Introduction: How to Make a Foam Board RC Airfoil
Making and flying remote control aircraft is a pastime that has intrigued hobbyists for decades. However due to expensive material costs and the time it takes to build an aircraft, many prospective hobbyists are turned away from the sport. Foam board provides a fast and cheap build material that can be used to create sturdy and lightweight aircraft. This article will walk you through the steps for making your own RC airfoil for your foam board aircraft.
Step 1: Gather Your Materials.
Materials you will need:
- 1/8 inch foam board
- 1 sheet of printer paper
- Pen, Pencil or Marker
- 1 Box Cutter
- 1 Hot glue gun
- Hot glue sticks
Step 2: Determine the Wingspan.
Determine the wingspan of the aircraft for which you are constructing the airfoil. In this example, we will be scaling our aircraft to a 30 inch wingspan.
Step 3: Determine Chord Length.
Determine the chord length of the airfoil based on the span. The chord length of a wing is the distance from the leading edge to the trailing edge of the airfoil. In our case, we are going to make our airfoil chord 5 inches.
Step 4: Determine Airfoil Shape.
Determine the desired shape of the airfoil. This can be accomplished by selecting a nominal thickness for the wing or, if building a scale aircraft, by measuring the airfoil from a drawing. In this example, we will be using the Clark Y airfoil.
Step 5: Create an Airfoil Template.
Create a template for your airfoil using a sheet of printer paper.
Step 6: Cut Airfoil Ribs.
Cut the desired number of airfoil ribs from the foam board using the template created in step 4. Then cut the back third of each rib off. This is done to create clearance for the ailerons.
Step 7: Draw the Shape of Your Wing Skin.
Trace the shape of the wing skin on the sheet of foam board.
Things to keep in mind:
- The airfoil is created by folding the skin around the airfoil ribs we cut, so make sure to cut enough material to make it all the way around the airfoil rib.
- The rear third of the airfoil rib has been removed so the material BELOW the wing only needs to extend to the cut line of the airfoil rib.
Step 8: Draw an Access Panel for Servo Wires.
In RC aircraft, control surfaces such as ailerons, elevators and rudders are controlled by small electronic actuators called servos. These servos are controlled by the flight control board or receiver by servo wires. Trace an access hole in the bottom center of the wing to run servo wires through.
Step 9: Cut the Wing Skin From the Foam Board.
Carefully cut out the wing skin and access panel but DO NOT cut the ailerons yet.
Step 10: Mark the Leading Edge.
Draw a straight line across where the leading edge of your airfoil rib will be.
Step 11: Score the Leading Edge Line.
Using the box cutter, cut along the line making sure only to cut through one side of the paper and not the foam!
Step 12: Remove the Paper From the Upper Surface.
Carefully peel the separated piece of paper off of the upper surface of the wing.
Step 13: Crease the Leading Edge Line.
Run your ruler along the edge of the papered section, pressing firmly to create a crease in the foam.
Step 14: Bend the Upper Half of the Wing Skin.
Carefully bend the upper portion of the wing skin to create a permanent bend in the board. This is to ensure the skin will form around the airfoil ribs.
Step 15: Glue the Ribs in Place.
Place the airfoil ribs in the desired location of the papered portion of the foam board and glue them down using a bead of hot glue.
Step 16: Create a Path for Servo Wires.
Cut a gap in the outer ribs to create a channel for servo wires.
Step 17: Cut the Wing Spar.
The next step is to cut the wing spar. The spar is the element of a wing that gives it its rigidity and strength and carries the majority of the load. Cut a strip of foam board as long as your wing and as wide as the thickest part of your airfoil ribs.
Step 18: Measure Spar Length.
Measure the distance between the ribs.
Step 19: Cut the Spar to Length.
Take the foam strip that was cut in step 16 and cut from it the lengths of measured in step 17. Be sure to make 90 degree cuts!
Step 20: Glue the Spar in Place.
Glue these pieces vertically between the ribs. This makes up your wing spar.
Step 21: Check to Ensure Your Wing Skin Is Large Enough.
Once the glue dries, wrap the non-papered section of the wing over your spars. Ensure there is enough wing skin left to cover the upper surface of the wing. Note: You should have plenty of extra foam board hanging over at the trailing edge of the wing.
Step 22: Add Glue to the Wing Structure.
Open the wing back up and place a bead of hot glue on the top of your airfoil ribs and spar. Note: You need to do this step quickly before the glue cools!
Step 23: Wrap the Skin Over the Structure.
Before the glue cools, quickly wrap the non-papered portion of the wing up and over the airfoil ribs and apply pressure while the glue cools.
Step 24: Cut the Ailerons Free.
Using the box cutter, cut your ailerons free. Note: Only cut completely through the foam board on the cuts perpendicular to the spar. The cuts parallel with the spar should have the foam core cut from beneath the wing, but the top paper should be intact.
Step 25: Create a Gap for Aileron Clearance.
Run a ruler down the perpendicular cuts to create a gap and prevent the aileron from rubbing.
Step 26: Cut a Bevel for Aileron Movement.
Using the paper as a hinge fold the aileron up and cut away the foam at a 45 degree angle making sure not to cut through the paper.
Step 27: Reinforce the Aileron Hinge With Hot Glue.
Run a bead of hot glue in the crevice you just created in step 25. Then use a piece of scrap foam as a squeegee to remove the excess glue. This helps reinforce the hinge point of the aileron. Note: Do not close the hinge until the glue has completely cooled or the aileron will become inoperative.
Step 28: Congratulations!
Your RC wing is ready to have the servos installed and be attached to your aircraft!