their AL 80m are lighter????

We were on a dive to the Spiegel Grove the other day and the dive guide told our group that every one needed to put an extra 4 - 6 lbs of lead on because their AL 80 tanks are 6 pounds lighter than everyone elses tanks? :shocked2: I thought that pretty much all aluminum tanks were about the same in weight, we're not talking the super 80 which are shorter and thicker or any other special AL 80 tank, just your average run of the mill tank. I assumed he wanted everyone overweighted so we could all get down to the wreck faster/easier. Which would have been fine with me if he had just said so. What do you guys think?

scuubaadoo:

We were on a dive to the Spiegel Grove the other day and the dive guide told our group that every one needed to put an extra 4 - 6 lbs of lead on because their AL 80 tanks are 6 pounds lighter than everyone elses tanks? :shocked2: I thought that pretty much all aluminum tanks were about the same in weight, we're not talking the super 80 which are shorter and thicker or any other special AL 80 tank, just your average run of the mill tank. I assumed he wanted everyone overweighted so we could all get down to the wreck faster/easier. Which would have been fine with me if he had just said so. What do you guys think?

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In scuba, it is often easier to deceive customers than to tell them the truth. I think they must give out prizes for who can sell the biggest whopper.

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

In my mind, the only way this comment by the guide would make any sense at all is if the charter provided tanks that were lighter than usual (the "neutral 80's TS&M mentioned), and I would think (like her) that those would not be the gear that the majority of charter services would be providing to customers. I have to think that divers on the Grove would be experienced enough to have the proper weighting with standard tanks, so it is indeed intriguing as to why the guide would say this.

scuubaadoo:

We were on a dive to the Spiegel Grove the other day and the dive guide told our group that every one needed to put an extra 4 - 6 lbs of lead on because their AL 80 tanks are 6 pounds lighter than everyone elses tanks? :shocked2: I thought that pretty much all aluminum tanks were about the same in weight, we're not talking the super 80 which are shorter and thicker or any other special AL 80 tank, just your average run of the mill tank. I assumed he wanted everyone overweighted so we could all get down to the wreck faster/easier. Which would have been fine with me if he had just said so. What do you guys think?

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I'm interested to know which operation is telling their divers this crap

Don't believe everything you are told.
If a DM told me that before a dive, I would have a few questions for him:

• Does the "six pounds lighter" comment refer to buoyancy specs or absolute weight?
• What make/model of tank does his dive op rent out?

If the DM is "certain" that the tank is six pounds lighter than a regular Catalina S80 (specifically with respect to the "empty" tank buoyancy spec), then I would politely request to be given the opportunity to conduct an in-water weight check prior to the first dive.
Perhaps the DM misspoke. Hopefully, he wasn't purposefully trying to overweight customers. I consider proper weighting to be a fundamental safety issue. I will not tolerate a dive op that instructs me to do something I deem to be unsafe.

It's not difficult at all to read the tank markings and identify the details of make/model/capacity.
If you feel so inclined, take that info and cross-reference it with a couple of convenient tank specs charts posted online: Tech Diving Limited, Huron Scuba.
Understand that the numbers listed on the charts are believed to be true. There may be some inaccuracies, so when using the info to weight yourself, know that there is still no substitute for a proper in-water weight check. Personally, I have found the charts to be accurate. YMMV.

TSandM and Guba brought up the existence of neutral 80 tanks...
FWIW, using the referenced online tank spec charts, neutral AL80 tanks (Catalina C80) are -0.2 lbs. buoyant when empty. Run-of-the-mill, more common Catalina S80 tanks are +4 lbs. buoyant when empty. If the dive op in question had the rarer Catalina C80 tanks in service, then the buoyancy of their tanks would actually be 4 lbs. heavier when empty vs. the common Catalina S80 tanks. This would mean that he should be informing his customers to decrease their ballast by approx. 4 lbs. Therefore, the DM could not have been referring to a situation in which his dive op rents out neutral 80 tanks to customers.

Personally I've never heard of an AL80 tank that was +10 lbs. buoyant when empty. That's what the tank spec would have to be in order to be consistent with what the DM was saying.

Educate yourself. Your safety is at stake. The most likely scenario is that the DM is sorely mistaken about his dive op's rental tanks.

Actually the neutral 80's are HEAVIER and more negative than standard 80's. They are neutral when empty. Not full. So if the op was supplying neutral 80's AND advocating more weight, the divers would be severely over weighted.


Catalina S80 3000 77.4 7.25 25.8 31.6 4 -1.8
Catalina C80 3300 77.4 7.25 25.1 34.4 -0.2 -5.9

Last column is buoyancy full. 2nd to last is buoyancy empty. To the left of that is empty weight.

C-80 is the neutral 80.

Maybe their tanks are empty?

Ron

Thanks for the replies guys. Pretty much what I thought. I went down with the same amount of lead I always use and I was fine. So moral of the story, Watch out for what Dm's say, I'm sure at the end of the day they get paid per dive not per hour and the incentive is to get back to the dock as soon as possible, if they don't hurt anyone and can make you feel like you owe them a big tip so m uch better.

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