MIL-B-81743A

Abstract

This specification covers the design requirements for one type of marker buoy for use as an aid to navigation. <b><u>Intended Use:</u></b> The marker buoy covered by this specification is a small navigational marker intended to be planted in the water by being launched (dropped) from a helicopter. The protective support containing the marker buoy and anchor weight is planted by dropping it into the water from a helicopter. Through the force of the water on impact and the buoyancy of the float, the upper tube with marker flag extends to maximum length, and the buoy emerges from the protective support. As the protective support and anchor weight sink, the lower tube with the ratchet wind-up mechanism extends to maximum length. The weight of the descending anchor places sufficient tension on the mooring line to extend the coil spring and fully depress the lever arm. When the lever arm is fully depressed, both pawls disengage from the spool ratchet wheel and allow the spool to turn freely. Upon reaching the bottom, the mooring line is relieved of the anchor weight, and the line tension decreases. The coil spring returns the lever arm to a neutral position, end both pawls re-engage the ratchet teeth. The length of the mooring line paid out will have been determined by the water depth. Rising tidal action causes more of the float body to be immersed, and the mooring line tension to increase. The lever arm is depressed, disengaging the pawls, and the spool is freed to rotate until enough line has been paid out to relieve the tension. A taut moor is maintained by natural wave action. As a wave passes the float, a larger portion of the float is submerged, and the increased buoyancy is translated to increased tension on the mooring line. The lever arm will be slightly depressed in response to the increased tension. Pawl No. 1 (item 167AS14) clicks freely as the lever arm is depressed. Pawl No. 2 (item 167AS113) engages the spool causing it to rotate as the lever arm is depressed. As the wave crest passes the float, the float tends to drop into the trough, with a slackening of the tension on the mooring line as the result. When the tension on the mooring line becomes less than the force exerted by the coil spring on the lever arm, the lever moves back toward the neutral position. Pawl No. 1 engages a tooth of the spool ratchet wheel preventing its rotation as the lever arm is pulled back, taking some of the slack out of the line. For a particular prevailing wave amplitude, the mechanism alternately pays out and retracts mooring line each time a wave passes by the float, and seeks to maintain the mooring line as taut as possible under the circumstances. <br>