Sidemounting Faber HP100 Steels (M100DVB)

[Taath]

Hi all,

I am looking at getting a pair of Faber HP100 steel tanks. The M100DVB, not the FX series. The M100DVB are supposed to be -6.69 lbs buoyant when empty. I am figuring this is a great way for me to shed some ballast weight.

Has anyone tried sidemounting these? Are they manageable?

Using Xdeep Stealth Tec, wondering if I'd need to get a buttplate or if I can use the stage rings or waist clip them.

Thanks in advance!

 

[James R]

I would not want to SM those tanks. I have the FX100 and they are really F'n heavy in the water in SM, the DVB are even heavier. Just getting them rigged up in the water will be a struggle IMO.

I can dive dry, with thick undergarments, and zero weight with two LP85 or FX100 easily, your individual needs for buoyancy will vary, of course.

 

[Taath]

I am a bit buoyant I guess. In fresh water with my thermal fusion UG and fusion drysuit I am needing 24 lbs ballast. That's to account for two AL80s. Salt water that jumps to 32 or so lbs. LP85s are 2.32 lbs positive at empty (SALT), so figure close to neutral at reserve pressure.

So that'd let me take roughly 6 lbs off since I don't have to account for the positive buoyancy associated with the AL80s. Not sure how in the world people are able to sink in a drysuit with just LP85s or similar near neutral steels, no or little additional ballast, and be neutral at a safety stop with low tank pressures.

 

[JellyMan777]

Hey @Taath,

Coincidentally, I'm sidemounting AL80s on an XDeep Tec rig, but I plan to upgrade to Faber 100s next year. My story is almost identical to yours in that I dive cold using a drysuit, but I require slightly more ballast than you (36lbs).

After a lengthy analysis, I came to roughly the same conclusion as you probably did. The problem with LP85s, other than their trim characteristics, is that they don't really offer a significant advantage on AL80s. I concluded that 100s are really the way to go despite the obvious weight issues mentioned by James R.

Here is my rationale:

• The gas reserve provided by 100s is critical to my use case. Using 100s, I can strictly observe the rule of thirds, which can be difficult when using AL80s.
• Removing 12lbs collectively (6lbs per tank) from my harness is REALLY appealing.
• Being positively buoyant sans tanks could be construed as a safety measure. A lot of the weight that you and I are carrying is non-ditchable (located in the spinal weight system). In an emergency, it would be nice to know that I can simply ditch my tanks to bob like a cork on the surface. I suppose that you could argue that you can achieve the same effect by ditching your waist pouches if diving AL80s or LP85s, but the delta is not nearly the same.

Incidentally, I do know a guy that sidemounts 100s using a custom rig. He agrees with James R regarding the weight of SM 100s. He said, and this is a direct quote, "it feels like you have two anchors strapped to your sides." He said that he did get used to it eventually, but it IS an adjustment. Also, I noted that he was diving 100s on rails, so I would guess that you might need to invest in the butt plate.

I recommend test diving 100s before you commit to the solution. That's what I am panning on doing before I purchase. See if you can borrow or rent a pair form a local dive shop or a friend. Dive them in the shallows using your current rig and allow that experience to inform your decision.

Also, by all means, please post your decision. I'm sure that we aren't the only ones out here that are looking at this exact same question.

 

[Taath]

Hey @Taath,

Coincidentally, I'm sidemounting AL80s on an XDeep Tec rig, but I plan to upgrade to Faber 100s next year. My story is almost identical to yours in that I dive cold using a drysuit, but I require slightly more ballast than you (36lbs).

After a lengthy analysis, I came to roughly the same conclusion as you probably did. The problem with LP85s, other than their trim characteristics, is that they don't really offer a significant advantage on AL80s. I concluded that 100s are really the way to go despite the obvious weight issues mentioned by James R.

Here is my rationale:

• The gas reserve provided by 100s is critical to my use case. Using 100s, I can strictly observe the rule of thirds, which can be difficult when using AL80s.
• Removing 12lbs collectively (6lbs per tank) from my harness is REALLY appealing.
• Being positively buoyant sans tanks could be construed as a safety measure. A lot of the weight that you and I are carrying is non-ditchable (located in the spinal weight system). In an emergency, it would be nice to know that I can simply ditch my tanks to bob like a cork on the surface. I suppose that you could argue that you can achieve the same effect by ditching your waist pouches if diving AL80s or LP85s, but the delta is not nearly the same.

Incidentally, I do know a guy that sidemounts 100s using a custom rig. He agrees with James R regarding the weight of SM 100s. He said, and this is a direct quote, "it feels like you have two anchors strapped to your sides." He said that he did get used to it eventually, but it IS an adjustment. Also, I noted that he was diving 100s on rails, so I would guess that you might need to invest in the butt plate.

I recommend test diving 100s before you commit to the solution. That's what I am panning on doing before I purchase. See if you can borrow or rent a pair form a local dive shop or a friend. Dive them in the shallows using your current rig and allow that experience to inform your decision.

Also, by all means, please post your decision. I'm sure that we aren't the only ones out here that are looking at this exact same question.

Yeah, I will ask around to see if any of my associates have HP100s. Most of the shops here just rent AL80s. Arizona is not a big dive spot, lol.

 

[decompression]

if I may, there is a lot to be said for "neutral" tanks as opposed to using your tanks for negative buoyancy. Most instructors will tell you that tank weight should be independent of "personal" weight. Just my 2 PSI.

 

[James R]

if I may, there is a lot to be said for "neutral" tanks as opposed to using your tanks for negative buoyancy. Most instructors will tell you that tank weight should be independent of "personal" weight. Just my 2 PSI.

My SM instructor taught us to configure our kit such that we were able to ditch one of the two tanks and remain neutral. I think this is reasonable, and in that situation I agree with what you are saying. I wouldn't weight myself with a belt or weight harness such that I would be neutral with no tanks, then sling a couple FX100 or even LP85s on - I would prob need a lift bag to stay off the bottom

 

[DA Aquamaster]

An FX100 is about 3 pounds negative when empty, and about 11 pounds negative when full, when you consider the valve and first stage.

In comparison, a M100DVB is about 9 pounds negative in the same configuration.

When you actually fill them, the M100DVD will now be about 17 pounds negative. That ends up being slightly heavier than a cave filled LP 95 with valve and reg (129 cu ft of gas). Thus the M100DVB is a good boat anchor, but a poor choice for a side mount tank.

Part of the issue is the overall negative weight, and part of it is that it's nearly impossible to swing a tank forward and still maintain level trim - an important consideration in sidemount.

I used to dive Worthington X7-100s and they were about 10 pounds negative with valve and first stage when full. They dove ok (I would not want to go any more negative than that) but were still a couple pounds heavier than the Faber LP 85s I dive now, which are only about 7-8 pounds negative when cave filled to 3600 psi (115 cu ft of gas), with valve and first stage.

My recommendation would be to get the FX 100 if you are limited to fills to service pressure, and get LP 85s if you have access to 3600 psi cave fills.

I know a few side mount divers who use FX100 tanks and they are workable and are perhaps a good balance for cold water diving - depending on on your definition of "cold". I use a compressed neoprene dry suit and light weight undergarments in water temps down to the low 50s and I am plenty warm on long dives. This configuration works for me with both steel 72s and LP 85s, with no weight required. If I'm in AL 80s I'll need to add about 6 pounds.

In 35 degree water however, I'll use a much heavier undergarment, and that will then necessitate adding more weight - up to 16 pounds with 400 gram underwear. My preference however is to add it via weight plate or spine strap rather than doing it via more negatively buoyant tanks.

You most definitely do not want to put yourself in a situation where removing one or both tanks leaves you positively buoyant, and potentially corking away from your tanks. That gets people killed.

 

[Pastor G]

I just got a set of M100DVB's 'cause as a BIG diver the math makes sense. I can dive sidemount with fx80dvb's in a three mil with no additional weights (does look strange with those little cylinders). I'm looking forward to diving with the 100's as singles and side mount with cold water gear on and see how it goes.