How to Use Styrofoam SM for Flotation

Styrofoam's dense, water-resistant composition makes it an excellent material to use in flotation devices, like these pool noodles.

Styrofoam SM is the brand name for extruded polystyrene foam, a dense yet lightweight plastic used commonly as insulation in building projects. Invented by Dow Chemicals in 1941, Styrofoam's unique composition of closed cells that do not allow water to easily penetrate makes it a popular insulator to both resist water leakage and prevent heat from escaping a home's walls. This dense, watertight quality also means Styrofoam is buoyant, making it an excellent material for boats and flotation devices. You can make a small Styrofoam boat appropriate for a bathtub or pool; the scale can be increased for larger projects.

Things You'll Need

• 5 Styrofoam Brand SM Insulation boards
• Box cutter or sharp scissors
• Hot glue or Krazy Glue
• Spray sealant

Instructions

Building a Styrofoam Boat

1. Cut one Styrofoam board into a 12-by-8-inch rectangle. Cut two into 8-by-5-inch rectangles. Cut two into 12-by-5-inch rectangles.

2. Lay the 12-by-8-inch board float on workspace. This will be the bottom, or hull, of the boat.

3. Align the 12-by-5-inch boards along the long sides of the hull board at 90-degree angles and seal the joint with glue. Hold the sides in place until glue partially dries, at least 60 seconds.

4. Align the 8-by-5-inch boards along the short sides of the hull at 90-degree angles and seal the bottom and side joints with glue, to form a box.

5. Allow the glue to dry at least two hours or overnight, depending on the strength and dry time indicated on the glue instructions.

6. Invert the boat after the glue has hardened and spray bottom and sides with sealant. Allow it to dry per dry time indicated on sealant can.

7. Test the boat in a sink or bathtub full of water. Add weight in small increments to determine load capacity.

Tips & Warnings

• If you want to get crafty, decorate your boat with personalized designs before spraying sealant. Just be sure to use paint that isn't water-soluble.

References

• Universal Foam Products: About Styrofoam
• Foam Products Corporation: Buoyancy Billets and Encapsulated Foam Flotation
• Dow Chemicals: Styrofoam Brand SM Insulation
• Northland Construction Supplies: Styrofoam SM Insulation