Help with Planning a 100m Dive?

[Andy the Coastie]

Originally Posted by Ainsleyberryman

Didnt someone post somthing about DAN and insurance saying Id be OK to 100m ? but ring them if its deeper ? Or was it OK on Normix - cant remember. As for loved ones Im OK, they would be happy that Im happy, and Im not responsible for anyone.

So, if the fan gets pooh splattered... they will pay out for a SOLO DIVER past the 100 mt mark ?

[Digger]

Course they won't. You'd need a whole lot of tickets for that. and even then you're goign to be on thin ice anyway if you ask me. DAN has said some very interesting things to me in the past, but I'd call if they're your insurers.

To be honest, it strikes me a bit (and I can only apologise if this comes across badly, it's not my intention) that if you need to ask questions like some of those coming up, you're probably not ready for the dive. I would think twice. The advice from those who've been there and done the dives at similar sites is that this is not an easy dive and with the timescale you have, I don't think you even have time to set up a safe dive, let alone all the other logistics that you don't seem to have thought of.

Just 2c worth. But you might want to think about it some more.

Digs.

[Brian Donaghy]

If your heart set on hitting the 100m mark, have you considered doing a course? A lot of people debate the value of deep trimix training but if you have lots of questions, you might learn some versions of the answers. It would also provide an experienced team for you to dive with. I know a lot of instructors don't go anywhere near the depth limit on the ticket during training but those would not be the instructors to go for anyway. I'm sure a lot of tech instructors would understand you quest.

For a number of reasons (including cost) it might make sense to do this dive somewhere other than the Red Sea.

Dive safe,
Brian

[Andy the Coastie]

Originally Posted by Digger

Course they won't. You'd need a whole lot of tickets for that. and even then you're goign to be on thin ice anyway if you ask me. DAN has said some very interesting things to me in the past, but I'd call if they're your insurers.

Digs,

Thats why i put up the post.

They wouldn't insure me for a week to do just ONE ice dive to a max of 42 mts in Norway....... excuse was that i had a no clear surface.

and that was with then being fax'ed a HSE dive plan risk assessment etc etc etc ......

and you know what quailifications and experience i have.

[ray]

Phew it seems like a lot of hard work, good luck anyway

[Mark Chase]

Personally I can understand the desire to hit 100m for the sake of hitting 100m its a goal in its self that you will never be able to explain or justify to someone who isn’t of the same mind. It’s selfish & dangerous and if you are in a situation where life insurance is important don’t bother doing it. I am not so I did.

You worked in Sharm so you should know more about the sea there than I do but I was under the impression that Shark and Thomas Canyon were prone to fast / strong currents?? Dave's (Dave and Margaret dive guides) description of flying through Thomas canyon was pretty impressive I must say

The Blue hole is a guaranteed safe dive in terms of currents but it has the big advantage of being warm clear viz and interesting unlike Dotti. Doing the arch you have a sandy bottom at about 110m and a visual reference to avoid blue water vertigo attacks so it’s as safe a 100m site as you're likely to get ignoring the chamber issue.

I think a week is plenty of time to build up and do the dive if you have a pre prepared plan and I think getting, as much information on the net or anywhere else is valid too.

When Andrew and I did it we had a duel plan. Do the arch and do the 100m. If we felt wrong or things didn’t go to plan we would just do the arch as shallow as possible. If the plan was good and we were good we would drop and do the depth. I couldn’t see any point in staying down there. The min deco per min at depth was outrageous so we just bounced the 100 spending a total of 2mins at max depth. That was plenty for a look around to appreciate what we had done shake hands and bugger off.

If you’re properly prepared physically and mentally and the rig is de bugged and tested there is no reason to get bent. Just stick to conservative profiles that you have had previous safe dives on at depth and add a bit for good measure.

ATB

Mark Chase

[Mark Powell]

Originally Posted by Ainsleyberryman

What about the difference in using Helium in all the mixes as oppose to going from TMX backgas and perhaps a TMX travel gas stright to say a 40% Nitrox on to 70% etc.

The thinking behind keeping Helium in the mixes is that you don't want to switch to a gas which ends up in a higher ppN2 than the one you just came off. If you switch from Trimix backgas to a Nitrox travel then yes you will be flushing out the Helium as the Helium gradient is now at maximum. However you will have increased the ppN2 and so you will now be on-gassing Nitrogen. If you switch at any depth then the on-gassing of Nitrogen can be significant in terms of deco.

As we understand more about Helium it is comming clear that Helium is a comparitively friendly gas with regard to deco than Nitrogen. It's true that Helium is less forgiving in terms of rapid ascents, but over the course of the deco it is a friendlier deco gas. Yes it ongasses faster but it also offgasses faster so high tissue tensions of Helium drop off faster then high tissue tensions of Nitrogen.

This led to the idea of including Helium in Travel. Essentially keeping the Nitrogen partial pressure under control.

For example lets say you are using 12/60 and you ascend up and change onto Air as a travel gas at 50m. This would start to flush out all that 60% Helium but look what is happening to the Nitrogen. At 51m while you are still on your back gas (28% Nitrogen) the PPN2 is 1.7. We switch to Air as a travel and our PPN2 jumps up to 4.74 so we start to on-gas Nitrogen and as we still have a lot of stops to do at depth we will continue to on-gass for quite some time. In addition our END has now gone from a comfortable level to 50m.

The same situation occurs when you switch to your first deco gas. You want something which is going to reduce the Helium but not at the expense of increasing the Nitrogen. If we assume that we are not using a travel gas and instead breath our back gas up to 30m where we switch to 40%. At 31m while you are still on your back gas (28% Nitrogen) the PPN2 is 1.15. We switch to 40% as a deco and now our PPN2 jumps up to 2.4 so again we start to on-gas Nitrogen.

Bruce Wienke as well as the WKPP have done a lot of work on this and have incorporated Helium into all mixes up to the 6m O2 stop.

[Ainsleyberryman]

Hi, Thanks for all the input guys. And Digger dont worry, its listening to comments like yours that bring me back to earth now and again. I have posted this here to get the kind of feedback Im getting. Yes its selfish and dangerous, but those issues dont apply to my personal circumstances. It would be more dangerous if I did it without your input.

I have done all the courses, including deep Trimix and dived to 75 and 86 in the Red Sea several times (Blue Hole, Thomas Canyon being my favorites). I have experience enough to make me feel ready to try the dive. (which is not the same as actually being ready) As Mark said - If I dont feel right I will make it a shallow dive. Ive done that before and have no problem doing it again. I also have a week to practice it, plus the constant practice Im getting here at Stony and the NDC. As for further practice Im doing a solo course just before I go which should just be a refresher from what I did on my advanced Trimix one - albiet in the cold dark NDC as oppose to the warm bright fish full Red Sea.

Im not uncomfortable with it or anxious about it, but obviously its more serious than my previous 86m dive - which actually was no harder than the 75m dives, which were not harder than the 60m dives. Once you are OK with the deco, kit, switches, multiple tanks, physics etc the actual number of meters is a mental thing. Im OK with that. Ive also not got any dependants to worry about. My family dont seem to mind when Im racing my off road bike at 70mph in the woods. Perhaps deep diving has a bad reputation.

However, none of my courses gave me the kind of real advice ive been getting. Sure I can work out the gasses etc, but its things like diet, keeping the Nitrogen % the same or less, people buggering off with your O2 hang tank, etc. Its all very cold theory and Ive actually learned more doing my own research on things like high or low Helium % in the mix, taking or not taking asprin, how to drink underwater and eat underwater, decostations, yellow blobs for signalling, which type of deco software actual deep divers feel is better for them and why. If you read the informaton in the manuals on things like counterdiffusion and gas choice you realise they fall short of complete advice.

I will continue to draw up my plans and improve them with the informaiton you continue to provide and stick them up for you to see, criticise, etc. I will do the dive and get back to you on how it went and what it was like.

I reckon the Blue Hole is going to be the best location (apart from the big hill and fast taxi to the chamber). I will have surface support with my O2 hang tank. I still prefer to do it on my own, Im not comfortable about being responsible for someone else down there. I know what thats like haveing taught and guided out there before. Its fine in sub 30m situations. All my previous post Trimix dives have been solo to all intents and purposes.

Cheers everyone.

[ChrisP]

Originally Posted by Ainsleyberryman

your not suppose to dive below 30m ! Which is a good rule. When I worked there I was always surprised that the chamber was never full !

Cheers

The law in Egypt has been changed. Recreational dives are not allowed below 30m and many dive places enforce that rule religiously but others can be persuaded to break it.
However, technical diving is now allowed under Egyptian law. In addition it does not require you to have a buddy either.
Chris

[PrettyFishies]

Hi. I can certainly understand the desire to hit 100m for the sake of it. I was the original depth junkie a few years back. But obsessing about depth nearly killed me after getting trapped at 104 metres for 15 minutes which is why I say take a step back, the water's not going anywhere. I now take the mindset that the depth is not the challenge, getting back alive is and the depth is just a consequence of a mission-specific dive.

Also, to do 100m for the first time in deep dark cold conditions is more challenging than blue water but that doesn't mean it can't go wrong in blue water just the same. I'd reel this in a bit and keep practicing in the 80-90 metre range. Also - any one can bounce down to 100 and back out, the real skill is doing some bottom time and managing the gases to avoid DCI. Bounce diving is bad for the brain and spinal cord and there is very little point in it unless there is an end goal.

Re gas switching I would NEVER advocate adding N2 on ascent, this is madness. People were switching to air at 30m on the rebreathers and getting well bent. I'm an advocate of keeping He in the mix as long as possible and then getting onto HIGH O2. Same goes for OC. Regards AnneMarie