Tech 40 Trim and buoyancy

[Wibble]

You implied I mentioned using a V-weight on a CCR. If you had paid more attention to the OP’s query, you would have noted he was concerned with trim while using doubles.

For your reference CCRs are extremely sensitive to being overweighted as there’s not the massive gas supply to mask the BCD overuse nor variable lung buoyancy.

 

[Windmutt]

The three key variables to technical diving are knowledge, technique and configuration. It can take several attempts to sustain proper trim when using doubles of various sizes (some trim better than others). The focus should be: can you reach the manifold valves during a shutdown drill? Many a would be technical diver has been duped into buying the first CCR they set eyes on, or were easily persuaded by their peers’ lack of good taste and judgement— particularly when there are options to try several units and configurations. Therefore, I would not be disheartened by past experiences. Placing a V-weight may mitigate the problem in the short term.

Achieving results for little outlay is what distinguishes adept technical divers from the rest.

Thanks for the advice. The tec instructor removed my V-weight because my wing wasn’t keeping me at the surface when fully inflated. I’ve switched instructors and courses from PADI to TDI. Also bought my own gear instead of renting from the instructor. Already I’m discovering the reading material to be much better. Looking forward to getting this done right.

 

[Marie13]

Thanks for the advice. The tec instructor removed my V-weight because my wing wasn’t keeping me at the surface when fully inflated. I’ve switched instructors and courses from PADI to TDI. Also bought my own gear instead of renting from the instructor. Already I’m discovering the reading material to be much better. Looking forward to getting this done right.

The Alaskan is apparently a language bot. Suggest you use the ignore function

 

[Heat Miser]

Yes I have but the issue I have is that nitrox is not available everywhere. Logistically air is a lot more convenient in my area as shops insist on having cylinders overnight. I just want to fill and go. Seattle traffic isn't the best.

When I did Fundies, I asked the instructor "What about when Nitrox 32 is not available and it's only Nx 26 or Nx 27?" He said he wouldn't dive Nx 26/27. I was a bit shocked about that, but didn't discuss it further except for me to say "Sometimes that's all that's available."

In practical terms your on an island in the Maldives, there is a membrane machine it produces Nx 32 over the day to a bank. The bank gets drained down by a rush of tank fills and so the Nx 32 is topped up with air you end up with Nx 26. All dives in the Maldives are shallower than 30 meters by law.

 

[Wibble]

When I did Fundies, I asked the instructor "What about when Nitrox 32 not available and its only Nx 26 or Nx 27?" He said he wouldn't dive Nx 26/27. I was a bit shocked about that, but didn't discuss further except for me to say "Sometimes thats all that available."

Dogma eh!

Mine was exceedingly fussy about kit config too. When asked about a second backup computer the answer was it's on your team-mate's wrist. Quickly learned not to bother asking questions like that.

After diving for a while one becomes a lot more chilled about equipment and gas contents. Diving to 45m/150ft -- then some helium is good, 35% is just being extravagant in these times of helium shortages. Of course one should be using the standard gasses for the depth - 35m/115ft then it should be 21/35. Or nitrox 30% as pragmatists call it.

 

[Windmutt]

I'm an experienced diver (Master Diver with 100 dives per year for the last 4 years) and have been able to establish perfect trim and buoyancy in my recreational kit. During the last two sessions of Tech 40, I have been unable to keep my head up in a horizontal position. Its as if someone put 20 pounds on my head. My instructor says my trim sucks. We have made no adjustments to my kit with the exception of switching my Apex RK3 fins to ScubaPro Jetfins.

Note, the training is taking place in FRESH WATER. My kit consists of: Hollis Drysuit, Twin steel 100's, 40 bailout bottle, Hollis stainless backplate, Hollis DT 50, OrcaTorch canister light, extra mask, DSMB, manifold, spool, 2 knives, two additional backup lights, fourth element 7mm hood, three reg setups.

The only instruction I am getting is to keep my head up. I have my head touching the manifold knob and still I will angle down unless I put air in my drysuit. The fins (my idea) helped a little. Is it really my technique or do I need to adjust my rig (we never made any adjustments, move the tanks etc...)? Do I need a larger wing. My instructor says their is no need to adjust and it is all about technique.

Update - I have started TDI Training and have noticed a significant difference in the manual compared to what I learned from PADI. For one thing, it is more current (e.g. recognizes dive computers have been around awhile). Also, my PADI instructor told me as stated before to not move the weights or tanks to maintain horizontal positioning. He said, "just tighten your butt and your head will rise up."

Amazingly, here is TDI's instruction, "Once weighting and buoyancy are mastered, the skilled diver will next focus upon his balance. A diver should be able to hover naturally in a horizontal posture, without any need to scull with his hands or feet. If he finds, while hovering, that he tends to rotate towards a head-up position, he will move some of his weight to a higher position on his body, or shift his cylinder slightly upward on the BCD If he tends to rotate to a head-down position, he will move some of the weight to a lower position on his body (perhaps even using ankle weights), or shift his cylinder slightly downward on the BC. Alternately, if he finds, while hovering, that he remains horizontal but tends to roll over onto his back, he will shift some of his weight towards the front of his body."

So far, my recommendation to anyone is to use TDI for Tech training. The good news is I am having a much better experience. I think Tech diving should also be learned from a boat rather than the shore since this is the environment where most diving takes place IMHO.

 

[wetb4igetinthewater]

I think Tech diving should also be learned from a boat rather than the shore since this is the environment where most diving takes place IMHO.

May I introduce you to your Lord and Savior, DPV?

 

[crofrog]

Amazingly, here is TDI's instruction, "Once weighting and buoyancy are mastered, the skilled diver will next focus upon his balance. A diver should be able to hover naturally in a horizontal posture, without any need to scull with his hands or feet. If he finds, while hovering, that he tends to rotate towards a head-up position, he will move some of his weight to a higher position on his body, or shift his cylinder slightly upward on the BCD If he tends to rotate to a head-down position, he will move some of the weight to a lower position on his body (perhaps even using ankle weights), or shift his cylinder slightly downward on the BC. Alternately, if he finds, while hovering, that he remains horizontal but tends to roll over onto his back, he will shift some of his weight towards the front of his body."

I think you'll find that sometimes this weighting is very counter-intuitive though. A lot of people are head heavy and trim into a head up position to balance the center of buoyancy and center of lift, and you'll find that shifting weight lower on the diver will correct a head up trim.

 

[inquis]

A lot of people are head heavy and trim into a head up position to balance the center of buoyancy and center of lift

+1. My suggestion is to get horizontal and then see where you go from there when you stop skulling/kicking.

 

[Wibble]

Update - I have started TDI Training and have noticed a significant difference in the manual compared to what I learned from PADI. For one thing, it is more current (e.g. recognizes dive computers have been around awhile). Also, my PADI instructor told me as stated before to not move the weights or tanks to maintain horizontal positioning. He said, "just tighten your butt and your head will rise up."

Amazingly, here is TDI's instruction, "Once weighting and buoyancy are mastered, the skilled diver will next focus upon his balance. A diver should be able to hover naturally in a horizontal posture, without any need to scull with his hands or feet. If he finds, while hovering, that he tends to rotate towards a head-up position, he will move some of his weight to a higher position on his body, or shift his cylinder slightly upward on the BCD If he tends to rotate to a head-down position, he will move some of the weight to a lower position on his body (perhaps even using ankle weights), or shift his cylinder slightly downward on the BC. Alternately, if he finds, while hovering, that he remains horizontal but tends to roll over onto his back, he will shift some of his weight towards the front of his body."

So far, my recommendation to anyone is to use TDI for Tech training. The good news is I am having a much better experience. I think Tech diving should also be learned from a boat rather than the shore since this is the environment where most diving takes place IMHO.

It’s more to do with your instructor than the agency. Someone who walks the walk not talks the talk.

Pretty much any fully competent technical diver will give you that advice as they’ve all been through that process.

Being still and flat in the water takes a huge amount of practice to truly master.