What if...? Computer Issues

[boulderjohn]

And definitely don't try to read Bruce Wienke until you've gotten a very good understanding of multcompartment dissolved gas (aka neo-Haldanian, aka Buhlmann) models.

...and great math skills. Don't forget the math.

 

[SoccerJeni]

Unfortunately I haven't answered the What if scenarios, and now since I've read the whole thread and discussed it with people I feel like I would be cheating if I did answer.

So, here is my big delimma that I always face that I'd like to hear feedback about. I considered starting a new thread about this and if it would be better to do so, I will do that. I honestly wonder how many other new divers face this same issue. I do not own a computer. And every dive I've made, my buddy has a computer. My buddies have been DMs, Instructors, Guides (that are DMs) and a couple of times a friend with just a few less dives than me, but this was on a guided dive. So...what do you do if you don't have a computer and your buddy does? Do you force your buddy to dive a square table profile? Or, do you stick close to your buddy and follow the computer (keeping in your mind the table profile)?

I wonder who else struggles with this as a new diver...

 

[Cave Diver]

I do not own a computer. And every dive I've made, my buddy has a computer. My buddies have been DMs, Instructors, Guides (that are DMs) and a couple of times a friend with just a few less dives than me, but this was on a guided dive. So...what do you do if you don't have a computer and your buddy does? Do you force your buddy to dive a square table profile? Or, do you stick close to your buddy and follow the computer (keeping in your mind the table profile)?

I wonder who else struggles with this as a new diver...

This opens up a can of worms. Your basic OW instruction should have contained the warning that two people can't dive one computer. But before I answer your question, let me throw another one at you.

Why are you cautioned not to share computers?

 

[SoccerJeni]

This opens up a can of worms. Your basic OW instruction should have contained the warning that two people can't dive one computer. But before I answer your question, let me throw another one at you.

Why are you cautioned not to share computers?

To answer this question I will say that it is impossible to have the exact same profile as the person you are diving with.

 

[Cave Diver]

To answer this question I will say that it is impossible to have the exact same profile as the person you are diving with.

Correct. Because you don't have the exact same profile and time at each depth, attempting to share computers will add inaccuracies to something that's already based on a lot of assumption and guess work.

So while I don't advocate the practice, I recognize there are reasons why people may find themselves in that situation. The best answer would probably be to advise you to dive tables and have your buddy follow your square profile. But it may be difficult to find a buddy willing to limit their time when they have a computer.

What choices does this leave? Obviously the best choice is to get your own computer. Your next option would be to borrow or rent one. Depending on your diving location, you may be able to rent one fairly cheaply for short trips until you can buy your own.

Another option is to use advanced planning software and plan your dives ahead of time and cut your own tables. I'd also advise doing some research and study on deco and educating yourself about various methods of manually computing, including stuff like depth averaging or ratio deco. Learning to use a multilevel planning table like the PADI Wheel may help as well.

Finally, if you are determined to share a computer, I'd advise you to build in a safety factor. Make sure you spend more time a little above your buddy *(this brings up the issue of potential separation though), and make sure that your buddy does not ride the computer to the edge of NDL's. Above all, don't have them ride NDL's all the way up during the ascent. A lot of people will do this, by ascending slightly when they only have a few minutes remaining, then staying there til they're almost in deco, then ascend slightly again, repeating the process.

While technically you're not exceeding the NDL's using this method, by riding the edge you're almost guaranteeing that more of your compartments are going to be saturated than if you made just made your ascent.

The best advice I can give you, is that if you're going to violate the rules, be sure you understand what they are, why they're in place and what the consequences are so you can make an informed decision.

* another danger to this method is that if you do have a buddy separation issue, you've pretty much thrown any chance of repetitive diving out the window. There's no way to accurately predict how close the separated profiles are, and diving again is going to require special considerations. I'll address this in another post a bit later.

 

[gcbryan]

For the most part I'd say if you can afford to fly to a tropical destination you can probably afford a cheap computer. If you are diving locally you probably aren't on guided dives and in any event if you are diving locally the other diver probably doesn't mind cutting the dive short

 

[SoccerJeni]

Correct. Because you don't have the exact same profile and time at each depth, attempting to share computers will add inaccuracies to something that's already based on a lot of assumption and guess work.

So while I don't advocate the practice, I recognize there are reasons why people may find themselves in that situation. The best answer would probably be to advise you to dive tables and have your buddy follow your square profile. But it may be difficult to find a buddy willing to limit their time when they have a computer.

What choices does this leave? Obviously the best choice is to get your own computer. Your next option would be to borrow or rent one. Depending on your diving location, you may be able to rent one fairly cheaply for short trips until you can buy your own.

Another option is to use advanced planning software and plan your dives ahead of time and cut your own tables. I'd also advise doing some research and study on deco and educating yourself about various methods of manually computing, including stuff like depth averaging or ratio deco. Learning to use a multilevel planning table like the PADI Wheel may help as well.

Finally, if you are determined to share a computer, I'd advise you to build in a safety factor. Make sure you spend more time a little above your buddy *(this brings up the issue of potential separation though), and make sure that your buddy does not ride the computer to the edge of NDL's. Above all, don't have them ride NDL's all the way up during the ascent. A lot of people will do this, by ascending slightly when they only have a few minutes remaining, then staying there til they're almost in deco, then ascend slightly again, repeating the process.

While technically you're not exceeding the NDL's using this method, by riding the edge you're almost guaranteeing that more of your compartments are going to be saturated than if you made just made your ascent.

The best advice I can give you, is that if you're going to violate the rules, be sure you understand what they are, why they're in place and what the consequences are so you can make an informed decision.

* another danger to this method is that if you do have a buddy separation issue, you've pretty much thrown any chance of repetitive diving out the window. There's no way to accurately predict how close the separated profiles are, and diving again is going to require special considerations. I'll address this in another post a bit later.

I understand all that you have stated above. This is why I think the computer might be the first thing I think I should buy. I don't want to depend on someone to keep me safe when I really can't fully rely on them. But what do you do? You've got a double edge sword here. What person would want to limit themselves to the dive table square profile when they have a computer?

So let's say I rent a computer...how would I be able to take the time to learn all that you need to know about the computer? So, while it would be good to do that, is it really going to be okay?

I like the idea of planning out the dives on the software ahead of time. However, at times this could be challenging since you are not always aware of the plans until you are at the dive site...at least as a newbie I am not aware of them ahead of time.

I agree I need to do some research on deco and manually planning. Truly, I think this would be good for me to do regardless of whether I got a computer or not. This way I would be able to handle a situation if my computer did fail. And I would not be completely reliant on my computer either.

However, I wish I was as lucky as my cute friend who had a guy that liked her just give her a computer. But, I'm not...so looks like I need to do some research and shopping.

 

[Bubbletrubble]

Why are you cautioned not to share computers?

To answer this question I will say that it is impossible to have the exact same profile as the person you are diving with.

Correct. Because you don't have the exact same profile and time at each depth, attempting to share computers will add inaccuracies to something that's already based on a lot of assumption and guess work.

Y'all are forgetting about something...
In addition to the issue of having the same profile on the dive in question, the act of sharing one computer between two divers presumes that the nitrogen loading prior to the start of the dive is the same for both divers. If you've been diving with the same buddy for this particular dive trip and you always dive together on every dive, then that may be more or less true. If you pick up an insta-buddy who's on dive #1 of his dive trip and you've been doing a lot of diving in the last few days (and in particular in the last few hours), then sharing his computer would likely increase your chance of DCS risk.

 

[SoccerJeni]

For the most part I'd say if you can afford to fly to a tropical destination you can probably afford a cheap computer. If you are diving locally you probably aren't on guided dives and in any event if you are diving locally the other diver probably doesn't mind cutting the dive short

Very good point...but I don't want to lose my travel uppy:

What price range is a cheap computer? At least $300, right?

 

[SoccerJeni]

Y'all are forgetting about something...
In addition to the issue of having the same profile on the dive in question, the act of sharing one computer between two divers presumes that the nitrogen loading prior to the start of the dive is the same for both divers. If you've been diving with the same buddy for this particular dive trip and you always dive together on every dive, then that may be more or less true. If you pick up an insta-buddy who's on dive #1 of his dive trip and you've been doing a lot of diving in the last few days (and in particular in the last few hours), then sharing his computer would likely increase your chance of DCS risk.

Oh yes, sorry, I just made that assumption because I've never done anything different. Very good point though.