Jon lines

[Braunbehrens]

bridgediver once bubbled...

friends?

I didn't mean come off as unfriendly, sorry if I did. I think the cold issue is not that relevant to begin with...but since we are on the subject.
Heat loss through the head is amazing. I was sitting with my wife and she complained that her feet were cold. I suggested she put her hood on. She looked at me with that "what are you, an idiot?" look ;-)

I finally got her to put on the hood, and a few minutes later her feet were fine.

A proper hood is an oft overlooked part of diving equipment. I got a 10 mm hood, and it actually made a difference in how warm I felt during deco.

 

[GearHead]

OK, I assume we're still going with the hypothetical situation of a wreck charter anchored to the wreck, no chase boat, and high current.

Braunbehrens once bubbled...
Ok, so you're doing this wreck dive with deco etc., and you're hanging on the anchor line with your jon line. Let's say that there are 4 teams at different depths.

What do you do if 2 teams don't make it or get blown off?

If that highly improbably scenario occurs, then the teams that get blown off are going to have to do drift deco, and hopefully spotters on the boat will see their SMBs and keep track of them until pickup.

Braunbehrens once bubbled...
What do you do if the boat has to leave, and puts a float on the anchor? Typically this will lower the anchor line quite a bit, possibly causing people at the 70 and 20 ft stops to tox?

Why would a chartered boat have to leave divers in the water? The only two scenarios I can think of are:

1. A diver or dive team blows their deco and need to get to a chamber.
If I'm the charter captain and I still have teams in the water, depending on my location, I'll probably stay put and call the Coast Guard for an airlift. Floating the anchor line on a buoy and ditching the dive site doesn't make any sense to me at all . . . except in scenario #2

2. Godzilla surfaces 200 yards away and starts heading for the boat.
Cut the lines gentleman, we're outta here!

 

[Rick Murchison]

Braunbehrens once bubbled...
pez, when you are drifting less water passes over your suit and you cool off less. When you are hanging in a current more water passes over the suit.

Same as windchill.

Sorry Braun,
It just ain't so.
There's no evaporative cooling underwater, and there's no conductive warming of the water around the dry suit.
Nope, current makes no difference.
Now, if you're in a wetsuit, or in bare skin, that's a different matter. But a dry suit... nope.
Rick

 

[LUBOLD8431]

I use a jon line and I'm not ashamed of it... I just dont get why you wouldnt when we dive up here in NE with currents, and no liveboating. You really NEED to go back up the upline.

 

[Rick Murchison]

MikeFerrara once bubbled...
Paul is right about heat transfer. Divers loose most heat through convection and conduction. Water can't pass through a dry suit but heat can. Every one knows that scootering is colder than swimming. If you don't believe me as the OCDA guys. They're doing long scooter dives in cold caves.

I think you're overstating the change in conductive heat transfer through a dry suit. Scootering is probably colder because (1) there's more conductive heat loss in the face and hands, and (2) you're not working as hard and therefore generating less body heat.
The inner surface of a shell is going to essentially be the same as the outside water temp regardless of water movement across it, and as the air inside is trapped, there's no reason that the conductive transfer of heat across the shell should be any greater in moving than still water.
I haven't done any really long scooter trips, but my limited experience tells me that I get colder scootering than swimming, but colder still during a deco hang with no activity - even if there's no current.
Rick

 

[Braunbehrens]

LUBOLD8431 once bubbled...
I use a jon line and I'm not ashamed of it... I just dont get why you wouldnt when we dive up here in NE with currents, and no liveboating. You really NEED to go back up the upline.

Well, what you really want is a live boat and a chase boat for each team...but I understand why you guys use jon lines.

I was just looking through the quest archives because I remember discussing jon lines with Trey. At the time I was arguing for them...well not really arguing for them, just presenting them as an inevitable part of diving in some circumstances.

Funny how things change...

I still think they are dangerous. But I understand why they are used...basically, it's cheaper than to have a live boat and a bunch of chase boats.

 

[ericfine50]

Paul,

I don't think Jon Lines are the "cheaper" alterative to live boating. Another thing that has not come up, is a lot of divers go out on charters that are not all made up of the same team. So, you could have 6, 8,10 teams of divers on different dive plans and some boats go to two different wreck sites. It is another optiuon on how to deco and needs to be considered. And thanks f or the explaination of how to use the spool as a Jon Line.

Eric

 

[Rick Murchison]

On my list of dangerous things you can do while diving, drifting out of sight of the boat is way, way above anything you can do to yourself with a jon line.
Rick

 

[O-ring]

ericfine50 once bubbled...
Paul,

I don't think Jon Lines are the "cheaper" alterative to live boating. Another thing that has not come up, is a lot of divers go out on charters that are not all made up of the same team. So, you could have 6, 8,10 teams of divers on different dive plans and some boats go to two different wreck sites. It is another optiuon on how to deco and needs to be considered. And thanks f or the explaination of how to use the spool as a Jon Line.

Eric

We get that a lot down here too...especially on the marginally technical stuff - i.e. wrecks in the 110-130 range. There may be 3 buddy teams of divers planning to do deco dives on the wreck and then another 4-5 teams just doing a no-deco recreational dive on the wreck. They all come up at different times and are not all trained to do a drifting deco/drifting safety stop. These mixed boats would make it really hard to pull the anchor and go chase divers that decided to come up off the line.

 

[ericfine50]

exactly.
Eric