F4U Corsair Swappable w/Downloadable Plans

If you've been waiting for a downloadable F4U Corsair swappable, wait no further.  Download the plans at the end of this article and get building!

The wing is the only part of this model that's challenging to build.  There's a detailed video later in this article to walk you through the process.

The Design

This model of the Chance Vought F4U Corsair is scaled from the original F4U-1A structural schematics.  The profile of the fuselage, and the shape and geometry of the wings and control surfaces are very close to those of the original plane.  The original, of course, had a round nose to accomodate the Pratt and Whitney Double Wasp radial engine.  We, however, are using a small electric motor, so to keep the build simple and to use a standard swappable power pod, the sides of the fuselage in this model are flat.

The wing is mounted with about two degrees of positive incidence, just like the original plane.  This makes it climb with airspeed, and results in scale behavior.  If you don't want this, you can cut the wing opening flat in yours so the wing sits level, and it will behave more like other swappables.  You may also wish to experiment with down-thrust on the motor.  The original plane actually had about 2.5 degrees of down thrust.

The original corsair killed a lot of airmen due to its abrupt stall characteristic.  It would drop the starboard wing abruptly and enter a spin.  If the pilot applied power suddenly in an aborted landing, it would drop the port wing, with similar results.  This model uses David Windestål's undercambered wingtip design from the Spitfire to to overcome these challenges, resulting in a very stable, predictable airframe.

Build the Fuselage

The fuselage of the F4U Corsair goes together in the same way as the Spitfire and other Flite Test swappables.  The bottom of the fuselage is a B-style fold, as usual.  You will probably want to just score the wing openings and leave the foam in place while gluing up the fuselage.  This will make it much easier to get good pressure on the bottom joints.

Instead of being straight, like the Spitfire, the bottom plate of the tail has a couple of creases in it so it follows the curve of the fuselage.  Once you have the box of the front fuselage closed and glued, go ahead and bend the bottom plate up and the sides of the tail in and glue them in place before mounting the tail.

Build and Install the Tail

Before you glue the tail together, reinforce the elevator with a popsicle stick, or use a strip of carbon fiber, as shown in the pictures.

The vertical stabilizer has a tab that fits into the horizontal stabilizer.  Fit the horizontal stabilizer into the slot in the vertical stabilizer/rudder and glue these pieces together.  You will probably need to bend the elevator upward as you slip the horizontal stab into place.  Use a square to align the pieces at right angles while the glue sets.

The front of the vertical stabilizer has a tab that fits into the back turtle deck former.  Go ahead and glue the tab into the slot so the back former, the vertical stabilizer and the horizontal stabilizer are all a single unit before installing them into the fuselage.

Drop the whole tail assembly into the rear of the fuselage from the top.  The tabs on the top of the fuselage will fit into the horizontal stabilizer.  The bottom of the vertical stabilizer will fit into the notch in the bottom plate and the rear turtle deck former will come to rest between the sides of the tail, with its shoulders sitting on top of the fuselage.  If you cut and glued everything accurately, it will all fit.  If something is a little off, now is the time to trim tabs or slots as needed to get good fit before gluing.

Once you're satisfied with the fit, glue the tail in place, one joint at a time.  Add a bead of glue to one of the joints and hold everything straight while it sets.  Then check to make sure the tail is still square and glue another joint.  Leave the vertical joints at the back of the tail for last.  Set the fuselage on a flat surface and make sure the horizontal stabilizer is level.  If you check and adjust as you go, by the time the last joint is secured, everything will be solid and straight.

Install the Tail Servos

Now would be a great time to install the tail servos.  You will want 12 inch (30cm) extensions on both servos, and you will want to route the wires through the fuselage before you glue on the turtle deck.

Fit the Power Pod

Next, fit the power pod.  Align the tabs with the slots in the top of the fuselage and make sure it fits.  Insert the skewers through the firewall and glue them in place in the fuselage top plate.  Make sure they're left long enough to retain the power pod, but short enough that you can still pull the power pod forward and drop it out once the front cowl former is installed.

Note the use of a plastic spoon as a ram air intake for cooling the ESC.

Install the Cowl and Turtle Deck

Glue the formers in place for the cowl and the turtle deck, as shown in the diagram.  The front cowl former fits between the sides of the fuselage.  It has small triangular tabs to provde extra gluing surface.  The middle and rear cowl formers fit into tabs in the top of the fuselage.  Make sure the larger one is in the rear position.  The front turtle deck former fits between the fuselage sides against the back of the top plate, as shown in the photo.  The rear turtle deck former is already installed as a part of the tail assembly.

Cut the cowl and turtle deck skins out of thin poster board and make sure they fit properly over the formers.  If you have cut and glued everything accurately, they should fit exactly.  If you're not sure, cut them a little oversize.  You can always trim them after they're installed.

NOTE: you may want to leave the turtle deck skin off until the very end of the build.  It's much easier to route the servo wires without it installed.

Build the Wing

The inverted gull wing is the most challenging part of the build, but it's also the most satisfying.  It's the signature feature that makes the F4U Corsair stand out, on the ground and in the air, and it's probably the reason you wanted to build this model.

This video walks through the construction of the wing step-by-step.

Trivia:  The Corsair's inverted gull wing was not, primarily, an aerodynamic feature.  It was designed to provide ground clearance for the massive 13'4" propeller while still allowing the landing struts to be short enough to fully retract into the wing.  One side effect of the wing design was that the wing root joined to the round fuselage at a right angle, minimizing interference drag.

Install the Wing into the Fuselage

The wing fits into the fuselage in the same way as in the Spitfire.  The main difference is that it won't slide in, because it's bent.  You'll need to cut the floor out of the fuselage, fit the wing and glue the piece of fuselage you cut out to the bottom of the wing.  Glue alignment blocks to the top of the wing and mount it with skewers and rubber bands.  You will probably want to build up foam under the skewers to reinforce them and glue popsicle sticks to the bottom of the wing, as shown in the photos.

You can glue the wing in permanently, if you like, but this requires very long servo wire extensions and makes it difficult to route all of the wiring.  I find it easiest to connect the servo wires to the receiver in the power pod, and then slide the pod in, firewall first, through the hole in the bottom of the fuselage.  Once the firewall is hooked on the front and the pod is skewered in place, you can install the wing, attach a battery and fly.

Check the Center of Gravity

The center of gravity should be 25-30% back from the leading edge of the wing.  This is right under the wing spar.  If you're running the recommended 2826 motor and a 3s2200 battery, this should be easy to achieve.  If you have a heavier or lighter power system, you may need to add weight or move components around to get the center of gravity correct.

Notes on Landing

You will want to belly-land the Corsair in grass whenever possible.  Because of the geometry of the wing, it will contact the ground first and bear most of the landing forces.  Cover the protruding edges of the wing with bidirectional fiber tape to prevent damage.

Flaring when landing is important.  If you don't get a good flare and settle into the grass gently, the forward edges of the wing can dig in, stopping the plane abruptly.  If this happens, the weight of the battery will pull the power pod forward, tearing the fuselage where the skewer is holding it in place.  If this happens, you can repair and reinforce the skewer hole with fiber tape, or you can glue on a piece of popsicle stick with a hole drilled through it.  This makes the joint strong enough to endure almost anything but a nosedive into the ground.

Flight Video

Here's a short video of the Corsair in flight.  It is smooth and graceful in the air.

Downloadable Plans

F4U Corsair Plans

Recommended Electronics

Motor: RCTimer BC2826-10 1400KV or Turnigy D2826-10 1400KV

ESC: 30A BlueSeries Brushless Speed Controller

Prop: 8x5 Electric

Servos:  Hextronic HXT900 9g

Battery:  3s2200