reducing trimix costs

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lermontov

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planning a trip to Aaron Ward (65m) and thinking about using air to say 40m and carrying a 12l stage with trimix for last 20 m then swapping back to air for ascent ( then to deco gas) any issues /problems anyone can see with this? main reason is to keep costs down - regularly dive to 36m on air and feel pretty comfortable at that depth in low vis cold water
Im a sidemount diver and usually dive with deco and travel gas so also pretty comfortable with gas switches
 
With your experience and personal risk assessment appearing sound, I don't have a concern at all. Are you team planning or diving solo? What will the other divers be on?

Without knowing you at all, perhaps a generic caution about your own skills assessment and what "pretty comfortable" means in case of real trouble at depth. At a glance your number of dives seem low to be doing trimix dives at all but I realize that's within minimum standards and respect you know your own limits and training progression.

Either way, a personal question to ask yourself is how many hours have you around 35m on air? There's a huge difference between a dozen 10 minute dives at depth and feeling ok compared to being ok with a few dozen hours at depth where you're down long enough face and overcome problems.

Hypercapnia is no fun, being dark narced in low viz while problem solving sucks. Deep, cold air dives are fine until something needs extra exertion that's where gas densities compound the issue and narcosis quickly make a comfortable dive dangerous.

For gas switch to air at 40m (or 65m if I'm being candid) I wouldn't give it another thought personally but would rather advise caution to another. Rather warn you unnecessarily than tell you everything is fine and be wrong.

I'd love to be doing that wreck, glad you're taking the opportunity.

All the best,
Cameron

P.s.Trimix is stupid expensive OC, it's why I went to a rebreather
 
Just checked your post history to better help answer your question.

2016 January, self described new diver.
2016 February, considering sidemount
2017 March, Advanced wreck class
2017 June, planning a challenging dive on trimix in sidemount configuration.

An issue I see with your plan is it seems you may not yet have the skills and experience to safely plan your dive being aware of the risks involved. Without having gradually build up the muscle memory, knowledge and tools to safely carry out your plan it could be a problem.

You and those diving with you only know if my potentially spotted issue is real, but since you asked, here's my attempt at providing valuable feedback.

Respectfully,
Cameron
 
What gas will you have available to donate >40m and >56m?

What is your gas redundancy >40m and >56m?
good points will need to calculate this and may indeed change things
 
With your experience and personal risk assessment appearing sound, I don't have a concern at all. Are you team planning or diving solo? What will the other divers be on?

Without knowing you at all, perhaps a generic caution about your own skills assessment and what "pretty comfortable" means in case of real trouble at depth. At a glance your number of dives seem low to be doing trimix dives at all but I realize that's within minimum standards and respect you know your own limits and training progression.

Either way, a personal question to ask yourself is how many hours have you around 35m on air? There's a huge difference between a dozen 10 minute dives at depth and feeling ok compared to being ok with a few dozen hours at depth where you're down long enough face and overcome problems.

Hypercapnia is no fun, being dark narced in low viz while problem solving sucks. Deep, cold air dives are fine until something needs extra exertion that's where gas densities compound the issue and narcosis quickly make a comfortable dive dangerous.

For gas switch to air at 40m (or 65m if I'm being candid) I wouldn't give it another thought personally but would rather advise caution to another. Rather warn you unnecessarily than tell you everything is fine and be wrong.

I'd love to be doing that wreck, glad you're taking the opportunity.

All the best,
Cameron

P.s.Trimix is stupid expensive OC, it's why I went to a rebreather
thanks cameron

yes I appreciate the relative lack of experience and on face value id agree - but to give some extra background I've been a professional mountaineer and problem, solving under pressure is a given to succeed at a professional level. Im reluctant to blow my trumpet but in all honestly I've relished the exactness of technical diving and have found it a pretty easy transition
I did my ADV wreck in 2016 so over a year ago and have since done over 100 or so wreck dives some considerably challenging
bearing in mind the Aaron ward is in tropical warm water with excellent vis ( compared to what im used to)
Just to add more information 99% of my dives over 30m have been no light penetration dives

Ive done my solo dive course and have started an EX-range course that hopefully will be completed soon. Gas planning is of course mandatory and gathering views and ideas is why im posting

there are 6 of us going on the trip (august) my buddy is a very experienced TDI instructor diver with over 7000 dives - in fact we often dive together -knowing how cautious he is is reassuring for me

The plan is to undertake a few dives in the solomons to get all out configurations sorted and assess as we go before taking on the Aaron Ward
 
How much He are you going to save descending on Air? 65m depth should be a bit over 2 mins or so on decent. I personally would not be a big fan of going from trimix to air for the deco -maybe switch to 32 Nitrox at depth for a deep deco gas.
 
How much He are you going to save descending on Air? 65m depth should be a bit over 2 mins or so on decent. I personally would not be a big fan of going from trimix to air for the deco -maybe switch to 32 Nitrox at depth for a deep deco gas.
are you saying use trimix from surface to bottom and back up to 33m then switch to 32%? plus any further deco gas with higher f02 higher up as required
 
What Tmx will you be using? How rich a He mix do you need? What deco gasses? Will air be of any use for deco, or will it be an extra bottle to carry, adding complication and risk, not to mention encumbrance? As mentioned above, how much gas will you use on descent and ascent to first deco switch?

Deep diving costs what it costs, and, with all due respect, the sort of planning that you are mentioning indicates to me inexperience and unfamiliarity of the risks associated with multiple bottles and dive planning. KISS is a great review to apply to any procedure.

-Mark
 
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