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

[Sidemount_Stu]

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

The thought has crossed my mind as I've never dived with Ali's sidemount!

My main concern is with the amount of weight in the spine system causing a problem for RHIB diving! Leaving that much weight on and hauling my ass back into the boat at the end of dive could be an issue?

 

[rick00001967]

i could see that as a def problem for you for sure.

allum may also allow me to spread my weight out better. example......right now my 10lbs is all in the spinal pockets. so i have no ditchable weight which i am less than happy about. i know i have my drysuit as "back up" so to speak and i can always drop a complete cylinder if i had to but with the extra weight when using allum, i could keep the 10lbs in the spinal pockets and then have 10lbs ditchable on my waist or wherever

 

[bada3003]

...
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

An accurate description. I think the discussion may have gotten mixed up with the one on using a drysuit for buoyancy control and as my question indicated it wasn't clear to me if gearhound was advocating the same.

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

Nope, too heavy for me. In restrictions, you can unclip them without stirring up silt and push them through an opening (using a ledge as support) but some silting is unavoidable. Just preventing blackout by flailing around to unclip/reclip heavy steels with no slack.

 

[gearhound]

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).



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.

I have been responding to specific comments.

a) It was stated that you must use a butt plate to dive steels. I've presented video evidence to the contrary. And then like an ex-wife, you ignored the evidence and brought up a different topic (trim and cylinder manipulation) If you want to use the butt plate, go ahead. But to say you need it to dive steels is wholly inaccurate. In my conversations with Patrick, the plate was added to placate the old school divers that moved over from another system that had a butt plate (of which I am one). I find it much easier to dive without it, as do a number of other divers that have moved over from the Nomad, sms100 and the Armadillo, all of which I have owned or dived. Can you say the same about the Stealth? Have you tried one that is set up properly? Your premise seems to be since you and your friends can't do it, then it can't be done. My friends and I can't build a nuclear bomb, but I'm sure they exist.


b) It was stated that you need a bigger wing the deeper you go. Archimedes principle says otherwise. Just to make sure, I went into the garage to look at my lift bag. It says 100 lbs of lift. Not 100 lbs of lift at 10 feet, but only 70 lbs of lift at 50 feet and only 30 lbs of lift at 100 ft. That lift bag will provide the same amount of lift no matter what the depth. You still need to add air to it, but the volume will stay the same. The bag does not grow. I do not need a bigger bcd the deeper I go (unless I'm hauling a few more tanks for deco).

Thanks, I do know how to dive a drysuit the "tec" way with only adding air to get rid of squeeze. It's also how I teach it. I am quite aware of how to remove tanks and push them forward through restrictions. More videos for your viewing pleasure. I'm the one in the blue helmet in the cave videos.

https://www.youtube.com/watch?v=oMQYcog2j0g
https://www.youtube.com/watch?v=rVcjiJaDSpw&list=UUpcZMrGBhIQOD_TpJkc3vkA
https://vimeo.com/78358626

I dive the same way, whether using al80s or steels. I like to maintain consistency. In fact, with my Fusion drysuit, I don't even have to adjust the harness when switching back and forth between it and my 7mm wetsuit. All I do is add a bit more weight.

 

[mddolson]

i could see that as a def problem for you for sure.

allum may also allow me to spread my weight out better. example......right now my 10lbs is all in the spinal pockets. so i have no ditchable weight which i am less than happy about. i know i have my drysuit as "back up" so to speak and i can always drop a complete cylinder if i had to but with the extra weight when using allum, i could keep the 10lbs in the spinal pockets and then have 10lbs ditchable on my waist or wherever

I am in similar situation, I wear 12 lbs of weight with my steels & 20 with aluminums.
All but 4 lbs ditchable/on my waist.
Mike D

 

[tbone1004]

gearhound, on B he actually is correct based on his statement. He might only be adding an extra 2-3lbs, but if he's diving his suit with more of a squeeze at depth than he does at the surface which I think most of us do, then it would mean more air in the wing at depth than at the surface or deco.....

 

[gearhound]

Then he's going to have issues shallow also, not just at depth tbone. Remember, the majority of compression happens shallow. If we look at that theoretical upside down glass full of air. It compresses to 1/2 at 33 feet, 1/3 at 66 feet, 1/4 at 99 feet. The change is much greater going from 0-33 feet, than from 66-99 feet or 99-132 feet. If he's overweighted, he should notice it shallow. I think the majority of drysuit divers are diving a trilaminate of some sort. The actual drysuit doesn't compress. Your drysuit underwear does, but I'm assuming you're adding air to it to offset squeeze as you descend. The only thing on you that you're not equalizing as you descend is your hood. Take a slightly deeper breath if thats going to throw you over. It's a different story if you're diving wet in a 14mm wetsuit.

I'm not advocating diving overweighted, but I stand by my statement: A wing that has 35lbs of lift at 10 feet has 35lbs of lift at 100 feet. I'm pretty sure the laws of physics backs me up on this one.

The targets keep changing, but remember his original statement was that the Stealth did not have enough lift for diving Worthington tanks, especially at depth. For me, his logic is quite flawed. Dive a balanced rig and it's more than adequate. How much does 200 cubic feet of air weigh?

 

[tbone1004]

I'm agreeing with you there, but at depth could mean 10 ft

16lbs for the 200cf, and yes a wing has 35lbs of lift. I was just stating that surface vs. any sort of depth could be a different lift requirement. When I do weight calculations for wings and what not, I treat my trilam as having 0lbs of inherent buoyancy because in the event of a suit flood, it doesn't have anything going for it. I am also about the same buoyancy wise with a drysuit in relatively warm water *above 65f* as I am in a 5mm full suit, slightly more if it's cold and I have more air in there, but usually it's a suit squeeze for me.

 

[gearhound]

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)?

I'm just using the numbers he used tbone

 

[rick00001967]

I was just stating that surface vs. any sort of depth could be a different lift requirement.

this is true. if we are at the surface we of course want our whole head comfortably out of the water. so you now have to have more lift avail as your head and hood are no longer displacing water. also, depending on what style of diving you are doing, if any gear is sticking up out of the water (ie: if using back mount doubles) like tops of the tanks, valves, a manifold, 1st stages, these also are no longer displacing any water and again you will require more lift to compensate for this.
i suppose this may be a small benefit of SM. when on the surface, the only part of me out of the water might be my head and hood. it has been suggested to me to use aprox 10lbs as a rough idea of how much extra lift may be needed for head and hood. thats the rough number i used when i was calculating my weight and lift requirements.

---------- Post added September 18th, 2014 at 01:08 PM ----------

My friends and I can't build a nuclear bomb, but I'm sure they exist.

so you are with aqua sport ?? thats where i got my stealth from. nice !! great service from them !!