It is imperative that you know your scooter's burn time with the
gear you are using. You must burn test the batteries on a regular
basis to be sure you can depend on this. I calculate my burn times
based on full cave gear, stages, towed DPVs, dry suit and full prop
pitch when stating burn times.
You never want to
run one DPV to its max. The best bet is to run one scooter for
about 40% of its burn time and then switch to the next scooter on
the way in, reverse the procedure on the way out. This way you
always have something that will get you back to your last scooter.
You do not want a situation where you have one scooter with
depleted batteries and another that has a full charge but then
breaks blades or otherwise gets messed up. Want to go further? Get
more sea scooters and take more gas.
Beyond short dives,
we require dive teams to tow scooters in the WKPP. Three-man teams
can tow one for a moderate dive, two-man teams must tow two, and
long dives must have full coverage. The number of scooters needed
for a dive can be figured using the 40% guideline.
Gas management for
scooter diving is not a function of whether you can swim out,
except in rare cases of high outflow, shallow springs, where your
ingoing scooter gas will likely equal your outgoing swim gas.
Scooter gas management is a function of common sense. You will not
swim out of a 300-foot deep siphon, like some that we dive, or a
300 foot deep non flowing cave, or 300 feet of anything. The
correct way to handle this is to breathe only the stages, saving
the back gas for emergencies, and to place safety bottles in the
cave at the same intervals as stages. You must assume that with
everything going wrong and towing with no primary lights, you will
take twice as long to get out so you will need twice the gas. For
instance, on light failures, you will have to be on the line and
moving more slowly. If the line is on the floor and you rode the
ceiling going in, then you will need much more gas. If you have one
problem, expect several more. DIR is designed to prevent,
anticipate and or handle anything that gets thrown at you. When,
not if, you have a problem scooter diving, you will either learn
why I am so insistent on following Rule Number One, or you will die
finding out how right I am.
We dive 1/2 plus
the amount of gas needed during a bottle switch on our stages,
usually 1/2 plus 300. We deduct 300 from our starting gas due to
the fact that you will not drain that last 300 without using the
purge button in real deep water. If the bottle has 3300 in it to
start with, you consider it to have 3000 "effective", so the
halfway mark is 1800, and adding the 300 for switching, you would
then only go to 2100 before dropping the bottle.
On the way out, you
either switch bottles with each stage recovery, or be sure you are
proficient enough to switch without stopping if you keep breathing
a bottle past the next pickup on the way out (only done if there is
excess gas in the bottle relative to the depth of the water).
Usually, this is not a good idea since you will not get enough
additional time to make up for the Charlie Foxtrot you will cause
if something goes wrong that needs your attention in the middle of
an on-the-fly switch. Play it by the book. NEVER pass through a