Doubles - which tanks??

[Lobzilla]

Hp80s suck as doubles. They are short and hard to get into (cause they sit low on the bench). They are top heavy on almost everyone so they make most people rear-back and drop their knees for horrid trim. They are rarely filled to actual capacity - usually you'll end up with 3200psi in them after a hotter fill. They have modest resale value.

They have almost no good qualities honestly and should not be compared with AL80s at all. AL80s are easy to trim out and can be resold for prices like you bought them for used - or used as stages.

Carrying around lead is not that big a deal.

Thanks for the input on weight distribution.

Are spun HP80 steel tanks any better? They tend to be a little more butt heavy.

Fill pressure is not a concern. I can get up to 4500psi both at the LDS and at home/boat.

Height on boat benches is not a concern anymore since this contraption. Hey, I had to do something with all those boots laying around

As far as unnecessary weight is concerned: I am 52 years of age and there is not one joint or disc in my body that is "acting up". One reason is that I never lug stuff around that I do not have to. It started as lazyness, now it is self-preservation.

Being a pilot also has something to do with it. A pound saved on passengers and luggage is another pound of fuel in the tanks. As a diver, I rather carry back-gas than lead and aluminum.

Thirdly, as a mechanical engineer I know that and why aluminum is great for thin-shelled structures (airplanes, boats) but very inefficient for thick-walled pressure vessels.

However, if the HP80s cannot be trimmed out, all that does not matter.

 

[rjack321]

However, if the HP80s cannot be trimmed out, all that does not matter.

If you are quite short and (ehem) "wide" you might be able to trim hp80s out. Most people either can't trim them out or at best struggle to trim them out and spend an inordinate amount of time and energy on the dive just managing the tanks.

LP85s (esp of filled to 3000-3200) or hp100s are a VASTLY better choice in this size range. Almost everyone can dive these pretty easily. I think you've seen that in this thread, they are a fairly universally recommended for moderate deco diving in the ocean (up to about ~180ft, <30mins). Beyond that you need more gas with bigger doubles or an Al80 stage. Double AL80s are a bit smaller and more restrictive on depth/time but still easy to dive.

Hp80 doubles are some of the hardest tanks of all to dive they aren't worth buying or setting up honestly since there's a <1% chance they will work well for you and serve your needs instead of LP85s/hp100s. Single hp80s are popular with women for shallower shore dives, that's a whole different non-technical scenario tho. Most people hate hp80 doubles so I'm fairly confident you won't like them either, maybe I'm wrong.

 

[Lobzilla]

If you are quite short and (ehem) "wide" you might be able to trim hp80s out. Most people either can't trim them out or at best struggle to trim them out and spend an inordinate amount of time and energy on the dive just managing the tanks.

LP85s (esp of filled to 3000-3200) or hp100s are a VASTLY better choice in this size range. Almost everyone can dive these pretty easily. I think you've seen that in this thread, they are a fairly universally recommended for moderate deco diving in the ocean (up to about ~180ft, <30mins). Beyond that you need more gas with bigger doubles or an Al80 stage. Double AL80s are a bit smaller and more restrictive on depth/time but still easy to dive.

Hp80 doubles are some of the hardest tanks of all to dive they aren't worth buying or setting up honestly since there's a <1% chance they will work well for you and serve your needs instead of LP85s/hp100s. Single hp80s are popular with women for shallower shore dives, that's a whole different non-technical scenario tho. Most people hate hp80 doubles so I'm fairly confident you won't like them either, maybe I'm wrong.

Thanks for the feedback.

I am 6'6" with only 178 lbs. The tail-heavy Ashai HP100 spun tanks work great for me. I have bands and manifolds for them as well.

The only reason I wanted a lighter rig is for the purpose you mentioned: shore dives. I like lobstering and that is rarely a tight-team endeavor. So, I was looking for redundancy without the risk of breaking back or limbs on the rock entries.

A little more bottom time would also increase the catch. The hour I get out of a single HP100 at an average of 20 feet is over pretty quickly when you have to swim out, find bugs, catch them, and drag the bounty back home.

I guess, it is single HP100 with H-valves for the shore dives and HP100 doubles for the deeper dives and tech training. Unless someone can come up with some 'miracle' tanks that weigh very little, are not too buoyant, hold lots of air, and balance out nicely, while allowing you to reach the valves.

(Slightly off-topic: If someone wonders why I do not simply surface on the shallow dives when a technical problem occurs: I do not want to form bad habits - like I do not just jump out of my airplane when some system goes nuts. How about a slung tank? I am going to try but I am a little sceptical about drag and clumsiness when covering some ground or pursuing "the one that wants to get away")

 

[Gombessa]

(If someone wonders why I do not simply surface on the shallow dives when a technical problem occurs: I do not want to form bad habits - like I do not just jump out of my airplane when some system goes nuts.)

Just remember not to sacrifice plain good judgment in favor of building up some sort of habit for an entirely unrelated environment. While many issues can be solved underwater, if something happens on an NDL, non-overhead dive and it would be advantageous to be at the surface, that's where I'm heading. I'd not want to take the attitude that doing so is reinforcing some bad habit.

 

[Lobzilla]

Just remember not to sacrifice plain good judgment in favor of building up some sort of habit for an entirely unrelated environment. While many issues can be solved underwater, if something happens on an NDL, non-overhead dive and it would be advantageous to be at the surface, that's where I'm heading. I'd not want to take the attitude that doing so is reinforcing some bad habit.

I know, I should not have touched that can of worms.
Shall we start a new thread on "Punish yourself early for doing things that will harm you later"?

Of course, I am not going to stay down with no deco obligation when I experience symptoms of a severe medical problem, have a flooding drysuit, am out of air with no buddy in sight, etc. But I doubt that my brain will decide in these cases "Let's just stay here and drown like a rat". It is the other cases, where one should stay down but bolts uncontrolled, out of instinct, without rational analysis, that I am worried about.

I have seen the enemy, it is between our ears.

 

[Rainer]

I had a little over 300 dives in MA before moving to CA, so I know your local waters well enough.

I'm only 6'0", but I've tried HP80s as singles and doubles (friend had them). I could just manage to trim them as singles and I was pretty worthless in doubles (and I'm a lot shorter than you). Another worry with such short cylinders, though, is that they're shorter than most wings. That means when you go to sit down, there's a good chance each time that you might puncture your wing (that is, cause a pinch flat). Me, I wouldn't bother with HP80s.

I also had a pair of Asahi HP100s. Love them as singles. I'd hate them as doubles. Just way too heavy in my book (something like -6# each empty).

For my deeper recreational diving, I was quite happy with double LP85s (even for two dives). Everything in MA is basically either a square profile (from the boats) or really shallow (from shore). Big doubles just don't serve you well there unless you're doing big (deeper than 200') dives. I really didn't have much use for my double HP130s...

If you're not finding a HP100 big enough for shore dives, there's something wrong. Both Cape Ann and Cape Cod rarely get deeper than 40' from shore (25' was my usual average at most of the shore sites). In 2 ATAs, a HP100 is going to last you close to 90 minutes. In water that rarely gets into the 50sF (mid-30sF in winter!), that's usually long enough. Of course, you can always do two dives (you already have a pair of singles).

In any case, I'd work on just building up some general experience before worrying about even bigger cylinders, H valves, or doubles. If you want to spend money, get in touch with Ed Hayes about a Fundamentals class. That will likely do a lot more to keep your diving fun and safe.

Enjoy your diving; there's some really good sites there in MA!

Thanks for the feedback.

I am 6'6" with only 178 lbs. The tail-heavy Ashai HP100 spun tanks work great for me. I have bands and manifolds for them as well.

The only reason I wanted a lighter rig is for the purpose you mentioned: shore dives. I like lobstering and that is rarely a tight-team endeavor. So, I was looking for redundancy without the risk of breaking back or limbs on the rock entries.

A little more bottom time would also increase the catch. The hour I get out of a single HP100 at an average of 20 feet is over pretty quickly when you have to swim out, find bugs, catch them, and drag the bounty back home.

I guess, it is single HP100 with H-valves for the shore dives and HP100 doubles for the deeper dives and tech training. Unless someone can come up with some 'miracle' tanks that weigh very little, are not too buoyant, hold lots of air, and balance out nicely, while allowing you to reach the valves.

(Slightly off-topic: If someone wonders why I do not simply surface on the shallow dives when a technical problem occurs: I do not want to form bad habits - like I do not just jump out of my airplane when some system goes nuts. How about a slung tank? I am going to try but I am a little sceptical about drag and clumsiness when covering some ground or pursuing "the one that wants to get away")

 

[Lobzilla]

I had a little over 300 dives in MA before moving to CA, so I know your local waters well enough.

I'm only 6'0", but I've tried HP80s as singles and doubles (friend had them). I could just manage to trim them as singles and I was pretty worthless in doubles (and I'm a lot shorter than you). Another worry with such short cylinders, though, is that they're shorter than most wings. That means when you go to sit down, there's a good chance each time that you might puncture your wing (that is, cause a pinch flat).

Excellent point. Thanks.

Me, I wouldn't bother with HP80s.

I also had a pair of Asahi HP100s. Love them as singles. I'd hate them as doubles. Just way too heavy in my book (something like -6# each empty).

I will give them a try as doubles and report results. The book says -4 empty and -11.5 full but I will check that. Fabers are worse and PST were better according to listed data. I think the Asahi HP100s will be fine with 300-type jumpsuit, plus 300-type vest, if and only if the trim is there. I will let you guys know. BTW: Should we start a database somewhere with verified, working combinations rather than everyone going through the same trial and error thing?

...snip...

If you're not finding a HP100 big enough for shore dives, there's something wrong.

Yes, my insistence to swim out twice as far as everyone else. However, you don't catch lobsters that already got bagged by someone else.

Both Cape Ann and Cape Cod rarely get deeper than 40' from shore (25' was my usual average at most of the shore sites).

True.

In 2 ATAs, a HP100 is going to last you close to 90 minutes.

I am getting close to that when I float around leisurely.

In water that rarely gets into the 50sF (mid-30sF in winter!), that's usually long enough. Of course, you can always do two dives (you already have a pair of singles).

My quota is to empty four tanks per weekend. But I hate to swim the "to" and "from" distance eight times. On the other hand, burning calories (with air) keeps you warm and the bum toned.

In any case, I'd work on just building up some general experience before worrying about even bigger cylinders, H valves, or doubles. If you want to spend money, get in touch with Ed Hayes about a Fundamentals class. That will likely do a lot more to keep your diving fun and safe.

Done deal. Talked to Ed last weekend about Fundies in FL when the white stuff piles up here. However, I would like to do the Fundies with tech options (skills 16 thru 19). Hence the interest in doubles and this thread.

Enjoy your diving; there's some really good sites there in MA!

I'll ping you when business or vacation brings me to the left coast. I heard you got some nice sites too

 

[rjack321]

BTW: Should we start a database somewhere with verified, working combinations rather than everyone going through the same trial and error thing?

You're no fun

Although seriously, everyone has different needs. I have 5 unique sets of doubles in the garage and use what I need when I need it. Sometimes that's huge & heavy, sometimes its smaller and more mobile. Sometimes with a stage sometimes without. Even across manufacturers a given size can have wildly different characteristics (e.g. Faber vs. PST vs Worthington lp95s)

 

[Cruisin Home]

I don't see them as particularly big dives ... just a bit deep.

I'd probably consider some of the dives you do bigger in terms of planning and preparation ... it boils down to familiarity.

This is one of my dive buddy's garage ... most of those doubles are 130's ...

... Bob (Grateful Diver)

Man thats some freeaking garage!!! Nice!!!!