*Hijack alert*
DA what sort of depth do you take your hp100's to when tech diving? I have my lp108's, but I've been toying with the idea of selling them off and making room for hp100's for my deco class in the spring.
Jim
I am in the process of expanding my depth range with normoxic and possibly hypoxic trimix courses. I am fortunate enough to have the input of some current wreck divers who have experience in the 200-240ft depth range.
Realistically there are only a handful of wrecks below 200 ft that I will potentially dive on, so that became one of the criteria.
200 cu ft of gas will allow me to do 25 minutes at 200 feet with about 50 minutes of deco. My impression is that this is about as long a run time as you may want in atlantic given the potential for weather and sea changes where the boat captain may not want to wait forever to pull the hook and depart, so that became another criteria.
For dives to those depths with a two gas deco plan, the backgas reserve is still 1/3 and that reserve is more than adequate for the contingency plan in the event either deco gas is lost. So...200 cu ft is enough.
For that handful of wrecks where I may go to 250 ft, 250 ft for 25 minutes is easily doable by adding an 80 cu ft stage with bottom mix, leaving 1/3 of the total in reserve in the doubles which is again more than enough for a single lost deco gas contingency plan.
And for the normal run of the mill wreck dives in the 115-150 ft range, 200 cu ft is enough for a 150 for 40 min profile with 1/3 reserve and enough for a back gas only deco.
It could be argued that 120's or 130's would be better under the more gas is better argument, but 100's trim nicely for me and are not unnecessarily heavy and the only real advantage I have heard for larger doubles would be the increased potential to do two moderate deco dives in the 115-150' range one set of tanks on crowded boats here 2 sets of tanks are not real welcome due to space/tank rack concerns. But again, an AL 80 stage and a single set of doubles will acheive the same thing.
One additional consideration was that the X7-100 has the same tank factor and very similar bouyancy traits as the sets of double steel 72's I also have (and that will be very useable in the 115-150 ft range as well). It's nice to have several sets of tanks as getting lown out in Atlantic wreck diving is common and it sucks to show up at the boat with trimix when the boat captain decides they need to show closer in shore. with several sets of tanks you could potentially have tanks with a range of mixes including 18/45, 26%, 30% and air to meet what ever dive presents itself without having to waste a $130 trimix fill on a 100' wreck.
For cave diving, it is potentially a different story as, particularly in shallower caves in Mexico, it is often dive time rather than deco that begins to present the critical limit and larger tanks may offer much more of an advantage without the potential downsides in Atlantic wreck diving.
So in short, what works for a particular diver depends on the diver and the types of diving they plan to do.
That said, one of the major factors in gping with 100's versus the only slightly heavier and longer 120's was the great deals I got on 100's.
