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Appendix A - Spar sizes

Modern F1A spars are greatly over engineered for other model types. Bear in mind that nobody uses less than a 5.8 mm high-tensile steel joiner in a modern wing and that the spar is engineered to match! The spar can be made a lot lighter for other classes. Carbon D-box structures should be sized along the following lines:
Class D-box Spar
F1A 2 x 83gsm cloth, 1 x 120gsm unidirectional cloth 1mm flanges, 8 mm -> 1 mm wide, 8 -> 1.5 balsa end-grain web, 15mm diameter (4.5 g/m) carbon sock SC1045
F1B/F1J 1 x 83 gsm cloth 0.2 mm flanges, 3 mm -> 1.5 mm wide, 3.0 -> 1.5mm med. balsa web (spanwise grain), 10 mm diameter (3.2 g/m) carbon sock SC1032
Stab/fin 1 x 83 gsm cloth 0.2 mm flanges, 1.5 mm wide, 1.5 mm medium balsa web (spanwise grain), 1 layer 83gsm cloth (set at 45 degrees) on the rear of the web as a D-box closure

The assumptions made in constructing this table are:

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