Why bungees on side mounts?

[scubaalblake]

Now I'm not afraid of asking stupid questions...so here's another one. Please remember its just a question and the answer while it may be obvious to you - isn't to me
I have stage bottle rigged with snap bolts top and bottom. Bottom snap clips to ring on waist belt on wing - top bolt clips to shoulder ring. Sits nicely and works well. So why, given that I see this all the time with stages don't we mount side mounts in the same way? Like - everyone has the bottom clip but uses bungee round the valve at the top. Why?
Wouldn't a snap bolt at the top hold things tighter, closer and easier?
Just trying to understand why it's obviously better cos everyone does that (and I don't have a SM diver around to talk to so I thought I'd talk to to worldwide diver community!)
Cheers
Al

 

[beanojones]

I would say asking that question in the sidemount forum would work best (but unfortunately that is a sub forum under the overall Technical Diving Forum so it requires permission to read/post in the sidemount section.)

The sidemount bungie system is actually a better, more trimlined, more secure* way to carry stage bottles as well, so you probably would be better asking the question the other way:

Why don't we carry stage bottles the same way as we carry sidemount tanks?

I know that working out my sidemount has made carrying a stage bottles much easier, because putting sidemount ideas into practice makes it like not carrying a stage tank.

 

[Quero]

Sidemount developed as a streamlining configuration for narrow passages so that a diver can slip through with just the thickness of her/his body without removing gear and passing it ahead through the restriction. Also, with the bottles perfectly parallel with the diver's body, the bottoms of the tanks are about at knee level. Adding bottles clipped to the shoulder d-ring makes the diver's profile "thicker" to the extent that the bottle rests against the diver's chest, and when clipped to the shoulder and the hip the bottle will automatically tip at an angle with the tail of the bottle poking upwards, which means not being able to get as close to (for example) the ceiling of a cave as is possible with a well-configured sidemount system. We need the top clip of the tank on a bungee so we can pull it down to check for bubbles, to reach the handwheel, to find the pressure gauge, etc.

 

[DevonDiver]

Using bungee for sidemount provides a source of horizontal and vertical tension upon the top of the cylinder, pulling into a desired position in line with the divers' torso. Stage configuration, using direct bolt-snap to D-ring does not provide that tension, it allows the cylinder to hang down below the attachment points.

In practical terms, bungee can mean the difference in cylinder trim. Between this:

and this:

It also permits the diver to disconnect lower attachments and swing the cylinder/s in front of them - a technique beneficial when navigating through restricted/confined areas. The stretch of the bungee attachment provides superior maneuverability in that respect, compared to a direct snap-to-ring connection.

 

[beanojones]

(Who's that dude in the second picture?)

Also, is the Wikipedia sidemount article still mostly your work? That article has gotten so much better since your first round of rewrites, to the point where it's worth pointing someone to it now.

http://en.wikipedia.org/wiki/Side_mount_diving
Remember what the only picture used to be? Of the guy with BM doubles and a deco bottle?

Once you think the English version is pretty much ready, I am going to write the Japanese version of it with some Japanese people, because while I can translate, I cannot write.

 

[DevonDiver]

(Who's that dude in the second picture?)

One of my students - did sidemount/tec with me. He's also trained with Rob Neto. Good diver...

Also, is the Wikipedia sidemount article still mostly your work? That article has gotten so much better since your first round of rewrites, to the point where it's worth pointing someone to it now...Remember what the only picture used to be? Of the guy with BM doubles and a deco bottle?

It was pretty uninformative before. The photos/details were quite inaccurate in some instances - not actually written by a sidemount diver I suspect. Once it was kick-started it did attract some more informed contributors. One of the main things was keeping the 'politics' out... some of the entries were leaning towards agency/philosophy-bias (you can probably guess).