THE PATENT STOCKLESS ANCHOR
This anchor is also illustrated in Figure. It has no stock, and can therefore be hove right home into the hawse pipe, quickly secured, and is ready for instant letting go. The entire head, including the arms and flukes, is able to pivot about the end of the shank. Its angle of rotation is limited by stops to 45 degrees from the axis of the shank. In some designs this angle is as low as 30 degrees. The head must weigh at least 60% of the total weight of anchor.
If it strikes the sea-bed with the fluke’s vertical, their tripping palms chafe the surface and start rotation of the arms. The anchor has good holding power, in the region of three to four times its weight in efficient holding ground, but has s moving part which can become choked with sea-bed material. This may well because the flukes to fail to re-trip should the anchor be broken out of its holding position. For this reason, when anchoring for some time, it is a good practice to regularly weigh the anchor and sight it. This applies particularly on sandy and muddy sea beds, and an opportunity is afforded to hose the anchor using a high-pressure water jet. Some shipping companies insist upon this being done.
Having no stock this type of anchor is unstable, and when dragging under heavy load is liable to rotate through 180 degrees. If the flukes fail to re-trip, any holding power remaining is due entirely to weight and, in turn, friction. The size of the flukes is a direct measure of the holding properties.
Disadvantages such as are noted above are generally overlooked in the light of its easy stowage. It is an ideal (non- compulsory) stream anchor for vessels fitted with stern hawse pipes.
Both the stocked and the stockless anchor may have a ring secured to the shank at the anchor’s center of gravity. This is the gravity band.
The most common types found in the merchant service are the Byer’s, Hall’s, and Taylor’s patent stockless anchors. Two are carried as bower anchor in the hawse pipes and a third is carried as a space or sheet anchor. Typical dimensions of a 5-tonne anchor would be 3.5 m overall length; 2.1 m extreme length of head; 1m measured in side elevation.
HALL’S PATENT – STOCKLESS ANCHOR
Across tripping palms of one fluke and 1.7m from fluke tip to crown. Tests at the admiralty experimental works have shown that:
1. Holding power is raised by increasing the fluke area.
2. It is also increased by having smooth, un-ribbed flukes.
3. A holding power of ten times the weight can be obtained.
4. Stability can be effected by using stabilizing fins.
5. A dihedral surface on the flukes gives a greater holding power.
6. Such a surface is more easily obtained with hollow flukes.
The stockless anchor with tumbling flukes was introduced in 1840, and since that date effective changes in design have been negligible. In the latter half of the nineteenth century the admiralty conducted tests in order to select the most efficient type, but little was done to improve efficiency.
Tests were reintroduced in 1943 after much complaint by personnel during the war of the inefficiency of anchor. After four or five modifications to a prototype, a new design was effected.
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