How to answer "what is your highest certification level"?

[BlueTrin]

To add to @Wibble said, I don’t think you’d learn to use a twinset or a pony on the day of a solo class.

You are pretty much learning to plan a solo dive, making sure that your config is sufficient and you understand that you shouldn’t do a too complicated dive for a solo dive compared to your previous experience.

Therefore all the skills you’ll do are skills you are supposedly familiar with: manipulating valves on a twinset, changing masks, … etc

In my class there was problem solving for the valves: the instructor would show us card to say what happened after you close the isolator valve, for example, one card will say that your SPG is moving down therefore the failure is on the same side than the SPG … etc

It’s important to note that Solo is a SDI class and not TDI, so it’s not only for people who did tech classes.

 

[tursiops]

If SDI Solo and PADI Self-Reliant are both taught to their respective standards, they are almost identical, including prerequisites. One big difference is SDI allows a Spare-Air as a redundant gas source, which is silly IMHO. Another difference is SDI has a 2-dive requirement, but PADI requires 3 OW dives, of which the third can be indirectly supervised (actually a solo dive). When I've taught it, I teach the PADI class and offer the students an SDI card also if they want it for any narrow-minded dive sites. The converse is not true; if you teach the SDI class you can't offer a PADI card, because there are more requirements for the PADI card, like the 3rd dive, for example.

 

[Marie13]

I did two supervised dives on day one of solo class. Day two was two SOLO dives. Boy, it was kinda freaky diving by myself the first time.

 

[SlugLife]

One big difference is SDI allows a Spare-Air as a redundant gas source, which is silly IMHO.

Wow, that's shocking. I own a 19cu pony, 2x 6cu, 3cu spare-air, and 1.5 cu spare-air. A few times, I've done some test "dives" at about 15ft or less with fins, and a couple pounds of lead. TLDR, the 1.5cu and 3cu are DANGEROUSLY small, and Spare-Airs themselves suck (regardless of size).

• The 1.5 cu Spare Air was barely a few breaths (I didn't count) but it was gone almost instantly, near impossible to breathe, and I'd classify it as dangerous!
• The 3 cu Spare Air was a few more, but gone shockingly fast. Also VERY difficult to breathe. It might save you from drowning, if you're relatively shallow, and emergency-ascend. I'd suggest nothing is better than 3cu, because it's less stuff to carry, no false-confidence, and by the time you fumble the 3cu pony in your mouth, you could have been half-way to the surface.
• The 6 cu pony came with "bottle-regs" (1st stage screws into bottle) I replaced the 2nd-stage regulator with a Scubapro G250, tuned it, so it breathes great! During a pool "dive" I observed about 100psi used per-breath, at about 8ft deep. (about 30 breaths at surface?). This is my travel/vacation redundant air-supply (I'd prefer 13cu for travel). At 60ft to 90ft feet, I would look for any nearby diver, and if unavailable, ascend immediately at a safe rate, and based on air-left severely abbreviate or skip the safety-stop.
• My 19 cu is my primary redundant-supply; I strongly recommend this (or similar) size! Theoretically enough for recreational depths, including safety stop. A near-worst-case of a panicked diver and 130ft, you might have a short or skipped safety stop. This IMO is the ideal size for solo; it's super-convenient and small enough you have no excuse to leave it at home. A 19cu is no worse to carry than a 1.5cu, so I'd suggest skipping smaller sizes unless you travel a lot and maybe et 13cu.
• My friends who own 30 to 40cu leave their pony-bottles at home. Maybe they're lazy? Maybe that size is inconvenient? Regardless I'd like to try those sizes on a few dives in place of my 19cu, to see how cumbersome they are. (I've been trying to snipe them off Craigslist, but no luck so far)

 

[BlueTrin]

Wow, that's shocking. I own a 19cu pony, 2x 6cu, 3cu spare-air, and 1.5 cu spare-air. A few times, I've done some test "dives" at about 15ft or less with fins, and a couple pounds of lead. TLDR, the 1.5cu and 3cu are DANGEROUSLY small, and Spare-Airs themselves suck (regardless of size).

• The 1.5 cu Spare Air was barely a few breaths (I didn't count) but it was gone almost instantly, near impossible to breathe, and I'd classify it as dangerous!
• The 3 cu Spare Air was a few more, but gone shockingly fast. Also VERY difficult to breathe. It might save you from drowning, if you're relatively shallow, and emergency-ascend. I'd suggest nothing is better than 3cu, because it's less stuff to carry, no false-confidence, and by the time you fumble the 3cu pony in your mouth, you could have been half-way to the surface.
• The 6 cu pony came with "bottle-regs" (1st stage screws into bottle) I replaced the 2nd-stage regulator with a Scubapro G250, tuned it, so it breathes great! During a pool "dive" I observed about 100psi used per-breath, at about 8ft deep. (about 30 breaths at surface?). This is my travel/vacation redundant air-supply (I'd prefer 13cu for travel). At 60ft to 90ft feet, I would look for any nearby diver, and if unavailable, ascend immediately at a safe rate, and based on air-left severely abbreviate or skip the safety-stop.
• My 19 cu is my primary redundant-supply; I strongly recommend this (or similar) size! Theoretically enough for recreational depths, including safety stop. A near-worst-case of a panicked diver and 130ft, you might have a short or skipped safety stop. This IMO is the ideal size for solo; it's super-convenient and small enough you have no excuse to leave it at home. A 19cu is no worse to carry than a 1.5cu, so I'd suggest skipping smaller sizes unless you travel a lot and maybe et 13cu.
• My friends who own 30 to 40cu leave their pony-bottles at home. Maybe they're lazy? Maybe that size is inconvenient? Regardless I'd like to try those sizes on a few dives in place of my 19cu, to see how cumbersome they are. (I've been trying to snipe them off Craigslist, but no luck so far)

Now the real question: why do you own both a 1.5 and 3cu spare air if you feel like they are dangerous?

 

[Wibble]

Weren't "Spare Air" designed for people to escape from a capsized boat/whatever? Certainly not appropriate for diving.

Anyway, the point is that anyone diving solo should be able to work out if they've got enough redundant gas to reach the surface when the primary gas supply has failed.

This is calculated in a minute by minute basis as the depth in atmospheres multiplied by the expected SAC (Surface Air Consumption)
The SAC needs to be adjusted to a high "panic" rate. Your ascent rate needs to be moderate and any stops added.

All of that means a spare air is just not enough gas.

An ali40 might be enough, but obviously the deeper you go the more gas you need.

 

[SlugLife]

Now the real question: why do you own both a 1.5 and 3cu spare air if you feel like they are dangerous?

I got a good deal on the pair (compared to market-price), and not realizing they're paper-weights. Just taking up space right now in a "random scuba crap I don't use and need to sell" bin. Speaking of which, anyone want to buy these pieces of ?

The two 6cu, I got an absurdly good deal. Two 6cu bottles, two pony-reg-sets (spg, 1st & 2nd stage), all for $75 ($37.5 each). I don't really need them, but they are kinda fun for shallow/short shore-dives, or travel redundancy.

 

[Rayk]

Weren't "Spare Air" designed for people to escape from a capsized boat/whatever? Certainly not appropriate for diving.

First examples of that idea comes from aviation, bail out oxygen bottle designed for fighter pilots. It was strapped to the seat.

Same concept still in use today for HALO jumps.

 

[BlueTrin]

I got a good deal on the pair, and not realizing they're paper-weights. Just taking up space right now in a "random scuba crap I don't use and need to sell" bin. Speaking of which, anyone want to buy these pieces of ?

The two 6cu, I got an absurdly good deal. Two 6cu bottles, two pony-reg-sets (spg, 1st & 2nd stage), all for $75 ($37.5 each). I don't really need them, but they are kinda fun for shallow/short shore-dives, or travel redundancy.

I’ll dispose of them for less than $75.

 

[SlugLife]

Weren't "Spare Air" designed for people to escape from a capsized boat/whatever? Certainly not appropriate for diving.

An ali40 might be enough, but obviously the deeper you go the more gas you need.

Yes, spare-air was designed for things like a boating-accident or aircraft-water-crash.

For solo-diving, my personal philosophy is similar to "Rule of Thirds" plus Redundancy.

Rule of thirds (diving) - Wikipedia

en.wikipedia.org

For example, my main gas-supply, I follow rule-of-thirds. I always have 2x the gas I would need for the return trip. As it works out, that usually means I'll have extra gas towards the end of a dive, so I might start deep (usually 90ft or less), but then end shallow (usually 45ft or less) to use the remaining gas, and surface with about 500psi.

My redundant air is usually, whatever I need to safely surface at any point in the dive, and a little more than whatever a "third" would be in rule-of-thirds. A 19cu can "theoretically" do that from 130ft with safety stop and no panick. Intuitively, I don't like diving beyond 90ft solo with 19cu redundant, regardless my calculations.

I'm a Sidemount-diver, so if I was ever considering a 100+ft dive, I'd just do Sidemount (2x 80cu), because why not.

As a side-note, the deeper I go, the more cautious I am, looking for entanglements, taking my time, etc.

Well if you pay me $75 I guess I can take them.

The 1.5 and 3cu spare-airs are garbage. The 6cus aren't garbage!

(I think I spend about $60 to $70 on each of the spare-airs. The 6cus were $75 for two, an absurdly good deal)