====== Construction Materials ======

===== Payload container foam =====






==== Expanded Polystyrene ====

Typically white foam made from beads - used for packing - density 15 to 45Kg/cu m - thermal conductivity 33mW/mK (for typical 20Kg/cu m foam). Can be cut with a [[guides:Hot Wire Cutter]].

There are two types of Expanded Polystyrene - //Open Cell// and //Closed Cell//.  Open cell is where there are gaps between the beads, and closed cell where there are not. Open cell is not waterproof and closed cell is (as in polystyrene cups).







==== Extruded Polystyrene ====

Extruded polystyrene is a thermal insulation material used in building construction. There are a couple of brands: Styrofoam by Dow and Polyfoam by Kanuf.  Styrofoam (density 32Kg/cu m - thermal conductivity 27mW/mK) is light blue or pink in colour, while Polyfoam (density 38kg/m3 - thermal conductivity 35 mW/mK) tends to be orange or beige.

Extruded polystyrene has a foam texture, moisture resistant, significantly more rigid than Expanded Polystyrene and can be machined (with care). Can be cut with a [[guides:Hot Wire Cutter]].


Tips for working with Styrofoam:

**Cutting:** STYROFOAM™ brand foam cuts easily with a serrated knife, hacksaw, etc.  Wax the knife blade with an old candle for easier, smoother cuts

**Painting:** Paint with an acrylic craft paint. Solvent-based paints may damage the foam.  Daler Rowney System 3 acrylic paint works well and comes in Fluorescent Pink (other colours are available).

**Gluing:** For a fast, sure bond, use a low-temperature glue gun. Hot glue guns can be used but the hot glue may melt a small portion of the foam

**Sanding:** For smooth, rounded edges, "sand" the foam with another piece of STYROFOAM Brand Foam

===== Glues =====

Polystyrene foam tends to be difficult to glue - because the solvents in some glues attack it. Here are 3 glues that work well and don't attack polystyrene.

**UHU Por glue** - this is specifically for polystyrene foam.  Coat each part, wait for 10 minutes then press together.

**PVA wood glue** - this works but you have to allow a long time for it to dry - especially on thick sections. Allow at least a day when working with sections of 1" or more.

**Epoxy resins** - these set normally - between a few minutes to a day depending on type.  

**Silicone Rubber** - as used for sealing plumbing & worktops - allow 24 hours to set.

**Hot Glue Gun** - set quickly and are relatively easy to apply. Use the gun on its low heat setting.


===== Cord =====




==== Braided Nylon cord  ====

Indicative strength (natural colour):

^Diameter^Breaking Strain^
|1.0 mm|22 Kg|
|1.2 mm|35 Kg| 
|1.5 mm|45 Kg|
|2.4 mm|130 Kg|
|2.8 mm|170 Kg|
|3.2 mm|220 Kg|
|3.6 mm|300 Kg|
|4.0 mm|350 Kg|
|4.4 mm|480 Kg|
|6.0 mm|680 Kg|

Braided cord works better than twine as twine tends to twist/untwist during the flight - causing the payload to spin.

===== Tapes =====

==== 2" Wide Tape  ====

Various 2" wide sticky tapes often used for covering payloads etc.

^Tape Type^Weight (g/m)^
|White Duck Duct| 12 |
|Grey Generic Duct| 9 |
|Black Cheap Generic Duct| 7 |
|Ultratape single sided cloth tape| 7 |
|Aluminium| 6 |
|Spinnaker Repair| 5 |
|Clear Packing (Staples)| 3.5 |
|Pro-Gaff Fluourecent Pink Gaffer| 16g |