TDI intro to tech review

[Compressor]

Done my intro to tech course with Mark Culwick at cardiff scuba over the weekend and would like to fully review the course as I found it.

Arrived at quarry at 8.00 on saturday and went though book and theory skills also picking up the benefits and disadvantages of 3 man team diving and quite a bit on gas selection and benefits of gear. After 3 hours we went up to inspect my gear and assemble gear.

I have the following:
Apeks 40lb double wing
Single harness
Twin 12 euros
Apeks xtx 100 1st and 2nd stages

7l ali stage with dst and xtx 40 2nd stage.

Northern diver HID drysuit

After adding some inner tube to retain my inflator hose and advising me to buy a suit inflation kit for when i start diving trimix and finally changing some gear between pockets ( right pocket having spare cutter wet notes and spare mask. Left pocket 2x dsmb and spools) we were ready to go down for first dive.

1st dive was to correct weighting and trim and working on basic diving skills going from trim by moving arms in and out and extending to the left and right to see effects on their trim.
Weight was changed to a 2kg tail weight and 1kg v weight and bands moved 2inches to get me in trim frim starting the dive being very head heavy. Tanks were then drained down to 10bar for a final weight check. Am diving 1kg over weight which i am ok with as gives me a bit of play with gas in my suit.
A full video debrief occured and then after food we parted for the day.

Day 2
Dive 1
Start drills
Bubble checks at 5m and s drills
Bouyancy drills (picking 2kg weight up off container then using breath control to adjust for change then resetting boyancy and desending the container using breath control before dropping weight on floor picking it back up and ascending bacj to the top using breath control.)
10mins on finning techniques using flutter, frog, modified frog and modified flutter before changing to backwards finning and helicopter turns.
Removing stage and leaving it on container then re-attaching stage and exchanging stage cylinders back and fro.
A few out of air drills and valve shut down drills brought an end to the container work and a dive followed with me as number 2 diver focusing on torch placement ended up with a dsmb deployment from 13m and me leading the ascent as deco captain stopping at 9, 6, 3, 2 and 1m.

After full debrief picking up on things i need to focus on (use kidney dump, more snap on my frog kick and my helicopter turns could be more ineficient i do small movements to turn so even though i turn in place could turn a bit better and extend legs further on recovery stage on back finning)

Dive 2.
Start drills
Bubble check and s drills
Ascent to 24m with me being dive lead and going on a swim.
Instructer went ooa twice (second time was because i had dropped down to 25.5m while traversing mid water and was below planned depth so had to swim to him)
After 25 went back to the 6m training platform where we focused on more stage exchanging drills and more on finning techniqes and more valve shut downs and 1 final ooa after I had slightly trapped my long hose after clipping off my torch.
Another swim out to 15m for a dsmb deployment and leading ascent occured again stopping at 12, 9, 6, 3, 2 and 1m.

Full debrief and now i know where i have to focus before i do my Andp in August.
It was the hardest course i have had to do and can recomend to anyone looking to go into tech diving.

Enjoyed your report; thank you.

 

[DanielRJones]

Can't beat wireless AI for logging and analysing how much your SAC/RMV really was during different phases of the dive. It is amazing how much you can breath during more complex drills.

Your course sounds really nice!

I run a petrel 2 so not got ai and have 2 backup mares puck pro in gauge mode unless i decide to buy a perdix ai i am going to stay away from ai

 

[Kevrumbo]

At 30m mine works out at 32bar at 40m its 39bar below 30 it falls away a bit more with 14bar at 10m

Surely that will be tank dependent to a great extent?

Quick maffs:
15 litres/min on a single 15L tank at 20m for 10 minutes is (15 x 3ATA x 10min= 450 litres thus 30 bar)
Same RMV on twin 15L will be 15 bar for same
. . .

He was talking aboit twin 12s. Where it works but yes twin 10s and below it does not work the best

It's somewhat easier to see for argument's sake to use an example RMV of 20 liters/min per ATA for nominal gas planning conservatism, along with utilising a manifolded backmount twinset of Aluminium 11L Cylinders (the most common tanks for rental/hire at dive-ops worldwide).

Here's why, showing for a RMV Range of 17 to 22 liters/min per ATA:

17 L/min. @ 20M (3ATA) = 51 L/min.
20 L/min. @ 20M (3ATA) = 60 L/min.
22 L/min. @ 20M (3ATA) = 66 L/min.

Dividing by the total metric cylinder rating of the double Alu 11L twinset (total 22 liters/bar), yielding a pressure consumption rate in BAR using the depth example of 20M (3ATA):

51 L/min. = 2.3 BAR/min.
60 L/min. = 2.7 BAR/min.
66 L/min. = 3.0 BAR/min.

For further conservatism, just round to the next higher integer in BAR, and create a depth consumption rate table:

Surface (1ATA) = 1BAR/min.
10M (2ATA) = 2BAR/min.
20M (3ATA) = 3BAR/min.
30M (4ATA) = 4BAR/min.
40M (5ATA) = 5BAR/min.

It's easy, it works for me as a rough planning tool, knowing that my "Magic RMV Range" at ten minutes time at a particular operational depth will correspond to a consumption in bar units similar in value to the depth in meters, or at most in ATA. . .