Foam Board Tools & Techniques
Become an expert at using foam board. Learn how to cut, fold, shape and glue this versatile material into excellent airplane models.
Foam board (also called foam-core) is made by placing a layer of low-density polystyrene foam between two layers of paper. This makes it much stiffer than paper while still being lightweight. If you use regular paper for wide wings, they can droop and bend, which hurts flight performance. Foam board’s high strength-to-weight ratio lets you build wings that are larger and stiffer than what you could make with paper.
In our Foam Board Airplanes article we listed several different kits that you can purchase and then build at home. We even have a Basic Foam Glider available on our website. If you build one of these kits, you'll get a well designed, high performance airplane. With a little practice and experimentation you can also design your own airplane!
Working with foam board is a bit different than working with paper. For one thing, foam board doesn't fold as easily. Here are some tools, techniques and tips for becoming an expert at working with foam board.
Types of Foam Board
There are several different types of foam board to choose from. Some have different thicknesses, some are heavier or lighter than others. Some are made with paper coverings and some have plastic coatings which can make it more durable and waterproof. They come in a wide variety of sizes and colors too. You can even use cardboard as a substitute for foam board. In general, light weight materials work best for airplanes, so look around in your local stores and find the material that will work best for you.
Foam board is easy to cut, bend and glue. It also handles impacts better than paper, which means that airplanes made from it are more durable. You can easily find foam board online or at most hobby shops and convenience stores. A 20x30" sheet is inexpensive and can make several airplanes. It's a great choice for building flying models!
Utility Knife
Unlike paper, foam board cannot be cleanly cut with scissors. A hobby knife with a sharp blade is necessary to make clean, precise cuts. It's important to take safety precautions when working with sharp knives. Children should be supervised. Always keep the cap on the knife when not in use so you cannot get accidentally cut. Knives with round handles can roll off the table and fall into your lap or onto your foot, so you definitely want a cap on them. When cutting, always be aware of where the knife will go if it slips and keep your fingers away from that danger zone. The motion of the knife should be away from your hands and body whenever possible. Never use excessive force.
Dull blades tend to tear the foam rather than cutting cleanly through it, so always use a sharp blade. If you feel the knife grabbing the foam and you see that the cut edge is jagged and torn, then it's time to switch to a fresh blade. New hobby knife blades are very inexpensive, so swap them out as often as necessary.
The best way to cut foam board is with multiple light passes. If you dig the blade all the way through the foam and drag it in an attempt to cut through in one pass, you will end up with a wobbly cut. Instead, make a light pass at first, trying to cut through only the top layer of paper. Then, make a second pass with the goal of cutting through the foam. Finally, make a third pass to cut through the bottom layer of paper. By practicing this three-pass method, you will start to get a feel for how deep your cuts are. This will be an important skill for the following techniques.
Cutting Mat
Always use your utility knife on a flat cutting mat. These are designed to protect the underlying surface from the blade. You don't want to mark up your favorite dining table. For safety reasons, never cut on your lap or with the material balanced precariously on a knee or on unstable objects. Cutting mats come in a variety of shapes and sizes and many have measuring marks printed right on the mat, so you can use them instead of a ruler for some procedures.
Beveled Edges
The natural edges of foam board have a squared off boxy shape. This may not be desirable for aesthetic or aerodynamic reasons. Beveled cuts can be used to make tapered edges. For example, a beveled edge on the front of a wing or tail surface can make it more streamlined and aerodynamic. By tapering the front edge of the wing, the airplane will slice through the air better without producing as much drag. It is generally desirable to have the trailing edges of wings be tapered as well.
Not every beveled edge needs to be 45°. You may want a steeper or shallower angle for different purposes. You may even want to round off the edge so it has a nice curve. You can do this with sandpaper (see below). If you want a very accurate beveled cut, you can purchase tools to do this. You can even 3D print your own angled utility knife holders if you have access to a 3D printer.
Score and Fold
Sometimes you may want to connect two pieces of foam board at an angle. You could cut two pieces and glue or tape them together, but there is a better way. The "Score and Fold" technique is a great way to make an accurate, angled joint.
To make the joint, lightly score the foam with a utility knife. The goal is to cut through the first layer of paper and some of the foam, but not into the bottom layer of paper. Once you have scored the line, bend the foam board away from the cut and it should snap along the line, leaving one layer of paper attached, like a hinge. Then you can fold the board along that hinge to the desired angle and secure it in place with tape or glue. When making a precise measurement, keep in mind that the measurement to the cutting line is the inside measurement. After doing the fold, the outer dimension will be about 5mm more (the thickness of the board).
Beveled Cut Folds
If you make a "Score and Fold" joint you will notice that it results in a rough corner that has a stair-step appearance. You can put a piece of tape over this if you want, but there is a more advanced technique that can solve this problem too. To start, make a Score and Fold fold as in the previous step. Now, instead of folding it away from the cut, we are going to fold into the cut. If we try to do this right now, the foam will be in the way, so we first need to cut away some of the foam. The ideal way to do this is to make a 45° angled cut on each side of the joint. Now, when you fold the foam board into a 90° angle, it will fit together perfectly and the remaining paper layer will make a perfect, clean corner.
To make the 45° beveled cut, fold one piece backwards so it's touching the other piece with the connected layer of paper in the middle. Place this on the edge of a table and hold it firmly in place. Then hold your blade firmly and place it at a 45° angle and cut through the top layer of paper and foam. Be careful that you do not cut into the bottom layer of paper. It's okay if you cut too little or if your cut is wobbly because this will be hidden from view when you are finished. Flip the board around and make the beveled cut on the other side. Now that both sides of the joint have a 45° bevel, when you fold them together it should make a perfect corner. Use some hot glue in the joint (see below) to fix the angle in place and make a very strong connection. When making a precise measurement, keep in mind that the measurement to the cutting line is the outside measurement. After doing the fold, the inner dimension will be about 5mm less (the thickness of the board).
Overlap Fold
Another technique can be used to make strong 90° corners that are very clean. It may be a little easier than the beveled cut fold described above. First, use the score and fold technique to make two side-by-side parallel cuts that leave the back piece of paper intact. The distance between the two cuts should be the thickness of the foam board, usually 4-5mm.
Next, fold the board away from the cuts and use your fingers to peel away the small strip of foam that is between the two parallel cuts. You should end up with a 4-5mm trench between two pieces of foam board that is composed of only one layer of paper. Now, fold this up so the loose paper layer is touching the side of one of the cuts and fold the other side over so the cut edge is resting on top of the other side. Use hot glue (see below) in the joint to make a strong connection. The resulting corner will have a very clean appearance. When making a precise measurement, you have options when doing this type of fold. You can have either of the cut lines be the outer dimension, depending on how you fold it.
Metal Ruler
While you can cut foam board freehand with a utility knife, if you want your airplane to be symmetrical and accurate you will need to make precise cuts along straight edges. A metal ruler is the perfect tool for this purpose. Wood or plastic rulers are not recommended because your utility knife can cut into the wood or plastic, damaging the ruler and making it no longer straight. The knife cannot cut into metal, so it will always be a reliable straight edge. Metal rulers commonly have a non-slip cork layer added to one side. When the cork side is down, the edge of the ruler is elevated off the material by a few millimeters. As you run your knife through the material, down the edge of the ruler, this gap can cause the angle of the knife to be inconsistent.
We recommend turning the ruler over so the cork side is up, or buying a metal ruler without the cork layer. This will place the edge of the ruler flush against the material, which will result in a more accurate cut. As you gain experience, you will start to get into a rhythm of putting the cork side down to make a measurement which you mark with a pencil. Then flip the ruler over, cork side up, and swap your pencil for a knife to make the cut. Then flip it back over, swap and repeat.
Hot Glue
Regular super glue has chemicals in it that can melt foam, so always use foam-compatible adhesives. Our personal favorite type of glue for foam board is hot glue because it holds strong and dries fast so you can get onto the next step without waiting too long. However, one thing to keep in mind is that hot glue is very hot, especially the tip of the dispenser. You need to always be mindful of this, because you can get a serious burn if you touch the tip of the hot glue dispenser, or if some hot glue drips on your finger. We recommend using low-temperature hot glue and finding a nice flat, uncluttered surface so you have a good place to place the hot glue dispenser between uses.
Keep in mind that hot glue has a tendency to slowly ooze out of the nozzle, so you should put something under it to collect the drips. Also, when you are done with your project, don't forget to unplug the hot glue dispenser. If you leave it unattended, it could create a fire hazard. Some hot glue dispensers have safety mechanisms that will automatically turn them off after a period of time, so we recommend one of these.
Some glues, especially spray adhesives, can produce harmful fumes, so make sure you are using these items in a well ventilated work space. Always read the warning labels and follow any of the recommended precautions.
One of the best uses of hot glue is to reinforce joints. When making a "Beveled Fold" or "Overlap Fold" as describe above, place a bead of hot glue inside the joint before folding it up. Hold it at the right angle for a few seconds until the glue dries. Now you will have a very sturdy joint.
Tape
Double-sided tape is another good option if hot glue isn't available. Double-sided tape is less messy and easier to apply, but it only works for flat surfaces, so you won't be able to adhere two pieces of foam board end to end using tape; for that you'll still need to use hot glue or some other type of adhesive.
Clear packing tape is also a great tool to use when working with foam board. It can be used to seal a seam or reinforce a connection. Tape produces a smooth surface, which is beneficial for flying airplanes because smooth surfaces will produce less drag. For some extra strength you can also purchase fiber reinforced tape which is extra strong when used with the fibers going perpendicular to the cut edge.
Sandpaper
Fine-grit (200+) sandpaper can be used to smooth the edges of the foam board. If you accidentally make a wobbly cut or need to flatten out a bump on one of the edges, a few strokes from some sandpaper can even it out.
When you sand something by hand with a single piece of flexible sandpaper it can be difficult to produce a flat surface because the sandpaper will bend around in your hand and on the material. A better way to use sandpaper is to make yourself a sanding block. You can do this by getting a small piece of flat wood and then gluing a piece of sandpaper to the wood. This will ensure that the sandpaper remains flat as you move it over your material and this will produce a better result. You can purchase sanding blocks and you can also purchase sanding sticks in a variety of shapes and sizes. Sanding sticks can be very handy.
Sanding can create fine particles of dust that might irritate your eyes and lungs, so you should wear protective eyeglasses and a dust mask and work in a well ventilated area.
Painting
Once you have completed your masterpiece you may want to paint it to give it a little pizzazz. One thing to keep in mind is that certain paints contain solvents which can melt the foam. We recommend water-based paints, but you should always check to make sure your paints are foam-safe.
To protect your lungs when using certain types of paints, please ensure that you wear a mask and work in a well ventilated area.
Transferring Templates
You may find a cool drawing or airplane template on the internet (like ours) or you may end up drawing your plans using a CAD program. Once you have the drawing, you will need a way to transfer this to the foam board so you can cut it out. The first step is to print the design on regular paper. If the scale is larger than a single piece of paper, you can split it across multiple pieces of paper. This is called "tiling" and most computer programs will have this capability built in. After you have printed all the pieces, you can line them up and tape them together.
Once you have the template on paper, you can use spray adhesive to attach it to the foam board. If you use a light misting of the adhesive, you will be able to peel off the paper template after you cut out the pieces.
If you don't want to use spray adhesive, here is another technique that works well. Use regular tape to pin the corners of the template to the foam board. Now, get a toothpick, sewing pin or some other pointy tool and use it to poke a hole through the template and into the foam board at each corner and along the lines of the template. You can then remove the paper template and use a ruler to connect the dots.
Either way, once you have transferred the template to the foam board, you will then be able to use your ruler and utility knife to cut out the pieces.
Other Tools
You may also want to get a protractor, T-square, circle cutter, cutting stencil or other measuring tools to help you make more sophisticated measurements. You can find these online or in your local hobby shop.
You may also want to experiment with toothpicks or wood dowels which can be used to reinforce the wings or other components. The toothpicks can simply be poked through several layers of foam board to make a strong connection. They can also be used to make joints that can freely pivot or swivel.
If you are making very large airplanes from foam board, you may need to reinforce the wings so they don't sag. You can use carbon-fiber rods, or wooden dowels for this purpose.
Wrap Up
In this article we have explored the tools and techniques needed for building foam board airplanes. We covered the advantages of using foam board and we discussed the essential tools and safety steps needed for success. We practiced cutting, folding, and joining methods, and learned ways to finish and reinforce our designs for better performance. By practicing these techniques, you will master the skills necessary to create durable, accurate, and aerodynamic airplanes. Hopefully you have felt inspired to keep experimenting, refining, and pushing your designs to higher heights!
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