The design load is the maximum load that will be imposed on the drogue, towline and attachments in the event of a very severe breaking wave strike. A load of this magnitude would be encountered rarely if at all, possibly once or twice in the lifetime of the equipment. To estimate the load it is necessary to assume a breaking wave crest velocity. A velocity of 39 ft/sec. corresponding to a wave length of 300 feet was used for this report. Such a breaking wave would be approximately 40 feet in height and is considered to be representative of the worst waves in the 1979 Fastnet storm.
Drogue loads were calculated using the computer program in Appendix B. Figure 26 shows the recommended design load plotted against displacement. It will be noted that at a displacement of 7500 lbs. the design load is equal to the displacement and at a displacement of 60,000 lbs. the design load is 60% of the displacement.