Why such a big step to technical diving?

[chrisch]

...
What would be so difficult or risky about switchable twin tank diving using either air or trimix from say 35m to 55m and nitrox for the shallower parts of the dive?...

Take the courses and you will find out. There are books you can read that will answer that question too.

 

[RainPilot]

Can I ask you a few questions:

1. What did you include for 1k in class and 1k in equipment ?
2. If I dive a twin-set, can I just buy a manifold and rent cylinders or is it hard to get matching cylinders ? I live in a flat so not keen on having cylinders at home as they take a lot of space
3. I saw a Halcyon evolve 60lb wing second hand at a good price (roughly half the price of a new one), should I just snatch it if I know I’ll dive with a twin-set at some point ? I’ll be probably diving dry most of the year and when going on holidays I’ll be more likely to take my single cylinder wing. I saw a lot of threads about 40lbs vs 60lbs wings ...

No, manifolding rental tanks IS possible, but so is winning the lottery 2 weeks in a row. It really is a huge pain and very unlikely to be successful as a long term strategy. The easiest way to dive 2 tanks from where you are now, without buying any tanks, is probably sidemount. It is pretty simple to take any two tanks rented and put a strap kit on them. That will involve more training and will need a different harness / wing system, so its not much cheaper. Many places have doubles available for rental, so depending where you are diving that may be easier.

The RAID Deco40 course trains you to dive to 40m, with up to 20 min of deco obligation, while carrying a stage tank of a rich gas. This is NOT used to accelerate deco, but for multi level diving. So for example, you might do a dive to 40m for 20 min on a 21/35 or equivalent light trimix (or air even), ascend up to a 18m portion of the wall, then switch to a 50% and continue the dive on that. This still involves carrying and switching to a gas that may be lethal during portions of your dive, that requires training and practice.

Other agencies have similar courses to allow you to extend the limits of rec diving in a small way before deciding to go "full tech".

 

[Storker]

Everything changes when you can't safely surface directly.

A decompression obligation means you have a mandatory stop between you and a healthy return to the surface. That's new.

Problems must be solved underwater prior to surfacing. That's a substantial shift in mindset and training for some divers which is one of the reasons I tend to think makes "technical diving" more technical.

This is the reason I avoid deco obligations and overheads. I want to be able to head for the surface at any time if SHTF. Having the skills and the training to solve any foreseeable issue underwater instead of just heading for that big, big tank of gas some 10-30m away requires a level of training and commitment that I'm not willing to put in.

That doesn't mean that I don't strive to be the best diver I can be, within the constraints of time and money I'm willing to spend, though. I'm happy to be a rec diver with decent skills, decent situational awareness and decently safe practices. At least at ISO 24801-2 Autonomous diver level

 

[Ryan Mcshane]

The surface not being an option is a big one for some people. You have to be able to deal with any problems in the water.

Even bigger is the oxygen toxicity issue. Switching to the wrong gas has killed a lot of people.

The gain? Deeper wrecks become open to you and even 100ft range you can spend double the time you would on a rec dive for very little deco.

 

[Superlyte27]

To the OP, to answer your question to me, tell me what gear you own now? Specifically, what tanks, what regs, what computer, what lights. What's your highest cert? Are you AOW and Nitrox?

 

[JohnnyC]

Why such a big step? Because the risk profile is much greater.

Read as: you screw up, you can die in any number of ways.

 

[Ryan Mcshane]

Read as: you screw up, you can die in any number of ways.

Horribly, twice.

 

[W W Meixner]

My longest dive to date is 60 minutes under water and I don't in the foreseeable future expect to dive much longer than that. If I did want to do longer or deeper dives (with decent bottom time) I would have to log 100 dives and do technical diving or do CCR. CCR is expensive and I don't know what you would have to achieve before starting the course. Long decompression stops do not appeal to me either.
What would be so difficult or risky about switchable twin tank diving using either air or trimix from say 35m to 55m and nitrox for the shallower parts of the dive?
Not considering a large gain, just really a possibility of spending say 30 minutes at 40m then ending with shallower dive (upper parts of wreck or nearer shore) on nitrox.

60plus...

Realizing I'm a little late to the party...also realizing that some ''things'' aren't that clear to everyone...

Here's the short answer...you're embarking on a long and difficult journey...that only a handful become truly successful at...where what was once considered deep at 60 ft...is now considered deep at 600 ft...

Without the proper training...and lots of practical application...playing with algorithms...PPO2 theories...and mis-information is the recipe for disaster...

With only 25 dives completed...who are you finding willing to sell you ''TRIMIX''...and how deep was your 60 minute dive...I've completed 2 1/2 hour single quarry dives above two ATM...get down a little deeper and everything changes...

''Knowledge gained through training and practical application makes you far less susceptible to bad ideas''

Best...

Warren

 

[60plus]

I certainly am not about to do anything stupid. Regarding PO2 and decompression obviously a good understanding of these is essential before exceeding normal NDLs. Post #15 asked my current quals. I am qualified to dive to 40m amd nitrox qualified. My own kit is single 15 L tank. I am basically a warmer water holiday diver. I could go to my local quarry and do loads of <20 m dives just to get my numbers up, but other than doing a few to keep in practice that seems pointless. I am a member of a BSAC club and quite a few of them use rebreathers. For the relatively small number of extended deeper dives I would want to do, a rebreather does not seem to be worth it. The expense of an extra cylinder and regs is small by comparison and additionally the maintenance requirements are much less / simpler. Bearing in mind the high "per minute deep bottom time" cost of holiday diving a twin tank 2 gas setup be the simplest way of increasing deep bottom time and extending it a bit over 40m may be to use a bottom gas, may be air or something with less nitrogen and use a high O2 % nitrox for the shallower / accelerated decompression parts of the dive.
My previous dives to 30m + seem all too short, hardly enough time to relax and get a good look round a wreck.

 

[runsongas]

ask around your bsac club a bit more. most likely somebody is doing uk wreck diving on twins with light deco.