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You wrote:
>
>
> Up and down lines. Are your wrecks intact enough to tell which
>is port and starboard, bow and stern, or are they amorphous? What line
>do you guys put on the reel to prevent cutting on the metal? -G
>
>
George,
This 'line' discussion has been on for ever. Are you fanning the
embers?
Wrecks run the gamut - from 'intact', to scattered with only
twisted/mangled elements (usually the shallower ones that have been
depth charged & wire dragged so that they will not be hazard to
navigation). Some will be but a few ribs (lobster snags). So no
generalozations about the state. Low viz usually is not conducive to
'beholding' them anyway.
What is apparent is that for deco purposes there are two methods in
wide use. It depends on the diving area & thus the manner in which the
boat handles that. Your buddy Raimo did not comprehend that difference
& ripped into some guys from the UK.
1. Method I - Dive boat anchored
Deco carried out on anchorline, with or without jon lines, or on
down lines dropped from boat.
If diver does not find anchor line, or returning to it is
impractical a deco line is deployed (using a Jersey reel).
The traditional system assumes that the line is to be cut and
discarded in the ocean (NOTE - ocean or marine environment). Thus
adequate strength, low cost and biodegradability led to the choice of
unoiled sisal.
1/4" sisal - easy to find (at stores), adequate strength but bulky
3/16" sisal - not widely available, less strength, less bulk
There are two principal ways of deploying it; the pros and cons
have beeb covered elsewhere. Again no method is absolutely better than
the other. Awareness & selection of best is essential.
a. Tie line and ascend to stop depths, unreeling as you ascend.
Stop and cinch of at stop lengths, do time, etc & surface.
b. Holding reel (in a manner that allows belaying it), send up
free end attached to lift bag. When bad hits surface (or when you
think it has!), tie end to wreck after cutting at reel, ascend the line
to stop depths & finally surface.
Notice I have written nothing about cutting the line of the surface
yet. I want to make sure that Raimo does not jump, fallaciously, on my
case for advocating 'untethered' deco.
Methods using less bulky equipment are & have been tried. The
Jersey Reel still rules supreme. Using a cross-wreck line is a
practical approach. Biodegradability of nylon leaves a lot to be
desired. Double lining with the one end sent up on a lift bag and then
unreeling while ascending allows retrieval of line. However, the
length of line required (and to be retrieved) is at least 2x the depth
(200 ft depth = 400 + ft).
When choosing where to tie on wreck - rule of thumb: high up on
wreck, away from sharp edges, or parts that could chafe line, on a
sturdy piece, preferably one that allows the line to be passed through
and tied taught (minimum pivoting movement).
The issue of cutting the line upon ascent (assumes using sisal) or
releasing it for retrieval - Surface, look around & assure that dive
boat is there before cutting it.
2. Live boat - drift diving.
As the boat is not anchored, there is no anchorline - Duh!
At end of dive diver ascends & when convenient, deploys a line
attached to a lift bag (or sausage) via a reel. Plankton ascent & deco
is very practical in high current diving (West Palm - Boynton, UK,
apparently, the Bosphorus/Dardenelles [though not w/o problems in
these], etc).
This method relies on the diver being picked up by the boat, a
method routinely utilized when drift diving. Logistic problem arises
when a large number of divers with different bottom times & deco
schedules are involved. For that purpose planning becomes essential to
assure that all surface @ approx. the same time.
Regards
Esat
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