latest SM set up with pics - for anyone getting started it may help....or not

[rddvet]

(b) In cold waters with very thick undergarms, many will need to add extra lead. Obviously the exact amount differs by person. The drysuit is there to take the squeeze out, not for buoyancy control (unless you follow a PADI drysuit course). 100+ feet down, your wing will need to be inflated close to max capacity. A wing with lift in the mid-40s or higher is more adequate for these conditions. I'm not talking generically but specifically to the environment that I mostly dive in and, it seems, the OP does from the initial description. If that's not the case, my comments are not relevant.

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While I don't dive the Great Lakes, I have dove the Stealth in similarly cold environments with similar or more depth. Yes, the wing will have air in it. Is it an unrealistic amount? Absolutely not, and nowhere near the point of being unsafe or teetering on the edge of over-inflation. I guess I don't see it the same way as you do.

I know people carrying 95s, stage, and twin deco bottles for trimix dives with no issue on that wing. I'm considering worthington's, a stage, and a steel 72 deco bottle for trimix and have no concern of over-expansion or inflation of the wing.
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And not to start down another path, but what's wrong with using your drysuit as a means of lift (although I do believe if it is done the diver needs to be aware of what happens in their current weighting if they have a wing failure and need redundant buoyancy). I regularly use a combination of drysuit and wing for buoyancy and trim. I do have a healthy understanding of the weight limits I can expect my drysuit to be able to bail me out of.

 

[decompression]

Drysuit=warmth
Wing=bouyancy compensation for consumed gas

A drysuit is a horrible BCD and possibly dangerous used in that way. As an emergency means, acceptable.


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[rddvet]

Drysuit=warmth
Wing=bouyancy compensation for consumed gas

A drysuit is a horrible BCD and possibly dangerous used in that way. As an emergency means, acceptable.


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Using it as a solitary means of buoyancy other than emergency is dangerous. I think there's a big debate on it's use for minor buoyancy and trim adjustments. I sit on the side that there's absolutely nothing wrong with its use for minor adjustments.

Here's an example. Diving aluminum tanks in Mexico, and the tank butts get floaty. Regardless of how much you adjust the tanks with a sliding d-ring and the tanks are in perfect trim, it's not uncommon to still feel a little butt light. An easy correction would be adjusting the bubble of air in your suit to adjust some trim up to your shoulders. It can help to feel more comfortable without having to adjust posture to correct for the perceived feel in trim. To accomplish, you may need less air in the wing, and a little more in the suit. How is that a bad idea? As you become used to that particular cave, you can prepare by choosing to inflate your suit over your wing.

I've had instructors teach me both sides of the debate. If you're not relying solely on that lift in the suit, there's nothing unsafe about it.

 

[bada3003]

This statement is totally wrong. Buoyancy is a function of water displacement. We treat water as incompressible. The only thing that compresses is air. If you need to displace a cubic foot of air to remain neutrally buoyant at 10 feet, you'll need to displace a cubic foot of air to remain neutrally buoyant at a 100 feet...whether it's in your bcd or drysuit. You do not need a bigger wing the deeper you go. Otherwise we would see rebreather divers with gigantic wings.

So you have the same amount of air in your wing at 10 feet as at 100 feet? And without using your drysuit as a buoyancy control device (i.e., putting in just enough air to alleviate squeeze and add a bit of warmth)?

Not the best clips, but what I have handy right now: https://www.youtube.com/watch?v=5uAR-c0UKM0
No one is using the buttplate. You'll have to excuse some of the "danglies", as the students are using my Stealths and I have extra webbing just in case I need to make them larger. Same for hose routing. I left one with a long inflator hose just in case someone wanted their inflator routed to the left instead of across the chest.

Thanks for posting the video. And the same to Sidemount_Stu. In your clip, the student with the HP120 looks similar to the OP's trim with the cylinders hanging low. For the HP100's, it seems there's zero slack from the cam band to the waist ring. That is, the distance is the length of the bolt snap. How do you do drills/manipulate cylinders under water in horizontal trim with those heavy steels? In vertical position, sure.

I'm getting the sense that some of the confusion stems from "open water SM" that may not fully consider that the myriad of drills should be doable in horizontal trim. It's not about looking pretty while gliding along when not task loaded. If that were the criterion, you could solve the AL80 tail floating problem by tying a rope between the cam bands across your belly and the cylinders will stay put when gas gets depleted. That's not considered an adequate solution since the rope attachment itself becomes a potential safety factor when the cylinders need to be manipulated under water. Hence other Hogarthian solutions are preferred. Keep these factors in mind when stating that you have solutions to this and that.

---------- Post added September 16th, 2014 at 09:14 PM ----------

... An easy correction would be adjusting the bubble of air in your suit to adjust some trim up to your shoulders. It can help to feel more comfortable without having to adjust posture to correct for the perceived feel in trim. To accomplish, you may need less air in the wing, and a little more in the suit. ...

Not sure where you got your technical training but controlling air bubbles within a drysuit as a means of buoyancy control isn't typically taught as a viable technique.

 

[Patoux01]

Bada, would you mind showing us a video of those "uber drills of death" you're talking about?
I'm fairly new to diving, but can't see ANY reason why you wouldn't be horizontal during the drills. If you can stay in trim without task loading, you can do it with it. The fact that your hand is moving somewhere has nothing to do with your trim.

Oh, as for the Al80s, that has been solved quite a while ago, I don't really see what you're trying to prove here.

What's the problem with having only the boltsnap with nearly no leash between the tank and the snap?

And again, the forces don't care about you being 50 or 500m down. If you're neutral at 50, since there's no compression, you'll be neutral at 500. You WILL add air because that air compresses, but the volume stays constant.

Edit: I did feel a need to check on the volumes available, Z-tec pro is 15, z-plus pro is 21, razor BAT is 21, SMS100 is 23, sms50 is 10.5, sms75 is 18. What's the big deal with the stealth having "only" 16.5 ? It might be on the lower end, does that make it not enough for 2 tanks? I doubt it. But according to your logic, suppose you have 2 of those steel tanks, and let's say the dive requires 2 stages (or decos, whatever), then there is only the sms100 doing the job?

 

[gearhound]

Somebody help Bada out here. I think buoyancy is covered in chapter 1 of the Open water diver manual.

And we have no problems doing valve drills in correct trim and hovering in position. And yes, I am a cave diver and use those standards when I teach.

 

[decompression]

Using it as a solitary means of buoyancy other than emergency is dangerous. I think there's a big debate on it's use for minor buoyancy and trim adjustments. I sit on the side that there's absolutely nothing wrong with its use for minor adjustments.

Here's an example. Diving aluminum tanks in Mexico, and the tank butts get floaty. Regardless of how much you adjust the tanks with a sliding d-ring and the tanks are in perfect trim, it's not uncommon to still feel a little butt light. An easy correction would be adjusting the bubble of air in your suit to adjust some trim up to your shoulders. It can help to feel more comfortable without having to adjust posture to correct for the perceived feel in trim. To accomplish, you may need less air in the wing, and a little more in the suit. How is that a bad idea? As you become used to that particular cave, you can prepare by choosing to inflate your suit over your wing.

I've had instructors teach me both sides of the debate. If you're not relying solely on that lift in the suit, there's nothing unsafe about it.

Air is dynamic, it moves, it compresses and it expands......easy to control in a small, purpose built volume but significantly more difficult in a large bag with arms and legs and valves and when heavily task loaded such as watching deco, navigating, no mask, OOA. Why learn bad habits that you'll have to change later? And again, there is potential for bad things....you mention caves, your buoyancy must be exceptional, a silt out or lost line can happen faster than a blink of an eye......the difficulty of managing buoyancy with a drysuit and BCD while in an overhead keeps one far too distracted. I find it much easier to let my lungs do the work.....once I've compensated for the gas and I'm toasty......make sense?


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[Sidemount_Stu]

how do i explain / ask this....... if looking at you from behind it looks like the clip on the left tank band (for example) is at about 3 oclock (12 oclock being the top side of the tank) which helps keep the tank higher toward the back. but what prevents the tank from "rolling" or "torquing" to the outside (l/h rolling counter clockwise - r/h rolling clockwise) ?? is the strength of your bungee enough to hold it in that position ??

i hope this all makes sense ??

Yes this makes sense totally. My lower attachment boltsnap is directly in line with the valve blanking plug on the modular valve. And you are correct that it's the bungee that rotates the cylinder and holds it in place.

As I mainly cold water dive, I've opted for 8mm thick bungee, but anything from 6-8mm should be ok. The thicker the bungee the higher the elastic strength, but the less actual stretch.

When attaching the bungee, I put my thumb in the loop stretch it out, wrap it around but under the valve handle, along the front and then slip the loop over the modular valve extension. This means the tension of the bungee is working to rotate the cylinder, keeping the 1st stage tucked in nicely and it keeps tension on the cylinder pulling up from the boltsnap attachment.

I hope that makes sense, if not, let me know I'll try and take a picture.

 

[bada3003]

Somebody help Bada out here. I think buoyancy is covered in chapter 1 of the Open water diver manual.

I think it's be more informative to respond to specific questions than keep repeating Archimedes' principle which I'm glad to find you seem to comprehend (at least as described in an OW diver manual).

And we have no problems doing valve drills in correct trim and hovering in position. And yes, I am a cave diver and use those standards when I teach.

See the comments about donning/doffing cylinders. If you and your students can do that in horizontal trim with with the bolt snap attachments you seem to be using, kudos to you.

---------- Post added September 17th, 2014 at 12:26 PM ----------

I sent a detailed reply but it somehow got lost due to timeout. Here's the gist:

1. Donning/doffing of cylinders under water is an important skill. If you're inside a wreck, the floor is silty, and you gotta go through a restriction which entails unclipping a cylinder w/o silting out, doing so in horizontal trim is important. I find it hard to do so when there's no slack between the cam band and the bolt snap. See below.

2. The solutions to deal with floating AL80 cylinders to achieve good trim are potentially many. Among those only a small subset are used in practice which introduce the least complications in actual diving situations where, for example, unclipping cylinders may be required. Similarly, one could attach the cylinder cam bands with using a quick link which would "solve" the OP's low running cylinder problem. Not many would consider this a viable solution.

3. Without some slack, I've found it difficult to do donning/doffing of heavy steel cylinders under water in horizontal trim. That couple of inches of stretch, in my case, makes all the difference. If others can do that with the attachment method that gearhound seems to be using, kudos to them.

4. Yes, you're repeating Archimedes' principle. When I'm at the surface, even with venting the air from my drysuit, the volume is greater than at 10 feet. At higher depth, I add just enough air to reduce squeeze but do not compensate all the volume lost due to compressed gas by adding commensurate gas. I do so through the wing. With the weight I'm wearing for thick undergarment, only compensating part of the volume lost in my drysuit through equalization, and the neoprene hood compressed maximally at depth, I find lift in the mid-30's to be marginal. This has been, in my experience, a shared experience by some cold water divers, but apparently not all agree.

5. Other SM rigs with lift in the mid-40 lbs and higher range include Dive Rite XT and HOG.

Bada, would you mind showing us a video of those "uber drills of death" you're talking about?
I'm fairly new to diving, but can't see ANY reason why you wouldn't be horizontal during the drills. If you can stay in trim without task loading, you can do it with it. The fact that your hand is moving somewhere has nothing to do with your trim.

Oh, as for the Al80s, that has been solved quite a while ago, I don't really see what you're trying to prove here.

What's the problem with having only the boltsnap with nearly no leash between the tank and the snap?

And again, the forces don't care about you being 50 or 500m down. If you're neutral at 50, since there's no compression, you'll be neutral at 500. You WILL add air because that air compresses, but the volume stays constant.

Edit: I did feel a need to check on the volumes available, Z-tec pro is 15, z-plus pro is 21, razor BAT is 21, SMS100 is 23, sms50 is 10.5, sms75 is 18. What's the big deal with the stealth having "only" 16.5 ? It might be on the lower end, does that make it not enough for 2 tanks? I doubt it. But according to your logic, suppose you have 2 of those steel tanks, and let's say the dive requires 2 stages (or decos, whatever), then there is only the sms100 doing the job?

---------- Post added September 17th, 2014 at 12:37 PM ----------

Interesting solution. I would not have thought that the rotational tension applied at the cylinder valve would suffice to hold up the tail end of a heavy steel cylinder and prevent rolling over, but apparently it does. Will have to try it out.

Yes this makes sense totally. My lower attachment boltsnap is directly in line with the valve blanking plug on the modular valve. And you are correct that it's the bungee that rotates the cylinder and holds it in place.

As I mainly cold water dive, I've opted for 8mm thick bungee, but anything from 6-8mm should be ok. The thicker the bungee the higher the elastic strength, but the less actual stretch.

When attaching the bungee, I put my thumb in the loop stretch it out, wrap it around but under the valve handle, along the front and then slip the loop over the modular valve extension. This means the tension of the bungee is working to rotate the cylinder, keeping the 1st stage tucked in nicely and it keeps tension on the cylinder pulling up from the boltsnap attachment.

I hope that makes sense, if not, let me know I'll try and take a picture.

 

[rick00001967]

Yes this makes sense totally. My lower attachment boltsnap is directly in line with the valve blanking plug on the modular valve. And you are correct that it's the bungee that rotates the cylinder and holds it in place.

As I mainly cold water dive, I've opted for 8mm thick bungee, but anything from 6-8mm should be ok. The thicker the bungee the higher the elastic strength, but the less actual stretch.

When attaching the bungee, I put my thumb in the loop stretch it out, wrap it around but under the valve handle, along the front and then slip the loop over the modular valve extension. This means the tension of the bungee is working to rotate the cylinder, keeping the 1st stage tucked in nicely and it keeps tension on the cylinder pulling up from the boltsnap attachment.

I hope that makes sense, if not, let me know I'll try and take a picture.

you explained it just fine. i'm glad you understood what i wrote. btw i also wrap my bungee on the tank valve in the same manor. but there is no way it can hold my steels from rotating. and they are tight. so i have to assume it is the difference in buoyancy between our tanks.

i actually am thinking of trying allum 80's to see the differences compared to the steels. i'm starting to think that having to add 10 lbs or so to my harness (if i use the allum's) is an easier solution to my tank trim issues than trying to get the steels to work better. i wear 20lbs anyway when i'm diving a single steel so carrying that much weight is no big deal

---------- Post added September 17th, 2014 at 12:52 PM ----------

So you have the same amount of air in your wing at 10 feet as at 100 feet? And without using your drysuit as a buoyancy control device (i.e., putting in just enough air to alleviate squeeze and add a bit of warmth)?

maybe i shouldn't stick my nose in between you fellas but i think you are just looking at this differently. bada i think you are looking at it from the point of view that air "must" be added as you go deeper. and that of course is true due to compression of the air in the bladder as you descend. but the other poster is looking at it from a "volume" stand point. so, yes you will have to add more air as you descend but the volume of the gas will remain constant.
that all being said......this is assuming that nothing else you are carrying can compress. otherwise you will need to add even more air to compensate for the other items compressing. an example may be someone who wears a really thick wet suit or even a non crushed neoprene dry suit

ps......as far as staying horizontal.....i know there is no way in hell i can disconn my steels in the water and push them forward. but i am assuming anyone with steels would not attempt this anyway