Intro to Tech

[Blackcrusader]

Commonly shops want nothing to do with deco dives. It is still the case that these deco courses require written plans on a slate

This is very true. It depends on the management but there has been a change in recent years. I did PADI ow in January 1986 before the RDP wheel came out then I moved to Brunei where I worked from 1986 - 1988 joined the BSAC club did BSAC Sports diver where air deco dives were taught. No DC's or Nitrox back in 1986. From 1989 I would be diving around Asia with PADI run dive centers. No internet back then and many felt I was very suspect diver to be with because I did that very dangerous thing, deco diving, which was of course was a big NO NO with PADI back then. So they initially said you can dive on your padi OW card and we will see if you can go to deeper than 18m dives later on. Many padi places had never heard of BSAC and said they thought I had some weird diving certificate. Malaysia Singapore Brunei were ex British so they knew about BSAC. I want to do a two week trip to Palau next year so having my TDI cert will allow me to do some dives that are off limits to most recreational divers.

So now to me doing the TDI Course the place I am doing it the last manager was no to TDI courses, no to deco diving he was just PADI and no to even padi tec 40 45 50. The new manager who I have already done other courses with is now sure TDI course and deco dives no problem. We have known each other for 8 years.

There are a couple of dive sites where wrecks are at 35m - 45m depth I would like to see the outsides of. The TDI course is perfect for that. There are now more dive centers that also now have SSI TDI advertized as well in addition to padi.

Attitudes are changing. DC's are convenient and make me lazy. Slates and tables make my dive plans more carefully laid out.

 

[boulderjohn]

Let's take a look at a different activity with the same sort of goals. I started skiing as a poor young adult, and I did it with just the training my wife could give me. I practiced my skills regularly for many years before I could afford lessons. I then took some lessons so I could excel on the most difficult slopes and so I could do better in citizen racing. Those lessons showed that I had over the years thoroughly ingrained really bad habits that were hurting my performance. After many lessons and much effort to overcome those bad habits, I became a much better skier, but I never fully overcame those bad habits.

If you know you want to do technical diving some day, the first thing to do is to find someone you can trust who can evaluate your present skill level and recommend a path custom designed to you to best find your way to that goal.

 

[Pearlman]

TDI simply says your instructor will advise what equipment is required. So yes they can decide. Now I was told you must have have a backup to my DC which has depth and a bottom timer so I can use my Cressi Digi 2 Console so I do not need to have an extra dive computer as you will use tables and a bottom timer for the dive anyway. Maybe some instructors will insist on the diver having two dive computers.

Aah I was very tempted to get that but the price quoted to me was almost 3/4th the price of a shearwater Peregrine lol. In any case I already have my old DC to use in gauge mode so not worth it for me even at fair price because it is still costlier than an analogue gauge and I have two DC anyways…

 

[Wibble]

Attitudes are changing.

Not sure. PADI places still see "no deco" diving as the only way to dive.

DC's are convenient and make me lazy. Slates and tables make my dive plans more carefully laid out.

Once you're over the initial post-course dives, you'll start to develop your own way of doing things as you gain experience.

The first thing that goes is the slate. It'll move to the wetnotes and very soon will be too much effort for no return. The reason is simply that proper*** dive computers will give you all the info you need in realtime. You will -- or at least you really should -- be diving with two of them, one as a backup.


Your dive planning will be a session on Multideco to work out the overall plan -- have you enough gas for the planned dive leaving enough in reserve for failures. As you do more of those kinds of dives, e.g. 45m/150ft, you'll know what it looks like and can compare it with previous dives.

You'll then run the dive on the dive computers. Effectively you'll know the total runtime maximum (set by the skipper and available gas); the maximum decompression time (set by the available gas); and the minimum bottom gas (you need enough to get to the deco gas switch OR deco out on backgas if the deco gas has failed). With those thee things, the bottom time is whatever's left over.

It's similar on a rebreather, but the constraint is your bailout gas should you have a very bad day. A CCR dive, say to 45m/150ft will be constrained by max runtime. So jump in, enjoy the bottom, when the TTS plus Runtime hits your max runtime, ascend. Yes, it's good to have some reserve time

Rebreathers make diving at those depths exceedingly simple. You use very little of your gas and you don't, aside from checking, use your bailout gas. 40% helium for a 45m/150ft dive is very affordable.


*** "Proper" dive computers. Lots of discussions on here over computers. The entry-level ones simply don't cut the mustard; you need a computer that supports Buhlmann with Gradient Factors for decompression. The technical diving community has pretty much standardised on that decompression algorithm and you need to dive the same algorithm with your team-mates (like buddies, but have skills). This means you don't want Suunto and its ilk, you need Shearwater, OSTC, Ratio, etc. (Suunto as a backup will work, but will keep you in the water longer than necessary with the potential of "bricking it" should you not follow its petulance)

 

[Pearlman]

What about DCs using VPM (another bubble model algorithm)? Surely there must be Tech., dive shops where the instructor switches to using a Sunnto for your actual training dive sessions?

So are there underground forums where outcastes and rejects of diving society can secretly post messages like “looking for a Sunnto buddy…”?

 

[KenGordon]

What about DCs using VPM (another bubble model algorithm)? Surely there must be Tech., dive shops where the instructor switches to using a Sunnto for your actual training dive sessions?

So are there underground forums where outcastes and rejects of diving society can secretly post messages like “looking for a Sunnto buddy…”?

My first TDI deco course used VPM-2 to plan the dives.
80% of the people in my dive club have Suuntos.

Part of the hate seems to come from allegedly shorter no stop times. Once you decide to do deco the no stop times don‘t matter and the stop times matter. I find that a Shearwater set to a sensible GF is quite similar to a Suunto for sensible depth (the deepest I have dived with a Suunto buddy is 60m).

Many people start out diving with computers like the D5 or a Vyper Air that will do accelerated deco and so are good for ANDP level, like a Peregrine is.

 

[boulderjohn]

Once you decide to do deco the no stop times don‘t matter and the stop times matter. I find that a Shearwater set to a sensible GF is quite similar to a Suunto for sensible depth (the deepest I have dived with a Suunto buddy is 60m).

What do you mean by "sensible GF"? RGBM is very much a deep stop algorithm, and I saw a video of Bruce Wienke praising deep stops long after the bloom had gone off that rose.

 

[KenGordon]

What do you mean by "sensible GF"? RGBM is very much a deep stop algorithm, and I saw a video of Bruce Wienke praising deep stops long after the bloom had gone off that rose.

50/80 or 50/85

Suunto don’t run real RGBM. In any case a DS style 10/80 vs 50/80 makes little difference unless you really are going up at 10m/m. For a 20 minute 60m dive the 10/80 one is 10 minutes longer.

The thing I want is the ability to plan the dive with the setting I intend to use so I know how much gas I need. DM5 does that.

 

[Blackcrusader]

Aah I was very tempted to get that but the price quoted to me was almost 3/4th the price of a shearwater Peregrine lol. In any case I already have my old DC to use in gauge mode so not worth it for me even at fair price because it is still costlier than an analogue gauge and I have two DC anyways…

Peregrine can't tell you your gas level though and the price I paid was less than half what a Peregrine costs. I like it for the digital display.
It's not for everyone. In fact I have not seen anyone else with one. I do get lot's of people coming over to look at it when I am diving. A lot of people like the display. Cressi do not market it very well really.

 

[Wibble]

With Suunto et al you’re stuck with their barely adequate planners. With Bulhmann you’ve a wide range of planners running the same algorithms. I personally like MultiDeco which is available on most platforms.

Suunto DM5 is quite naff in comparison— and not available on tablets, phones, and is crap on a Mac.