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     Selected findings on 329Amphibian Performance and Hull Design

Hull Design
The final hull design involved research into several key hydrodynamic characteristics which would enable the aircraft to have low water resistance, stability and good landing attributes. Several hulls were considered in the evaluation of the most suitable hull to be used and the following discussion is a brief description of the main parameters that influenced the choice of the Model No. 185 of Reference 2, a compilation of NACA tow tank tests of a large number of flying boat hull shapes.

1. The forebody length/beam ratio is the main parameter that influences the water spray characteristics. An increase in forebody length/beam ratio leads to a reduction in spray. And since spray is a direct indication of hull drag it was important to choose a hull with a high ratio for the twin hull. The hull chosen has a forebody length/beam ratio of 5.80.

2. It is generally accepted that the forebody deadrise is the hull-shape parameter controlling the violence of the landing impact. A deadrise angle of 24.50 is chosen and this also generally increases the cleanness of running. This is slightly higher than the initial choice based on Raymer’s preliminary design equations. Water loads are a dynamic function increasing with velocity squared and therefore the values selected for the deadrise angle and landing speed are critical considerations for hull design because they affect the weight and cost. This relationship is illustrated in Table 14.