Figure 5-1

UH-1H composite main rotor blade. Source: Covington (1980).

The RTM process is utilized in the production of cooling tower fan blades up to 12.2 m (40 feet) in diameter. These blades look quite different from current wind turbine blades because of constraints of the process (Figure 5-2). The rigid inner mandrel must be removed from the cured blade; therefore, the root end must be the largest section of the blade. To live with this constraint, tower blades are made in two parts, an outer section extending from quarter span out to the tip and an inner portion containing a root end joint. These sections are joined by bonding, and both sections are at their largest cross section at the splice joint. Local fiber curvature can occur due to nonuniform flow of the resin through the preform. Cooling tower blades produced by this process sell for under $10/lb. (Monroe, 1990).