their AL 80m are lighter????

[Rich Keller]

They may have been using the original aluminum tanks from the late 70s that were quickly fazed out because they were far to light. They were much lighter on land but you had to make up for that with more lead on your belt. I have never heard of a neutral aluminum tank and would be interested in hearing more about that. The attached link should give you specs on the most common tanks in use today. Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

 

[Bubbletrubble]

I went down with the same amount of lead I always use and I was fine.

@scuubaadoo: How do you decide when it's OK to not follow a DM's instructions?
Before you disregarded the DM's instructions, did you perform an in-water weight check?
If not, why not?
Did you ask the DM for clarification on his curious instructions?

In my book, beginning a fairly deep dive (Spiegel Grove dive site ranges from 60-130 fsw with the majority of the wreck dive-able in the 80-90 fsw range) with questionable DM instructions, an unknown tank, and not knowing whether you are properly weighted is not the kind of diving that I want to do. Moreover, I'd be concerned about anxious newer divers who followed the DM's instructions unquestioningly. Being overweighted will only compound any in-water issues encountered. If I'm in the water with someone else experiencing an emergency, I feel some obligation to help out provided that the risk is acceptable. In this way, being in the water with overweighted divers can directly affect my safety even if I myself am properly weighted.

I understand that some people have a personality that abhors confrontation. In fact, under many circumstances, I'm one of those non-confrontational people. However, in order to dive safely, it's incumbent upon us to push ourselves to be more assertive. If you won't stand up for your own safety, who will? I think a compelling argument can be made that assertiveness training should be incorporated into basic OW training.

 

[Splitlip]

I'm not familiar with that dive location, but possibly the DM has some freshwater divers transitioning to salt water ???

Good point.

 

[RonFrank]

It may have been the DMs way of trying to ensure that folks were not diving light. Regardless it is BS. The average alum tank is about -1.5lbs full, and 3.4lbs empty. That may vary by +/- 1lbs for the common AL80's, but not much more than that.

BTW the neutrally buoyant AL80's are about -.5lbs neg at the end of a dive. Cool, but a bit pricey for skipping 4lbs of lead. You can get a steel LP85 or HP100 for a bit more and it has a better form factor IMO.

 

[nikko]

There ARE neutral 80s, but I've never been anywhere where they were the rental tanks.

A LDS in Guam rents what we call Compact 80s. These are neutral

 

[redacted]

I'm not familiar with that dive location, but possibly the DM has some freshwater divers transitioning to salt water ???

That transition would be in the range of 5 to 8 pounds for most divers.

Only way I see his statement making any truthful sense is if "everyone else" (dive operators) normally dove steel tanks.

 

[redacted]

They may have been using the original aluminum tanks from the late 70s that were quickly fazed out because they were far to light. They were much lighter on land but you had to make up for that with more lead on your belt. I have never heard of a neutral aluminum tank and would be interested in hearing more about that. The attached link should give you specs on the most common tanks in use today. Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

The Catalina C80 in your link is a neutral 80. Here is another: XS Scuba 80 Cubic Foot Aluminum Neutral Scuba Tank ALN80 with reviews at scuba.com

You get to pay almost $100 more for about 5 extra pounds of aluminum to replace the 4 pounds of lead you would otherwise use.

 

[MX727]

Which boat/shop were you diving with?

 

[Mossman]

I'm not familiar with that dive location, but possibly the DM has some freshwater divers transitioning to salt water ???

The Spiegel Grove is off Key Largo. Most of the water surrounding the Keys is salt water, AFAIK

(Besides, that wouldn't excuse the DM's lie, he could have simply informed any fresh water divers that they'd be more buoyant in salt water, as if they didn't already receive that important tidbit of knowledge in their dive training.)

 

[mselenaous]

Maybe I can help shed some light here. I do get to dive with quite a few ops in Key Largo. Yes the Spiegel Grove is in KL, yes this is saltwater.

Although the shop hasn't been named, one of the bigger ops recently replaced all of it's tanks. They went from steel tanks to AL80's (S80). Their briefings now include mention of this change so that repeat customers will adjust their lead accordingly. Additionally, there is at least one dive op that uses the neutrally bouyant C80s, and they include this information in their briefings so that customers adjust their lead accordingly as well.

When in doubt, ask the DM for clarification. If the DM isn't able to give you an answer that you understand, have a chat with the Captain. Sometimes hearing an explanation from another person using slightly different wording can clarify the issue for you. Remember that it is their job to get to know each group's experience level so that we can give you the best information to complete a safe fun dive. It is very rare that divers with no salt water experience are taken to this deep wreck. Shallow dive sites are highly recommended for a First salt water experience, before tackling a challenging deep wreck dive - even under direct instructor supervision. These dive boats usually have local instructors aboard with students. We are also happy to help out with questions.