I need your help. DSMBs, what are people's questions/concerns/etc.?

[wetb4igetinthewater]

Another thing most people shouldn’t be doing…

You and I may have very different long term goals.

 

[grantctobin]

You and I may have very different long term goals.

You and I have very, very different experience levels when it comes to long range diving. Best of luck, and I hope at some point you understand why you get so much pushback from people like RJack, TBone, and others. A quote from Don below on BOBs:

When I finally got to the point that I was entering a cave with my back mount RB, 6 BO tanks, 2 scooters, and a camera; it was time to think about a BOB.

I talked to everybody that was willing and got a lot of good advice and suggestions. I spent over 2 years doing the research on a BOB and figuring out exactly what I wanted. I quickly discovered that there was nothing out there that fit the bill for me and I was forced to make my own, which I am still diving to this day.

The number one thing, is that it must have a perfectly simple and reliable ADV. This one thing will completely negate the functionality of the BOB quicker than anything else.

I decided that BOB should be completely self contained and not reliant on any shared resources. It should be as reasonably simply built as it is to operate. It should be able to plug in offboard gasses. It should be able to sidemount and remain streamlined. It should be quick and easy to monitor po2. It should be dewaterable. It should be neutral in the water.

Some of the particulars I decided on were as follows:
1 - It is a full manual unit with no leaky valve or needle valve. O2 is only added when I use the MAV. This way the O2 is turned on and ready to use without me having to remember to turn anything on. At depth it takes so little effort to maintain SP that it is not a concern even when task loaded. It does take a bit more attention as I get shallow but by then I am more relaxed and it is easily managed.
2 - The ADV also serves as the dil MAV, and the O2 MAV is secured near it so each are there when I want them.
3 - I monitor with a rEvo dream. Yes I hate them with a passion, but it works perfect for this project. All I have to do is glance down to see if the green light is on and the loop is breathable. I like to verify this all during the dive to maintain that warm and fuzzy feeling that I am not going to die this dive.
4 - It has an OPV on the bottom of the scrubber that allows dewatering. I used one of the original lower OPVs from a rEvo 2 since they have more tension than a wing opv but still vent before blowing the counterlungs apart.
5 - I carry one alum 80 on the opposite side with deep mix. I also stage 40cf of oxygen. I will carry the oxygen if in the ocean.
6 - the DSV is clipped to my lower shoulder d-ring

This works fine for dives of 300' for 6 hours or less. If I am going deeper then I change it up a bit and fill both onboard tanks with O2 and plumb in the offboard for dil. This gives me redundant O2 on the BOB itself if needed.

This is obviously a very simplified short story of my life with BOB.

To get back on topic, good luck w the guide.

 

[Vicko]

Or a backup rebreather.

Most sane people are using a BoB as an alternate source of scrubber, not bailout gas.
The rest are usually fine not taking any bailout at all.

 

[lowwall]

Ummm. Basic Scuba forum.

 

[wetb4igetinthewater]

Ummm. Basic Scuba forum.

After a first page, does anyone really expect things to remain on topic?

This thread was about a DSMB manual which is a basic skill as it is in open water courses (yes, I know optional for many agencies, something I vehemently disgree with. Should be mandatory, but let's acknowledge that I'm never going to convince any agency to do so, except maybe the my future agency theAssociation of Recreational Scuba Educators).

Let's hope we can get back on track and the mods don't move this to some other forum. At best, delete the rebreather comments to restore sanity here.

 

[lowwall]

After a first page, does anyone really expect things to remain on topic?

This thread was about a DSMB manual which is a basic skill as it is in open water courses (yes, I know optional for many agencies, something I vehemently disgree with. Should be mandatory, but let's acknowledge that I'm never going to convince any agency to do so, except maybe the my future agency theAssociation of Recreational Scuba Educators).

Let's hope we can get back on track and the mods don't move this to some other forum. At best, delete the rebreather comments to restore sanity here.

I was responding to the rebreather stuff. I have no problem with your initial topic

 

[wetb4igetinthewater]

I was responding to the rebreather stuff. I have no problem with your initial topic

OT: Putting on my pedantic hat: you technically can take an open water course with a rebreather. See PADI's GS&P on standard diver equipment.

Back to sanity....

 

[NothingClever]

@wetb4igetinthewater - are you familiar with the technique of blowing a small amount of air (a ‘knot’) into the DSMB to get it to properly unfurl and behave as you prep for real inflation and release?

That’s all I’m talking about with the amount of air in the portion of DSMB that passes between the legs and extends up. Your drawing is mostly correct but I wouldn’t try to position the center of the DSMB at my ‘tweenda’. Think Sleestak tail.

Yes, you want the inflator valve and OPV in front of your work space for control.

I trained on this twice in an AL80 twinset from 40m and felt confident in the control and results. It’s a lot less work (for me) than trying to wind my way up with a spool.

 

[SlugLife]

Okay, first, no requests for graphics design work. With the quality I demonstrate here, I'm much too busy:
View attachment 758979
I am not sure if my description was clear enough, so I created a photo quality, life-like image you see above.
How do you handle the expanding gas in the part of the DSMB that is behind your back/head?

If I hadn't been reading the thread, this pic would make a good guessing-game.

Ideally, your DSMB doesn't need much gas to get you neutral, and therefore no gas is back there. However that's not always possible if one is overweighted, or something like a flooded drysuit.

Guys, seriously.
Just shoot it to the surface and climb the rope.
A 2m dsmb has less than 10kg of lift btw, so don't expect to do it with a twinset and stages.

I think this is the right approach 90% of the time. The other 15%, lets say you're in an overhead environment (which I have heard of a BCD failing in a cave before), then using a DSMB as a BCD of sorts makes a little more sense. When you get back to open water, it might make more sense to switch back and go the climbing-rope option. It may also be necessary if someone doesn't have a long enough spool.

In other words, it's useful to describe both, even if you point out that one option is usually more practical.

 

[wetb4igetinthewater]

@wetb4igetinthewater - are you familiar with the technique of blowing a small amount of air (a ‘knot’) into the DSMB to get it to properly unfurl and behave as you prep for real inflation and release?

Yes, I'm familiar with that method and recommend it

That’s all I’m talking about with the amount of air in the portion of DSMB that passes between the legs and extends up. Your drawing is mostly correct but I wouldn’t try to position the center of the DSMB at my ‘tweenda’. Think Sleestak tail.

A Land of the Lost reference. I had to Google that as I watched that as a kid.

Yes, you want the inflator valve and OPV in front of your work space for control.

I trained on this twice in an AL80 twinset from 40m and felt confident in the control and results. It’s a lot less work (for me) than trying to wind my way up with a spool.

I'm still not getting it. I'm going to leave this idea out of the document for now. There's always a possibility of version 2. After all, my dive planning guide for open water students has a few minor revs of new resources, new dive charters, and ones no longer operating.