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In-Reply-To: <v01510100ac78be6edf11@[199.165.213.106]> > After, that long explanation, my question essentially is what do others do > to make sure that they "hit" the wreck dead on on these deep dives? My > "Bruce/Plow" anchor does go down at about a 45=B0 angle and certainly doesn't > drop straight down. > A common method in the UK is to use a special 'grapnel' on a shot line. The system only works in tidal conditions or where there is some current. The system also works best with a 'soft' seabed, ie sand, gravel, mud etc. The 'grapnel' is typically made from old reinforcing steel bar, with a central one inch diameter (or greater) bar, say two feet long, and with an eye welded on one end to tie the rope to. The other end has four thin (quarter inch diameter) bars, also say two feet long, welded on with a six inch 'overlap'. The thin bars are equally spaced around the diameter of the central bar. The four thin bars are then bent back into 'U' shapes to form four prongs for the grapnel. A shot rope is fastened to the grapnel, with a buoy at the top. If the wreck stands up high off the sea bed (say 10m), set the rope length to say 3-5m less than the water depth. If the wreck doesn't stand up much over a reasonable area, set the rope length to say 3-5m more than the water depth. Arrive at the dive site before slack water, so there is *some* current running. Find the wreck with the echo sounder such that you motor into the tide/current over the wreck, and shoot the shot line just as the sounder shows you going off the (uptide) edge of the wreck. The grapnel should drag over the wreck, and catch in. On a high wreck, if the grapnel misses it will just float by and continue to drift with the tide. On a low wreck, if it misses/ doesn't catch it should drag along the seabed, being too light to hold in sand etc. In either case, if it does catch, the buoy will be seen to stop moving. If the grapnel dosn't catch, pull it out and have another go. (A fast rope winch is desirable for the deeper wrecks). UK practice is for the dive boat to motor in the vicinity of the shot, and not moor up to it. If all is well, wait until the tide slackens to a divable degree, and put the first pair of divers in. They should have a 2m length of sacrificial 'string', thinner than the shot line, and use this to tie the grapnel/ shot line into the wreck (ideally at the highest part of the wreck), then send up a signal pellet to indicate all is well. The other divers then enter the water. To recover the shotline, the buoy at the top of the shot line is hooked with a boat hook, and the top of the shot line wrapped round a samson post. Then use the boat engines to break the sacrifical 'string' and straighten out the prongs of the grapnel which were hooked into the wreck. Then haul in the shot line. Finally, re-bend the straightened prongs on the grapnel ready for the next dive. Once upon a time, anchors were used and boat skippers asked for the last pair of divers to leave the bottom to release the anchor. After a few incidents of the anchor being released by divers who thought they were the last down but weren't, that idea was 'outlawed' and the extractable-by-the-boat grapnel used instead. This system is regularly used in the UK on wrecks down to 70m and more, and has proved to have a high success rate. The main problem that can occur is if the first pair in pull themselves down the shotline, ie are not weighted correctly, and pull the grapnel out before they reach the bottom. Upside-down hulls and submarines can be tricky, especially if the are aligned with the tide. Hope this hasn't bored to many people, Dave.
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