Question Dive planning exercise, please check my work

[lairdb]

No that is completely prohibited. 1) you'd need a permit from DNR (they own all submerged lands) and they aren't going to give you one, and 2) you'd kill all the waterskiers blasting around when they run into your buoy.

Straying a bit, but FWIW the dive mooring buoys I’m most familiar with are the Halas design used by the Malama Kai Foundation, and they are hung to be at 10ft depth. See Day Use Moorings — Malama Kai Foundation for drawings.

 

[306dive306]

I recently heard about a bunch of wrecks at around 120' FFW in Lake Washington. It will probably be another year or two before I am ready to dive them, but I figured I would take a stab at the planning process for this sort of dive. I was also curious about the utility of nitrox at depths of 100-130', and so I am self teaching tables.

Before someone asks, no, I am not nitrox certified. I am trying to teach myself the process of this because I will have a better understanding from figuring it out on my own before I take the class.

So, working from the NOAA air tables a 120' dive on air would give me a NDL bottom time of 15 minutes, and no possibility of a repetitive dive within a reasonable surface interval. If I stayed to 20 minutes, I would have a 2 minute deco penalty at 20'.

On the other hand, if I used EAN28, that would give me a NDL bottom time of 20 minutes at a PPO2 of 1.3. If I stayed to 25 minutes, that would incur a 3 minute deco penalty.

EAN 30 would increase my PPO2 to 1.39 without changing NDL times.

Questions: 1, do I have this right? And 2, does the fact that this is fresh, rather than saltwater make any difference at these depths?

Let’s see… you are not even nitrox certified, you do not use a computer, you are considering deco in ur calculations, i’m 100% confident u dive with 1-80cuft tank, i’m 100% confident you do not know ur sac rate, i’m 100% confident you do not know how to stage tanks AND YET you write about staying at 120’ for 20min.

To me, it sounds/lools like ur planning ur own death.

 

[Cthippo]

Let’s see… you are not even nitrox certified, you do not use a computer, you are considering deco in ur calculations, i’m 100% confident u dive with 1-80cuft tank, i’m 100% confident you do not know ur sac rate, i’m 100% confident you do not know how to stage tanks AND YET you write about staying at 120’ for 20min.

To me, it sounds/lools like ur planning ur own death.

I don't know why this is so hard to understand.

This is my trying to figure out aspects of diving by myself over the winter when I'm not in the water. Appearently that is a forbidden form of learning around here. There are wrecks out there I want to eventually get to. Not this year, not next, but maybe in 5 when I have a little more training and experience. That said, I was curious about the intersection of nitrox and deep, and of there is still an advantage to it at these depths. And so I looked up the tables, worked through it, and asked if my numbers looked right. That is all.

One does not need to be nitrox certified to understand the capabilities and limitations of using nitrox in a certain dive regime.

I do use a computer on every dive.

This exercise was specifically for NDL dives based on NDL tables. I was only looking at deco as a contingency plan. We are all trained that if you accidentally go into deco, follow your computer. Being aware that this dive would be close to the NDL line, I was looking to see what the penalty would be if I accidentally crossed it. Likewise, because it is a deep, cold dive, I might consider adding the deco time to my safety stop, even though I am still within the NDL limit.

And for the record, my primary tank is not an. AL80...

It's a steel 72!

 

[306dive306]

I don't know why this is so hard to understand.

This is my trying to figure out aspects of diving by myself over the winter when I'm not in the water. Appearently that is a forbidden form of learning around here. There are wrecks out there I want to eventually get to. Not this year, not next, but maybe in 5 when I have a little more training and experience. That said, I was curious about the intersection of nitrox and deep, and of there is still an advantage to it at these depths. And so I looked up the tables, worked through it, and asked if my numbers looked right. That is all.

One does not need to be nitrox certified to understand the capabilities and limitations of using nitrox in a certain dive regime.

I do use a computer on every dive.

This exercise was specifically for NDL dives based on NDL tables. I was only looking at deco as a contingency plan. We are all trained that if you accidentally go into deco, follow your computer. Being aware that this dive would be close to the NDL line, I was looking to see what the penalty would be if I accidentally crossed it. Likewise, because it is a deep, cold dive, I might consider adding the deco time to my safety stop, even though I am still within the NDL limit.

And for the record, my primary tank is not an. AL80...

It's a steel 72!

PROBLEM #1 --> "we are all trained that if you accidentally go into deco, follow your computer." If this is how you were trained, you should go find your instructor, sue him/her, and get your money back. In reality, if you "accidentally go into deco" that means you are a horrible diver who is very close to dying in the water. If you "accidentally go into deco", that means you were not able to properly plan and properly execute the dive within NDL, which is what every single diver who is NOT trained in decompression should be doing. Aside from having a catastrophic event that led you to slipping into deco world, there is NO plausible excuse for a rec diver to considering the possibility of entering deco.

PROBLEM #2 --> "Being aware that this dive would be close to the NDL line, I was looking to see what the penalty would be if I accidentally crossed it." If is close to the "NDL line", STEP AWAY from the line, then read "Problem #1" again.

PROBLEM #3 --> "I might consider adding the deco time to my safety stop, even though I am still within the NDL limit." You show - clearly - that you are intentionally thinking about deco. You, repeatedly, address deco and "deco time" to your plans, when - in fact - you should be planning your dives well within NDL and with a safety margin added to it so you DO NOT slip into deco.

PROBLEM #4 --> "And for the record, my primary tank is not an. AL80... It's a steel 72!" So you're carrying even less gas than you would if you were diving an Al80.

"I don't know why this is so hard to understand!!"

 

[rx7diver]

I don't know why this is so hard to understand. ...

@Cthippo,

I (for one) strongly encourage this type of thing--you know, attempting to learn things on your own, and then having a free discussion with more knowledgeable folks in order to check/correct/fine-tune your learning.

For me, the early days of my own tech diving was so much fun particularly because we were all trying to figure out stuff. Those were the early days of the www, and participating in threads on Aquanaut (for example) was tres bon, beaucoup fun, with a lot of people freely sharing what they had learned or were learning.

Don't become discouraged.

rx7diver

 

[306dive306]

@Cthippo,

I (for one) strongly encourage this type of thing--you know, attempting to learn things on your own, and then having a free discussion with more knowledgeable folks in order to check/correct/fine-tune your learning.

For me, the early days of my own tech diving was so much fun particularly because we were all trying to figure out stuff. Those were the early days of the www, and participating in threads on Aquanaut (for example) was tres bon, beaucoup fun, with a lot of people freely sharing what they had learned or were learning.

Don't become discouraged.

rx7diver

I agree.

Do not get discouraged.

Do things correctly.

Develop the proper mindset from the early days.

Do not expect people to agree with everything/anything you state.

Dive properly.

All the best and safe dives!