper than making your own.

Update: and here's the power distribution board. If your motor and ESC wires are long enough, you can just solder the power leads from the ESC directly to the board.

Step 7: Flight Control Board

Start by attaching the receiver to your flight control board according to the flight control board documentation.

Figure out which end of the flight control board is the front end. Most boards will have an arrow pointing to the front.

Cut a piece of the foam to be a bit larger than your flight control board. This is an important piece in that it helps protect the board from vibrations, whick will make the sensors go crazy. Any 1/2'' or so thickness electronics packaging foam will be fine. It should be the spongy kind, not the styrofoam kind.

Hot glue the foam to the frame and attach two strips of velcro as shown.

Align the flight control board so it's centered and pointing forward properly. Then, for each of the four holes in the board, put some hot glue on the sharp end of a skewer and poke it through the hole into the foam. The skewer will anchor into the foam, and the hot glue will form a gasket shape that keeps the flight control board from sliding around into an incorrect orientation, which will cause it to crash. Snip off the skewers then the glue has cooled.

Put a strip of velcro across the top of the flight control board to hold it in place. Along with the skewers, this will hold the board securely. If your flight control board mentions something about covering the barometer chip (so it's not affected by the wind), the velcro strip might do this as well.

Loop the velcro strip over, wrap it around your receiver, and attach the velcro strip back to itself on the body.

If your receiver has dangling antennas, tape them to the down so they don't fly into the props.

Finally, attach each of the 4 ESC control wires to the flight control board.

Step 8: Finishing Up

Finally, flip the unit upside down and install the battery in the battery holder. Don't attach the battery power. It should fit snugly and when you shake the quad around it shouldn't slide loose.

Flip it back over, and you've finished your quad build and are ready to get it configured and flying.

Congratulations! Upload some pictures of your first flight!

It's not a bad idea to make some kind of cover, so in case you flip and land upside down your electronics will have some protection. Here's a simple method using a tomato container.

Step 9: Configuration

General Configuration

We'll briefly cover a few of the general configuration steps, but since this is so tied to the brand of flight control board, radio, etc, you're best off following the instructions provided with those units.

(note: we skipped a few of these steps because we had just removed the flight controller and radio from a working quad, but we do these steps whenever we're building out a new unit. And we NEVER skip steps related to prop safety.)

Prop Safety Warning

REMOVE YOUR PROPS BEFORE YOU POWER UP THE FIRST TIME.

IF YOU HAVE SOMETHING MISCONFIGURED, THE UNIT COULD POWER ON AT FULL THROTTLE AND HURT YOU.

Radio Binding

Many radios have a "bind" procedure which pairs your receiver and transmitter. Do that if necessary, following the manufacturer's directions. Perform any other necessary configuration steps as well. It's typical to power on the radio before powering on the aircraft, and power off the aircraft before powering off the transmitter. Be sure and follow that order if your radio manufacturer recommends it.

Testing Power

With the props off, plug in the battery and immediately watch for any indications of miswiring or short circuits. Most flight control boards have some kind of power indicator, and most ESCs will beep.

Setting Blade Rotation and General Check

With your blades still off, arm (as per the manufacturer) your system and apply throttle. The more throttle, the faster the motors should spin.

Now you need to carefully check your motor rotation direction. Each motor has a direction it should spin, clockwise or counter-clockwise.

If one of the motors is spinning backwards, stop the motors and switch any two of the three power wires for that motor. That will reverse the direction of the motor. Double-check all four motors.

Now, with blades still off, power up your motors, pick up your quad, and do these tests:

- tip quad to left. left side motors should speed up, right side motors should slow down.
- likewise, tipping quad to right, front, back.
- likewise, tipping at 45 degrees. In general, a lowered arm arm should always try to compensate by speeding up, and vice versa for a raised arm.

- holding the quad level, pull the aileron (right stick) stick to the left. left side motors should slow down, right side motors should speed up.
- likewise for pushing the right stick forward, right, and back.
- pull the rudder (left stick) left and right. opposite pairs of motors should speed up and slow down to rotate ("yaw") the quad. For example, opposite motors 1 and 3 will speed up, and opposite motors 2 and 4 will slow down.

(note, these stick directions are the most common, but might be different according to your transmitter).

Propeller Test

Finally, unplug your battery, attach your blades, and tie your quad to something heavy. I use a barbell weight.

Repeat the tests above. All the props should be blowing air down, not up. If a prop is blowing air up, the motor needs to be reversed.
Doing the stick tests should make the quad lean in the appropriate direction, of course constrained because you've got it tied down.

When everything checks out, you're ready to fly!

Step 10: Flying

As with configuration, there's a lot of details you will need to get from your flight controller documentation, but here's some general hints for getting started.

- It's great if you can find an experienced quad pilot to try things out for you. We didn't know any when we first got started, so it's definitely doable to teach yourself.

- buy extra props (in both directions).

- If you have a minor crash and crack or chip a prop, replace it. It's uninteresting for a cracked prop to finish breaking off in the air.

- try to find a large area with plenty of soft grass to cushion your landings.

- don't fly with anybody around, especially pets and kids who might run up to unit.

- don't fly over houses, cars, people, or anything else expensive to replace.

- when taking off, "hop" out of the prop wash. When the unit is within one or two feet of the ground it's not very stable because of the air being blown back up off the ground.

- be super-gentle on the sticks, You usually don't need much stick motion to move around. Definitely less than you might be used to from playing video games.

- Keep track of your orientation, know which way is front. We put red balls on the back arms.

- Bring it up to about 6-8 feet, and just try to hover in place to get the feel of things.

- A unit this size will probably get 10 minutes or so of gentle flight. Bring it down and check the battery level to get a feel for how much juice you have left.

- If it's starting to get away from you, reduce throttle gently so that it lands wherever it's at.

- If you panic, still try to reduce the throttle gently. But if necessary, cut the throttle completely. It's cheaper to replace some blades or arms than to lose the unit altogether.

- Have fun, and send us a picture of your creation!