Double HP100s for Cave or NOT??

[tonka97]

I just purchased double Worthington X7 Steel HP100s, in prep for IntroCave/Full Cave;

Has anyone cave diving experience with these tanks? (Each tank is 3.4 lbs lighter than the older steel HP 100s.)

Here is the argument against these tanks:

"Double steel HP100s position too much weight on the upper part of your body, and you will be struggling to maintain horizontal trim during cave diving, as compared to double LP85s. The preferred LP85s are lighter, and can be overfilled 10%, providing nearly the same amount of gas as the HP100s. The LP85s are longer (avoiding excessive weight toward the divers head) thereby enabling the cave diver to better maintain the necessary horizontal trim. Skilled cave divers who use double steel HP100s are essentially non-existent".

BTW: The older steel HP100s weighed 36.4 lbs empty, compared to the newer Worthington tanks that weigh only 33 lbs empty. Perhaps that 3.4 x 2 = 6.8 lbs difference for doubles contributed to the initial criticism of steel HP 100s.

By contrast the empty weight of the OMS LP85 is listed at 31 lbs.

Old Double steel HP 100s: 72.8 lbs.

New X7 Double steel HP 100s: 66 lbs

Double steel LP 85s: 62 lbs

Buoyancy X7 Steel HP 100: Full -10 Empty -2.5 pounds each tank.

 

[Meng_Tze]

I just purchased double Worthington X7 Steel HP100s, in prep for IntroCave/Full Cave;

Has anyone cave diving experience with these tanks? (Each tank is 3.4 lbs lighter than the older steel HP 100s.)

Here is the argument against these tanks:

"Double steel HP100s position too much weight on the upper part of your body, and you will be struggling to maintain horizontal trim during cave diving, as compared to double LP85s. The preferred LP85s are lighter, and can be overfilled 10%, providing nearly the same amount of gas as the HP100s. The LP85s are longer (avoiding excessive weight toward the divers head) thereby enabling the cave diver to better maintain the necessary horizontal trim. Skilled cave divers who use double steel HP100s are essentially non-existent".

BTW: The older steel HP100s weighed 36.4 lbs empty, compared to the newer Worthington tanks that weigh only 33 lbs empty. Perhaps that 3.4 x 2 = 6.8 lbs difference for doubles contributed to the initial criticism of steel HP 100s.

By contrast the empty weight of the OMS LP85 is listed at 31 lbs.

Old Double steel HP 100s: 72.8 lbs.

New X7 Double steel HP 100s: 66 lbs

Double steel LP 85s: 62 lbs

Buoyancy X7 Steel HP 100: Full -10 Empty -2.5 pounds each tank.

I have a set of X7-100's and did many cave dives on them. I like them. That 'argument' against the 100's is BS in my opinion. Whoever wrote that, either is biased, or does not understand that the relation of lower legs to the rest of your body has biggest impact to trim.....if 'top heavy', lower legs, if bottom heavy, raise legs...

Successfully managed to do cave dives in small and large system passages in perfect trim. As a matter of fact I did my cave courses in these 100's


The only limitation I found was the gas volume..... but as you progress that becomes an issue with any tank...:blinking:

 

[tonka97]

I have a set of X7-100's and did many cave dives on them. I like them. That 'argument' against the 100's is BS in my opinion. Whoever wrote that, either is biased, or does not understand that the relation of lower legs to the rest of your body has biggest impact to trim.....if 'top heavy', lower legs, if bottom heavy, raise legs...

Successfully managed to do cave dives in small and large system passages in perfect trim. As a matter of fact I did my cave courses in these 100's


The only limitation I found was the gas volume..... but as you progress that becomes an issue with any tank...:blinking:

Thanks Meng_Tze for the information and for sharing your experience. It is appreciated.

 

[Mike Edmonston]

I just purchased double Worthington X7 Steel HP100s, in prep for IntroCave/Full Cave;

Has anyone cave diving experience with these tanks? (Each tank is 3.4 lbs lighter than the older steel HP 100s.)

Here is the argument against these tanks:

"Double steel HP100s position too much weight on the upper part of your body, and you will be struggling to maintain horizontal trim during cave diving, as compared to double LP85s. The preferred LP85s are lighter, and can be overfilled 10%, providing nearly the same amount of gas as the HP100s. The LP85s are longer (avoiding excessive weight toward the divers head) thereby enabling the cave diver to better maintain the necessary horizontal trim. Skilled cave divers who use double steel HP100s are essentially non-existent".

BTW: The older steel HP100s weighed 36.4 lbs empty, compared to the newer Worthington tanks that weigh only 33 lbs empty. Perhaps that 3.4 x 2 = 6.8 lbs difference for doubles contributed to the initial criticism of steel HP 100s.

By contrast the empty weight of the OMS LP85 is listed at 31 lbs.

Old Double steel HP 100s: 72.8 lbs.

New X7 Double steel HP 100s: 66 lbs

Double steel LP 85s: 62 lbs

Buoyancy X7 Steel HP 100: Full -10 Empty -2.5 pounds each tank.

Yeah, that's BS. Dive them, you'll enjoy them.

Cheers

 

[Jeff Toorish]

I agree with the above posts, BS pure and simple.

Jeff

 

[Curt Bowen]

I just purchased double Worthington X7 Steel HP100s, in prep for IntroCave/Full Cave;

Has anyone cave diving experience with these tanks? (Each tank is 3.4 lbs lighter than the older steel HP 100s.)

Here is the argument against these tanks:

"Double steel HP100s position too much weight on the upper part of your body, and you will be struggling to maintain horizontal trim during cave diving, as compared to double LP85s. The preferred LP85s are lighter, and can be overfilled 10%, providing nearly the same amount of gas as the HP100s. The LP85s are longer (avoiding excessive weight toward the divers head) thereby enabling the cave diver to better maintain the necessary horizontal trim. Skilled cave divers who use double steel HP100s are essentially non-existent".

HP Tanks initially were not used for cave diving because in the early years they did not exist. Most cavers used LP104’s because of the gas volumes required.

After the introduction of HP tanks, many still chose not to use them because of the difficulties of partial pressure gas blending and the higher oxygen and helium PSI pressures needed to mix the same gas percentages. Standard bank oxygen and helium come in 2200-2400 psi bank cylinders.

http://www.advanceddivermagazine.com/GasStationPage.htm

See the above gas mixing charts to determine the different psi pressures of oxygen needed to mix the same nitrox percentage using LP 2640’s and HP 3500’s. (same volume higher pressures needed) Of course these pressures are no problem, IF you have a booster pump or compressor gas blending system at hand. Gas boosters and compressors in the field were, and still are expensive and difficult to transport.

Today, if there is a good dive facility within acceptable driving distances it is rather easy to get higher pressure gas fills for both nitrox and trimix. (IF the facilities compressor is set to reach higher pressures)

BTW: The older steel HP100s weighed 36.4 lbs empty, compared to the newer Worthington tanks that weigh only 33 lbs empty. Perhaps that 3.4 x 2 = 6.8 lbs difference for doubles contributed to the initial criticism of steel HP 100s.

By contrast the empty weight of the OMS LP85 is listed at 31 lbs.

Old Double steel HP 100s: 72.8 lbs.

New X7 Double steel HP 100s: 66 lbs

Double steel LP 85s: 62 lbs

Buoyancy X7 Steel HP 100: Full -10 Empty -2.5 pounds each tank.

The weight above water of a cylinder means zero, (except for breaking your back trying to get into the water) its the weight of the cylinders underwater, full and empty that makes all the difference.

Example if the cylinder is 6 pounds negative full, but 3 pounds possitive empty and you begin the dive a couple pounds slightly negative. At the end of the dive (when your trying to do your decompression stops) with almost empty tanks you will be floating like a cork. A diver must be properly weighted for thier cylinders at their most bouyant (empty), even if that requires them to be overweighted and compensate with the use of larger wings (BCD)

 

[MichaelBaranows]

If you don't want the tanks I would be more than happy to take them off your hands. I am not a cave diver so I have no problem using the HP 100. In fact I have pair on order right now.

 

[rjack321]

I have not used HP100s in a cave but I wreck dive with them in freshwater all the time. They are almost as easy to trim out as LP85s (which I also have). With a drysuit, 200gm thinsulate, and 6lb plate I use no extra weight. They are nice and compact and carry just the right amount of gas for me to do 25mins at 160ft.

 

[Sideband]

The preferred LP85s are lighter, and can be overfilled 10%, providing nearly the same amount of gas as the HP100s.

Overfilling an 85 by 10% does not "provide nearly the same amount of gas as the HP100s". It provides 85cft. You have to overfill them to a bit over 3100psi to get 100 cft. That's about a 30% overfill. Not that that is a big deal, just an inaccuracy. I've dove a set of 85s filled to 4000 before.

 

[tonka97]

Great responses to the original post.

I am facing a learning curve with both a new dry suit purchase (my first) AND new (my first) doubles set. The responses on this thread have removed my doubts concerning the HP100s.

Thank you!

I plan to proceed with expert instruction toward cavern, intro/full cave certification.

Scubaboard continues to be the best!

Thanks NetDoc!