|Airframe construction||- Airframe Construction|
Computer Numerically Controlled (CNC) machine cutting of materials for use in an aircraft wing.
See http://www.klasskote.co.uk/index.htm for more information on the Klass Kote range of epoxy paints.
Suppliers of balsa, plywood and other materials one might use in the construction of an airframe.
Farnell supplies a wide variety of:
Expanded Polypropylene (EPP) foam is heavier in weight but more durable material compared to rigid foams such as white beaded Expanded Polystyrene (EPS) FOAM. EPP is suitable for scale or sport models.
Originally developed for motor vehicle and aerospace applications, EPP is an impact resistant bead cell foam, with good memory effect due to the molecular structure. This material is excellent for crash / impact protection, and is used extensively in crash helmets, car bumpers, and aircraft cockpit.
EPP models are typically covered with cross weave and Coloured Tape, or a low temperature heat shrink covering. EPP is not suitable for surfaces that you intended to sheet with balsa wood.
Rigid EPS foams are better suited for covering with sheet balsa.
Working with EPP foam
To ensure a good adhesion to EPP, always spray any foam surface with 3M-77 type Spray (or latex) adhesive before applying Coloured or cross weave tape. This helps the tape to stick.
You can even spray a light coat on the balsa elevons before applying Coloured Tape. After you apply any self adhesive tape to your model, take a credit card shaped piece of cardboard and smooth the edge from the middle to the edge. Use it stick like a squeegee to iron out any remaining air bubbles and smooth the tape to the foam, then use a covering iron on the lowest temperature to iron down the sticky tape to the foam.
Warning: go gentle or you will warp the EPP.
It only takes a few minutes to do this to a completed glider, and it really makes the whole covering job look great. It will also increase the efficiency of your model by making the smooth surface fly that much better.
Glues that are compatible with EPP foam (test first)
You can decorate with foam friendly felt tip pens and paints. You can shave EPP FOAM with a sharp blade. You can sand it smooth with a sanding block and abrasive paper. You can hot wire cut EPP FOAM, but be warned, it is an acquired skill that comes at the expense of practice!
EPP sheets can be purchased in 600 mm x 900 mm sheets with thicknesses of: 3, 5, 8, 10, 12, 15 and 20 mm.