1st time past 100ft for a big guy, Advice needed!

[lsorenson]

Background: I'm going to Roatan in December and the first dive each day is to 90-110ft. My dive buddy is a 5'3" 120lbs female AOW (15 dives), I am 6'7" 230 lbs male AOW (25 dives up to 75ft). Her SAC rate is about half of mine (.45 vs .9) and the dive operator does not have any tanks bigger than Al80s. I dive a Deep Sea Supply SS BP/W and have a 19cf bailout slung for the deeper stuff.

My Question: Is this smart for me to go past 100 (probably on EA32) on a single Al80 + 19cf bailout (not part of my gas plan) at my size and experience level, it just doesn't seem like enough gas to me? I have considered getting training on independent twins for safety and to even up dive times, but this seems like a huge hassle and too much to worry about for my first major dive trip...Yet I don't want to skip the morning dives.

Thank you everyone, just trying to dive smart...

Where are you diving...? West End? Are you really going to haul that pony with you? I would not worry about the pony since you WILL have a buddy close by and with you paying attention to your air consumption there should really be no reason too....!

In my 25 dives at Roatan, all of which were on the southern side, I broke 100' maybe once or twice and that would have only been for a few minutes... I was diving a bp/w with EAN32 alu80 and tho I am somewhat of a air hog it never deterred me from any of the dives... Sometimes I was the first up but then who cares if I or anyone else for that matter calls their dive 5-10 minutes early??? There was never a dive where the DM called the dive cause 1 person or 5 people when up... We all came up when the SPG indicated it was time to leave... To clarify, "time to leave" is with plenty of gas for a safety stop and any/all contingency that may come into play!

In all honesty, If these are your first ocean dives I would be more concerned with you and your buddies comfort level in the ocean than I would be about breaking 100'. If your going for a week then please for your buddies sake, make sure both of you are ready to go that deep! Its pretty unforgiving 100' under the sea...

Relax, take your time and get ready to enjoy Roatan... I know I did as we are already set to return in 11 months....!

lee

PS I would rather spend 90 minutes at 50' than 25 minutes at 100'...!

 

[txapacheguy]

My first three dives following AOW were 100' dives with a pair of instabuddies. One of the guys was a hoover(worse than me), could not control his buoyancy, and did not communicate very well. He took off to the surface from about 90' because he thought he was about to run out of air, and proceeded to blow off his safety stop due to being underweighted and low on air. On subsequent dives, he did better about communicating his air supply situation to us, but still failed to complete his safety stops. In hindsight, going on that chartered trip in the gulf was probably was not the right way for me to get started after having recently completed OW and AOW in Santa Rosa, NM at Blue Hole. Fortunately, no one ran out of air, drowned, or got bent from the experience. It sounds like the OP is in a lot better position to deal with the depth than I was at that time. I like the idea of the pony bottle, and have already planned to obtain at least a 19cf bottle before I do any more dives to 100' with an AL80...

 

[Garrobo]

I routinely dive 120-130 feet on ship "wrecks" around the Upper Keys such as the Eagle, Speigle Grove, Duane, Bidd, etc. on one AL80. Usually get around 25 minutes bottom time with a group but have done 40 minutes with other experienced divers. A couple times it was close on the air but nothing life-threatening. I remember once when I came up and one of my computers was still in the caution zone and the other was not. No problemo tho. I tried dragging a pony bottle around for a while but never had to use it.

 

[HIGHwing]

Your best strategy is to get that SAC rate down. I have a bit more weight than you and when i first started diving deeper I think a tank lasted about 6 minutes. Now my SAC is down to a pretty comfortable .55 warm, and about .67 cold. I have friends that get all the way into the .3 range, but I believe they're skip breathing. Anyway, it's really about practice, comfort, and good equipment. The largest factor in reducing my SAC was going from a cheapie reg to an ST1 Atomic. The air delivery is so smooth it just calmed me right down

So - why not do as many possible practice dives as you can. It's likely you can reduce your SAC by 30-40% just by relaxing and getting in the zone.

 

[highdesert]

I think you're fortunate that you're diving with a company that will at least advise the possibility of a 90'+ dive in the morning, and applaud your concern about preparing for that. I don't know what company you're diving with, or which sites, but after several trips to Roatan, I doubt that we hit 90', and then only briefly, on more than 5-10% of our dives. Roatan is very largely wall diving, and the attraction is working yor way up the wall as the dive progresses. I'm 6'3" and 220 lb, and always finished 60+ min dives there with about 500 psi, even on our first trip there when I had 20 dives total.

I'm not making light of the depth. Again, being conservative is a wise thing, but don't let it cut your dives there short.

 

[DA Aquamaster]

Technically, a square profile to 100' with a SAC of .9 will use 76 cu ft of gas - basically all of the useable gas in a fully filled AL 80. If you back off the bottom time to 15 minutes, it drops the total gas used to 56 cu ft, leaving you 21 cu ft and 800 psi in reserve.

In reality, you will probably not be doing a square profile, will descend a little slower, and spend much of the dive shallower than 100' so if you call the dive on time at 15 minutes you will be fat on gas. In practice, it makes more sense to figure your rock bottom to ascend from depth to the surface.

Roughly speaking given your SAC rate and possible stress induced increases, figure 15 cu ft for ascent gas for you and your buddy from 100 ft, plus another 15 cu ft for a 5 minute safety stop, and that would require that you start up from the bottom around 1100-1200 psi - not a bad idea on a 100 ft dive anyway.

-----

A not so great gas extention option is to bring along a stage - in this case a 30 to 40 cu ft tank that you would breathe down to about 500 psi before switching to your main AL 80. The cautions here are that many boat operators frown on a diver using a "pony" in this manner, it requires that you be able to get it filled between dives, it requires a certain skill set in terms of reg switching and it requires that you still ensure an adequate reserve, so training and discipline are required.

To do it safely requires the same basic skills as diving independent doubles, so that is a much better way to go. In a two tank recreational dive situation, diving independent doubles lets you use a full 77 cu ft on the first dive with a healthy reserve. And in practice you won't use quite all of it, increasing the reserve available on dive two, as you are taking the "left over" gas from dive one along on dive two. Again, it requires proper training and discipline, but it involves no extra tanks so boat operators tend to be less concerned - providced you explain what you are doing and do it in a convincing and confidence inspiring manner. (This means you really need to have the skills down and be comfortabel in the configuration before you go on the trip.

______

Personally, I think at your experience and skill level, doubles are probably going to be a bit of a reach, so your best bet is just carefully planning and watching the SPG and then starting the ascent with an adequate reserve.

 

[redacted]

Your SAC rate will come down in time but not likely by December.

You should have the option of you and your buddy staying 20 to 30 ft above the group which will extend you dive time. Talk to the DM about your concern.

 

[BigHarryDiver]

One question I haven't seen asked yet.. Where were you diving with a SAC of .9 and what was your dive kit? I see you are in North Jersey... My SAC on local dives (Dutch Springs quarry and NJ/DE/MD ocean dives) is in the .8-1.0 range. When I dive in the carrib, I'm in the .3 to .4 range. If all of your diving to date has been local, you will be amazed how well do do on consumption in warm clear water with a lighter wet suit.

 

[drbill]

Given your SAC rate, it may not be a good idea to dive to such depths despite having a pony. I liked the suggestion of looking into yoga to try to bring the SAC rate down. Of course given your size, and probable lung volume it may be difficult to bring it to the level of your buddy. Don't the sites allow for shallower dives than that?

It took me decades before I ventured down past 100 ft. As a kelp forest ecologist, most of what I needed to look at was above that depth. By the time I finally descended past 100 (and to as deep as 200 ft on numerous occasions), my SAC rate was pretty good, I always carried a 19 cu ft pony and had no trouble. And the reason I ventured to those depths was for scientific work.

 

[robjackson_97]

With time your air consumption will improve. You only have 25 dives under your belt so you are still a fairly new diver. I'm half your size and at your number of dives I had the same amount of bottom time as you. Work very hard on controlling your breathing. I now average 60 minutes on most dives in the 80' range. The good thing about Cozumel is most dives are drift dives so you don't have to work very hard.