Sec. 6S.11 



ABOVE WATER-FORM LAYOIH^ 



,559 



Anchorinq Dioqrom Showinq Both 

 Choins Tonqent to Bed Surface at pp 



Respective Anchor Positions 



Hull Openinq 



Fig. 68.1 Proposed Under-the-Bottom Mushroom Anchor for ABC Ship 



The ABC proposal involves: 



(a) One 13,000-lb centeiiine bower anchor above 

 water, of the U. S. Navy lightweight type, known 

 as an LWT anchor, housed in the manner shown 

 by Fig. 67.E 



(b) One extra-heavy centerline mushroom anchor, 

 below water, housed within and dropping out of 

 the bulb at the keel, indicated in Fig. 68. H. 



The mushroom anchor is proposed because it is 

 more free of fouling by the chain than any other 

 type, and because it houses reliably and firmly, 

 out of sight, in a hawsepipe of simple shape and 

 sturdy construction. Above the mushroom anchor 

 and to a point just under the wildcat, at the main 

 deck level. Fig. 68. H shows a length of chain 

 several sizes heavier than the regular anchor 

 chain. This is to insure that no breakage occurs 

 in a section which is not easily accessible when 

 the ship is afloat. The heavier chain next to the 

 anchor also increases its holding power. Both 

 chains going over the wildcats are of the standard 

 size for this vessel. 



An alternative arrangement for housing the 

 bottom anchor farther aft is shown in Fig. 68.1. 

 If the anchor windlass is to be kept well forward, 

 it is necessary to move the hawsepipe as far aft 

 as the vicinity of Station 1, at about 0.05L, in 

 order to house the anchor completely above the 

 baseplane and to provide a slope of 15 deg in the 

 hawsepipe leading from the anchor recess to the 

 wildcat. A slope of this order is necessary to 



prevent the chain from rattling and banging in 

 the chainpipe with the ship underway. Indi- 

 dentally, this arrangement provides a full half- 

 turn of chain around a horizontal wildcat, 

 possibly 1 or 2 hnks more than is customary on 

 bow-anchor windlasses of the orthodox type. 



One great advantage of anchoring through a 

 keel-line hawsepipe is that a much flatter "lie" 

 of the anchor and chain is obtained, with a much 

 shorter scope of chain, illustrated by the box 

 diagram of Fig. 68.1, than if the chain is led from 

 a hawsepipe many feet above the surface. This is 

 especially true in the shallow water of rivers, 

 estuaries, and harbors, where the ship occupies a 

 much smaller mooring circle. On the ABC ship 

 the difference in level of the hawsepipe openings 

 is some 50 ft, or well over 8 fathoms, indicated in 

 the small-scale diagram of Fig. 68.1. The heavy 

 chain pendant next to the mushroom anchor, 

 some 46 ft or over 6.5 fathoms long, is of great 

 assistance here. These factors combined might 

 permit reducing the weight of the mushroom 

 anchor, which must be normally at least 2.5 times 

 as heavy as a stockless anchor for the same holding 

 power in firm ground. It is, furthermore, far 

 easier to obtain a three- link bearing for the chain 

 leading out of the morning-glory-shaped bottom 

 anchor recess than out of any known shape of 

 abovewater hawsepipe and bolster. Lastly, the 

 anchor and hawsepipe are mounted much lower 

 in the vessel than is customary, helping to lower 

 the CG. 



