Section 2 

 Calculations By Naval Research Laboratory 



Studies were made by the Naval Research Laboratory to determine static and dynamic 

 loads generated by ship motions for three types of line: 



4!/2-inch-circumference nylon rope 



8-inch-circumference polypropylene rope 



0.7-inch-diameter steel cable. 



This static load was assumed to be 10,000 pounds. Calculations (based on A.D. Little 

 Report No. 3030365 of March 1965) were conducted for (1) retrieval of a mass through the 

 center well of the ship; and (2) retrieval over the side — approximately 27 feet off the center- 

 line. 



These calculations showed that: 



1. Using a larger line caused the peak loads to be larger. 



2. Steel cable produced its fundamental resonance at a length greater than either nylon 

 or polypropylene lines. 



3. Lifting through the center well of the ship was found to be the safest mode of re- 

 trieval. (The overside lifting capacity was limited to 30,000 pounds.) 



4. The line exhibiting the shortest fundamental resonant length was chosen for the lift. 



The program, shown on page 79 of this appendix, was written in BASIC computer lan- 

 guage, and was used in solving for the dynamic and static loads from the equations: 



2 



U 



C, 



/U\^ I km \ ^ /km0\^ /U\^ 



^ sir? kL 



U^ 



and 



[E^k^ 





2 2 



cos ky 



77 



