Lights
Main Lights
The Main light used is a canister light type, which provides on average
a 50 w, 3 hour burn time 
(usually
an Exteme Exposure (the photograph to the left shows the Extreme Exposure
Explorer Pro 6 (on the left) and Explorer Pro 14), American Underwater
Lights (AUL) or a Barry Miller WKP unit). The battery canister is
mounted on the waist, on the right side. It is held in place right
back against the backplate under the shoulder (in the streamline) by the
belt buckle from the harness which does not fasten at the navel as expected
but goes all the way around to the right hand side to hold the main light
canister.
A slight modification to this mounting method is to use a simple plastic weight belt buckle, which is slid on to the waist strap and used to hold the light in place - this system is excellent for UK RIB diving, in that you can undo the waist strap ready to get out of the water at the end of a dive and the battery canister is still held in place.
The
Extreme Exposure lights have an excellent battery connection system.
The system has no free floating wires, which can fail and break with the
constant connection/disconnection for diving/transport that would occur.
The Extreme lights use positive mating banana plugs which, allow the lid
to be mated to the battery connections for use.
The light head is a "Goodman handle" which is the wrap round hand / palm grip style. These handles give you back your hand for working on things whether that be a scooter trigger or a lump hammer. The length of the cord is kept to an absolute minimum which is effectively the length needed to go into the left hand whilst the left arm is fully outstretched in front of you..
Why is "Butt" mounting
bad ?
If you butt mount you will need to sit your cylinders on on your battery
canister whilst kiting up. In order to butt mount you will need to add
d-rings to your tanks which are another potential snag point. This
also leads to metal to metal connections (see why this is bad here).
Butt mounting a light on the bottom of your cylinder will mean that the
battery canister sits on the backs of your legs during normal swimming
- this can become very uncomfortable over a long dive.
Many people believe that butt mounting is more streamlined, however the light on the hip is in the lee of the shoulder where it is protected.
The cable on a butt mounted light will need to be extra long which potentially will catch on everything unless it has some routing which is a real mess and interferes with the stages and all of the other gear.
Butt mounted lights are very difficult to work on with one hand (which is all you might have free) in an emergency - e.g. trying to take it off to free yourself.
The position where the battery canister would sit is where we keep reels and/or the lift bag in wreck diving. We park our long hose under the canister in its routing. Note that the long hose does not need the canister to sit properly, but it is much neater, and the hose will be tight to that point and not catch anything
Backup Lights
In cave/penetration wreck diving it is normal that two backup lights be
carried by each diver. These backup lights are usually twist on
(no buttons or switches to fail) 3 battery C cell. They need to be secured
at two points and hidden away on the harness straps which run under the
shoulders. They are aatched one on each side to the shoulder D ring
and under a piece of inner tubing or Tank neck O ring which is on the
webbing. Put a spare piece of inner tube / O ring on each side so
that if you snap the one holding the light you can still mount the light
without dangling. These torches are easily got to by feel and again are
out of the way under the shoulders so not creating more drag or getting
in the way of other gear. Improper mounting and deployment of backup lights
is as dangerous as using the wrong backup light. To deploy one, pull it
out from the inner tube retainer, leaving it still clipped to the D Ring
and turn it on, then unclip it. If you drop it, you can see it. Remember
this is a piece of safety equipment used in the event of a main light
failure.
Hanging a bouquet of backup lights from a tank d-ring is dangerous and impractical. The location is a natural snagger of everything, they slap back and forth on the tanks breaking the filaments in the bulbs. They are in the way of other gear and access to them is blocked by other gear, and it is impossible to properly deploy them.
The best backuplight available today are the Extreme Exposure Scouts.
Bulbs & Batteries
Avoid rechargeable batteries in backup lights and make sure that the voltage
of the bulb matches the combined voltage of the batteries. Check the batteries
- some manufacturers think they are doing you a favour to pump the voltage
up to 1.6. If there is not a match, go get new bulbs. If you can't get
the right bulb, don't use the light. The "correct" voltage rating
of the bulb (itself a compromise between maximum expected life and colour
temp of the light emitted) will depend on the types of batteries used
and the current drawn by the filament. If you continue to over volt
the bulb, the result is that you stress the bulb every time you use it
and it will blow earlier.
High currents and alkaline batteries don't go well together (Lithium's don't like high currents either). NiCds and gel lead-acids are much better in this respect because of their low-internal impedance's: the terminal voltage remains about the same irrespective of the current drawn - so the Primary light (needing 50 watts) needs to be driven from a Lead acid battery. NiCads have the unfortunate characteristic of working perfectly then tailing off very quickly. As such you may not notice this and be without light before you can get a backup light deployed.
For the backup lights it's hard however to beat alkaline batteries capacity for their size. Also as alkaline batteries die slowly its possible to "see" the backup failing and prepare either an alternative light or change the dive team order to protect the diver without a light. Nicads work full tilt boogie then fail rapidly, as such they don't lend them selves to a backup light application
Copyright © 2001 [Gas - Diving].
All rights reserved.
Revised:4 March, 2002