as an explosive anchor, the design tension is often governed by the 

 operation tension. But if clump anchors of the gravitational type are 

 to be used for the guideline, the design tension is often the maximum 

 deployment tension. The dynamic tension caused by surface excitations 

 can be calculated by a method presented in both References 8 and 9. 

 Surface motion compensation methods should reduce considerably the dynamic 

 tensions. Size of the lift line for the payload package should be chosen 

 in a manner similar to that of choosing the guideline. 



After both the guideline and the lift line are selected, the 

 possible payload rotations should be checked, using a design current 

 profile and various guideline tensions. One should chose a larger-sized 

 guideline if required. 



4. Rotational Qualities. Nonrotational or low-rotational rope 

 construction is essential in preventing kink formations in the guidelines. 

 A roller-bearing swivel should be inserted between the guideline and the 

 guide post or anchor block (see Figure 3). 



Appendix B presents a method for calculating the rotation of a 

 payload along a single guideline caused by the torque in the lift line, 

 neglecting the wave action and the current drag. This method is useful 

 in designing high-tension guideline systems for heavy payloads in shallow 

 depths. 



Anchor. 



1. Weight. To prevent possible movement of the anchor on the 

 seafloor, the weight of the anchor should be at least 50% higher than 

 that required for the guideline operational tension. Either steel or 

 concrete can be used for making gravity anchors. The steel anchor, with 

 its small volume, is easier to handle on the surface. Concrete, less 

 expensive, can be cast into any shape. 



2. Guide Post. The guide post on the anchor block is used 

 only for bottom guidance when seafloor mating of a payload to an anchor 

 block is expected. Two guide posts on an anchor block can provide fine 

 guidance for the alighnment of payloads. The maximum stress on the 

 guide post would occur when the anchor block is being lowered to the 

 seafloor at a tilted position. A large moment could be created at the 

 base of the post, and this must be considered in the design. 



The length of the guide post is determined by the position of 

 the guide cone on the guide frame. The guide post should be long enough 

 to mate completely within the guide cone. For best mating results, the 

 guide post should be as free of protrusions as possible (see Figure 3) . 



Guide Frame. The configuration of the guide frame depends largely 

 on the geometry of the payload package. The horizontal dimension of the 

 frame (i.e. , the spacing between the lift line and the guideline) should 

 be as large as possible, but the size of the guide frame should not be 

 so large that smooth handling of the payload package is jeopardized. 

 The frame should be tall enough that the guide frame can always be main- 

 tained in a horizontal position by applying vertical tensions on the side 

 members . 



13 



