Foam Model Airplanes: EPS, EPO, EPP and Depron Explained
Most RC and hand-launch model airplanes today are made of foam, because it’s light, cheap to mould and easy to repair. The foam type changes how a plane behaves: EPS is cheap and stiff but brittle; EPO (used in most ready-to-fly planes) is smooth, paintable and dents rather than shatters; EPP is extremely tough but flexible; and sheet foams such as Depron or paper-faced foam board are what scratch builders cut their own planes from. Picking the right foam for the job matters more than the brand.
By Kyle HilsonUpdated: October 20263 min read
Foam types
| Foam | Strength | Surface | Typical use |
|---|---|---|---|
| EPS (expanded polystyrene) | Brittle | Visible beads | Cheap gliders, foam cores |
| EPO (expanded polyolefin) | Tough, dents | Smooth | Most RTF/PNP planes |
| EPP (expanded polypropylene) | Very tough, flexible | Rough | Trainers, combat, FPV wings |
| Depron / XPS sheet | Stiff, snaps on impact | Very smooth | Scratch builds, indoor |
| Paper-faced foam board | Stiff, cheap | Paper | Scratch builds, foam-board plans |
EPP and Depron are covered in more detail in EPP planes and Depron model aircraft.
About EPS
EPS is the white bead foam used in packaging and many very cheap toy gliders. It’s light and stiff but cracks along bead lines on impact, and many glues and paints melt it. It’s still useful for wing cores that are then sheeted with balsa or covered with glass cloth, which makes them strong. Searches for “EPS model foam” usually come from people building such cores or cheap hand-launch gliders.
Ready-made or scratch-built?
Ready-made EPO planes come with detailed moulding, paint and installed electronics, and they’re the quickest way to fly. Scratch-building from foam board or Depron costs less per airframe, teaches building, and makes crashes cheap to repair, but you supply the electronics and do the setup. Many pilots do both: a ready-made trainer to learn and scratch builds to experiment.
Gluing foam
- EPO: foam-safe CA with kicker, or flexible foam glue.
- EPP: contact glue or hot glue; CA bonds poorly.
- EPS and Depron: foam-safe CA, white glue, or solvent-free foam glues; avoid solvent glues.
- Foam board: hot glue is the standard.
Painting and covering
Water-based acrylic paints are safe on most foams. Solvent spray paints melt EPS and Depron, so test first. Some builders cover foam board planes with low-temperature heat-shrink film or laminating film, which adds strength and water resistance; use a low iron temperature and test on scrap, since too much heat melts the foam. Packing tape on leading edges protects them cheaply.
Choosing a foam plane
- First plane: EPO trainer with stabilisation.
- Learning to crash less painfully: EPP trainer.
- Indoor flying: thin Depron or EPP.
- Building on a budget: foam board plans.
- Scale looks: EPO warbirds and jets.
Repairs
Clean the break, glue with the right adhesive for the foam, and add tape or a thin carbon strip across long cracks. Dents in EPO can often be lifted with gentle heat or hot water. Replace badly crushed parts with spare wings or fuselages if the maker sells them.
Weight and wing loading
Foam lets designers keep weight low, which means slow, gentle flying. Adding paint, tape and heavy batteries quickly raises the wing loading, so the plane flies faster and lands harder. Weigh your plane and compare it with the maker’s figure before and after modifications.
FAQ
What foam is best for model airplanes?
EPO for ready-made planes; EPP for toughness; Depron or foam board for scratch builds.
Can I use EPS packaging foam?
For cores and simple gliders; it’s brittle on its own.
Can I cover foam with heat-shrink film?
With low-temperature film and careful heat.
What paint is safe on foam?
Water-based acrylics.
More on this topic: the complete RC Airplanes guide covers the basics behind this article.
About 20 years in RC. Mostly boats in the NAVIGA Mini Eco Expert class, with many self-made parts; also a King Motor Baja 5B, a home-built electric plane, home-built nitro planes he has flown, and an RC helicopter. More about SwellRC
