Fabric styles at a glance
| Style | Weave | Weight, oz/yd² | Weight, g/m² | Thickness | Count, warp × fill per in | Breaking strength, warp / fill, lbf/in |
|---|---|---|---|---|---|---|
| 120 | 4 harness satin | 3.16 | 107 | 3.5 mil (0.09 mm) | 60 × 58 | 160 / 160 |
| 1581 | 8 harness satin | 8.79 | 298 | 8.50 mil (0.22 mm) | 57 × 54 | 450 / 380 |
| 7781 | 8 harness satin | 8.81 | 299 | 8.6 mil (0.22 mm) | 57 × 54 | 570 / 450 |
Source for every row: Hexcel HexForce product data sheets for styles 120, 1581 and 7781 (links below). Thickness is dry fabric thickness, not cured ply thickness; cured ply thickness depends on resin content and compaction and is set by the SRM or the material spec.
Reading the table
Weight and thickness. Weight is the dry fabric weight per unit area. 1581 and 7781 are almost the same cloth in weight, count and thickness; they differ in yarn (ECG 150 1/2 on 1581, ECDE 75 1/0 on 7781), and breaking strength is higher on 7781 in this data.
Weave. The AMT Handbook's weave figure shows style 120 as a 4-shaft satin and style 1581 as an 8-shaft satin (Figure 7-5, p. 7-5), matching the data sheets.
Count is the number of yarns per inch in the warp and in the fill. With no warp indication on the fabric, the handbook defaults 0° to the direction the fabric comes off the roll (p. 7-3).
What fiberglass is used for
The AMT Handbook says fiberglass is often used for secondary structure such as fairings, radomes and wing tips, and for helicopter rotor blades. E-glass is the common type, with S-glass and S2-glass the higher-strength structural types. Advantages are lower cost than other composites, chemical and galvanic corrosion resistance, and no electrical conduction. It is white and comes as dry fabric or prepreg (p. 7-4).
Style 120 appears in the handbook as a thin outer “sanding ply” in a repair layup, over film adhesive and carbon plies (Figure 7-13, p. 7-10). The handbook does not assign a use to 1581 or 7781; where they appear in a repair, the SRM says so.
To turn fabric weight into ply count for a thickness, see laminate plies.
Questions people actually ask
Is 7781 the same as 1581?
Close in weight, count and thickness in the Hexcel data (8.81 against 8.79 oz/yd², both 8 harness satin). They are different styles, and a repair calls for the one named in the SRM.
How much heavier is 1581 than 120?
About 2.8 times: 298 g/m² against 107 g/m² (8.79 against 3.16 oz/yd²) in the Hexcel data.
Limits — when NOT to use this
- Not a ply schedule. A repair uses the plies, orientation and material in the SRM. Weight and thickness here do not choose them.
- Not a substitution table. A different style, weave, finish or weaver is a material change. Approved data decides.
- Greige values. They describe the fabric before finishing and are typical, not minimum.
- Dry fabric only. Prepreg and wet layup properties depend on the resin, which is not covered here.
Sources
- Hexcel HexForce Style 120 Product Data (DSF_120) — 3.16 oz/yd² (107 g/m²), 4 harness satin, 60 × 58, 3.5 mil (0.09 mm), 160 / 160 lbf/in.
- Hexcel HexForce Style 1581 Product Data (DSF_1581) — 8.79 oz/yd² (298 g/m²), 8 harness satin, 57 × 54, 8.50 mil (0.22 mm), 450 / 380 lbf/in.
- Hexcel HexForce Style 7781 Product Data (DSF_7781) — 8.81 oz/yd² (299 g/m²), 8 harness satin, 57 × 54, 8.6 mil (0.22 mm), 570 / 450 lbf/in.
- FAA-H-8083-31, AMT Handbook — Airframe, Volume 1, Chapter 7, pp. 7-3 to 7-5, 7-10 — fiberglass types and use, weave styles (Figure 7-5), style 120 as a sanding ply (Figure 7-13).